阅读说明：本技术 基于法布里珀罗腔的成像系统 (Fabry-Perot cavity-based imaging system ) 是由 郭斌 黄锦标 于 2020-06-30 设计创作，主要内容包括：公开了一种基于法布里珀罗腔的成像系统,包括单色成像芯片以及设置在所述单色成像芯片的上游光路中的带通滤光片和法布里珀罗腔,所述带通滤光片与所述法布里珀罗腔为相互分立的元件,并且所述带通滤光片被配置为具有包括从430nm到760nm在内的第一光学响应范围,并且所述法布里珀罗腔是可调的以使得其光学响应波峰可在所述第一光学响应范围内之内或完全在所述第一光学响应范围之外。本发明利用宽光谱覆盖的可调的法布里珀罗腔和具有从430nm到760nm在内的第一光学响应范围的带通滤光片,且通过单色成像芯片即可实现RGB成像、IR成像和ON-OFF成像的成像系统,并且可以解析出任意波段的光谱图像。(A Fabry-Perot cavity based imaging system is disclosed, comprising a monochromatic imaging chip, and a bandpass filter and a Fabry-Perot cavity arranged in an upstream optical path of the monochromatic imaging chip, the bandpass filter and the Fabry-Perot cavity being separate elements from each other, and the bandpass filter being configured to have a first optical response range including from 430nm to 760nm, and the Fabry-Perot cavity being tunable such that its optical response peak may be within or completely outside the first optical response range. The invention utilizes the adjustable Fabry-Perot cavity with wide spectrum coverage and the band-pass filter with the first optical response range from 430nm to 760nm, and can realize an imaging system of RGB imaging, IR imaging and ON-OFF imaging through a monochromatic imaging chip, and can analyze the spectrum image of any waveband.)

1. A fabry-perot cavity based imaging system comprising a monochromatic imaging chip and a bandpass filter and a fabry-perot cavity disposed in an upstream optical path of the monochromatic imaging chip, the bandpass filter and the fabry-perot cavity being separate elements from each other, and the bandpass filter being configured to have a first optical response range including from 430nm to 760nm, and the fabry-perot cavity being tunable such that its optical response peak may be within or completely outside the first optical response range.

2. The fabry-perot cavity based imaging system of claim 1, further comprising a collimating lens group disposed in an upstream optical path location of the bandpass filter.

3. The fabry-perot cavity based imaging system of claim 1, wherein the bandpass filter is disposed in an optical path upstream of the fabry-perot cavity.

4. The fabry-perot cavity based imaging system of claim 1, wherein the reflective mirrors in the fabry-perot cavity are made of a broad spectrum reflective material.

5. The Fabry-Perot cavity based imaging system of claim 4, wherein the reflective mirror in the Fabry-Perot cavity is made of silver.

6. The fabry-perot cavity based imaging system of claim 1, wherein the optical distance between the two mirrors of the fabry-perot cavity is tunable between 300 and 1125 nm.

7. The fp cavity-based imaging system as recited in claim 1, wherein the fp cavity adjusts the peak order m of the incident light by a voltage variation, an optical distance between two mirrors of the fp cavity is d, and an optical response of the bandpass filter has a wavelength λ, where m is 2d/λ.

8. The fabry-perot cavity based imaging system of claim 7, wherein the number of peaks in the first optical response range in which the optical response of the fabry-perot cavity is 0, 1, 2, or 3.

9. The fabry-perot cavity based imaging system of claim 7, wherein the optical distance d between the two mirrors of the fabry-perot cavity can be adjusted such that a 1-order peak (m-1) of the fabry-perot cavity's optical response occurs at λ > 750nm and a 2-order peak (m-2) occurs at λ < 450nm to achieve turn-off of the imaging system.

10. The fabry-perot cavity based imaging system of claim 1, wherein the collimating lens group collimates incident light to less than 30 ° of incident light.

11. The fabry-perot cavity based imaging system of claim 1, wherein the monochromatic imaging chip is a silicon-based optical imaging chip.

12. The fabry-perot cavity based imaging system of claim 1, wherein the spectral response range of the monochromatic imaging chip is 380nm-1050 nm.

Technical Field

The invention relates to the technical field of optical imaging, in particular to an imaging system based on a Fabry-Perot cavity.

Background

The tunable optical filter based on Fabry-Perot cavity interference can be applied to a micro spectrometer, a small hyperspectral camera and a mini hyperspectral camera, and compared with other solutions, the Fabry-Perot cavity provides the simplest optical path and system structure in the field of hyperspectral imaging of visible light-far infrared (such as 400nm-1050nm wavelength), so that the cost and the volume of the hyperspectral camera are greatly reduced.

