阅读说明：本技术 基于光学游标珐珀干涉的空气折射率波动测量装置和方法 (Air refractive index fluctuation measuring device and method based on optical vernier Fabry-Perot interference ) 是由 张鹏 崔建军 陈恺 崔京远 康岩辉 于 2021-08-10 设计创作，主要内容包括：本申请公开了基于光学游标珐珀干涉的空气折射率波动测量装置和方法,本装置包括：光源系统、解调系统、光电转换单元、平面镜单元、反射镜单元；光源系统用于产生波长不能的两束原始光束,平面镜单元和反射镜单元用于形成两束干涉光束,光电转换单元用于得到干涉信号,解调系统用于对干涉信号进行解调,计算空气折射率波动；本方法步骤包括：同时产生两束波长不等的原始光束,进而得到两束原始光束对应的干涉光束以及干涉信号,通过判断两个干涉信号是否同时到达干涉峰值,计算空气折射率波动。本装置结构简单,操作方便。(The application discloses air refracting index fluctuation measuring device and method based on optics vernier enamel amber interferes, and this device includes: the device comprises a light source system, a demodulation system, a photoelectric conversion unit, a plane mirror unit and a reflector unit; the light source system is used for generating two original light beams with different wavelengths, the plane mirror unit and the reflector unit are used for forming two interference light beams, the photoelectric conversion unit is used for obtaining interference signals, and the demodulation system is used for demodulating the interference signals and calculating air refractive index fluctuation; the method comprises the following steps: simultaneously generating two original light beams with different wavelengths, further obtaining interference light beams and interference signals corresponding to the two original light beams, and calculating the air refractive index fluctuation by judging whether the two interference signals reach an interference peak value simultaneously. The device has simple structure and convenient operation.)

1. Air refractive index fluctuation measuring device based on optics vernier enamel amber interferes, its characterized in that: the method comprises the following steps: a light source system (21), a demodulation system (22), a photoelectric conversion unit, a plane mirror unit, and a reflecting mirror unit;

the light source system (21) is used for simultaneously generating a first original light beam and a second original light beam, and the wavelength of the first original light beam is different from that of the second original light beam;

forming a first interference light beam corresponding to the first original light beam and a second interference light beam corresponding to the second original light beam through the plane mirror unit and the reflector unit, respectively;

the photoelectric conversion unit is used for respectively acquiring a first interference signal corresponding to the first interference light beam and a second interference signal corresponding to the second interference light beam;

the demodulation system (22) is used for demodulating the first interference signal and the second interference signal and calculating air refractive index fluctuation according to the demodulation result; the demodulation system (22) is also used for controlling the reflector to generate displacement.

2. The air refractive index fluctuation measuring device based on optical vernier Fabry-Perot interference according to claim 1, characterized in that: the plane mirror unit comprises a first resonance plane mirror (1) and a second resonance plane mirror (2), wherein the first resonance plane mirror (1) is used for generating resonance effect on the first original light beam, and the second resonance plane mirror (2) is used for generating resonance effect on the second original light beam.

3. The air refractive index fluctuation measuring device based on optical vernier Fabry-Perot interference according to claim 2, characterized in that: the reflectivity of the first resonance plane mirror (1) is a first preset reflectivity, the reflectivity of the second resonance plane mirror (2) is a second preset reflectivity, and the first preset reflectivity and the second preset reflectivity are both greater than 2.5% and less than 97.6%.

4. The air refractive index fluctuation measuring device based on optical vernier Fabry-Perot interference according to claim 3, characterized in that: the reflectivity of the upper end 1/4 part and the lower end 1/4 part of the second resonant plane mirror (2) are both second preset reflectivity, the rest part of the second resonant plane mirror (2) is hollow, the second original light beam passes through the upper end 1/4 part of the second resonant plane mirror (2), and the second interference light beam passes through the lower end 1/4 part of the second resonant plane mirror (2).

5. The air refractive index fluctuation measuring device based on optical vernier Fabry-Perot interference according to claim 4, characterized in that: the distance between the first resonant plane mirror (1) and the second resonant plane mirror (2) is a resonant distance.

