阅读说明：本技术 光模块、信号处理系统和信号处理方法 (Optical module, signal processing system, and signal processing method ) 是由 铃木智史 岩崎裕也 港谷恭辅 杉本达哉 户塚弘伦 于 2020-01-17 设计创作，主要内容包括：光模块的信号处理部具有：电压信号控制部,其控制电压信号,以使具有用于使可动反射镜进行谐振动作的频率的电压信号被施加于反射镜器件；强度获取部,其实施强度获取处理。强度获取处理是如下处理,即：在电压信号中连续的P周期中的多个周期的各个周期内,以基于电压信号的频率的第一时间间隔,获取M次测定光的干涉光的测定光强度,且获取相互对应的同一次的测定光强度的相加值,并且在该多个周期的各个周期内,以基于电压信号的频率的第二时间间隔,获取N次激光的干涉光的激光强度,且获取相互对应的同一次的激光强度的相加值。(The signal processing unit of the optical module includes: a voltage signal control unit that controls a voltage signal so that a voltage signal having a frequency for causing the movable mirror to perform a resonant operation is applied to the mirror device; and an intensity acquisition unit that performs intensity acquisition processing. The intensity acquisition process is a process of: in each of a plurality of periods of P periods consecutive in the voltage signal, the measurement light intensity of the interference light of the measurement light M times and the added value of the measurement light intensities of the same time corresponding to each other are acquired at first time intervals based on the frequency of the voltage signal, and in each of the plurality of periods, the laser light intensity of the interference light of the laser light N times and the added value of the laser light intensities of the same time corresponding to each other are acquired at second time intervals based on the frequency of the voltage signal.)

1. A light module, comprising:

a mirror device having: a base; a movable mirror including a mirror surface; an elastic support portion connected between the base and the movable mirror, and supporting the movable mirror so that the movable mirror is movable in a direction intersecting the mirror surface; a first comb-tooth electrode provided on the base and including a plurality of first comb teeth; and a second comb-tooth electrode provided on at least one of the movable mirror and the elastic support portion, and including a plurality of second comb-teeth arranged to intersect the plurality of first comb-teeth;

at least one fixed mirror;

at least one beam splitter constituting an interference optical system together with the movable mirror and the at least one fixed mirror;

a first photodetector that detects interference light of the measurement light emitted from the interference optical system;

a second photodetector that detects interference light of the laser light emitted from the interference optical system; and

a signal processing unit electrically connected to the mirror device, the first photodetector, and the second photodetector, respectively,

the signal processing unit includes:

a voltage signal control unit that controls a voltage signal so that a voltage signal having a frequency for causing the movable mirror to perform a resonant operation in the mirror device is applied between the first comb-teeth electrode and the second comb-teeth electrode; and

and an intensity acquisition unit that performs an intensity acquisition process of acquiring, at first time intervals based on the frequency, measured light intensities of the interference light of the measurement light M times (an integer equal to or greater than M: 2) and acquiring mutually corresponding addition values of the measured light intensities at the same time in each of a plurality of periods of P periods (an integer equal to or greater than P: 2) that are consecutive in the voltage signal, and acquiring, at second time intervals based on the frequency, laser intensities of the interference light of the laser light N times (an integer equal to or greater than N: 2) and acquiring mutually corresponding addition values of the laser intensities at the same time in each of the plurality of periods.

2. The light module of claim 1,

the intensity acquisition section performs at least one of a first intensity acquisition process and a second intensity acquisition process as the intensity acquisition process,

the first intensity acquisition process is a process of: acquiring the M times of first measured light intensities as the measured light intensities at the first time intervals and acquiring mutually corresponding added values of the first measured light intensities at the same time in each odd number of periods (P: an integer of 4 or more) among consecutive P periods in the voltage signal, and acquiring the N times of first laser intensities as the laser intensities at the second time intervals and acquiring mutually corresponding added values of the first laser intensities at the same time in each odd number of periods,

the second intensity acquisition process is a process of: in each of the even-numbered cycles in the P cycle (P: an integer of 4 or more), the second measured light intensity of the M times is acquired as the measured light intensity at the first time interval, and the added value of the second measured light intensities of the same time corresponding to each other is acquired, and in each of the even-numbered cycles, the second laser light intensity of the N times is acquired as the laser light intensity at the second time interval, and the added value of the second laser light intensities of the same time corresponding to each other is acquired.

3. The light module of claim 2,

further comprising a memory portion having at least one of a first memory area and a second memory area,

the first storage area is an area in which the first measured light intensity and the first laser light intensity acquired in each of the odd-numbered periods are accumulated or averaged for each period when the first intensity acquisition process is performed,

the second storage area is an area in which the second measured light intensity and the second laser light intensity acquired in each of the even-numbered cycles are accumulated or averaged for each cycle when the second intensity acquisition process is performed.

4. The light module of claim 3,

the storage section further has a third storage area,

the third storage area is an area in which, when the first intensity acquisition process is performed, each of the first measured light intensity and the first laser light intensity acquired in the latest 1 cycle of the P cycles (P: 4 or more integers) is stored until the transfer to the first storage area, and when the second intensity acquisition process is performed, each of the second measured light intensity and the second laser light intensity acquired in the latest 1 cycle of the P cycles (P: 4 or more integers) is stored until the transfer to the second storage area.

5. The light module according to any one of claims 2 to 4,

an optical path difference zero position of the movable mirror is shifted from a center position of a resonant operation of the movable mirror, the optical path difference zero position of the movable mirror is a position where an optical path length of the movable mirror side generating the interference light of the measurement light is equal to an optical path length of the at least one fixed mirror side generating the interference light of the measurement light,

the strength acquisition unit is configured to acquire the strength of the light beam,

as the first intensity acquisition process, the following processes are performed, that is: acquiring the added values of the first measured light intensities of the same time and the added values of the first laser intensities of the same time in the first half or the second half of each of the odd-numbered periods,

as the second intensity acquisition process, the following processes are performed, that is: the first half or the second half of each of the even-numbered periods is acquired with the added values of the second measured light intensities corresponding to each other at the same time, and the added values of the second laser intensities corresponding to each other at the same time are acquired.

6. The light module according to any one of claims 1 to 5,

the first time interval and the second time interval are the same time interval.

7. The light module according to any one of claims 1 to 6,

the voltage signal control section adjusts the frequency of the voltage signal based on a change with time of a capacitance generated between the first comb-tooth electrode and the second comb-tooth electrode.

8. A signal processing system comprising an optical module and a signal processing device electrically connected to the optical module,

the optical module includes:

a mirror device having: a base; a movable mirror including a mirror surface; an elastic support portion connected between the base and the movable mirror, and supporting the movable mirror so that the movable mirror is movable in a direction intersecting the mirror surface; a first comb-tooth electrode provided on the base and including a plurality of first comb teeth; and a second comb-tooth electrode provided on at least one of the movable mirror and the elastic support portion, and including a plurality of second comb-teeth arranged to intersect the plurality of first comb-teeth;

at least one fixed mirror;

at least one beam splitter constituting an interference optical system together with the movable mirror and the at least one fixed mirror;

a first photodetector that detects interference light of the measurement light emitted from the interference optical system; and

a second photodetector that detects interference light of the laser light emitted from the interference optical system,

the signal processing device has:

a voltage signal control unit that controls a voltage signal so that a voltage signal having a frequency for causing the movable mirror to perform a resonant operation in the mirror device is applied between the first comb-teeth electrode and the second comb-teeth electrode; and

and an intensity acquisition unit that performs an intensity acquisition process of acquiring, at first time intervals based on the frequency, measured light intensities of the interference light of the measurement light M times (an integer equal to or greater than M: 2) and acquiring mutually corresponding addition values of the measured light intensities at the same time in each of a plurality of periods of P periods (an integer equal to or greater than P: 2) that are consecutive in the voltage signal, and acquiring, at second time intervals based on the frequency, laser intensities of the interference light of the laser light N times (an integer equal to or greater than N: 2) and acquiring mutually corresponding addition values of the laser intensities at the same time in each of the plurality of periods.

9. A signal processing method which is performed in an interference optical system including a mirror device, at least one fixed mirror, and at least one beam splitter, and which is performed when detecting interference light of measurement light emitted from the interference optical system, and when detecting interference light of laser light emitted from the interference optical system, the mirror device includes: a base; a movable mirror including a mirror surface; an elastic support portion connected between the base and the movable mirror, and supporting the movable mirror so that the movable mirror is movable in a direction intersecting the mirror surface; a first comb-tooth electrode provided on the base and including a plurality of first comb teeth; and a second comb-tooth electrode provided on at least one of the movable mirror and the elastic support portion and including a plurality of second comb-teeth arranged to intersect the plurality of first comb-teeth,

the signal processing method includes the steps of:

a step of controlling a voltage signal so that a voltage signal having a frequency for causing the movable mirror to perform a resonant operation in the mirror device is applied between the first comb-teeth electrode and the second comb-teeth electrode; and

and performing an intensity acquisition process of acquiring measurement light intensity of the interference light of the measurement light M times (an integer of M: 2 or more) at first time intervals based on the frequency and acquiring a sum of the measurement light intensities of the measurement light corresponding to each other at the same time, and acquiring laser light intensity of the interference light of the laser light N times (an integer of N: 2 or more) at second time intervals based on the frequency and acquiring a sum of the laser light intensities corresponding to each other at the same time in each of the periods.

10. The signal processing method according to claim 9,

in the step of performing the intensity acquisition process, at least one of a first intensity acquisition process and a second intensity acquisition process is performed as the intensity acquisition process,

the first intensity acquisition process is a process of: acquiring the M times of first measured light intensities as the measured light intensities at the first time intervals and acquiring mutually corresponding added values of the first measured light intensities at the same time in each odd number of periods (P: an integer of 4 or more) among consecutive P periods in the voltage signal, and acquiring the N times of first laser intensities as the laser intensities at the second time intervals and acquiring mutually corresponding added values of the first laser intensities at the same time in each odd number of periods,

the second intensity acquisition process is a process of: in each of the even-numbered cycles in the P cycle (P: an integer of 4 or more), the second measured light intensity of the M times is acquired as the measured light intensity at the first time interval, and the added value of the second measured light intensities of the same time corresponding to each other is acquired, and in each of the even-numbered cycles, the second laser light intensity of the N times is acquired as the laser light intensity at the second time interval, and the added value of the second laser light intensities of the same time corresponding to each other is acquired.

11. The signal processing method according to claim 10,

an optical path difference zero position of the movable mirror is shifted from a center position of a resonant operation of the movable mirror, the optical path difference zero position of the movable mirror is a position where an optical path length of the movable mirror side generating the interference light of the measurement light is equal to an optical path length of the at least one fixed mirror side generating the interference light of the measurement light,

in the step of performing the intensity acquisition process,

as the first intensity acquisition process, the following processes are performed, that is: acquiring the added values of the first measured light intensities of the same time and the added values of the first laser intensities of the same time in the first half or the second half of each of the odd-numbered periods,

as the second intensity acquisition process, the following processes are performed, that is: the first half or the second half of each of the even-numbered periods is acquired with the added values of the second measured light intensities corresponding to each other at the same time, and the added values of the second laser intensities corresponding to each other at the same time are acquired.

12. The signal processing method according to any one of claims 9 to 11,

the first time interval and the second time interval are the same time interval.

13. The signal processing method according to any one of claims 9 to 12,

in the step of controlling the voltage signal, the frequency of the voltage signal is adjusted based on a temporal change in capacitance generated between the first comb-tooth electrode and the second comb-tooth electrode.

14. The signal processing method according to any one of claims 9 to 13,

the method further includes a step of performing spectrum acquisition processing for acquiring an intensity value at a time when at least one of a maximum value and a minimum value appears in a temporal change of the added value of the measurement light intensity, based on a temporal change of the added value of the laser light intensity, acquiring a relationship between an optical path difference and the intensity value based on a wavelength of the laser light, and acquiring a spectrum of the measurement light by fourier transform.

Technical Field

The present disclosure relates to an optical module, a signal processing system, and a signal processing method.

Background

As a signal processing method for fourier transform type spectrum analysis, patent document 1 describes a method in which: at the time when the signal indicating the intensity of the interference light of monochromatic light generated by the interferometer intersects with the reference voltage, a plurality of pieces of measurement data are acquired from the signal indicating the intensity of the interference light of light to be measured generated by the interferometer, and a plurality of interferograms formed from the plurality of pieces of measurement data are integrated while being aligned at the position of the center pulse train.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-250127

Disclosure of Invention

Problems to be solved by the invention

In the signal processing method described in patent document 1, since it is necessary to perform alignment at the position of the center pulse train in order to integrate a plurality of interferograms, it is difficult to perform fourier transform-type spectrum analysis in a short time.

An object of the present disclosure is to provide an optical module, a signal processing system, and a signal processing method capable of performing fourier transform-type spectrum analysis in a short time.

Means for solving the problems

An optical module of an aspect of the present disclosure includes: a mirror device having: a base; a movable mirror including a mirror surface; an elastic support portion connected between the base and the movable mirror and supporting the movable mirror so that the movable mirror can move in a direction intersecting the mirror surface; a first comb-tooth electrode provided on the base and including a plurality of first comb teeth; and a second comb-tooth electrode provided on at least one of the movable mirror and the elastic support portion, and including a plurality of second comb-teeth arranged to intersect the plurality of first comb-teeth; at least one fixed mirror; at least one beam splitter which constitutes an interference optical system together with the movable mirror and the at least one fixed mirror; a first photodetector that detects interference light of the measurement light emitted from the interference optical system; a second photodetector that detects interference light of the laser light emitted from the interference optical system; and a signal processing unit electrically connected to the mirror device, the first photodetector, and the second photodetector, respectively, the signal processing unit including: a voltage signal control unit that controls a voltage signal so that a voltage signal having a frequency for causing the movable mirror to perform a resonant operation in the mirror device is applied between the first comb-teeth electrode and the second comb-teeth electrode; and an intensity acquisition unit that performs an intensity acquisition process of acquiring measurement light intensity of interference light of the measurement light M times (an integer of M: 2 or more) at first time intervals based on the frequency and acquiring addition values of the measurement light intensity of the same time corresponding to each other, in each of a plurality of periods of P periods (an integer of P: 2 or more) that are consecutive in the voltage signal, and acquiring laser light intensity of interference light of the laser light N times (an integer of N: 2 or more) at second time intervals based on the frequency and acquiring addition values of the laser light intensity of the same time corresponding to each other, in each of the plurality of periods.

In this optical module, the voltage signal is controlled so that the voltage signal having a frequency for causing the movable mirror to perform the resonant operation in the mirror device is applied between the first comb-tooth electrode and the second comb-tooth electrode. The frequency of the voltage signal is preferably 2 times the resonant frequency of the movable mirror. Therefore, by acquiring the measurement light intensity of the interference light of the measurement light M times at the first time interval based on the frequency of the voltage signal and acquiring the added value of the measurement light intensities corresponding to each other the same time in each of the plurality of periods of the P periods consecutive in the voltage signal, the added value of the measurement light intensities can be acquired easily and highly accurately for each of the same positions when the movable mirror moves. Similarly, by acquiring the laser intensity of the interference light of the laser light N times at the second time interval based on the frequency of the voltage signal in each of the plurality of periods and acquiring the added value of the laser intensities of the same time corresponding to each other, the added value of the laser intensities can be easily and accurately acquired for each same position when the movable mirror moves. Therefore, the optical module can perform fourier transform type spectrum analysis in a short time.

In the optical module according to one aspect of the present disclosure, the intensity acquisition unit may perform at least one of a first intensity acquisition process and a second intensity acquisition process as the intensity acquisition process, the first intensity acquisition process being a process of acquiring, at a first time interval, M times of first measured light intensities as measured light intensities and acquiring mutually corresponding added values of the first measured light intensities at the same time in each odd number of periods among consecutive P periods (P: an integer of 4 or more) in the voltage signal, and acquiring, at a second time interval, N times of the first laser intensities as laser intensities and acquiring mutually corresponding added values of the first laser intensities at the same time in each odd number of periods, and the second intensity acquisition process may be a process of acquiring, at each even number of periods among the P periods (P: an integer of 4 or more), the second measured light intensity is obtained M times as measured light intensities at first time intervals, and the added values of the second measured light intensities of the same time corresponding to each other are obtained, and in each cycle of the even number of cycles, the second laser intensity is obtained N times as laser intensity at second time intervals, and the added values of the second laser intensities of the same time corresponding to each other are obtained. In this way, by acquiring the M times of the first measured light intensity as the measured light intensity at the first time interval in each of the odd-numbered periods of the P periods that are consecutive in the voltage signal and acquiring the added value of the first measured light intensities corresponding to each other at the same time, the added value of the first measured light intensities can be acquired easily and accurately for each of the same positions when the movable mirror moves in one of the reciprocation directions. Similarly, in each of the odd-numbered periods, the first laser light intensity is acquired N times as the laser light intensity at the second time interval, and the added values of the first laser light intensities of the same time corresponding to each other are acquired, whereby the added value of the first laser light intensity is easily and accurately acquired for each same position when the movable mirror moves in one of the reciprocating directions. Further, by acquiring the second measured light intensity M times as the measured light intensity at the first time interval in each of the even-numbered periods of the P periods consecutive in the voltage signal and acquiring the added value of the second measured light intensities corresponding to each other at the same time, the added value of the second measured light intensities can be acquired easily and accurately for each same position when the movable mirror moves in the other direction in the reciprocation direction. Similarly, by acquiring the second laser light intensity N times as the laser light intensity at the second time interval in each of the even-numbered cycles and acquiring the added value of the second laser light intensities corresponding to each other at the same time, the added value of the second laser light intensities can be acquired easily and highly accurately for each of the same positions when the movable mirror moves in the other direction of the reciprocation direction. Therefore, the optical module can perform fourier transform type spectrum analysis with higher accuracy in a short time.