6. Air refractive index fluctuation measuring method based on optical vernier Fabry-Perot interference is characterized by comprising the following steps:

generating a first original light beam and a second original light beam simultaneously, wherein the wavelength of the first original light beam is not equal to that of the second original light beam;

obtaining a first interference beam of the first original beam through a first resonant plane mirror (1) and a reflector unit, and obtaining a second interference beam of the second original beam through a second resonant plane mirror (2) and the reflector unit;

obtaining a first interference signal according to the first interference beam and obtaining a second interference signal according to the second interference beam;

demodulating the first interference signal and the second interference signal, controlling the displacement of the reflector unit according to the demodulation result, and obtaining the initial position of the reflector unit when the first interference signal and the second interference signal reach an interference peak point simultaneously;

moving the reflector unit, wherein the moving distance of the reflector unit does not exceed the length of an optical vernier, and when the first interference signal and the second interference signal simultaneously reach an interference peak point again, the scanning position of the reflector unit is obtained;

calculating air refractive index fluctuation based on the initial position of the mirror unit, the scanning position of the mirror unit, and the resonance distance between the first resonance plane mirror (1) and the second resonance plane mirror (2), and completing air refractive index fluctuation measurement.

7. The method for measuring air refractive index fluctuation based on optical vernier Fabry-Perot interference according to claim 6, wherein: the calculation formula of the optical vernier length is as follows:

wherein l_yIs the optical vernier length, λ₀Is the wavelength, λ, of the first original light beam₁Is the wavelength of the second original beam.

8. The air refractive index fluctuation measurement method based on optical vernier Fabry-Perot interference according to claim 7, characterized in that: the calculation formula of the air refractive index fluctuation is as follows:

where Δ n is the refractive index fluctuation of air,/₀For the initial position of the mirror unit,/₁L is the resonance distance between the first resonant flat mirror (1) and the second resonant flat mirror (2) for the scanning position of the mirror unit.

Technical Field

The application belongs to the field of air refractive index fluctuation measurement, and particularly relates to an air refractive index fluctuation measurement device and method based on optical vernier Fabry-Perot interference.

Background

The refractive index of air plays an important role in the fields of optical precision measurement and the like, and the accuracy of the final measurement result is often influenced. The air refractive index fluctuation is the fluctuation of the current air refractive index relative to the air refractive index at a certain moment, and the air refractive index fluctuation value is measured mainly by measuring the air refractive index indirectly at present.

However, in the current measurement method of the air refractive index, no matter the measurement method is a rayleigh interferometry, an F-P interferometric beat frequency measurement method, a bellows double interferometry, a total reflection phase jump method, or an Edlen formula calculation method, the measurement precision is low due to fast change of measurement conditions and a plurality of interference factors, and the device of the measurement method is generally complex and is not easy to operate, so that the measurement difficulty is increased.

Content of application

The application provides an air refractive index fluctuation measuring device and method based on optics vernier enamel amber interferes, obtains two different interference signals with two unequal light beams of wavelength through different level mirrors and the same speculum, through the demodulation to two different interference signals, realizes the undulant measurement of air refractive index, solves the problem that current measurement technique structure is complicated, and the measurement degree of difficulty is high.

In order to achieve the above purpose, the present application provides the following solutions:

air refractive index fluctuation measuring device based on optics vernier enamel amber is interfered includes: the device comprises a light source system, a demodulation system, a photoelectric conversion unit, a plane mirror unit and a reflector unit;

the light source system is used for simultaneously generating a first original light beam and a second original light beam, and the wavelength of the first original light beam is different from that of the second original light beam;

forming a first interference light beam corresponding to the first original light beam and a second interference light beam corresponding to the second original light beam through the plane mirror unit and the reflector unit, respectively;

the photoelectric conversion unit is used for respectively acquiring a first interference signal corresponding to the first interference light beam and a second interference signal corresponding to the second interference light beam;

the demodulation system is used for demodulating the first interference signal and the second interference signal and calculating air refractive index fluctuation according to the demodulation result; the demodulation system is also used for controlling the reflector to generate displacement.

Preferably, the plane mirror unit includes a first resonance plane mirror for generating a resonance effect on the first original beam and a second resonance plane mirror for generating a resonance effect on the second original beam.

Preferably, the reflectivity of the first resonant plane mirror is a first preset reflectivity, the reflectivity of the second resonant plane mirror is a second preset reflectivity, and both the first preset reflectivity and the second preset reflectivity are greater than 2.5% and less than 97.6%.