The optical module according to one aspect of the present disclosure may further include a storage unit having at least one of a first storage area and a second storage area, the first storage area may be an area in which the first measured light intensity and the first laser light intensity acquired in each of odd-numbered periods are integrated or averaged for each period when the first intensity acquisition process is performed, and the second storage area may be an area in which the second measured light intensity and the second laser light intensity acquired in each of even-numbered periods are integrated or averaged for each period when the second intensity acquisition process is performed. Thus, the first intensity acquisition process and the second intensity acquisition process can be reliably performed while the storage capacity of the storage unit is suppressed.

In the optical module according to one aspect of the present disclosure, the storage unit may further include a third storage area, and the third storage area may be an area in which, when the first intensity acquisition process is performed, each of the first measured light intensity and the first laser light intensity acquired in the latest 1 cycle of the P cycle (an integer equal to or greater than 4) is stored until the optical module is transferred to the first storage area, and when the second intensity acquisition process is performed, each of the second measured light intensity and the second laser light intensity acquired in the latest 1 cycle of the P cycle (an integer equal to or greater than 4) is stored until the optical module is transferred to the second storage area. In this way, it is possible to confirm whether or not each intensity data is correct while each intensity data is temporarily stored in the third storage area.

In the optical module according to one aspect of the present disclosure, the optical path difference zero position of the movable mirror may be shifted from the center position of the resonant operation of the movable mirror, the optical path difference zero position of the movable mirror being a position where the optical path length on the movable mirror side generating the interference light of the measurement light is equal to the optical path length on the at least one fixed mirror side generating the interference light of the measurement light, and the intensity acquiring unit may perform, as the first intensity acquiring process, a process of acquiring, in a first half or a second half of each period of the odd-numbered period, a mutually corresponding added value of the first measurement light intensity at the same time and acquiring, in a mutually corresponding added value of the first laser light intensity at the same time, and a process of acquiring, as the second intensity acquiring process, in a first half or a second half of each period of the even-numbered period, a mutually corresponding added value of the second measurement light intensity at the same time, and the added values of the second laser intensities of the same time corresponding to each other are acquired. This can reduce the resolution of each intensity data and increase the snr (signal to Noise ratio).

In the light module of the aspect of the present disclosure, the first time interval and the second time interval may be the same time interval. Thereby, the first intensity acquisition process and the second intensity acquisition process can be more easily performed.

In the optical module according to the aspect of the present disclosure, the voltage signal control unit may adjust the frequency of the voltage signal based on a change with time of a capacitance generated between the first comb-tooth electrode and the second comb-tooth electrode. Thus, for example, even if the resonant frequency of the movable mirror changes due to a change in the use environment, the frequency of the voltage signal can be adjusted so as to be 2 times the resonant frequency of the movable mirror, and as a result, the first intensity acquisition process and the second intensity acquisition process can be performed with higher accuracy.

A signal processing system of an aspect of the present disclosure includes an optical module and a signal processing apparatus electrically connected to the optical module, the optical module including: a mirror device having: a base; a movable mirror including a mirror surface; an elastic support portion connected between the base and the movable mirror and supporting the movable mirror so that the movable mirror can move in a direction intersecting the mirror surface; a first comb-tooth electrode provided on the base and including a plurality of first comb teeth; and a second comb-tooth electrode provided on at least one of the movable mirror and the elastic support portion, and including a plurality of second comb-teeth arranged to intersect the plurality of first comb-teeth; at least one fixed mirror; at least one beam splitter which constitutes an interference optical system together with the movable mirror and the at least one fixed mirror; a first photodetector that detects interference light of the measurement light emitted from the interference optical system; and a second photodetector that detects interference light of the laser light emitted from the interference optical system, the signal processing device including: a voltage signal control unit that controls a voltage signal so that a voltage signal having a frequency for causing the movable mirror to perform a resonant operation in the mirror device is applied between the first comb-teeth electrode and the second comb-teeth electrode; and an intensity acquisition unit that performs an intensity acquisition process of acquiring measurement light intensity of interference light of the measurement light M times (an integer of M: 2 or more) at first time intervals based on the frequency and acquiring addition values of the measurement light intensity of the same time corresponding to each other, in each of a plurality of periods of P periods (an integer of P: 2 or more) that are consecutive in the voltage signal, and acquiring laser light intensity of interference light of the laser light N times (an integer of N: 2 or more) at second time intervals based on the frequency and acquiring addition values of the laser light intensity of the same time corresponding to each other, in each of the plurality of periods.

In this signal processing system, the same signal processing as that of the optical module is performed. Thus, the signal processing system can perform Fourier transform type spectrum analysis in a short time.

A signal processing method according to an aspect of the present disclosure is a signal processing method performed in an interference optical system including a mirror device, at least one fixed mirror, and at least one beam splitter, the mirror device including: a base; a movable mirror including a mirror surface; an elastic support portion connected between the base and the movable mirror and supporting the movable mirror so that the movable mirror can move in a direction intersecting the mirror surface; a first comb-tooth electrode provided on the base and including a plurality of first comb teeth; and a second comb-tooth electrode provided at least one of the movable mirror and the elastic support portion and including a plurality of second comb teeth arranged to intersect the plurality of first comb teeth, the signal processing method including: a step of controlling a voltage signal so that a voltage signal having a frequency for causing the movable mirror to perform a resonant operation is applied between the first comb-teeth electrode and the second comb-teeth electrode; and a step of performing an intensity acquisition process of acquiring measurement light intensity of the interference light of the measurement light M times (an integer of M: 2 or more) at first time intervals based on the frequency and acquiring addition values of the measurement light intensities of the same time corresponding to each other, in each of a plurality of periods of P periods (an integer of P: 2 or more) that are consecutive in the voltage signal, and acquiring laser light intensity of the interference light of the laser light N times (an integer of N: 2 or more) at second time intervals based on the frequency and acquiring addition values of the laser light intensities of the same time corresponding to each other, in each of the plurality of periods.

In this signal processing method, the same signal processing as that of the optical module is performed. Therefore, the signal processing method can perform fourier transform type spectrum analysis in a short time.

In the signal processing method according to the aspect of the present disclosure, in the step of performing the intensity acquisition process, at least one of the first intensity acquisition process and the second intensity acquisition process may be performed as the intensity acquisition process, and the first intensity acquisition process may be a process of: in each odd-numbered period of the consecutive P periods (P: an integer of 4 or more) in the voltage signal, M times of the first measured light intensity are acquired as the measured light intensities at first time intervals, and the addition values of the first measured light intensities of the same time corresponding to each other are acquired, and in each odd-numbered period, N times of the first laser intensities are acquired as the laser intensities at second time intervals, and the addition values of the first laser intensities of the same time corresponding to each other are acquired, and the second intensity acquisition process may be a process of: in each of even-numbered periods in the P periods (P: an integer of 4 or more), M times of second measured light intensities are acquired as measured light intensities at first time intervals, and added values of the second measured light intensities of the same time corresponding to each other are acquired, and in each of the even-numbered periods, N times of second laser intensities are acquired as laser intensities at second time intervals, and added values of the second laser intensities of the same time corresponding to each other are acquired. Thus, the added value of the first measured light intensity can be obtained easily and accurately for each identical position when the movable mirror moves in one of the reciprocation directions. Similarly, the added value of the first laser light intensity can be easily and accurately obtained for each identical position when the movable mirror moves in one of the reciprocation directions. In addition, the added value of the second measured light intensity can be easily and accurately acquired for each identical position when the movable mirror moves in the other direction of the reciprocating direction. Similarly, the added value of the second laser light intensity can be easily and accurately acquired for each identical position when the movable mirror moves in the other direction of the reciprocation direction. Therefore, the signal processing method can perform fourier transform type spectrum analysis with higher accuracy in a short time.

In the signal processing method according to the aspect of the present disclosure, the optical path difference zero position of the movable mirror, which is a position where the optical path length on the movable mirror side where the interference light of the measurement light is generated is equal to the optical path length on the at least one fixed mirror side where the interference light of the measurement light is generated, may be shifted from the center position of the resonant operation of the movable mirror, and in the step of performing the intensity acquisition processing, the following processing may be performed as the first intensity acquisition processing: in the first half or the second half of each of the odd-numbered periods, the added values of the first measured light intensities corresponding to each other at the same time are obtained, and the added values of the first laser light intensities corresponding to each other at the same time are obtained, and the following processing is performed as second intensity obtaining processing: in the first half or the second half of each of the even-numbered periods, the mutually corresponding added values of the intensity of the second measurement light at the same time are obtained, and the mutually corresponding added values of the intensity of the second laser light at the same time are obtained. This can reduce the resolution of each intensity data and improve the SNR.

In the signal processing method of an aspect of the present disclosure, the first time interval and the second time interval may also be the same time interval. Thereby, the first intensity acquisition process and the second intensity acquisition process can be more easily performed.

In the signal processing method according to the aspect of the present disclosure, in the step of controlling the voltage signal, the frequency of the voltage signal may be adjusted based on a temporal change in capacitance generated between the first comb-tooth electrode and the second comb-tooth electrode. Thus, for example, even if the resonant frequency of the movable mirror changes due to a change in the use environment, the frequency of the voltage signal can be adjusted so as to be 2 times the resonant frequency of the movable mirror, and as a result, the first intensity acquisition process and the second intensity acquisition process can be performed with higher accuracy.

The signal processing method according to one aspect of the present disclosure may further include a step of performing spectrum acquisition processing of acquiring an intensity value at a time when at least one of a maximum value and a minimum value appears in a temporal change of the added value of the measurement light intensity from a temporal change of the added value of the measurement light intensity, acquiring a relationship between an optical path difference and the intensity value based on a wavelength of the laser light, and acquiring a spectrum of the measurement light by fourier transform. This makes it possible to easily and accurately acquire the spectrum of the measurement light. That is, fourier transform type spectrum analysis can be easily and accurately performed on the measurement light.

Effects of the invention

According to the present disclosure, it is possible to provide an optical module, a signal processing system, and a signal processing method capable of performing fourier transform type spectrum analysis in a short time.

Drawings

Fig. 1 is a cross-sectional view of an optical module according to an embodiment.

Fig. 2 is a plan view of the mirror unit shown in fig. 1.

Fig. 3 is a sectional view of the mirror unit taken along the line III-III shown in fig. 2.

Fig. 4 is a sectional view of the mirror unit taken along the line IV-IV shown in fig. 2.

Fig. 5 is a schematic cross-sectional view of the mirror device along the V-V line shown in fig. 2.

Fig. 6 is a partially enlarged view of the mirror device shown in fig. 2.

Fig. 7 is a plan view of the optical functional part shown in fig. 2.

Fig. 8 is a cross-sectional view of the optical module taken along line VIII-VIII shown in fig. 1.

Fig. 9 is a cross-sectional view of the optical module along line IX-IX shown in fig. 1.

Fig. 10 is a schematic sectional view of the mirror unit and the beam splitter unit shown in fig. 1.

Fig. 11 is a block diagram showing a configuration of the optical module shown in fig. 1.

Fig. 12 is a graph showing a temporal change in the position of the movable mirror performing the resonance operation and a temporal change in the intensity of the interference light of the measurement light.

Fig. 13 is a graph showing a temporal change in the position of the movable mirror performing the resonance operation and a temporal change in the intensity of the interference light of the laser light.

Fig. 14 is a graph showing a change with time in the position of the movable mirror performing the resonance operation and a voltage signal.

Fig. 15 is a graph showing a relationship between the frequency of the voltage signal and the amplitude of the movable mirror.

Fig. 16 is a graph showing a relationship between a rectangular wave input to a High voltage (High) terminal and a Low voltage (Low) terminal of the HVIC, respectively, and a voltage signal output from an output terminal of the HVIC.

Fig. 17 is a graph showing a change with time in the position of the movable mirror performing the resonance operation and a voltage signal.

Fig. 18 (a) is a graph showing a change with time in the intensity of the interference light of the measurement light, and (b) is a graph showing a change with time in the intensity of the interference light of the laser light.

Fig. 19 (a) is a graph showing the voltage logic and the change with time of the intensity of the interference light of the measurement light, and (b) is a graph showing the voltage logic and the change with time of the intensity of the interference light of the laser light.

Fig. 20 (a) is a graph showing the LSB logic and the time-dependent change in the intensity of the interference light of the measurement light, and (b) is a graph showing the LSB logic and the time-dependent change in the intensity of the interference light of the laser light.

Fig. 21 is a graph showing a temporal change in the intensity of the interference light of the measurement light and a temporal change in the intensity of the interference light of the laser light.

Fig. 22 is a block diagram showing a configuration of the storage unit shown in fig. 11.

Fig. 23 is a graph showing the change with time of the average value of the first measured light intensity and the change with time of the average value of the first laser light intensity with respect to the even-numbered periods.

Fig. 24 is a graph showing the change with time of the average value of the second measured light intensity and the change with time of the average value of the second laser light intensity with respect to the odd-numbered periods.

Fig. 25 is a graph showing a part of the change with time shown in fig. 23.

Fig. 26 is a graph showing a relationship between the optical path difference and the first intensity value.

Fig. 27 is a graph showing the spectrum of the measurement light.

Fig. 28 is a graph showing a voltage signal of a modification example.

Fig. 29 is a block diagram showing a configuration of a storage unit according to a modification.

Fig. 30 is a block diagram showing a configuration of an optical module according to a modification.

Fig. 31 is a graph showing a capacitance signal and a voltage signal.

Fig. 32 is a graph showing a change with time in the intensity of the interference light of the measurement light and a voltage signal.

Fig. 33 is a block diagram showing a configuration of a system including the optical module shown in fig. 1.

Fig. 34 is a cross-sectional view of an optical module according to a modification.

Fig. 35 is a configuration diagram of an interference optical system according to a modification.

Fig. 36 is a block diagram of a signal processing system according to an embodiment.

Detailed Description

Embodiments of the present disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding portions are denoted by the same reference numerals, and overlapping portions are omitted.

[ Structure of optical Module ]

As shown in fig. 1, the optical module 1A includes a mirror unit 2, a beam splitter unit 3, a light incident portion 4, a first photodetector 6, a second light source 7, a second photodetector 8, a support 9, a first support structure 11, and a second support structure 12. The mirror unit 2 is disposed on one side of the support 9 in the Z-axis direction (first direction), and is attached to the support 9 by, for example, an adhesive. The support 9 is made of, for example, copper tungsten, and has, for example, a rectangular plate shape. The mirror unit 2 includes a movable mirror 22 that moves in the Z-axis direction and a fixed mirror 16 that is fixed in position (details will be described later). The Z-axis direction is, for example, a vertical direction, and one side in the Z-axis direction is, for example, an upper side.

The beam splitter unit 3 is disposed on one side of the mirror unit 2 in the Z-axis direction and is supported by a first support structure 11. The first support structure 11 is attached to the support body 9 by, for example, an adhesive. The light incident portion 4 is disposed on one side of the beam splitter unit 3 in the X-axis direction (second direction intersecting the first direction), and is supported by the second support structure 12. The first photodetector 6, the second light source 7, and the second photodetector 8 are disposed on one side of the beam splitter unit 3 in the Z-axis direction, and are supported by a second support structure 12. The second support structure 12 is attached to the support body 9 by, for example, bolts.

In the optical module 1A, the beam splitter unit 3, the movable mirror 22, and the fixed mirror 16 constitute an interference optical system for each of the measurement light L0 and the laser light L10. The interference optical system configured for each of the measurement light L0 and the laser light L10 is, for example, a michelson interference optical system.

As for the measurement light L0, the interference light L1 of the measurement light is detected as described below. That is, when the measurement light L0 incident from the first light source (not shown) through the measurement object (not shown) or the measurement light L0 emitted from the measurement object (for example, light emission of the measurement object itself) enters the beam splitter unit 3 from the light entrance unit 4, the measurement light L0 is divided into a part and a remaining part in the beam splitter unit 3. Then, a part of the measurement light L0 is reflected by the movable mirror 22 that reciprocates in the Z-axis direction and returned to the beam splitter unit 3. On the other hand, the remaining part of the measurement light L0 is reflected by the fixed mirror 16 and returned to the beam splitter unit 3. Part and the rest of the measurement light L0 returned to the beam splitter unit 3 are emitted from the beam splitter unit 3 as interference light L1, and the interference light L1 of the measurement light is detected by the first photodetector 6.

As for the laser light L10, the interference light L11 of the laser light is detected as described below. That is, when the laser light L10 emitted from the second light source 7 enters the beam splitter unit 3, the laser light L10 is split into a part and the remaining part in the beam splitter unit 3. Then, a part of the laser light L10 is reflected by the movable mirror 22 that reciprocates in the Z-axis direction and returned to the beam splitter unit 3. On the other hand, the remaining part of the laser light L10 is reflected by the fixed mirror 16 and returned to the beam splitter unit 3. Part and the rest of the laser light L10 returned to the beam splitter unit 3 are emitted from the beam splitter unit 3 as interference light L11, and the interference light L11 of the laser light is detected by the second photodetector 8.

According to the optical module 1A, the position of the movable mirror 22 in the Z-axis direction can be measured based on the detection result of the interference light L11 of the laser beam, and the measurement target can be subjected to spectrum analysis based on the measurement result of the position and the detection result of the interference light L1 of the measurement light.

[ Structure of mirror Unit ]

As shown in fig. 2, 3, and 4, the mirror unit 2 includes a mirror device 20, an optical functional component 13, a fixed mirror 16, and a stress relaxation substrate 17. The mirror device 20 includes a base 21, a movable mirror 22, and a driving unit 23.

The base 21 has a first surface 21a (surface on one side in the Z-axis direction) and a second surface 21b on the opposite side of the first surface 21 a. The first surface 21a and the second surface 21b are main surfaces of the base 21. The base 21 has a rectangular plate shape, for example, and has a size of about 10mm × 15mm × 0.35mm (thickness). The movable mirror 22 includes a mirror surface 22a and a movable portion 22b on which the mirror surface 22a is disposed. The movable mirror 22 is supported on the base 21 so as to be movable in a Z-axis direction (a first direction intersecting the first surface) perpendicular to the first surface 21 a. The driving unit 23 moves the movable mirror 22 in the Z-axis direction.

The mirror device 20 is provided with a pair of light passing portions 24 and 25. The pair of light passing portions 24 and 25 are disposed on both sides of the movable mirror 22 in the X-axis direction. The light passing portion 24 constitutes a first part of the optical path between the beam splitter unit 3 and the fixed mirror 16. In the present embodiment, the light transmitting portion 25 does not function as a light transmitting portion.

Here, the structure of the mirror device 20 will be described in detail with reference to fig. 2, 5, and 6. Fig. 5 is a schematic cross-sectional view of the mirror device 20 shown in fig. 3, and fig. 5 schematically shows the mirror device 20 in a state where, for example, the dimension in the Z-axis direction is larger than the actual dimension.

The base 21, the movable portion 22b of the movable mirror 22, and the driving portion 23 are formed of an soi (silicon On insulator) substrate (semiconductor substrate) 100. That is, the mirror device 20 is a mems (micro Electro Mechanical systems) device formed of the SOI substrate 100. The mirror device 20 is formed in a rectangular plate shape, for example. The SOI substrate 100 includes a support layer 101, a device layer 102, and an intermediate layer 103. The support layer 101 is a first silicon layer (first semiconductor layer). The device layer 102 is a second silicon layer (second semiconductor layer). The intermediate layer 103 is an insulating layer disposed between the support layer 101 and the device layer 102. The SOI substrate 100 includes a support layer 101, an intermediate layer 103, and a device layer 102 in this order from one side in the Z-axis direction.

The base 21 is composed of the support layer 101, the device layer 102, and a part of the intermediate layer 103. The first surface 21a of the base 21 is the surface of the support layer 101 opposite to the intermediate layer 103. The second surface 21b of the base 21 is the surface of the device layer 102 opposite to the intermediate layer 103. The support layer 101 constituting the base 21 is thicker than the device layer 102 constituting the base 21. The thickness of the support layer 101 constituting the base 21 is, for example, about 4 times the thickness of the device layer 102 constituting the base 21. In the mirror unit 2, as described later, the second surface 21b of the base 21 and the third surface 13a of the optical functional component 13 are joined to each other (see fig. 3 and 4).

The movable mirror 22 is disposed with an intersection of the axis R1 and the axis R2 as a center position (center of gravity position). The axis R1 is a straight line extending in the X-axis direction. The axis R2 is a straight line extending in the Y-axis direction. When viewed from the Z-axis direction, the mirror device 20 has a shape that is line-symmetric about both the axis R1 and the axis R2 except for a portion overlapping with a sixth surface 21d of the base 21, which will be described later.

The movable mirror 22 (movable portion 22b) includes an arrangement portion 221, a frame portion 222, a pair of connection portions 223, and a beam portion 224. The arrangement portion 221, the frame portion 222, and the pair of connection portions 223 are formed by a part of the device layer 102. The arrangement portion 221 has a circular shape when viewed from the Z-axis direction. The arrangement portion 221 has a central portion 221a and an outer edge portion 221 b. On a surface 221as of the center portion 221a on one side in the Z axis direction, a mirror surface 22a is provided by forming a metal film (metal layer), for example. The mirror surface 22a extends in a circular shape perpendicular to the Z-axis direction. The surface 221as of the central portion 221a is the surface of the device layer 102 on the intermediate layer 103 side. The mirror surface 22a is located on the other side in the Z-axis direction than the first surface 21a of the base 21. In other words, the first surface 21a is located on the Z-axis direction side of the mirror surface 22 a. The outer edge portion 221b surrounds the central portion 221a when viewed from the Z-axis direction.

When viewed from the Z-axis direction, the frame portion 222 extends in a ring shape so as to surround the arrangement portion 221 at a predetermined interval from the arrangement portion 221. The frame portion 222 has, for example, an annular shape when viewed from the Z-axis direction. The pair of coupling portions 223 couple the arrangement portion 221 and the frame portion 222 to each other. The pair of coupling portions 223 are disposed on both sides of the disposing portion 221 in the Y-axis direction.

The beam portion 224 is composed of the support layer 101 and the intermediate layer 103 disposed on the device layer 102. The beam portion 224 includes an inner beam portion 224a, an outer beam portion 224b, and a pair of connection beam portions 224 c. The inner beam portion 224a is disposed on one surface of the outer edge portion 221b in the Z-axis direction. The inner beam portion 224a surrounds the mirror surface 22a when viewed from the Z-axis direction. For example, when viewed in the Z-axis direction, the outer edge of the inner beam portion 224a extends along the outer edge of the arrangement portion 221 at a predetermined interval from the outer edge of the arrangement portion 221. When viewed in the Z-axis direction, the inner edge of the inner beam portion 224a extends along the outer edge of the mirror surface 22a at a predetermined interval from the outer edge of the mirror surface 22 a. An end surface 224as of the inner beam portion 224a on one side in the Z-axis direction is positioned on the Z-axis direction side with respect to the mirror surface 22 a.

The outer beam portion 224b is disposed on one surface of the frame portion 222 in the Z-axis direction. When viewed in the Z-axis direction, the outer beam portion 224b surrounds the inner beam portion 224a and further surrounds the mirror surface 22 a. For example, when viewed in the Z-axis direction, the outer edge of the outer beam portion 224b extends along the outer edge of the frame portion 222 at a predetermined interval from the outer edge of the frame portion 222. When viewed in the Z-axis direction, the inner edge of the outer beam portion 224b extends along the inner edge of the frame portion 222 at a predetermined interval from the inner edge of the frame portion 222. The end surface 224bs of the outer beam portion 224b on the Z-axis direction side is positioned on the Z-axis direction side with respect to the mirror surface 22 a.

The pair of connection beam portions 224c are disposed on one surface of the pair of connection portions 223 in the Z-axis direction. Each of the connecting beam portions 224c connects the inner beam portion 224a and the outer beam portion 224b to each other. An end surface 224cs of the connecting beam portion 224c on the Z-axis direction side is located on the Z-axis direction side with respect to the mirror surface 22 a.

The thicknesses of the inner beam portion 224a, the outer beam portion 224b, and the connection beam portion 224c in the Z-axis direction are equal to each other. That is, the support layers 101 constituting the inner beam portion 224a, the outer beam portion 224b, and the connection beam portions 224c have the same thickness. The end surface 224as of the inner beam portion 224a, the end surface 224bs of the outer beam portion 224b, and the end surface 224cs of each connecting beam portion 224c are located on the same plane perpendicular to the Z-axis direction. The support layer 101 constituting the inner beam portion 224a, the outer beam portion 224b, and the connecting beam portions 224c is thinner than the support layer 101 constituting the base 21. Thus, the end surfaces 224as, 224bs, and 224cs are located on the Z-axis direction side of the first surface 21a of the base 21. In other words, the first surface 21a is located on the other side in the Z-axis direction than the end surfaces 224as, 224bs, 224 cs.

The width of the outer beam portion 224b is wider than the width of the inner beam portion 224a when viewed from the Z-axis direction. The width of the inner beam portion 224a as viewed in the Z-axis direction is the length of the inner beam portion 224a in the direction perpendicular to the extending direction of the inner beam portion 224a, and in the present embodiment, is the length of the inner beam portion 224a in the radial direction of the inner beam portion 224 a. This is also the same with respect to the width of the outer beam portion 224b when viewed from the Z-axis direction. The width of each of the connecting beam portions 224c is wider than the width of each of the inner beam portions 224a and the outer beam portions 224 b. The width of each of the connection beam portions 224c is the length of each of the connection beam portions 224c along the extending direction of the inner side beam portion 224 a.

The driving portion 23 has a first elastic support portion (elastic support portion) 26, a second elastic support portion (elastic support portion) 27, and an urging portion 28. The first elastic support portion 26, the second elastic support portion 27, and the actuator portion 28 are formed by a part of the device layer 102.

The first elastic support portion 26 and the second elastic support portion 27 are connected between the base 21 and the movable mirror 22, respectively. The first elastic support portion 26 and the second elastic support portion 27 support the movable mirror 22 so that the movable mirror 22 (movable portion 22b) is movable in the Z-axis direction (direction intersecting the mirror surface 22 a).

The first elastic support portion 26 includes a pair of rods 261, a first link member 262, a second link member 263, a pair of beam members 264, an intermediate member 265, a pair of first torsion bars (first torsion support portions) 266, a pair of second torsion bars (second torsion support portions) 267, a pair of nonlinear damper springs 268, and a plurality of electrode support portions 269.

The pair of rods 261 are disposed on both sides of the light passing portion 24 in the Y-axis direction, and face each other in the Y-axis direction. Each rod 261 has a plate shape extending along a plane perpendicular to the Z-axis direction. Each of the rods 261 has a first portion 261a, a second portion 261b disposed on the opposite side of the movable mirror 22 from the first portion 261a, and a third portion 261c connected to the first portion 261a and the second portion 261 b. The first portion 261a and the second portion 261b extend in the X-axis direction. The length of the first portion 261a in the X-axis direction is shorter than the length of the second portion 261b in the X-axis direction. The third portions 261c of the pair of rods 261 extend obliquely so as to be spaced apart from each other as they are spaced apart from the movable mirror 22.

The first link member 262 is bridged between the first end portions 261d of the pair of rods 261 on the opposite side to the movable mirror 22. The first link member 262 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The second link member 263 is bridged between the second ends 261e of the pair of levers 261 on the movable mirror 22 side. The second link member 263 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The width of the second link member 263 in the X-axis direction is narrower than the width of the first link member 262 in the X-axis direction. The length of the second link member 263 in the Y-axis direction is shorter than the length of the first link member 262 in the Y-axis direction.

A pair of beam members 264 are respectively bridged between the second portions 261b of the pair of rods 261 and the first link members 262. Each beam member 264 is plate-shaped and extends along a plane perpendicular to the Z-axis direction. The pair of beam members 264 extend obliquely so as to approach each other as they are farther from the movable mirror 22. The pair of rods 261, the first link member 262, the second link member 263, and the pair of beam members 264 define the light passing portion 24. The light passing portion 24 has a polygonal shape when viewed from the Z-axis direction. The light passing portion 24 is, for example, a hollow (hole). Alternatively, a material having translucency to the measurement light L0 and the laser light L10 may be disposed in the light passing portion 24.

The intermediate member 265 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The intermediate member 265 is disposed between the movable mirror 22 and the second link member 263 (in other words, between the movable mirror 22 and the light passing portion 24). As described later, the intermediate member 265 is connected to the movable mirror 22 via a nonlinear buffer spring 268.

A pair of first torsion bars 266 are respectively bridged between the first end 261d of one rod 261 and the base 21 and between the first end 261d of the other rod 261 and the base 21. That is, the pair of first torsion bars 266 are connected between the pair of rods 261 and the base 21, respectively. Each first torsion bar 266 extends in the Y-axis direction. The pair of first torsion bars 266 is disposed on the same center line parallel to the Y-axis direction. In the present embodiment, the center line of each first torsion bar 266 and the center line of the first link member 262 are located on the same line. A projection 261f projecting outward in the Y axis direction is provided at a first end 261d of each lever 261, and each first torsion bar 266 is connected to the projection 261 f.

A pair of second torsion bars 267 are respectively bridged between the second end portion 261e of one rod 261 and one end of the intermediate member 265 and between the second end portion 261e of the other rod 261 and the other end of the intermediate member 265. That is, the pair of second torsion bars 267 are connected between the pair of rods 261 and the movable mirror 22, respectively. Each second torsion bar 267 extends in the Y-axis direction. The pair of second torsion bars 267 are disposed on the same center line parallel to the Y-axis direction.

A pair of nonlinear buffer springs 268 are connected between the movable mirror 22 and the intermediate member 265. That is, a pair of nonlinear damper springs 268 are connected between the movable mirror 22 and the second torsion bar 267. Each of the nonlinear damper springs 268 has a meandering portion 268a extending in a meandering manner when viewed from the Z-axis direction. The meandering portion 268a includes a plurality of linear portions 268b arranged in the Y-axis direction and in the X-axis direction, and a plurality of folded portions 268c alternately connecting both ends of the plurality of linear portions 268 b. One end of the meandering portion 268a is connected to the intermediate member 265, and the other end of the meandering portion 268a is connected to the frame portion 222. The portion of the meandering portion 268a on the frame 222 side has a shape extending along the outer edge of the frame 222.

The nonlinear damper spring 268 is configured such that, in a state where the movable mirror 22 moves in the Z-axis direction, the amount of deformation of the nonlinear damper spring 268 in the Y-axis direction is smaller than the amounts of deformation of the first torsion bar 266 and the second torsion bar 267 in the Y-axis direction, and the amount of deformation of the nonlinear damper spring 268 in the X-axis direction is larger than the amounts of deformation of the first torsion bar 266 and the second torsion bar 267 in the X-axis direction. This can suppress the occurrence of nonlinearity in the torsional deformation of the first torsion bar 266 and the second torsion bar 267, and can suppress a decrease in the control characteristics of the movable mirror 22 due to the nonlinearity. The deformation amounts of the first torsion bar 266, the second torsion bar 267, and the nonlinear damper spring 268 in the Y-axis direction mean, for example, absolute values of torsion amounts (torsion angles). The amount of deformation of the first torsion bar 266, the second torsion bar 267, and the nonlinear damper spring 268 in the X-axis direction means, for example, an absolute value of the amount of deflection. The amount of deformation of a certain member about the Y-axis direction means the amount of deformation of the member in the circumferential direction of a circle centered on an axis passing through the center of the member and parallel to the Y-axis. These aspects are also similar to the first torsion bar 276, the second torsion bar 277, and the nonlinear damper spring 278, which will be described later.

The plurality of electrode supports 269 includes a pair of first electrode supports 269a, a pair of second electrode supports 269b, and a pair of third electrode supports 269 c. The electrode supports 269a, 269b, 269c each have a plate shape extending along a plane perpendicular to the Z-axis direction, and extend along the Y-axis direction. The electrode supports 269a, 269b, 269c extend from the second portion 261b of the rod 261 to the side opposite to the light passing portion 24. The pair of first electrode supporting portions 269a are arranged on the same center line parallel to the Y-axis direction. The pair of second electrode supporting portions 269b are disposed on the same center line parallel to the Y-axis direction. The pair of third electrode supports 269c are disposed on the same center line parallel to the Y-axis direction. The first electrode support 269a, the second electrode support 269b, and the third electrode support 269c are arranged in this order from the movable mirror 22 side in the X-axis direction.

The second elastic support portion 27 includes a pair of rods 271, a first link member 272, a second link member 273, a pair of beam members 274, an intermediate member 275, a pair of first torsion bars (first torsion support portions) 276, a pair of second torsion bars (second torsion support portions) 277, a pair of nonlinear damper springs 278, and a plurality of electrode support portions 279.

The pair of levers 271 are disposed on both sides of the light passing portion 25 in the Y-axis direction and face each other in the Y-axis direction. Each of the rods 271 has a plate shape extending along a plane perpendicular to the Z-axis direction. Each of the levers 271 has a first portion 271a, a second portion 271b disposed on the opposite side of the movable mirror 22 from the first portion 271a, and a third portion 271c connected to the first portion 271a and the second portion 271 b. The first portion 271a and the second portion 271b extend in the X-axis direction. The length of the first portion 271a in the X-axis direction is shorter than the length of the second portion 271b in the X-axis direction. The third portions 271c of the pair of levers 271 extend obliquely so as to be spaced apart from each other as they become farther from the movable mirror 22.

The first link member 272 is bridged between the first end portions 271d of the pair of levers 271 on the opposite side to the movable mirror 22. The first link member 272 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The second link member 273 is bridged between the second ends 271e of the pair of levers 271 on the movable mirror 22 side. The second link member 273 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The width of the second link member 273 in the X-axis direction is narrower than the width of the first link member 272 in the X-axis direction. The length of the second link member 273 in the Y-axis direction is shorter than the length of the first link member 272 in the Y-axis direction.

The pair of beam members 274 are respectively bridged between the second portions 271b of the pair of rods 271 and the first link members 272. Each beam member 274 has a plate shape extending along a plane perpendicular to the Z-axis direction. The pair of beam members 274 extend obliquely so as to approach each other as they are farther from the movable mirror 22. The pair of levers 271, the first link member 272, the second link member 273, and the pair of beam members 274 define the light passing portion 25. The light passing portion 25 has a polygonal shape when viewed from the Z-axis direction. The light passing portion 25 is, for example, a cavity (hole). Alternatively, a material having translucency to the measurement light L0 and the laser light L10 may be disposed in the light passing portion 25.

The intermediate member 275 has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. The intermediate member 275 is disposed between the movable mirror 22 and the second link member 273 (in other words, between the movable mirror 22 and the light passing portion 25). As described later, the intermediate member 275 is connected to the movable mirror 22 via a nonlinear damper spring 278.

A pair of first torsion bars 276 are respectively bridged between the first end 271d of one bar 271 and the base 21 and between the first end 271d of the other bar 271 and the base 21. That is, the pair of first torsion bars 276 are connected between the pair of levers 271 and the base 21, respectively. Each first torsion bar 276 extends in the Y-axis direction. The pair of first torsion bars 276 are arranged on the same center line parallel to the Y-axis direction. In the present embodiment, the center line of each first torsion bar 276 and the center line of the first link member 272 are located on the same line. A projection 271f projecting outward in the Y axis direction is provided at the first end 271d of each lever 271, and each first torsion bar 276 is connected to the projection 271 f.