Preferably, the reflectivities of the upper end 1/4 and the lower end 1/4 of the second resonant plane mirror are both a second predetermined reflectivity, the remaining part of the second resonant plane mirror is hollow, the second original light beam passes through the upper end 1/4 of the second resonant plane mirror, and the second interference light beam passes through the lower end 1/4 of the second resonant plane mirror.

Preferably, the distance between the first resonant flat mirror and the second resonant flat mirror is a resonant distance.

The application also discloses an air refractive index fluctuation measuring method based on optical vernier Fabry-Perot interference, which comprises the following steps:

generating a first original light beam and a second original light beam simultaneously, wherein the wavelength of the first original light beam is not equal to that of the second original light beam;

obtaining a first interference light beam of the first original light beam through a first resonant plane mirror and a reflector unit, and obtaining a second interference light beam of the second original light beam through a second resonant plane mirror and the reflector unit;

obtaining a first interference signal according to the first interference beam and obtaining a second interference signal according to the second interference beam;

demodulating the first interference signal and the second interference signal, controlling the displacement of the reflector unit according to the demodulation result, and obtaining the initial position of the reflector unit when the first interference signal and the second interference signal reach an interference peak point simultaneously;

moving the reflector unit, wherein the moving distance of the reflector unit does not exceed the length of an optical vernier, and when the first interference signal and the second interference signal simultaneously reach an interference peak point again, the scanning position of the reflector unit is obtained;

calculating air refractive index fluctuation based on the initial position of the mirror unit, the scanning position of the mirror unit, and the resonance distance between the first resonance plane mirror and the second resonance plane mirror, and completing air refractive index fluctuation measurement.

Preferably, the calculation formula of the optical vernier length is as follows:

wherein l_yIs the optical vernier length, λ₀Is the wavelength, λ, of the first original light beam₁Is the wavelength of the second original beam.

Preferably, the calculation formula of the air refractive index fluctuation is as follows:

where Δ n is the refractive index fluctuation of air,/₀For the initial position of the mirror unit,/₁L is the resonance distance between the first resonance plane mirror and the second resonance plane mirror as the scanning position of the mirror unit.

The beneficial effect of this application does:

the application discloses based on optics vernier enamel amberThe device and the method for measuring the air refractive index fluctuation have the advantages that two original light beams with different wavelengths pass through different plane mirrors and a common reflector, so that a certain wavelength difference exists between the two interference light beams, and the electric signals of the two interference light beams are demodulated to realize the measurement of the air refractive index fluctuation; meanwhile, by fine tuning of two beams within an optical vernier, 10 can be realized^-11The air refractive index fluctuation measurement precision; in addition, because the optical paths of the two original light beams are different, the influence of other environmental fluctuations can be greatly inhibited, and the anti-interference capability is strong.

Drawings

In order to more clearly illustrate the technical solution of the present application, the drawings needed to be used in the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without inventive exercise.

FIG. 1 is a schematic diagram showing the effect of the change of Fabry-Perot cavity on the interference peak generated by laser light of different wavelengths;

FIG. 2 is a schematic structural diagram of an air refractive index fluctuation measuring device based on optical vernier Fabry-Perot interference in the embodiment of the present application;

FIG. 3 is a schematic flow chart of an air refractive index fluctuation measurement method based on optical vernier Fabry-Perot interference in the embodiment of the application.

Description of the drawings: 1. a first resonant mirror; 2. a second resonant mirror; 3. a pyramid reflector; 4. a stabilizing table; 5. a displacement table; 11. a first photoelectric converter; 12. a second photoelectric converter; 21. a light source system; 22. a demodulation system.

Detailed Description

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, the present application is described in further detail with reference to the accompanying drawings and the detailed description.

The vernier effect was originally applied to improve the resolution of length measurement (e.g. vernier caliper), and its working principle lies in that the length measurement is performed by skillfully utilizing the small scale difference between the first ruler and the vernier. The optical vernier principle is an application of vernier effect in optical interference, when two lasers with wavelength difference perform Fabry-Perot interference, two interference signals with small difference are formed, and the interference signals have the same work as the first ruler and the vernier of the vernier caliper. By demodulating the two interference signals, a sub-micron resolution displacement reading can be obtained through the optical vernier and the optical first ruler.