The pair of second torsion bars 277 are respectively bridged between the second end 271e of the one lever 271 and one end of the intermediate member 275 and between the second end 271e of the other lever 271 and the other end of the intermediate member 275. That is, the pair of second torsion bars 277 are connected between the pair of levers 271 and the movable mirror 22, respectively. Each second torsion bar 277 extends in the Y-axis direction. The pair of second torsion bars 277 is disposed on the same center line parallel to the Y-axis direction.

A pair of nonlinear buffer springs 278 are connected between the movable mirror 22 and the intermediate member 275. That is, a pair of nonlinear damper springs 278 are connected between the movable mirror 22 and the second torsion bar 277. Each of the nonlinear damper springs 278 has a meandering portion 278a extending in a meandering manner when viewed from the Z-axis direction. The meandering portion 278a includes a plurality of linear portions 278b arranged in the Y-axis direction and in the X-axis direction, and a plurality of folded-back portions 278c alternately connecting both ends of the plurality of linear portions 278 b. One end of the meandering portion 278a is connected to the intermediate member 275, and the other end of the meandering portion 278a is connected to the frame portion 222. The frame 222 side portion of the meandering portion 278a has a shape extending along the outer edge of the frame 222.

The nonlinear damper spring 278 is configured such that, in a state where the movable mirror 22 moves in the Z-axis direction, the amount of deformation of the nonlinear damper spring 278 in the Y-axis direction is smaller than the amounts of deformation of the first torsion bar 276 and the second torsion bar 277 in the Y-axis direction, and the amount of deformation of the nonlinear damper spring 278 in the X-axis direction is larger than the amounts of deformation of the first torsion bar 276 and the second torsion bar 277 in the X-axis direction. This can suppress the occurrence of nonlinearity in the torsional deformation of the first torsion bar 276 and the second torsion bar 277, and can suppress a decrease in the control characteristics of the movable mirror 22 due to the nonlinearity.

The plurality of electrode supporting portions 279 includes a pair of first electrode supporting portions 279a, a pair of second electrode supporting portions 279b, and a pair of third electrode supporting portions 279 c. Each of the electrode supporting portions 279a, 279b, 279c has a plate shape extending along a plane perpendicular to the Z-axis direction, and extends along the Y-axis direction. Each of the electrode supporting portions 279a, 279b, 279c extends from the second portion 271b of the stem 271 toward the opposite side of the light passing portion 25. The pair of first electrode supporting portions 279a are arranged on the same center line parallel to the Y-axis direction. The pair of second electrode supporting portions 279b are arranged on the same center line parallel to the Y-axis direction. The pair of third electrode supporting portions 279c are arranged on the same center line parallel to the Y-axis direction. The first electrode support portion 279a, the second electrode support portion 279b, and the third electrode support portion 279c are arranged in this order from the movable mirror 22 side in the X-axis direction.

The actuator 28 moves the movable mirror 22 in the Z-axis direction. The actuator 28 includes a fixed comb-tooth electrode (first comb-tooth electrode) 281, a movable comb-tooth electrode (second comb-tooth electrode) 282, a fixed comb-tooth electrode (first comb-tooth electrode) 283, and a movable comb-tooth electrode (second comb-tooth electrode) 284. The positions of the fixed comb-teeth electrodes 281, 283 are fixed. The movable comb electrodes 282 and 284 move in accordance with the movement of the movable mirror 22.

The fixed comb-teeth electrode 281 is provided in a part of the surface of the device layer 102 of the base 21 facing the electrode support 269. The fixed comb-tooth electrode 281 has a plurality of fixed comb-teeth (first comb-teeth) 281a extending along a plane perpendicular to the Y-axis direction. These fixed comb teeth 281a are arranged at a predetermined interval in the Y axis direction.

The movable comb-teeth electrodes 282 are provided on the surface of each first electrode support 269a on the movable mirror 22 side, on the surfaces of each second electrode support 269b on both sides in the X-axis direction, and on the surface of each third electrode support 269c on the movable mirror 22 side. The movable comb-tooth electrode 282 has a plurality of movable comb-teeth (second comb-teeth) 282a extending along a plane perpendicular to the Y-axis direction. These movable comb teeth 282a are arranged at predetermined intervals in the Y axis direction.

In the fixed comb-teeth electrode 281 and the movable comb-teeth electrode 282, a plurality of fixed comb-teeth 281a and a plurality of movable comb-teeth 282a are alternately arranged. That is, the fixed comb teeth 281a of the fixed comb-tooth electrode 281 are positioned between the movable comb teeth 282a of the movable comb-tooth electrode 282. The adjacent fixed comb teeth 281a and movable comb teeth 282a are opposed to each other in the Y-axis direction. The distance between the adjacent fixed comb teeth 281a and movable comb teeth 282a is, for example, about several μm.

The fixed comb-tooth electrode 283 is provided on a part of the surface of the device layer 102 of the base 21 facing the electrode support portion 279. The fixed comb-tooth electrode 283 has a plurality of fixed comb-teeth (first comb-teeth) 283a extending along a plane perpendicular to the Y-axis direction. The fixed comb teeth 283a are arranged at predetermined intervals in the Y-axis direction.

The movable comb-teeth electrodes 284 are provided on the surface of each first electrode support portion 279a on the movable mirror 22 side, the surfaces of each second electrode support portion 279b on both sides in the X-axis direction, and the surface of each third electrode support portion 279c on the movable mirror 22 side. Movable comb-tooth electrode 284 has a plurality of movable comb-teeth (second comb-teeth) 284a extending along a plane perpendicular to the Y-axis direction. These movable comb teeth 284a are arranged at predetermined intervals in the Y-axis direction.

In fixed comb-tooth electrode 283 and movable comb-tooth electrode 284, a plurality of fixed comb-teeth 283a and a plurality of movable comb-teeth 284a are alternately arranged. That is, each fixed comb-tooth 283a of fixed comb-tooth electrode 283 is positioned between movable comb-teeth 284a of movable comb-tooth electrode 284. Adjacent fixed comb-teeth 283a and movable comb-teeth 284a are opposed to each other in the Y-axis direction. The distance between adjacent fixed comb teeth 283a and movable comb teeth 284a is, for example, about several μm.

A plurality of electrode pads 211 are provided on the base 21. Each electrode pad 211 is disposed on the surface of the device layer 102 in an opening 213 formed in the first surface 21a of the base 21 so as to reach the device layer 102. Several of the plurality of electrode pads 211 are electrically connected to the fixed comb-teeth electrode 281 or the fixed comb-teeth electrode 283 via the device layer 102. The other ones of the plurality of electrode pads 211 are electrically connected to the movable comb-tooth electrode 282 or 284 via the first elastic support portion 26 or the second elastic support portion 27. Further, the base 21 is provided with a pair of electrode pads 212 serving as ground electrodes. The pair of electrode pads 212 are disposed on the first surface 21a so as to be positioned on both sides of the movable mirror 22 in the Y-axis direction.

In the mirror device 20 configured as described above, an electric signal for moving the movable mirror 22 in the Z-axis direction is input to the driving unit 23 via the lead post 113 and an electric wire (not shown) described later. Accordingly, for example, electrostatic forces are generated between the fixed comb-tooth electrode 281 and the movable comb-tooth electrode 282, which face each other, and between the fixed comb-tooth electrode 283 and the movable comb-tooth electrode 284, which face each other, so that the movable mirror 22 moves to one side in the Z-axis direction. At this time, the first torsion bars 266 and 276 and the second torsion bars 267 and 277 are twisted in the first elastic support portion 26 and the second elastic support portion 27, and an elastic force is generated in the first elastic support portion 26 and the second elastic support portion 27. In the mirror device 20, the movable mirror 22 can be reciprocated in the Z-axis direction at the resonance frequency level thereof by applying a periodic electric signal to the driving section 23. In this way, the driving unit 23 functions as an electrostatic actuator.

As shown in fig. 2, 3, 4, and 7, the optical functional component 13 includes a third surface 13a (surface on one side in the Z-axis direction) facing the second surface 21b of the base 21 and a fourth surface 13b on the opposite side of the third surface 13 a. The outer edge 13c of the optical functional member 13 is located outside the outer edge 21c of the base 21 when viewed from the Z-axis direction. That is, when viewed from the Z-axis direction, the outer edge 13c of the optical functional member 13 surrounds the outer edge 21c of the base 21. The optical functional member 13 is integrally formed of a material having optical transparency to the measurement light L0 and the laser light L10. The optical functional component 13 is formed of glass into a rectangular plate shape, for example, and has a size of about 15mm × 20mm × 4mm (thickness). The material of the optical functional component 13 is selected according to the sensitivity wavelength of the optical module 1A, and for example, glass is selected when the sensitivity wavelength of the optical module 1A is in the near-infrared region, and silicon is selected when the sensitivity wavelength of the optical module 1A is in the mid-infrared region.

The optically functional member 13 is provided with a pair of light transmitting portions 14 and 15. The light transmitting portion 14 is a portion of the optical functional component 13 that faces the light passing portion 24 of the mirror device 20 in the Z-axis direction. The light transmitting portion 15 is a portion of the optical functional component 13 that faces the light passing portion 25 of the mirror device 20 in the Z-axis direction. The surface 14a on the mirror device 20 side of the light-transmitting portion 14 and the surface 15a on the mirror device 20 side of the light-transmitting portion 15 are located on the same plane as the third surface 13 a. The light-transmitting portion 14 constitutes a second part of the optical path between the beam splitter unit 3 and the fixed mirror 16. The light transmitting portion 14 is a portion that corrects an optical path difference generated between an optical path between the beam splitter unit 3 and the movable mirror 22 and an optical path between the beam splitter unit 3 and the fixed mirror 16. In the present embodiment, the light transmitting portion 15 does not function as a light transmitting portion.

The optical functional component 13 has a fifth surface 13d facing the movable mirror 22 and the driving portion 23 of the mirror device 20. The fifth surface 13d is located closer to the fourth surface 13b side than the third surface 13 a. The fifth surface 13d extends to the outer edge 13c of the optical functional member 13 when viewed from the Z-axis direction. In the present embodiment, the fifth surface 13d surrounds the end portions of the light transmitting portions 14 and 15 on the mirror device 20 side, and extends to each of a pair of opposite sides extending in the Y-axis direction (a direction intersecting the first direction and the second direction) in the outer edge 13c of the optical functional member 13.

The third Surface 13a of the optical functional component 13 is joined to the second Surface 21b of the base 21 by direct joining (e.g., Plasma Activation joining, Surface-activated joining, Atomic Diffusion joining (ADB), Anodic joining, Fusion joining, hydrophilization joining (Hydrophilic joining), etc.). In the present embodiment, the third surface 13a extends on both sides of the fifth surface 13d in the Y axis direction so as to face the plurality of electrode pads 211, 212 provided on the base 21. Here, since the fifth surface 13d is located closer to the fourth surface 13b than the third surface 13a, the fifth surface 13d is distant from the mirror device 20 in a region facing the movable mirror 22 and the driving portion 23. The surface 14a of the light transmitting portion 14 and the surface 15a of the light transmitting portion 15 face the light passing portions 24 and 25 of the mirror device 20, respectively. Thus, in the mirror unit 2, when the movable mirror 22 reciprocates in the Z-axis direction, the movable mirror 22 and the driving portion 23 can be prevented from coming into contact with the optical functional member 13.

Further, a sixth surface 21d distant from the optical functional part 13 is provided on the base 21 of the mirror device 20 in a state where the third surface 13a of the optical functional part 13 and the second surface 21b of the base 21 are joined to each other. The sixth surface 21d is distant from the optical functional component 13 in a region including at least a part of the outer edge of the base 21 when viewed from the Z-axis direction. In the present embodiment, the sixth surface 21d is formed by removing the device layer 102 and the intermediate layer 103 by etching along a side of the outer edge of the base 21 extending in the Y-axis direction. In addition, a plurality of reference holes 13e are formed on the third surface 13a of the optical functional component 13. In the present embodiment, the plurality of reference holes 13e are formed in the third surface 13a so as to correspond to the plurality of corners of the base 21, respectively. When the third surface 13a of the optical functional component 13 and the second surface 21b of the base 21 are bonded to each other, the mirror device 20 is handled by holding a portion corresponding to the sixth surface 21d of the base 21, and the positions of the mirror device 20 in the X-axis direction and the Y-axis direction and the angle of the mirror device 20 in a plane perpendicular to the Z-axis direction are adjusted with reference to the plurality of reference holes 13e formed in the third surface 13 a.

As shown in fig. 3 and 4, the fixed mirror 16 is disposed on the opposite side of the mirror device 20 from the optical functional component 13, and the position of the mirror device 20 with respect to the base 21 is fixed. The fixed mirror 16 is formed on the fourth surface 13b of the optical functional component 13 by, for example, vapor deposition. The fixed mirror 16 has a mirror surface 16a perpendicular to the Z-axis direction. In the present embodiment, the mirror surface 22a of the movable mirror 22 and the mirror surface 16a of the fixed mirror 16 face one side (the beam splitter unit 3 side) in the Z axis direction. The fixed mirror 16 is continuously formed on the fourth surface 13b of the optical functional component 13 so as to reflect the light transmitted through the light transmitting portions 14 and 15 of the optical functional component 13, but a fixed mirror that reflects the light transmitted through the light transmitting portion 14 and a fixed mirror that reflects the light transmitted through the light transmitting portion 15 may be separately provided.

The stress relaxation substrate 17 is attached to the fourth surface 13b of the optical functional component 13 via the fixed mirror 16. The stress relaxation substrate 17 is attached to the fixed mirror 16 by, for example, an adhesive. When viewed from the Z-axis direction, the outer edge of the stress relaxation substrate 17 is located outside the outer edge 13c of the optical functional member 13. That is, when viewed from the Z-axis direction, the outer edge of the stress relaxation substrate 17 surrounds the outer edge 13c of the optical functional member 13. The stress relaxation substrate 17 has a thermal expansion coefficient closer to that of the base 21 of the mirror device 20 (more specifically, the thermal expansion coefficient of the support layer 101) than that of the optical functional component 13. In addition, the thickness of the stress relaxation substrate 17 is closer to the thickness of the base 21 of the mirror device 20 than the thickness of the optical functional component 13. The stress relaxation substrate 17 is formed of, for example, silicon into a rectangular plate shape, and has a size of, for example, about 16mm × 21mm × 0.65mm (thickness).

As shown in fig. 1, the mirror unit 2 configured as described above is attached to the support 9 by fixing the surface of the stress relaxation substrate 17 opposite to the optical functional component 13 to the surface 9a (surface on one side in the Z-axis direction) of the support 9 with, for example, an adhesive. When the mirror unit 2 is attached to the support 9, as shown in fig. 8, the positions of the mirror devices 20 in the X-axis direction and the Y-axis direction and the angles of the mirror devices 20 in a plane perpendicular to the Z-axis direction are adjusted with reference to the reference holes 9b formed in the support 9. In fig. 8, the second support structure 12 is not shown.

[ first support Structure and Structure of Beam splitter Unit ]

As shown in fig. 1 and 8, the first support structure 11 includes a frame 111, a transparent member 112, and a plurality of lead posts 113. The frame 111 is formed so as to surround the mirror unit 2 when viewed from the Z-axis direction, and is attached to the surface 9a of the support 9 with an adhesive such as silver solder, for example. The frame 111 is made of, for example, ceramic, and has, for example, a rectangular frame shape. An end surface 111a of the frame 111 on the side opposite to the support 9 is located on the side opposite to the support 9 with respect to the first surface 21a of the base 21 of the mirror device 20.

The light-transmitting member 112 is formed so as to close the opening of the housing 111, and is attached to the end surface 111a of the housing 111 with an adhesive, for example. The light-transmitting member 112 is made of a material having light transmittance with respect to the measurement light L0 and the laser light L10, and has a rectangular plate shape, for example. Here, since the end surface 111a of the housing 111 is located on the opposite side of the first surface 21a of the base 21 of the mirror device 20 from the support 9, the light transmitting member 112 is away from the mirror device 20. Thus, in the optical module 1A, when the movable mirror 22 reciprocates in the Z-axis direction, the movable mirror 22 and the driver 23 can be prevented from coming into contact with the light transmissive member 112. In the optical module 1A, the support 9, the frame 111, and the light transmitting member 112 constitute a package box for housing the mirror unit 2.

Each of the lead posts 113 is provided in the frame 111 such that one end portion 113a is located inside the frame 111 and the other end portion (not shown) is located outside the frame 111. One end portion 113a of the lead post 113 is electrically connected to the electrode pads 211, 212 corresponding to the lead post 113 by wires (not shown) in the mirror device 20. In the optical module 1A, an electrical signal for moving the movable mirror 22 in the Z-axis direction is input to the driving section 23 via the plurality of lead posts 113. In the present embodiment, stepped surfaces 111b extending in the X-axis direction are formed on the frame 111 on both sides of the optical functional component 13 in the Y-axis direction, and one end portion 113a of each lead post 113 is disposed on the stepped surfaces 111 b. Each lead post 113 extends in the Z-axis direction on both sides of the support 9 in the Y-axis direction, and the other end of each lead post 113 is positioned on the other side in the Z-axis direction than the support 9.

As shown in fig. 10, the beam splitter unit 3 is attached to a surface 112a of the light transmitting member 112 on the side opposite to the mirror device 20, for example, by an optical adhesive agent also serving as a refractive index matching agent. The beam splitter unit 3 has a first mirror surface (beam splitter) 31, a second mirror surface 32, and a plurality of optical surfaces 33a, 33b, 33c, and 33 d. The beam splitter unit 3 is configured by joining a plurality of optical blocks 34, 35, 36. Each of the optical blocks 34, 35, 36 is formed of a material having the same or similar refractive index as the optical functional part 13. Fig. 10 is a schematic cross-sectional view of the mirror unit 2 and the beam splitter unit 3 shown in fig. 1, and fig. 10 schematically shows the mirror device 20 in a state where, for example, the dimension in the Z-axis direction is larger than the actual dimension.

The first mirror surface 31 is a mirror surface (for example, a half mirror surface) inclined with respect to the Z-axis direction, and is formed between the optical block 34 and the optical block 35. In the present embodiment, the first mirror surface 31 is a surface parallel to the Y-axis direction, is a surface forming an angle of 45 ° with the Z-axis direction, and is a surface inclined so as to be farther from the light incident portion 4as it approaches the mirror device 20. The first mirror surface 31 has a function of reflecting a part of the measurement light L0 and transmitting the remaining part of the measurement light L0, and a function of reflecting a part of the laser light L10 and transmitting the remaining part of the laser light L10. The first mirror surface 31 is formed of, for example, a dielectric multilayer film. The first mirror surface 31 overlaps the light passing portion 24 of the mirror device 20, the light transmitting portion 14 of the optical functional member 13, and the mirror surface 16a of the fixed mirror 16 when viewed from the Z-axis direction, and overlaps the light incident portion 4 when viewed from the X-axis direction (see fig. 1). That is, the first mirror surface 31 faces the fixed mirror 16 in the Z-axis direction and faces the light incident portion 4 in the X-axis direction.

The second reflecting mirror surface 32 is a reflecting mirror surface (for example, a total reflection mirror surface) parallel to the first reflecting mirror surface 31, and is formed on the optical block 36 so as to be located on the opposite side of the first reflecting mirror surface 31 from the light incident part 4. The second reflecting mirror surface 32 has a function of reflecting the measurement light L0 and a function of reflecting the laser light L10. The second mirror surface 32 is formed of, for example, a metal film. The second reflecting mirror surface 32 overlaps with the reflecting mirror surface 22a of the movable reflecting mirror 22 of the mirror device 20 when viewed from the Z-axis direction, and overlaps with the first reflecting mirror surface 31 when viewed from the X-axis direction. That is, the second reflecting mirror surface 32 faces the movable reflecting mirror 22 in the Z-axis direction and faces the first reflecting mirror surface 31 in the X-axis direction.

The optical surface 33a is a surface perpendicular to the Z-axis direction, and is formed on the optical block 35 so as to be located on the opposite side of the first mirror surface 31 from the mirror device 20. The optical surface 33b is a surface perpendicular to the Z-axis direction, and is formed on the optical block 36 so as to be located on the mirror device 20 side with respect to the second mirror surface 32. The optical surface 33c is a surface perpendicular to the Z-axis direction, and is formed on the optical block 34 so as to be located on the mirror device 20 side with respect to the first mirror surface 31. The optical surface 33b and the optical surface 33c are located on the same plane. The optical surface 33d is a surface perpendicular to the X-axis direction, and is formed on the optical block 34 so as to be located on the light incident portion 4 side with respect to the first mirror surface 31. Each of the optical surfaces 33a, 33b, 33c, and 33d has a function of transmitting the measurement light L0 and a function of transmitting the laser light L10.

The beam splitter unit 3 configured as described above is fixed to the surface 112a of the light transmitting member 112 by the optical surface 33b and the optical surface 33c located on the same plane using, for example, an optical adhesive, and is attached to the light transmitting member 112. When the beam splitter unit 3 is attached to the light transmitting member 112, as shown in fig. 9, the position of the beam splitter unit 3 in the X-axis direction and the Y-axis direction and the angle of the beam splitter unit 3 in the plane perpendicular to the Z-axis direction are adjusted with reference to the reference hole 9b formed in the support 9. In fig. 9, the second support structure 12 is not shown.

Here, the optical path of the measurement light L0 and the optical path of the laser light L10 in the mirror unit 2 and the beam splitter unit 3 will be described in detail with reference to fig. 10.

As shown in fig. 10, when the measurement light L0 enters the beam splitter unit 3 in the X-axis direction via the optical surface 33d, a part of the measurement light L0 passes through the first mirror surface 31, is reflected by the second mirror surface 32, and reaches the mirror surface 22a of the movable mirror 22 via the optical surface 33b and the transparent member 112. Part of the measurement light L0 is reflected by the reflecting mirror surface 22a of the movable reflecting mirror 22, travels in the opposite direction on the same optical path P1, and is reflected by the first reflecting mirror surface 31. The remaining part of the measurement light L0 is reflected by the first mirror surface 31, passes through the optical surface 33c, the light transmitting member 112, the light transmitting portion 24 of the mirror device 20, and the light transmitting portion 14 of the optically functional member 13, and reaches the mirror surface 16a of the fixed mirror 16. The remaining part of the measurement light L0 is reflected by the mirror surface 16a of the fixed mirror 16, travels in the opposite direction on the same optical path P2, and passes through the first mirror surface 31. Part of the measurement light L0 reflected by the first mirror surface 31 and the remaining part of the measurement light L0 transmitted through the first mirror surface 31 become interference light L1, and the interference light L1 of the measurement light is emitted from the beam splitter unit 3 in the Z-axis direction via the optical surface 33 a.

On the other hand, when the laser light L10 enters the beam splitter unit 3 in the Z-axis direction via the optical surface 33a, a part of the laser light L10 is reflected by the first mirror surface 31 and the second mirror surface 32, and reaches the mirror surface 22a of the movable mirror 22 via the optical surface 33b and the transparent member 112. Part of the laser beam L10 is reflected by the mirror surface 22a of the movable mirror 22, travels in the opposite direction on the same optical path P3, and is reflected by the first mirror surface 31. The remaining portion of the laser light L10 passes through the first mirror surface 31, passes through the optical surface 33c, the light transmitting member 112, the light passing portion 24 of the mirror device 20, and the light transmitting portion 14 of the optically functional member 13, and reaches the mirror surface 16a of the fixed mirror 16. The remaining part of the laser beam L10 is reflected by the mirror surface 16a of the fixed mirror 16, travels in the opposite direction on the same optical path P4, and passes through the first mirror surface 31. Part of the laser light L10 reflected by the first mirror surface 31 and the remaining part of the laser light L10 transmitted through the first mirror surface 31 become interference light L11, and the interference light L11 of the laser light is emitted from the beam splitter unit 3 in the Z-axis direction via the optical surface 33 a.

As described above, the light passing portion 24 of the mirror device 20 constitutes the first part P2a of the optical path P2 of the measurement light L0 and the first part P4a of the optical path P4 of the laser light L10 in the optical path between the beam splitter unit 3 and the fixed mirror 16. The light-transmitting portion 14 of the optical functional component 13 constitutes a second portion P2b of the optical path P2 of the measurement light L0 and a second portion P4b of the optical path P4 of the laser light L10 in the optical path between the beam splitter unit 3 and the fixed mirror 16.

The second portion P2b of the optical path P2 of the measurement light L0 is formed of the translucent portion 14, and the optical path difference between the two optical paths P1 and P2 is corrected so that the difference between the optical path length of the optical path P1 of the measurement light L0 (the optical path length in consideration of the refractive index of each medium through which the optical path passes) and the optical path length of the optical path P2 of the measurement light L0 is reduced. Similarly, the second portion P4b of the optical path P4 of the laser beam L10 is composed of the translucent portion 14, and the optical path difference between the two optical paths P3 and P4 is corrected so that the difference between the optical path length P3 of the laser beam L10 and the optical path length P4 of the laser beam L10 is reduced. In the present embodiment, the refractive index of the transparent portion 14 is equal to the refractive index of each of the optical blocks 34, 35, and 36 constituting the beam splitter unit 3, and the distance between the first mirror surface 31 and the second mirror surface 32 along the X-axis direction is equal to the thickness of the transparent portion 14 along the Z-axis direction (i.e., the distance between the surface 14a of the transparent portion 14 and the fourth surface 13b of the optically functional member 13 along the Z-axis direction).

In the optical module 1A, the optical path difference zero position C0 is shifted from the center position C1 of the resonant operation (reciprocating operation at the resonant frequency) of the movable mirror 22 of the mirror device 20. The optical path difference zero position C0 is a position of the movable mirror 22 at which the optical path length on the movable mirror 22 side of the interference light L1 with the optical path length on the fixed mirror 16 side of the interference light L1 with the measurement light is equal. In the present embodiment, the optical path difference zero position C0 is the position of the movable mirror 22 when the optical path length between the first mirror surface 31 of the beam splitter unit 3 and the mirror surface 22a of the movable mirror 22 (i.e., the optical path length of the optical paths P1, P3) and the optical path length between the first mirror surface 31 of the beam splitter unit 3 and the mirror surface 16a of the fixed mirror 16 (i.e., the optical path length of the optical paths P2, P4) are equal. The amount of deviation of the optical path difference zero position C0 from the center position C1 is smaller than the amplitude of the resonant operation of the movable mirror 22. In the present embodiment, the optical path difference zero position C0 is the same as the position of the surface 14a of the light transmitting portion 14 in the Z-axis direction. The center position C1 is a position that is offset from the position of the surface 14a of the light-transmitting portion 14 in the Z-axis direction by the sum of the thickness of the device layer 102 and the thickness of the metal film constituting the mirror surface 22a toward the first mirror surface 31 side of the beam splitter unit 3 along the Z-axis direction.

[ second support Structure and Structure of light entrance part, etc. ]

As shown in fig. 1, the second support structure 12 includes a coupling unit 120. The connection unit 120 includes a body 121, a frame 122, and a fixing plate 123. The main body 121 includes a pair of side walls 124 and 125 and a top wall 126. The pair of side walls 124 and 125 face each other in the X-axis direction. An opening 124a is formed in the side wall portion 124 on one side in the X-axis direction. The top wall portion 126 faces the support body 9 in the Z-axis direction. The top wall portion 126 is formed with an opening 126 a. The body portion 121 is integrally formed of metal, for example. The body 121 is provided with a plurality of positioning pins 121 a. The body portion 121 is fitted into the reference hole 9b and the hole 9c formed in the support body 9 by the positioning pins 121a, positioned with respect to the support body 9, and attached to the support body 9 in that state by, for example, bolts.

The frame 122 is disposed on the surface of the side wall portion 124 opposite to the beam splitter unit 3. The opening of the frame 122 faces the beam splitter unit 3 via the opening 124a of the side wall 124. The light incident portion 4 is disposed on the housing 122. The fixing plate 123 is a member for fixing the light incident portion 4 disposed in the housing 122 to the body portion 121.

The light entrance unit 4 includes a holder 41 and a collimator lens 42. The holder 41 holds the collimator lens 42 and is configured to be connectable to an optical fiber (not shown) for guiding the measurement light L0. The collimator lens 42 collimates the measurement light L0 emitted from the optical fiber. When the optical fiber is connected to the holder 41, the optical axis of the optical fiber coincides with the optical axis of the collimator lens 42.

The holder 41 is provided with a flange portion 41 a. Flange 41a is disposed between frame 122 and fixed plate 123. In this state, the fixing plate 123 is attached to the side wall portion 124 by, for example, bolts, and the light incident portion 4 disposed in the housing 122 is fixed to the body portion 121. Thus, the light incident portion 4 is arranged on the side of the beam splitter unit 3 in the X-axis direction and supported by the second support structure 12. The light incident unit 4 causes the measurement light L0 incident from the first light source through the measurement object or the measurement light L0 (in the present embodiment, the measurement light L0 guided by the optical fiber) emitted from the measurement object to enter the beam splitter unit 3.

The filter 54 is attached to the frame 122. The filter 54 has a function of transmitting the measurement light L0 and absorbing the laser light L10. The filter 54 is formed in a plate shape from, for example, silicon. The filter 54 is disposed in the opening 124a of the side wall portion 124 in a state inclined with respect to the optical axis of the light incident portion 4. When viewed from the X-axis direction, the filter 54 closes the opening of the frame 122. In this way, the filter 54 is disposed between the light incident part 4 and the beam splitter unit 3, and is supported by the second support structure 12 in a state of being inclined with respect to the optical axis of the light incident part 4. In the present embodiment, the optical surface of the filter 54 is a surface parallel to the Z-axis direction and forms an angle of 10 ° to 20 ° with the Y-axis direction. The optical axis of the light entrance unit 4 is parallel to the X-axis direction.

The second support construction 12 also has a holding unit 130. The holding unit 130 includes a body portion 131. The body 131 is attached to the surface of the top wall 126 opposite to the support 9. Body portion 131 is positioned with respect to body portion 121 of coupling unit 120 by a plurality of positioning pins 131a, and in that state, is attached to top wall portion 126 by, for example, bolts. The body 131 has a first through hole 135, a second through hole 136, and a third through hole 137. The first through hole 135, the second through hole 136, and the third through hole 137 penetrate the body 131 in the Z-axis direction. The first through hole 135 is formed at a position facing the first mirror surface 31 of the beam splitter unit 3 in the Z-axis direction. The second through hole 136 is formed on the other side (i.e., the side opposite to the light incident portion 4) of the first through hole 135 in the X-axis direction. The third through-hole 137 is formed on the other side of the second through-hole 136 in the X-axis direction.

The first photodetector 6 is disposed in the first through hole 135. The first photodetector 6 includes a photodetector 62, a package case 64 including a light transmitting window 64a, a holder 61, and a condenser lens 63. The package case 64 houses the light detection element 62. The photodetector 62 detects the interference light L1 of the measurement light. The light detection element 62 is, for example, an InGaAs photodiode. The holder 61 holds the package case 64 and the condenser lens 63. The condenser lens 63 condenses the interference light L1 of the measurement light incident on the photodetector 62 through the light-transmitting window 64a to the photodetector 62. The optical axis of the photodetector 62 and the optical axis of the condenser lens 63 coincide with each other.

The holder 61 is provided with a flange portion 61 a. Flange portion 61a is positioned with respect to body portion 121 of coupling unit 120 by positioning pin 61b, and in that state, is attached to top wall portion 126 of body portion 121 by, for example, a bolt. In this way, the first photodetector 6 is disposed on the Z-axis direction side of the beam splitter unit 3 and supported by the second support structure 12. The first photodetector 6 is opposed to the first mirror surface 31 of the beam splitter unit 3 in the Z-axis direction. The first photodetector 6 detects the interference light L1 of the measurement light emitted from the beam splitter unit 3.

The second photodetector 8 is disposed in the second through hole 136. The second photodetector 8 has a light detecting element 82 and a package 84 including a condenser lens 84 a. The photodetector 82 detects the interference light L11 of the laser light. The light detection element 82 is, for example, a Si photodiode. The condenser lens 84a condenses the interference light L11 of the laser light incident on the photodetector 82 to the photodetector 82. The optical axis of the light detection element 82 and the optical axis of the condenser lens 84a coincide with each other.

The package 84 is fixed to the body 131 in the second through hole 136. In this way, the second photodetector 8 is disposed on the other side of the first photodetector 6 in the X-axis direction (the side of the first optical device in the direction intersecting the optical axis of the first optical device) so as to face the same side as the first photodetector 6, and is supported by the second support structure 12. The second photodetector 8 detects the interference light L11 of the laser light emitted from the beam splitter unit 3.

The second light source 7 is disposed in the third through hole 137. The second light source 7 has a light emitting element 72 and an enclosure 74 containing a collimating lens 74 a. The light emitting element 72 emits laser light L10. The light emitting element 72 is, for example, a semiconductor laser such as a VCSEL. The collimator lens 74a collimates the laser light L10 emitted from the light emitting element 72. The optical axis of the light emitting element 72 and the optical axis of the collimator lens 74a coincide with each other.

The package case 74 is fixed to the body 131 in the third through hole 137. In this way, the second light source 7 is disposed on the other side of the second photodetector 8 in the X-axis direction (on the side of the second optical device in the direction intersecting the optical axis of the first optical device) so as to face the same side as the first photodetector 6, and is supported by the second support structure 12. The second light source 7 emits laser light L10 incident on the beam splitter unit 3.

As described above, the holding unit 130 holds the first photodetector 6, the second photodetector 8, and the second light source 7 in this order such that the first photodetector (first optical device) 6, the second photodetector (second optical device) 8, and the second light source (third optical device) 7 face the same side, and such that the first photodetector 6, the second photodetector 8, and the second light source 7 are in this order. In the present embodiment, the holding unit 130 holds the first photodetector 6, the second photodetector 8, and the second light source 7 on one side of the beam splitter unit 3 in the Z-axis direction so that the first photodetector 6, the second photodetector 8, and the second light source 7 are all directed toward the other side in the Z-axis direction (i.e., the beam splitter unit 3 side). The holding unit 130 holds the first photodetector 6, the second photodetector 8, and the second light source 7 so that the first photodetector 6, the second photodetector 8, and the second light source 7 are arranged in this order from one side in the X-axis direction (i.e., from the light incident portion 4 side).

The first photodetector 6 facing one side means that the light receiving surface of the photodetector 62 faces one side (that is, the first photodetector 6 is disposed so as to detect light incident from one side). In that case, the lead post of the light detecting element 62 extends, for example, to the side opposite to the certain side. Similarly, the second photodetector 8 facing a certain side means that the light receiving surface of the photodetector 82 faces a certain side thereof (that is, the second photodetector 8 is disposed so as to detect light incident from a certain side thereof). In that case, the lead post of the light detecting element 82 extends, for example, to the side opposite to the certain side. The term "second light source 7 faces a certain side" means that the light emitting surface of the light emitting element 72 faces a certain side (that is, the second light source 7 is disposed so as to emit light to a certain side). In that case, the lead post of the light emitting element 72 extends, for example, to the side opposite to the certain side. Since the holding means 130 is a part of the second support structure 12, holding the holding means 130 with a certain structure means that the certain structure is supported by the second support structure 12.