Fabry-Perot interference is multi-beam interference, according to the formula of multi-beam interference:

wherein, P is the light intensity of transmitted light, a is the amplitude of incident light, R is the light intensity reflectivity of the Fabry-Perot cavity resonator mirror, d is the Fabry-Perot cavity length, and lambda is the wavelength of the incident light. The relationship between the separation Δ d of the folded Fabry-Perot cavity interference peaks and the interference wavelength λ can be expressed as:

as shown in fig. 1, interference peaks with different pitches appear with the change of the Fabry-Perot cavity according to the wavelength of the interference laser. If the interference wavelengths of the two Fabry-Perot cavities are very close, the interference peak intervals formed after the two Fabry-Perot cavities respectively interfere are also very close. For example, the difference between the intervals of interference peaks formed by interference at a wavelength of 633nm and 632.996nm is 1 pm. The optical first ruler and the optical vernier can be constructed by utilizing the two interference peaks with different equal intervals, and optical vernier scales with different resolutions can be formed according to different wavelength differences.

According to the principle, the air refractive index fluctuation measuring device based on optical vernier Fabry-Perot interference comprises: a light source system 21, a demodulation system 22, a photoelectric conversion unit, a plane mirror unit, and a mirror unit; as shown in fig. 2, the light source system 21 is used for simultaneously generating a first original light beam and a second original light beam 1, the wavelengths of the two original light beams are different and respectively marked as λ₀And λ; the plane mirror unit comprises a first resonant plane mirror 1 and a second resonant plane mirror 2, the first resonant plane mirror 1 is used for generating a resonant action on a first original light beam, the reflectivity of the first resonant plane mirror is a first preset reflectivity, the second resonant plane mirror 2 is used for generating a resonant action on a second original light beam, the reflectivity of the 1/4 part at the upper end and the reflectivity of the 1/4 part at the lower end are both second preset reflectivities, and the rest parts are hollow. The reflectivity of the two resonance plane mirrors is 2.5% -97.6%, and can be the same or different. In this embodiment, in order to ensure that the two resonant flat mirrors are fixed in position and the distance is maintained unchanged, the stabilizing table 4 made of zero-expansion glass is added, the first resonant flat mirror 1 and the second resonant flat mirror 2 are both fixedly connected with the stabilizing table 4, and the distance between the two resonant flat mirrors is kept as the resonant distance L. The speculum adopts pyramid speculum 3, like this, and first resonance level crossing 1, second resonance level crossing 2, pyramid speculum 3 set up in order, and first original light beam passes behind the first resonance level crossing 1 fretwork part directive pyramid speculum 3 that passes second resonance level crossing 2, can guarantee that the light path of two bundles of original light beams is unanimous basically, is favorable to calculating the accuracy. In addition, in order to ensure the displacement precision of the pyramid reflector 3, a displacement table 5 is added to be fixedly connected with the pyramid reflector 3, and the displacement table 5 drives the pyramid reflector 3 to generate displacement under the control of the demodulation system 22.

The photoelectric conversion unit comprises a first photoelectric converter 11 and a second photoelectric converter 12, wherein a first original light beam passes through the first resonant plane mirror 1, then irradiates to the pyramid reflecting mirror 3 from a hollow part in the middle of the second resonant plane mirror 2, and passes through the pyramid reflecting mirror 3Finally forming a first interference light beam after reflection, wherein the first interference light beam also passes through the hollow part in the middle of the second resonant plane mirror 2 and the first resonant plane mirror 1, and the first photoelectric converter receives the first interference light beam to generate a first interference signal I₀(ii) a The second original light beam partially passes through the upper end 1/4 of the second resonant plane mirror 2 and is reflected by the pyramid reflecting mirror 3 to finally form a second interference light beam, the second interference light beam partially passes through the lower end 1/4 of the second resonant plane mirror 2, and the second photoelectric converter receives the second interference light beam to generate a second interference signal I₁。

The demodulation system 22 is used for the first and second interference signals I₀、I₁Demodulating and judging I₀、I₁And calculating the fluctuation of the air refractive index if the interference peak value is reached simultaneously. The demodulating system 22 is also used for controlling the displacement table 5 to drive the pyramid reflecting mirror 3 to displace according to the demodulating result.