The first reflecting mirror 51, the second reflecting mirror 52, and the third reflecting mirror 53 are attached to the body portion 121 of the coupling unit 120. The first mirror 51 is attached to the ceiling wall portion 126 of the body portion 121 in the opening 126a so as to be located on the opposite side of the first photodetector 6 from the first through hole 135. The second reflecting mirror 52 is attached to the ceiling wall portion 126 of the body 121 in the opening 126a so as to be located on the opposite side of the second photodetector 8 from the second through hole 136. Third reflector 53 is attached to top wall portion 126 of main body portion 121 within opening 126a so as to be located on the opposite side of second light source 7 with respect to third through hole 137.

The first mirror 51 is a dichroic mirror that has a function of transmitting the measurement light L0 and reflecting the laser light L10, and is inclined with respect to the optical axis of the first photodetector 6. The first mirror 51 is disposed between the beam splitter unit 3 and the first photodetector 6. That is, the first mirror 51 is disposed to face the beam splitter unit 3 and the first photodetector 6. In the present embodiment, the optical surface of the first reflecting mirror 51 is a surface parallel to the Y-axis direction and forms an angle of 45 ° with the Z-axis direction. Further, the optical axis of the first photodetector 6 is parallel to the Z-axis direction.

The second mirror 52 is a mirror (e.g., a half mirror) that has a function of reflecting a part of the laser light L10 and transmitting the remaining part of the laser light L10, and is parallel to the first mirror 51. The second mirror 52 is disposed so as to overlap the first mirror 51 when viewed from the X-axis direction and overlap the second photodetector 8 when viewed from the Z-axis direction. That is, the second mirror 52 is disposed to face the first mirror 51 and the second photodetector 8. In the present embodiment, the optical surface of the second reflecting mirror 52 is a surface parallel to the Y-axis direction and forms an angle of 45 ° with the Z-axis direction.

The third mirror 53 is a mirror (for example, a total reflection mirror) having a function of reflecting the laser light L10 and being parallel to the second mirror 52. The third mirror 53 is arranged to overlap the second mirror 52 when viewed from the X-axis direction, and to overlap the second light source 7 when viewed from the Z-axis direction. That is, the third reflecting mirror 53 is disposed to face the second reflecting mirror 52 and the second light source 7. In the present embodiment, the optical surface of the third reflecting mirror 53 is a surface parallel to the Y-axis direction and forms an angle of 45 ° with the Z-axis direction.

A filter 56 is disposed between the first mirror 51 and the first photodetector 6. A grating 55 is disposed between the first mirror 51 and the filter 56. In the present embodiment, the grating 55 and the filter 56 are held by the holder 61 of the first photodetector 6. The grating 55 is a member in which a circular opening is formed when viewed from the Z-axis direction. The filter 56 has a function of transmitting the measurement light L0 and absorbing the laser light L10. In the present embodiment, the filter 56 is a member separate from the member in which the first mirror 51 is formed on the surface on the beam splitter unit 3 side (the surface facing the beam splitter unit 3). More specifically, the filter 56 is, for example, a silicon plate having an antireflection film formed on a light incident surface. In the present embodiment, since the filter 56 is a member separate from the member on which the first mirror 51 is formed, the degree of freedom in designing the first mirror 51 and the filter 56 is improved.

The laser beam absorbing portion 57 is disposed on the side opposite to the second photodetector 8 with respect to the second reflecting mirror 52. The laser light absorber 57 has a function of absorbing the laser light L10. In the present embodiment, the laser absorbing portion 57 is a part of the second support structure (support body) 12 that supports the second mirror 52. More specifically, the laser absorbing portion 57 is a portion protruding from the side wall portion 125 of the body portion 121 of the coupling unit 120 toward the beam splitter unit 3 side. The laser absorbing section 57 is formed by forming a black resist layer in this portion or by subjecting this portion to black alumite treatment. In the present embodiment, since the laser absorbing portion 57 is a part of the second support structure 12, an increase in the number of parts can be suppressed.

Here, an optical path and the like between the beam splitter unit 3 and the first photodetector 6 will be described. The interference light L1 of the measurement light emitted from the beam splitter unit 3 in the Z-axis direction passes through the first mirror 51, enters the first photodetector 6 via the grating 55 and the filter 56, and is detected by the first photodetector 6. On the other hand, the laser light L10 emitted from the second light source 7 is reflected by the third mirror 53, passes through the second mirror 52, is reflected by the first mirror 51, and enters the beam splitter unit 3 along the Z-axis direction. The interference light L11 of the laser beam emitted from the beam splitter unit 3 in the Z-axis direction is reflected by the first mirror 51 and the second mirror 52, enters the second photodetector 8, and is detected by the second photodetector 8. Further, a part of the laser light L10 reflected by the second reflecting mirror 52 is absorbed by the laser light absorber 57.

In the optical module 1A, the length of the optical path between the beam splitter unit 3 and the first photodetector 6 is shorter than the length of the optical path between the beam splitter unit 3 and the second photodetector 8, and is shorter than the length of the optical path between the beam splitter unit 3 and the second light source 7. Further, the length of an optical path refers to the physical distance along its optical path.

Specifically, the distance from the intersection of the optical path and first mirror surface 31 of beam splitter unit 3 to the light incident surface of first photodetector 6 is shorter than the distance from the intersection of the optical path and first mirror surface 31 of beam splitter unit 3 to the light incident surface of second photodetector 8, and shorter than the distance from the intersection of the optical path and first mirror surface 31 of beam splitter unit 3 to the light emitting surface of second light source 7. The distance from the intersection of the optical path and the first mirror surface 31 of the beam splitter unit 3 to the light incident surface of the condenser lens 63 of the first photodetector 6 is shorter than the distance from the intersection of the optical path and the first mirror surface 31 of the beam splitter unit 3 to the light incident surface of the condenser lens 84a of the second photodetector 8, and is shorter than the distance from the intersection of the optical path and the first mirror surface 31 of the beam splitter unit 3 to the light exit surface of the collimator lens 74a of the second light source 7. The distance from the optical surface 33a of the beam splitter unit 3 to the light incident surface of the first photodetector 6 is shorter than the distance from the optical surface 33a of the beam splitter unit 3 to the light incident surface of the second photodetector 8, and is shorter than the distance from the optical surface 33a of the beam splitter unit 3 to the light exit surface of the second light source 7. The distance from the optical surface 33a of the beam splitter unit 3 to the light incident surface of the condenser lens 63 of the first photodetector 6 is shorter than the distance from the optical surface 33a of the beam splitter unit 3 to the light incident surface of the condenser lens 84a of the second photodetector 8, and is shorter than the distance from the optical surface 33a of the beam splitter unit 3 to the light exit surface of the collimator lens 74a of the second light source 7.

In the present embodiment, the light incident portion 4 is configured to be capable of adjusting the angle of the holder 41 with respect to the housing 122. On the other hand, first photodetector 6 is fixed to top wall portion 126 of body portion 121 by, for example, a bolt in a state of being positioned with respect to body portion 121 of connection unit 120. Therefore, in a state where the first photodetector 6 is positioned, the angle of the holder 41 can be adjusted so that the detection intensity of the first photodetector 6 is maximized while the measurement light L0 is incident on the beam splitter unit 3. In addition, the light incident portion 4 can be fixed to the housing 122 in a state where the angle adjustment is performed.

In addition to the light entrance unit 4, the first photodetector 6 may be configured to be capable of adjusting the angle of the holder 61. In addition, the second light source 7 may be configured to be angularly adjustable in a state where the second photodetector 8 is positioned. Further, the second light detector 8 may be configured to be adjustable in angle in addition to the second light source 7.

[ Structure of Signal processing section, etc. ]

As shown in fig. 11, the optical module 1A further includes a signal processing section 200 and a storage section 300. The signal processing unit 200 is electrically connected to the mirror device 20, the second light source 7, the first photodetector 6, and the second photodetector 8, respectively. The signal processing unit 200 is an integrated circuit such as an FPGA (field-programmable gate array), and uses a clock divided from the crystal oscillator as a reference clock. The storage unit 300 is electrically connected to the signal processing unit 200. The storage unit 300 is a nonvolatile Memory such as an EEPROM (Electrically Erasable Programmable Read-Only Memory). The signal processing unit 200 is electrically connected to a pc (personal computer)500 via an external interface 410.

The signal processing section 200 controls voltage signals (details will be described later) applied to the mirror device 20 (specifically, between the fixed comb-tooth electrode 281 and the movable comb-tooth electrode 282, and between the fixed comb-tooth electrode 283 and the movable comb-tooth electrode 284) by the high voltage generation circuit 401. The high Voltage generation circuit 401 is, for example, an hvic (high Voltage ic). In addition, the signal processing section 200 outputs a digital signal for driving the second light source 7. The Digital signal is converted into an Analog signal by a DAC (Digital-to-Analog Converter)402 and input to the second light source 7.

The Analog signal output from the first photodetector 6 is amplified by an amplifier 403, converted into a Digital signal by an ADC (Analog-to-Digital Converter)404, and input to the signal processing unit 200. Thereby, the signal processing unit 200 acquires a digital signal indicating the intensity of the interference light L1 of the measurement light. The analog signal output from the second photodetector 8 is amplified by an amplifier 405, converted into a digital signal by an ADC406, and input to the signal processing unit 200. Thereby, the signal processing unit 200 acquires a digital signal indicating the intensity of the interference light L11 of the laser light.

The signal processing unit 200 includes a voltage signal control unit 201 and an intensity acquisition unit 202.

The voltage signal control section 201 controls the voltage signal so that the voltage signal having the frequency for causing the movable mirror 22 to perform the resonance operation in the mirror device 20 is applied to the mirror device 20. The voltage signal is output from the high voltage generation circuit 401 and applied to the mirror device 20.

Here, the control of the voltage signal will be described in detail. As a premise, in the optical module 1A, as shown in fig. 12, the temporal change in the position of the movable mirror 22 that performs the resonant operation (the position of the movable mirror 22 in the Z-axis direction) is sinusoidal. However, actually, the temporal change in the position of the movable mirror 22 is not an ideal sine wave, and the waveforms thereof show different tendencies in a period T1 during which the movable mirror 22 moves in one direction of the reciprocating direction (for example, in a direction approaching the beam splitter unit 3) and a period T2 during which the movable mirror 22 moves in the other direction of the reciprocating direction (for example, in a direction away from the beam splitter unit 3). Therefore, it is desirable to perform fourier transform type spectrum analysis on the intensity (interferogram) of the interference light L1 of the measurement light, divided into a period T1 and a period T2.

Therefore, it is desirable to detect the timing of switching from the period T1 to the period T2 and the timing of switching from the period T2 to the period T1. These timings correspond to the timings at which the maximum value M1 (for example, the position farthest from the beam splitter unit 3) and the minimum value M2 (for example, the position closest to the beam splitter unit 3) appear in the temporal change in the position of the movable mirror 22, and therefore, the timings at which the maximum value M1 and the minimum value M2 appear may be detected. However, as shown in fig. 13, it is difficult to detect the occurrence timing of the maximum value M1 and the minimum value M2 by increasing the calculation load or the like, based on the temporal change in the intensity of the interference light L11 of the laser light.

As shown in fig. 12, the center pulse train CB, which is a time-varying change in the intensity of the interference light L1 of the measurement light, appears in the first half of the period T1 and the second half of the period T2. This is because, as shown in fig. 10, the optical path difference zero position C0 of the movable mirror 22 is shifted from the center position C1 of the resonant operation of the movable mirror 22 toward the side opposite to the beam splitter unit 3.

From the above premise, the voltage signal control section 201 controls the voltage signal applied to the mirror device 20 so that fourier transform type spectrum analysis can be performed on the intensity of the interference light L1 of the measurement light divided into the period T1 and the period T2. Specifically, as shown in fig. 14, the voltage signal control unit 201 controls the voltage signal so that the voltage signal has a frequency 2 times the resonant frequency of the movable mirror 22. The voltage signal is a continuous pulse signal, and in the present embodiment, is a rectangular wave having a duty ratio of 0.5.

When a voltage signal having a frequency 2 times the resonant frequency of the movable mirror 22 is applied to the mirror device 20, the timing of the rising edge of the voltage signal coincides with the turning position of the movable mirror 22, that is, the timing at which the maximum value M1 and the minimum value M2 occur. In fig. 14, solid arrows indicate the moving direction of the movable mirror 22, and broken arrows indicate the direction of the force generated in the movable mirror 22. The fixed comb-teeth electrodes 281(283) hatched show the state where voltage is applied, and the fixed comb-teeth electrodes 281(283) hatched in the absence of voltage are shown in the state where voltage is not applied.

The relationship between the frequency of the voltage signal and the amplitude of the movable mirror 22 can be obtained by actually operating the mirror device 20. The relationship between the frequency of the voltage signal and the amplitude of the movable mirror 22 can be predicted by numerical analysis such as the longkutta method. In the numerical analysis example shown in fig. 15, when the frequency of the voltage signal is set to 566Hz, the amplitude of the movable mirror 22 becomes maximum, and the movable mirror 22 performs the resonance operation. In this way, the frequency of the voltage signal for causing the movable mirror 22 to perform the resonant operation in the mirror device 20 is obtained in advance by actual measurement, numerical analysis, or the like.

For example, when the High voltage generation circuit 401 is an HVIC, the voltage signal control unit 201 adjusts the timing of inputting a rectangular wave to each of a High voltage (High) terminal and a Low voltage (Low) terminal of the HVIC using a clock divided from a quartz crystal oscillator as a reference clock, and outputs a voltage signal having a desired frequency from an output terminal of the HVIC. As shown in fig. 16, in the HVIC, the timing of the rising edge of the rectangular wave input to the high-voltage terminal is the timing of the rising edge of the voltage signal output from the output terminal, and the timing of the rising edge of the rectangular wave input to the low-voltage terminal is the timing of the falling edge of the voltage signal output from the output terminal.

When the movable mirror 22 starts operating, the voltage signal control section 201 starts operating from the beginning so that a voltage signal having a frequency 2 times the resonance frequency of the movable mirror 22 is applied to the mirror device 20. In this case, since there is an influence of a manufacturing error of the mirror device 20, etc., if the movable mirror 22 is waited to reciprocate a predetermined number of times (for example, 50 times), the movable mirror 22 can be caused to perform the resonant operation. When the movable mirror 22 starts operating, the voltage signal control unit 201 may operate so that the frequency of the voltage signal is reduced every predetermined number of reciprocations (for example, 4 reciprocations) of the movable mirror 22, and a voltage signal having a frequency 2 times the resonance frequency of the movable mirror 22 may be finally applied to the mirror device 20.

When the movable mirror 22 starts the resonance operation, if a voltage signal having a frequency 2 times the resonance frequency of the movable mirror 22 is applied to the mirror device 20, as shown in fig. 17 (a), the timing of the rising edge of the voltage signal coincides with the timing at which the maximum value M1 and the minimum value M2 appear in the temporal change in the position of the movable mirror 22. Therefore, if the timing of the rising edge of the voltage signal is used as a reference, the period T1 during which the movable mirror 22 moves in one direction of the reciprocating direction and the period T2 during which the movable mirror 22 moves in the other direction of the reciprocating direction can be distinguished from each other, and as a result, the intensity of the interference light L1 of the measurement light can be subjected to fourier transform-type spectrum analysis in the period T1 and the period T2. When the frequency of the voltage signal deviates from 2 times the resonant frequency of the movable mirror 22, as shown in fig. 17 (b), the timing of the rising edge of the voltage signal does not coincide with the timing at which the maximum value M1 and the minimum value M2 appear in the temporal change in the position of the movable mirror 22.

The intensity acquisition unit 202 (see fig. 11) performs a first intensity acquisition process and a second intensity acquisition process. Next, the first intensity acquisition process and the second intensity acquisition process will be described in detail.

First, the intensity acquiring unit 202 acquires the intensity of the interference light L1 of the measurement light and the intensity of the interference light L11 of the laser light as shown in fig. 18, 19, and 20 (b) during a period corresponding to consecutive P cycles (P: an integer equal to or greater than 4) in the voltage signal, as shown in fig. 18, 19, and 20 (a). In the example shown in fig. 18, 19, and 20 (a), the intensity of the interference light L1 of the measurement light is indicated as the "ADC count" output from the ADC404 (see fig. 11), and in the example shown in fig. 18, 19, and 20 (b), the intensity of the interference light L11 of the laser light is indicated as the "ADC count" output from the ADC406 (see fig. 11). The intensity acquisition unit 202 acquires intensity data during a period corresponding to a P cycle (16 cycles in the examples shown in fig. 18, 19, and 20 (a) and (b)) using a signal input from the PC500 as a trigger.

Fig. 19 (a) is a graph showing the change with time and the voltage logic of the intensity of the measurement light interference light L1, and fig. 19 (b) is a graph showing the change with time and the voltage logic of the intensity of the laser light interference light L11. The voltage logic is a logic signal used by the voltage signal control section 201 to generate a voltage signal. A voltage logic "0" corresponds to a low level of the voltage signal, and a voltage logic "1" corresponds to a high level of the voltage signal.

Fig. 20 (a) is a graph showing the temporal change in the intensity of the measurement light interference light L1 and the LSB (LSB) logic, and fig. 20 (b) is a graph showing the temporal change in the intensity of the laser light interference light L11 and the LSB logic. The LSB logic is a logic signal for the intensity acquisition section 202 to distinguish between a period T1 during which the movable mirror 22 moves in one of the reciprocation directions and a period T2 during which the movable mirror 22 moves in the other of the reciprocation directions. As described above, since the timing of the rising edge of the voltage signal coincides with the time when the maximum value M1 and the minimum value M2 appear at the folding position of the movable mirror 22, the intensity data when the LSB logic is "0" corresponds to the intensity data of the period T1, and the intensity data when the LSB logic is "1" corresponds to the intensity data of the period T2. The signal processing unit 200 counts the number of cycles of the voltage logic, and generates the LSB logic using 1 bit.

The intensity acquiring unit 202 acquires the intensity of the interference light L1 of the measurement light at first time intervals and the intensity of the interference light L11 of the laser light at second time intervals during a period corresponding to consecutive P periods in the voltage signal. In this case, the intensity acquisition unit 202 references, for example, the rising edge of the voltage signal in each period of the voltage signal. When the intensity acquiring unit 202 acquires the intensity of the interference light L1 of the measurement light from the ADC 404M times (an integer equal to or greater than M: 2) in each of the periods T1 and T2, the first time interval is a value obtained by dividing 1 cycle of the voltage signal by M. When the intensity obtaining unit 202 obtains the intensity of the interference light L11 of the laser light N times (an integer equal to or greater than N: 2) from the ADC406 in each of the periods T1 and T2, the second time interval is a value obtained by dividing 1 cycle of the voltage signal by N. However, when the intensity of the interference light L1 of the measurement light is not acquired from the ADC404 at the time of the rising edge of the voltage signal, the first time interval is a value obtained by dividing 1 cycle of the voltage signal by M + 1. Similarly, when the intensity of the interference light L11 of the laser light is not acquired from the ADC406 at the time of the rising edge of the voltage signal, the second time interval is a value obtained by dividing 1 cycle of the voltage signal by N + 1. That is, the first time interval is set based on the length of 1 cycle of the voltage signal and the number of times of acquiring the intensity of the interference light L1 of the measurement light, and the second time interval is set based on the length of 1 cycle of the voltage signal and the number of times of acquiring the intensity of the interference light L11 of the laser light. In this way, the first time interval and the second time interval are both set based on the frequency of the voltage signal. In the present embodiment, as shown in fig. 21, the first time interval and the second time interval are the same time interval (that is, "M ═ N"). In fig. 21, the point on the solid line is the intensity of the interference light L1 of the measurement light acquired at the first time interval (i.e., the intensity data output from the ADC404 at the first time interval), and the point on the dotted line is the intensity of the interference light L11 of the laser light acquired at the second time interval that is the same as the first time interval (i.e., the intensity data output from the ADC406 at the second time interval that is the same as the first time interval).

As is clear from the above, the intensity acquiring unit 202 acquires the intensity of the interference light L1 of the measurement light M times as the first measurement light intensity at the first time interval in each odd number of periods in the P periods that are consecutive in the voltage signal, and acquires the intensity of the interference light L11 of the laser light N times as the first laser light intensity at the second time interval in each odd number of periods. The intensity acquiring unit 202 acquires the intensity of the interference light L1 of the measurement light M times as the second measurement light intensity at first time intervals in each even-numbered cycle of the P-th cycles that are consecutive in the voltage signal, and acquires the intensity of the interference light L11 of the laser light N times as the second laser light intensity at second time intervals in each even-numbered cycle. In the example shown in fig. 19 and fig. 20 (a) and (b), the odd-numbered period is a period in which the LSB logic is represented by "1" and corresponds to the period T2, and the even-numbered period is a period in which the LSB logic is represented by "0" and corresponds to the period T1.

When the first measured light intensity and the first laser light intensity are acquired in each odd-numbered cycle, the intensity acquiring unit 202 acquires the average value of the first measured light intensities of the same cycle corresponding to each other and acquires the average value of the first laser light intensities of the same cycle corresponding to each other (first intensity acquiring process). Further, when the second measured light intensity and the second laser light intensity are acquired in each of the even-numbered periods, the intensity acquiring unit 202 acquires the average value of the second measured light intensities corresponding to each other at the same time and acquires the average value of the second laser light intensities corresponding to each other at the same time (second intensity acquiring process). The first measured light intensities corresponding to each other at the same time are first measured light intensities obtained at the first same time by counting from a rising edge of the voltage signal in each period of the odd-numbered periods, and the first laser light intensities corresponding to each other at the same time are first laser light intensities obtained at the first same time by counting from a rising edge of the voltage signal in each period of the odd-numbered periods. Similarly, the mutually corresponding second measured light intensities at the same time are the second measured light intensities obtained at the first and the same time counted from the rising edge of the voltage signal in each of the even-numbered periods, and the mutually corresponding second laser light intensities at the same time are the second laser light intensities obtained at the first and the same time counted from the rising edge of the voltage signal in each of the even-numbered periods.

As shown in fig. 22, when the first intensity acquisition process is performed, the intensity acquisition unit 202 stores each of the first measured light intensity and the first laser light intensity acquired in each of the odd-numbered periods of the P period in the first storage area 301 included in the storage unit 300. The first storage area 301 is an area for accumulating the first measured light intensity and the first laser light intensity acquired in each of odd-numbered periods of the P-period for each period when the first intensity acquisition process is performed. That is, the first storage area 301 is an area in which the first measured light intensities obtained in the respective odd-numbered periods of the P period are accumulated and stored for the first measured light intensities of the same time that correspond to each other, and the first laser light intensities obtained in the respective odd-numbered periods are accumulated and stored for the first laser light intensities of the same time that correspond to each other. The first storage area 301 may be an area in which the first measured light intensities obtained in the respective odd-numbered periods of the P periods are averaged and stored for the first measured light intensities corresponding to the same time, and the first laser light intensities obtained in the respective odd-numbered periods are averaged and stored for the first laser light intensities corresponding to the same time.

When the second intensity acquisition process is performed, the intensity acquisition unit 202 stores each of the second measured light intensity and the second laser light intensity acquired in each of the even-numbered periods in the P period in the second storage area 302 included in the storage unit 300. The second storage area 302 is an area in which, when the second intensity acquisition process is performed, the second measured light intensity and the second laser light intensity acquired in each of the even-numbered periods of the P periods are accumulated and stored for each period. That is, the second storage area 302 is an area in which the second measured light intensities obtained in the even-numbered periods of the P period are accumulated and stored for the first measured light intensities of the same time that correspond to each other, and the second laser light intensities obtained in the even-numbered periods are accumulated and stored for the second laser light intensities of the same time that correspond to each other. The second storage area 302 may be an area in which the second measured light intensities obtained in the even-numbered periods of the P periods are averaged and stored for the corresponding second measured light intensities of the same time, and the second laser light intensities obtained in the even-numbered periods are averaged and stored for the corresponding second laser light intensities of the same time.

For example, when the sampling frequency of the ADC404 is 5MHz, the resonance frequency of the movable mirror is 250Hz, and the frequency of the voltage signal is 500Hz, the number of times of acquiring intensity data (data indicating the intensity of the interference light L1 of the measurement light) from the ADC404 in each of the periods T1 and T2 becomes 10000 times (5 × 10 times)⁶)/500). Therefore, as shown in fig. 22, intensity data from 1 to 10000 times is stored in each address 301a of the first storage area 301, intensity data from 10001 to 20000 times is stored in each address 302a of the second storage area 302, and thereafter, until the P cycle ends, storage into each address 301a of the first storage area 301 is alternately repeated until the storage into each address 301a of the first storage area 301 is repeated. When the number of bits of the ADC404 is 16 bits, the size of each address 301a becomes "16 bits × the number of times of accumulation" when accumulating the storage intensity data as described above.On the other hand, when the number of bits of the ADC404 is 16 bits, the size of each address 301a becomes 16 bits when averaging and storing the intensity data as described above. The same applies to the intensity data (data indicating the intensity of the laser interference light L11) obtained from the ADC 406.

As described above, by performing the second intensity acquisition process, the intensity acquisition unit 202 acquires the temporal change in the average value of the first measured light intensity and the temporal change in the average value of the first laser light intensity for the even-numbered cycles (the cycle in which the LSB logic is represented by "0", that is, the cycle corresponding to the period T1), as shown in fig. 23. Further, by performing the first intensity acquisition process, the intensity acquisition unit 202 acquires the temporal change in the average value of the second measured light intensity and the temporal change in the average value of the second laser light intensity for the odd-numbered periods (the period in which the LSB logic is represented by "1", that is, the period corresponding to the period T2), as shown in fig. 24.

When the first intensity acquisition process and the second intensity acquisition process are completed, the intensity acquisition unit 202 outputs data indicating the temporal change in the average value of the first measured light intensity, the temporal change in the average value of the first laser light intensity, the temporal change in the average value of the second measured light intensity, and the temporal change in the average value of the second laser light intensity to the PC500 (see fig. 11).

When acquiring these data, the PC500 performs the first spectrum acquisition process and the second spectrum acquisition process. Next, the first spectrum acquisition process and the second spectrum acquisition process will be described in detail.

As shown in fig. 25, PC500 acquires the first intensity value (blank spot in fig. 25) at the time when maximum value M3 and minimum value M4 appear in the temporal change of the average value of the first measured light intensity (the intensity of the interference light L of the laser light in fig. 25) from the temporal change of the average value of the first measured light intensity (the intensity of the interference light L of the measured light in fig. 25). The PC500 obtains the maximum value M3, the minimum value M4, and the first intensity value by operation. Next, as shown in fig. 26, the PC500 acquires a relationship between an optical path difference (a difference between the optical path length between the first mirror surface 31 of the beam splitter unit 3 and the mirror surface 22a of the movable mirror 22 and the optical path length between the first mirror surface 31 of the beam splitter unit 3 and the mirror surface 16a of the fixed mirror 16) and a first intensity value based on the wavelength of the laser light L10, and acquires a spectrum of the measurement light L0 as shown in (a) of fig. 27 by fourier transform (first spectrum acquisition processing). In the first spectrum acquisition process, the spectrum of the measurement light L0 when the movable mirror 22 moves in one of the reciprocation directions is acquired.

Similarly, the PC500 acquires the second intensity value at the time when the maximum value and the minimum value appear in the temporal change of the average value of the second measured light intensity, from the temporal change of the average value of the second measured light intensity. Next, the PC500 acquires the relationship between the optical path difference and the second intensity value based on the wavelength of the laser light L10, and acquires the spectrum of the measurement light by fourier transform as shown in (b) of fig. 27 (second spectrum acquisition processing). In the second spectrum acquisition process, the spectrum of the measurement light L0 when the movable mirror 22 moves in the other one of the reciprocation directions is acquired.

In the first spectrum acquisition process, the first intensity value at the time when the maximum value or the minimum value appears in the temporal change of the average value of the first measured light intensity may be acquired from the temporal change of the average value of the first measured light intensity, the relationship between the optical path difference and the first intensity value may be acquired based on the wavelength of the laser light L10, and the spectrum of the measured light L0 may be acquired by fourier transform. Similarly, in the second spectrum acquisition process, the second intensity value at the time when the maximum value or the minimum value appears in the temporal change of the average value of the second measured light intensity may be acquired from the temporal change of the average value of the second measured light intensity, the relationship between the optical path difference and the second intensity value may be acquired based on the wavelength of the laser light L10, and the spectrum of the measured light L0 may be acquired by fourier transform. In the first spectrum acquisition process, a first intensity value may be acquired at a time when an intermediate value (an intermediate value between consecutive maximum values and minimum values) appears in a temporal change of the average value of the first laser light intensity, and the first intensity value may be used to acquire the spectrum of the measurement light L0. Similarly, in the second spectrum acquisition process, a second intensity value for acquiring the spectrum of the measurement light L0 may be acquired at a time when an intermediate value (an intermediate value between consecutive maximum values and minimum values) appears in the temporal change of the average value of the second laser light intensity.

As described above, in the optical module 1A, a signal processing method is performed so that a voltage signal having a frequency for causing the movable mirror 22 to perform a resonance operation is applied to the mirror device 20, the signal processing method including: a step of controlling the voltage signal, and a step of performing a first intensity acquisition process and a second intensity acquisition process. In addition, in the optical module 1A and the PC500, a signal processing method is implemented such that a voltage signal having a frequency for causing the movable mirror 22 to perform a resonant operation is applied to the mirror device 20, the signal processing method including: the method includes a step of controlling a voltage signal, a step of performing a first intensity acquisition process and a second intensity acquisition process, and a step of performing a first spectrum acquisition process and a second spectrum acquisition process.

[ Effect and Effect ]

In the optical module 1A, the voltage signal is controlled so that the voltage signal having the frequency for causing the movable mirror 22 to perform the resonance operation is applied to the mirror device 20. The frequency of the voltage signal is preferably 2 times the resonant frequency of the movable mirror 22. Therefore, by acquiring the intensity of the interference light L1 of the measurement light M times as the first measurement light intensity at the first time interval based on the frequency of the voltage signal in each odd-numbered period of the P periods that are consecutive in the voltage signal, and acquiring the average value of the first measurement light intensities at the same time that correspond to each other, the average value of the first measurement light intensities can be easily and accurately acquired for each same position when the movable mirror 22 moves in one direction of the reciprocating direction. Similarly, by acquiring the intensity of the interference light L11 of the laser light N times as the first laser light intensity at the second time interval based on the frequency of the voltage signal and acquiring the average value of the first laser light intensities of the same time corresponding to each other in each of the odd-numbered periods, the average value of the first laser light intensities can be easily and accurately acquired for each same position when the movable mirror 22 moves in one of the reciprocating directions. Further, by acquiring the intensity of the interference light L1 of the measurement light M times as the second measurement light intensity at the first time interval in each of the even-numbered periods of the P periods that are consecutive in the voltage signal and acquiring the average value of the second measurement light intensities of the same time that correspond to each other, the average value of the second measurement light intensities can be easily and accurately acquired for each same position when the movable mirror 22 moves in the other direction of the reciprocation direction. Similarly, by acquiring the intensity of the interference light L11 of the laser light N times as the second laser light intensity at the second time interval in each of the even-numbered cycles and acquiring the average value of the second laser light intensities corresponding to each other at the same time, the average value of the second laser light intensities can be easily and accurately acquired for each same position when the movable mirror 22 moves in the other direction of the reciprocation direction. Therefore, the optical module 1A can perform fourier transform type spectrum analysis in a short time.

As described above, although the temporal change in the position of the movable mirror 22 performing the resonant operation shows different tendencies in the period T1 in which the movable mirror 22 moves in one direction of the reciprocating direction and the period T2 in which the movable mirror 22 moves in the other direction of the reciprocating direction, the intensity of the interference light L1 of the measurement light and the intensity of the interference light L11 of the laser light can be obtained as the average value of the P cycle amount by being divided into the period T1 and the period T2 according to the optical module 1A. When the intensity of the interference light L1 of the measurement light and the intensity of the interference light L11 of the laser light are obtained as the average value of the P period amounts, the noise level becomes 1/(P)^1/2) The SNR can be improved.

In addition, when the movable mirror 22 is caused to perform the resonant operation, the power consumed in the mirror device 20 can be suppressed to be low. Therefore, the intensity of the interference light L1 of the measurement light and the intensity of the interference light L11 of the laser light can be obtained at a desired timing while the movable mirror 22 is continuously operated to resonate. The period during which the intensity of the measurement light interference light L1 and the intensity of the laser light interference light L11 (i.e., the value of P in the P period) are acquired can be set in the PC500, for example.

In the optical module 1A, when the first intensity acquisition process is performed, the first storage area 301 of the storage unit 300 accumulates or averages the first measured light intensity and the first laser light intensity acquired in each of odd-numbered periods of the P periods for each period, and when the second intensity acquisition process is performed, the second storage area 302 of the storage unit 300 accumulates or averages the second measured light intensity and the second laser light intensity acquired in each of even-numbered periods of the P periods for each period, whereby the first intensity acquisition process and the second intensity acquisition process can be reliably performed while suppressing the storage capacity of the storage unit 300.

In the optical module 1A, the first time interval and the second time interval are the same time interval. This makes it possible to more easily perform the first intensity acquisition process and the second intensity acquisition process.

In addition, the PC500 performs a first spectrum acquisition process and a second spectrum acquisition process. This makes it possible to easily and accurately obtain the spectrum of the measurement light L0. That is, fourier transform type spectrum analysis can be easily and accurately performed on the measurement light L0.

[ modified examples ]

The present disclosure is not limited to the above embodiments. For example, the voltage signal applied to the mirror device 20 is not limited to a rectangular wave having a duty ratio of 0.5, and may be a signal in which a low level and a high level are alternately repeated. As an example, as shown in fig. 28, the voltage signal may be a signal in which a rising edge and a falling edge are inclined. In this case, the start point HL1 of the high level HL or the end point LL2 of the low level LL may be set as the timing of the rising edge. The start point LL1 of the low level LL or the end point HL2 of the high level HL can be set to the timing of the falling edge.

As shown in fig. 29, the storage unit 300 may further include a third storage area 303. The third storage area 303 is an area for storing each of the first measured light intensity and the first laser light intensity acquired in the latest 1 cycle of the P cycles until transfer to the first storage area 301 when the first intensity acquisition process is performed, and for storing each of the second measured light intensity and the second laser light intensity acquired in the latest 1 cycle of the P cycles until transfer to the second storage area 302 when the second intensity acquisition process is performed. In this way, while the intensity data are temporarily stored in the third storage area 303, it is possible to confirm whether or not the intensity data are correct.

The voltage signal control unit 201 may adjust the frequency of the voltage signal based on the temporal change in the capacitance generated between the fixed comb-tooth electrode 281 and the movable comb-tooth electrode 282 and between the fixed comb-tooth electrode 283 and the movable comb-tooth electrode 284. As an example, as shown in fig. 30, an analog signal indicating a capacitance is amplified by an amplifier 407, converted into a digital signal by an ADC408, and input to the signal processing unit 200. Thus, for example, even if the resonant frequency of the movable mirror 22 changes due to a change in the use environment, the frequency of the voltage signal can be adjusted so as to be 2 times the resonant frequency of the movable mirror 22, and as a result, the first intensity acquisition process and the second intensity acquisition process can be performed with higher accuracy.