In the embodiment, marking the first resonant plane mirror 1 and the pyramid reflecting mirror 3 to form a first Fabry-Perot cavity, marking the first resonant plane mirror 1, the pyramid reflecting mirror 3 and the displacement stage 5 to form a first Fabry-Perot interferometer, marking the second resonant plane mirror 2 and the pyramid reflecting mirror 3 to form a second Fabry-Perot cavity, and marking the second resonant plane mirror 2, the pyramid reflecting mirror 3 and the displacement stage 5 to form a second Fabry-Perot interferometer; and the second Fabry-Perot cavity is a common cavity of the first Fabry-Perot interferometer and the second Fabry-Perot interferometer. Therefore, two sets of interferometers are formed, the first interference light beam and the second interference light beam have a certain wavelength difference, the pyramid reflector 3 moves to form an optical vernier, and the air refractive index fluctuation can be accurately calculated by combining the size and the number.

In the embodiment, during measurement, the first resonant flat mirror 1 and the second resonant flat mirror 2 are fixed on zero-expansion glass, and a measurement cavity length with a fixed distance, namely a resonant distance L, is formed. The fluctuation change of the air refractive index can cause the optical path in the measuring cavity to change, so that the position of the first interference signal and the second interference signal which reach the interference peak point simultaneously changes, and the fluctuation amount of the air refractive index can be converted by detecting the position change, thereby simplifying the structure of the measuring device and the measuring process.

The embodiment also discloses an air refractive index fluctuation measurement method based on optical vernier Fabry-Perot interference, which comprises the following steps of:

s102, the light source system 21 outputs the wavelengths lambda respectively at the same time₀、λ₁The two original beams are respectively marked as a first original beam and a second original beam, and the length l of the optical vernier at the moment_yComprises the following steps:

wherein l_yIs the optical vernier length, λ₀Is the wavelength, λ, of the first original light beam₁Is the wavelength of the second original beam;

s104. wavelength is lambda₀Is directed to a first Fabry-Perot interferometer to form a first interference light beam with a wavelength lambda₁The second original light beam is emitted to a second Fabry-Perot interferometer to be interfered to form a second interference light beam;

s106, the first interference light beam is received by the first photoelectric converter to generate a first interference signal I₀The second interference light beam is received by the second photoelectric converter 12 to generate a second interference signal I₁；

S108. first and second interference signals I₀、I₁Simultaneously into the demodulation system 22, the demodulation system 22 to I₀、I₁Performing demodulation judgment, and simultaneously controlling the displacement table 5 to drive the pyramid reflector 3 to displace when the demodulation system 22 detects I₀、I₁When the interference peak point is reached, the displacement table 5 stops moving, and the initial position l of the displacement table 5 at the moment is recorded₀。

S110, the demodulation system 22 controls the displacement table 5 to repeatedly scan an optical vernier length l back and forth_ySo that the pyramid reflector 3 fixed thereon repeatedly scans back and forth for an optical vernier length l_yWhen demodulation system 22 again detects I₀、I₁When the interference peak point is reached, the displacement table 5 stops moving, and the scanning position l of the displacement table 5 at the moment is recorded₁。

S112, calculating air refractive index fluctuation:

where Δ n is the refractive index fluctuation of air,/₀To an initial position of the displacement table 5,/₁L is the measurement cavity length, i.e. the resonance distance, between the first and second resonant flat mirrors 1, 2 for the scanning position of the displacement stage 5.

The above operations are repeated, and the fluctuation of the air refractive index is continuously calculated.

Carry-over-typical value calculation: when the frequency difference of the two lasers is 1GHz, the positioning precision of the displacement table 5 is 20nm, the decimal demodulation peak value discrimination is 750nm, and the length L of the measurement cavity is 100mm, the measurement precision of the air refractive index fluctuation can reach 3.4 multiplied by 10^-11It can be seen that the calculation method of the present application can realize 10 by making a certain wavelength difference between the first and second interference beams and performing interference fraction analysis by using the optical vernier principle^-11The air refractive index fluctuation measurement accuracy.

The above-described embodiments are merely illustrative of the preferred embodiments of the present application, and do not limit the scope of the present application, and various modifications and improvements made to the technical solutions of the present application by those skilled in the art without departing from the spirit of the present application should fall within the protection scope defined by the claims of the present application.