As shown in fig. 31 (a), when the voltage signal is a rectangular wave having a duty ratio of 0.5, the timing of the falling edge of the voltage signal coincides with the timing of the peak appearing on the capacitance signal. This is because, when the voltage signal is a rectangular wave with a duty ratio of 0.5, the timing of the falling edge of the voltage signal coincides with the timing at which the movable mirror 22 is located at the center position C1 (see fig. 10) of the resonance operation, as shown in fig. 14. As shown in (b) of fig. 31, in the case where the timing of the falling edge of the voltage signal is later than the timing at which the peak appears on the capacitance signal, the frequency of the voltage signal is increased so that those timings coincide with each other. As shown in (c) of fig. 31, in the case where the timing of the falling edge of the voltage signal is earlier than the timing at which the peak appears on the capacitance signal, the frequency of the voltage signal is reduced so that those timings coincide with each other.

In this way, when the frequency of the voltage signal is adjusted so as to be 2 times the resonant frequency of the movable mirror 22, the validity of the intensity data acquired in each of the period T1 during which the movable mirror 22 moves in one direction of the reciprocation direction and the period T2 during which the movable mirror 22 moves in the other direction of the reciprocation direction is improved, and as a result, the resolution of the fourier transform type spectrum analysis is improved. In addition, when the frequency of the voltage signal is not adjusted as described above, for example, it is assumed that the resonant frequency of the movable mirror 22 changes due to a change in the use environment, and in the first intensity acquisition process and the second intensity acquisition process, the intensity data acquired at both end portions of the respective periods T1 and T2 are ignored, and only the intensity data acquired at the intermediate portion of the respective periods T1 and T2 is used.

The intensity acquiring unit 202 may perform, as the first intensity acquiring process, a process of acquiring the average value of the first measured light intensities of the same time in the first half (for example, 1/2 cycles in the first half) or the second half (for example, 1/2 cycles in the second half) of each of the odd-numbered cycles in the P cycle, and acquiring the average value of the first laser light intensities of the same time in the same time. Similarly, the intensity acquiring unit 202 may perform, as the second intensity acquiring process, a process of acquiring the average value of the second measured light intensities of the same time in the first half (for example, 1/2 cycles in the first half) or the second half (for example, 1/2 cycles in the second half) of each of the even-numbered cycles in the P cycle, and acquiring the average value of the second laser light intensities of the same time in the same time. In the optical module 1A, since the optical path difference zero position C0 of the movable mirror 22 is shifted from the center position C1 of the resonant operation of the movable mirror 22, as shown in fig. 12, the center pulse train CB in which the intensity of the measurement light interference light L1 changes with time appears in the first half of the period T1 and the second half of the period T2. Therefore, as shown in fig. 32, for example, by dividing each period into 1/2 periods in the first half and 1/2 periods in the second half with reference to the timing of the falling edge of the voltage signal, and performing the first intensity acquisition process and the second intensity acquisition process using 1/2 periods in which the center pulse train CB appears, the resolution of each intensity data can be reduced, and the SNR can be improved.

Further, as to which of the first half or the second half the center burst CB appears in each of the odd-numbered periods (that is, which of the first measured intensities of the first half or the second half is used to perform the first intensity acquisition processing in each of the odd-numbered periods), for example, it may be determined based on the magnitude of the first measured intensity of the first half and the magnitude of the first measured intensity of the second half. Also, as to which one of the first half and the second half the center burst CB appears in each of the even-numbered cycles (i.e., which one of the first half and the second half the second measured intensity is used to perform the second intensity acquisition process in each of the even-numbered cycles), for example, the magnitude of the first half the second measured intensity and the magnitude of the second half the second measured intensity may be used to determine.

As shown in fig. 33, the plurality of optical modules 1A may be electrically connected to the PC500 via a hub 600. As described above, the optical module 1A can perform fourier transform type spectrum analysis in a short time. Therefore, for example, it is possible to perform fourier transform type spectrum analysis at a desired timing while preparing the optical module 1A for each line on which a measurement object is conveyed, and switching the optical module 1A using a signal output from the PC500 as a trigger.

As shown in fig. 34, the signal processing unit 200 may be applied to an optical module 1B including a first light source 5 and a first photodetector 6, the first light source 5 emitting measurement light L0 incident on the beam splitter unit 3; the first photodetector 6 detects the interference light L1 of the measurement light emitted from the beam splitter unit 3 and entering through the measurement object.

In the optical module 1B, the holding unit 130 holds the first light source 5, the second light source 7, and the second photodetector 8 such that the first light source 5, the second light source 7, and the second photodetector 8 face one side in the Z-axis direction on one side of the mirror unit 2 in the X-axis direction, and such that the first light source 5, the second light source 7, and the second photodetector 8 are arranged in this order from the other side in the X-axis direction (i.e., the mirror unit 2 side). The first light source 5 has a light emitting element 5a and a condenser lens 5 b. The light emitting element 5a is a thermal light source such as a filament. The condenser lens 5b condenses the measurement light L0.

The holding unit 130 holds the first mirror 51, the second mirror 52, and the third mirror 53 in addition to the first light source 5, the second light source 7, and the second photodetector 8. The first mirror 51, the second mirror 52, and the third mirror 53 are formed of a plurality of optical blocks joined to each other.

The first reflecting mirror 51 is a dichroic mirror having a function of reflecting the measurement light L0 and transmitting the laser light L10, and is inclined with respect to the optical axis of the first light source 5. The first mirror 51 is arranged to overlap the beam splitter unit 3 when viewed from the X-axis direction, and to overlap the first light source 5 when viewed from the Z-axis direction. That is, the first mirror 51 is disposed to face the beam splitter unit 3 and the first light source 5. In this example, the optical surface of the first reflecting mirror 51 is a surface parallel to the Y-axis direction and has an angle of 45 ° with the Z-axis direction. Further, the optical axis of the first light source 5 is parallel to the Z-axis direction.

The second mirror 52 has a function of reflecting a part of the laser beam L10 and transmitting the remaining part of the laser beam L10, and is parallel to the first mirror 51. The second mirror 52 is disposed so as to overlap the first mirror 51 when viewed from the X-axis direction, and so as to overlap the second light source 7 when viewed from the Z-axis direction. That is, the second reflecting mirror 52 is disposed to face the first reflecting mirror 51 and the second light source 7. In this example, the optical surface of the second reflecting mirror 52 is a surface parallel to the Y-axis direction and has an angle of 45 ° with the Z-axis direction.

The third mirror 53 has a function of reflecting the laser light L10 and is parallel to the second mirror 52. The third mirror 53 is disposed so as to overlap the second mirror 52 when viewed from the X-axis direction and overlap the second photodetector 8 when viewed from the Z-axis direction. That is, the third mirror 53 is disposed to face the second mirror 52 and the second photodetector 8. In this example, the optical surface of the third reflecting mirror 53 is a surface parallel to the Y-axis direction and has an angle of 45 ° with the Z-axis direction.

In the optical module 1B, the measurement light L0 emitted from the first light source 5 in the Z-axis direction is reflected by the first mirror 51 and enters the optical surface 33d of the beam splitter unit 3 in the X-axis direction. The interference light L1 of the measurement light emitted from the optical surface 33a of the beam splitter unit 3 in the Z-axis direction is condensed by the condenser lens 58a, and is emitted to the outside of the housing 10 through the window 10a provided in the housing 10, and is irradiated to the measurement target (not shown). The interference light L1 of the measurement light reflected by the measurement object enters the housing 10 through the window 10a and is collected by the condenser lens 58 b. The interference light L1 of the condensed measurement light enters the first photodetector 6 in the X-axis direction and is detected by the first photodetector 6.

On the other hand, the laser light L10 emitted from the second light source 7 is reflected by the second mirror 52, passes through the first mirror 51, and enters the optical surface 33d of the beam splitter unit 3 in the X-axis direction. The interference light L11 of the laser beam emitted in the X-axis direction from the optical surface 33d of the beam splitter unit 3 passes through the first reflecting mirror 51 and the second reflecting mirror 52, is reflected by the third reflecting mirror 53, enters the second photodetector 8, and is detected by the second photodetector 8.

In the optical module 1B configured as described above, the same signal processing as that of the optical module 1A is performed. Therefore, the optical module 1B can perform fourier transform type spectrum analysis in a short time.

As shown in fig. 35, an interference optical system for the measurement light L0 and an interference optical system for the laser light L10 may be configured separately. The optical module 1C shown in fig. 35 includes one movable mirror 22, a pair of fixed mirrors 16, and a pair of beam splitters 30. In the mirror device 20, mirror surfaces 22a are provided on both sides of the movable mirror 22. The beam splitter 30A for the measurement light L0 is disposed so as to face the one mirror surface 22a and the mirror surface 16A of the fixed mirror 16A for the measurement light L0, respectively. The beam splitter 30B for the laser beam L10 is disposed so as to face the other mirror surface 22a and the mirror surface 16a of the fixed mirror 16B for the laser beam L10, respectively.

In the optical module 1C, the interference light L1 of the measurement light is detected as described below. That is, when the measurement light L0 enters the beam splitter 30A, the measurement light L0 is split into a part and the remaining part in the beam splitter 30A. Then, a part of the measurement light L0 is reflected by the mirror surface 22a on the side of the reciprocating movable mirror 22 and returned to the beam splitter 30A. On the other hand, the remaining part of the measurement light L0 is reflected by the mirror surface 16A of the fixed mirror 16A and returned to the beam splitter 30A. Part and the rest of the measurement light L0 returned to the beam splitter 30A are emitted from the beam splitter 30A as interference light L1, and the interference light L1 of the measurement light is detected by the first photodetector 6.

The interference optical system for the measurement light L0 may be configured such that the measurement light L0 emitted from the first light source (not shown) enters the beam splitter 30A via a measurement target (not shown), or such that the measurement light L0 emitted from the measurement target enters the beam splitter 30A. Alternatively, the interference optical system for the measurement light L0 may be configured such that the measurement light L0 emitted from the first light source enters the beam splitter 30A without passing through the measurement object, and the interference light L1 of the measurement light emitted from the beam splitter 30A enters the first photodetector 6 via the measurement object.

In the optical module 1C, the interference light L11 of the laser beam is detected as described below. That is, when the laser light L10 emitted from the second light source 7 enters the beam splitter 30B, the laser light L10 is split into a part and the remaining part in the beam splitter 30B. Then, a part of the laser light L10 is reflected by the other mirror surface 22a of the reciprocating movable mirror 22 and returned to the beam splitter 30B. On the other hand, the remaining part of the laser light L10 is reflected by the mirror surface 16a of the fixed mirror 16B and returned to the beam splitter 30B. Part and the rest of the laser light L10 returned to the beam splitter 30B are emitted from the beam splitter 30B as interference light L11, and the interference light L11 of the laser light is detected by the second photodetector 8.

As described above, the interference optical system configured in the optical module of the present disclosure may be configured by the movable mirror 22, the at least one fixed mirror 16, and the at least one beam splitter 30.

As shown in fig. 36, the PC (signal processing apparatus) 500 may include a signal processing unit 200. In the example shown in fig. 36, the optical module 1D and the PC500 electrically connected to the optical module 1D constitute a signal processing system 700. The optical module 1D is different from the optical module 1A described above in that it does not include the signal processing unit 200. However, as the interference optical system configured in the optical module 1D, it is possible to apply if it is configured by the movable mirror 22, at least one fixed mirror 16, and at least one beam splitter 30 (for example, an interference optical system configured in each of the optical modules 1A, 1B, and 1C, or the like). The signal processing unit 200 of the PC500 is configured as a computer device including a processor, a memory, a storage, a communication device, and the like. The signal processing unit 200 of the PC500 executes predetermined software (program) such as a read-in memory by a processor, and controls reading and writing of data from and to the memory and communication between the control devices by a communication device, thereby realizing the functions of the voltage signal control unit 201 and the intensity acquisition unit 202. Thus, the signal processing system 700 also performs the same signal processing as the optical module 1A described above. Therefore, according to the signal processing system 700, fourier transform type spectrum analysis can be performed in a short time. The signal processing unit 200 included in each of the optical modules 1A, 1B, and 1C is not limited to being configured as hardware, and may be configured as software.

In the mirror device 20, the movable comb-tooth electrode 282 may be provided on at least one of the movable mirror 22 and the first elastic support portion 26, and the movable comb-tooth electrode 284 may be provided on at least one of the movable mirror 22 and the second elastic support portion 27.

The intensity acquisition unit 202 may perform at least one of the first intensity acquisition process and the second intensity acquisition process. When the intensity acquisition unit 202 performs the first intensity acquisition process, the storage unit 300 may have the first storage area 301, and when the intensity acquisition unit 202 performs the second intensity acquisition process, the storage unit 300 may have the second storage area 302. Note that when the intensity acquisition unit 202 performs the first intensity acquisition process, the PC500 may perform the first spectrum acquisition process, and when the intensity acquisition unit 202 performs the second intensity acquisition process, the PC500 may perform the second spectrum acquisition process. The first time interval and the second time interval may be the same time interval.

The intensity acquiring unit 202 of the signal processing unit 200 may perform intensity acquisition processing of acquiring the measured light intensity of the interference light L1 of the measurement light M times (an integer equal to or greater than M: 2) at first time intervals based on the frequency and acquiring the average value of the measured light intensities of the mutually corresponding same times in each of a plurality of periods of the P periods (an integer equal to or greater than P: 2) that are consecutive in the voltage signal, and acquiring the laser intensity of the interference light L11 of the laser light N times (an integer equal to or greater than N: 2) at second time intervals based on the frequency and acquiring the average value of the laser intensities of the mutually corresponding same times in each of the plurality of periods. In this case, the average value of the measured light intensity can be easily and accurately obtained for the same position when the movable mirror 22 moves by obtaining the measured light intensity of the interference light L1 of the measured light M times at the first time interval based on the frequency of the voltage signal and obtaining the average value of the measured light intensities corresponding to each other the same time in each of the plurality of periods of the P period that are continuous in the voltage signal. Similarly, by acquiring the laser intensity of the interference light L11 of the laser light N times at the second time interval based on the frequency of the voltage signal in each of the plurality of periods and acquiring the average value of the laser intensities of the same time corresponding to each other, the average value of the laser intensities can be easily and accurately acquired for the same position when the movable mirror 22 moves.

When the intensity acquiring unit 202 of the signal processing unit 200 performs the intensity acquiring process of acquiring the average value of the measured light intensities corresponding to each other the same time in each of the plurality of periods and acquiring the average value of the laser intensities corresponding to each other the same time in each of the plurality of periods, the PC500 may perform the spectrum acquiring process, for example. The spectrum acquisition process is a process of acquiring an intensity value at a time when at least one of a maximum value and a minimum value appears in a temporal change of the average value of the measured light intensity from a temporal change of the average value of the measured light intensity, acquiring a relationship between an optical path difference and the intensity value based on the wavelength of the laser light L10, and acquiring the spectrum of the measured light L0 by fourier transform. Thus, Fourier transform spectrum analysis can be performed in a short time.

In any of the above embodiments, the intensity acquisition unit 202 of the signal processing unit 200 also acquires the average value of the measured light intensities (including the first measured light intensity and the second measured light intensity) at the same time corresponding to each other in each of the plurality of periods, and acquires the average value of the laser light intensities (including the first laser light intensity and the second laser light intensity) at the same time corresponding to each other in each of the plurality of periods, but may acquire the integrated value instead of the average value. That is, the intensity acquiring unit 202 of the signal processing unit 200 may acquire the integrated values of the measured light intensities (including the first measured light intensity and the second measured light intensity) corresponding to each other at the same time in each of the plurality of periods, and may acquire the integrated values of the laser intensities (including the first laser intensity and the second laser intensity) corresponding to each other at the same time in each of the plurality of periods. In this way, the intensity acquisition unit 202 of the signal processing unit 200 may acquire the added values of the measured light intensities (including the first measured light intensity and the second measured light intensity) corresponding to each other at the same time in each of the plurality of periods, and may acquire the added values of the laser light intensities (including the first laser light intensity and the second laser light intensity) corresponding to each other at the same time in each of the plurality of periods. The added value is a value corresponding to an accumulated value or an average value. In that case, as the spectrum acquisition process, a process is performed in which an intensity value at a time when at least one of a maximum value and a minimum value appears in a temporal change of the added value of the measurement light intensity is acquired from a temporal change of the added value of the measurement light intensity, a relationship between an optical path difference and the intensity value is acquired based on the wavelength of the laser light L10, and a spectrum of the measurement light L0 is acquired by fourier transform.

Description of the symbols

1A, 1B, 1C, 1D … optical module, 4 … light incident section, 5 … first light source, 6 … first photodetector, 7 … second light source, 8 … second photodetector, 16 … fixed mirror, 16a … mirror surface, 20 … mirror device, 21 … base, 22 … movable mirror, 22a … mirror surface, 26 … first elastic support section (elastic support section), 27 … second elastic support section (elastic support section), 281, 283 … fixed comb-tooth electrode (first comb-tooth electrode), 281A, 283a … fixed comb-tooth (first comb-tooth 282), 284 … movable comb-tooth electrode (second comb-tooth electrode), 282a, 284a … movable comb-tooth (second comb-tooth), 30 … beam splitter, 31 … first reflective beam splitter surface (elastic support section), 200 … signal processing section, 201 … voltage signal control section, 202 … intensity acquisition section, 300 … storage section, 301 … first memory region, 302 … second memory region, 303 … third memory region, 500 … PC (signal processing device), 700 … signal processing system, L0 … measurement light, L1 … measurement light interference light, L10 … laser light, L11 … laser light interference light.