In consumer applications, especially portable imaging applications such as mobile phones, there is an increasing need for CMOS imaging devices that can provide imaging in both RGB (color) and IR (far infrared) spectral ranges, but currently, the mainstream color imaging chip based on filter only has three channels, i.e., R (red), G (green), and B (blue). When the color filter is applied, the imaging chip based on the RGB filter film is matched with the IR-CUT filter so as to remove the influence of light with near infrared wavelength on color imaging. The color Response (RGB) typically represents a filter covering R, G or the B channel over a single pixel, with the response being the quantum efficiency of the pixel itself superimposed on the spectral response of the corresponding filter. To realize IR imaging, a single RGB chip cannot be completed, and an additional imaging chip is required to be added for acquiring images of near-infrared wavelengths, and the imaging chip is generally a monochromatic response device with an additional near-infrared filter.

In addition, the CMOS imaging chip on the mobile phone adopts an electronic shutter, including a rolling shutter and a global shutter, while a mechanical shutter is not used in portable imaging applications such as mobile phones due to the problems of large size and short service life of the mobile phone, the global shutter imaging chip is usually low in pixels and is less used in portable applications such as mobile phones, and the rolling shutter imaging chip has problems such as image tilt during high-speed imaging. And in applications such as high quality imaging and spectral image analysis, it is often desirable to obtain a temporal black frame reference in a manner that covers the entire imaging chip, which is very difficult to achieve in practical applications without a mechanical shutter.

Disclosure of Invention

In order to solve the technical problems that in the prior art, under a typical device structure and a working mode, a single Fabry-Perot cavity and a single imaging chip are not easy to obtain a spectrum imaging range capable of covering RGB and IR and simultaneously realize off-effect imaging, the invention provides an imaging system based on the Fabry-Perot cavity, and the technical problems that in the prior art, under the typical device structure and the working mode, the single Fabry-Perot cavity and the single imaging chip are not easy to obtain the spectrum imaging range capable of covering RGB and IR and simultaneously realize off-effect imaging are solved.

According to an aspect of the present invention, there is provided a fabry-perot cavity based imaging system comprising a monochromatic imaging chip, and a bandpass filter and a fabry-perot cavity arranged in an upstream optical path of the monochromatic imaging chip, the bandpass filter and the fabry-perot cavity being separate elements from each other, and the bandpass filter being configured to have a first optical response range including from 430nm to 760nm, and the fabry-perot cavity being tunable such that its optical response peak may be within or completely outside the first optical response range.

Further, the imaging system further comprises a collimating lens group arranged at an upstream optical path position of the band-pass filter.

Further, the band-pass filter is arranged in an upstream optical path of the Fabry-Perot cavity.

Furthermore, the reflecting mirror surface in the Fabry-Perot cavity is made of a broad spectrum reflecting material.

Preferably, the reflecting mirror surface in the Fabry-Perot cavity is made of silver.

Further, the optical distance between the two mirror surfaces of the Fabry-Perot cavity is adjustable between 300 and 1125 nm.

Furthermore, the Fabry-Perot cavity adjusts the crest order m of incident light through voltage change, the optical distance between two mirror surfaces of the Fabry-Perot cavity is d, the wavelength of the optical response of the band-pass filter is lambda, and m is 2 d/lambda.

Further, the number of peaks of the optical response of the fabry-perot cavity in the first optical response range is 0, 1, 2, or 3.

Further, the optical distance d between the two mirrors of the fabry-perot cavity is such that a 1-order peak (m ═ 1) occurs at λ > 750nm and a 2-order peak (m ═ 2) occurs at λ < 450nm, and the imaging system is turned off.

Further, the collimating lens group collimates the incident light to less than 30 ° of incident light.

Further, the monochromatic imaging chip adopts a silicon-based optical imaging chip.

Further, the spectral response range of the monochromatic imaging chip is 380nm-1050 nm.

The invention utilizes the adjustable Fabry-Perot cavity with wide spectrum coverage and the band-pass filter with the first optical response range from 430nm to 760nm, and can realize an imaging system of RGB imaging, IR imaging and ON-OFF imaging through a monochromatic imaging chip, and can analyze the spectrum image of any waveband. Therefore, the imaging system and the method for obtaining the spectrum imaging range capable of covering RGB and IR by using the single Fabry-Perot cavity and the single imaging chip and simultaneously realizing off-effect imaging are realized.

Drawings

The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments and together with the description serve to explain the principles of the invention. Other embodiments and many of the intended advantages of embodiments will be readily appreciated as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numerals designate corresponding similar parts.

FIG. 1 is a schematic diagram according to one embodiment of the present invention;

fig. 2 is a graph of quantum efficiency of an imaging chip according to an embodiment of the invention.

Figure 3 is a graph illustrating voltage control curves of a fabry-perot cavity according to an embodiment of the present invention;

FIG. 4 is a table of calculations of spectral response data for an imaging system in an exemplary embodiment in accordance with the invention;

FIG. 5 is a graph of a Fabry-Perot cavity spectral response according to an embodiment of the present invention;

Detailed Description

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology, such as "top," "bottom," "left," "right," "up," "down," etc., is used with reference to the orientation of the figures being described. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and logical changes may be made without departing from the scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

Fig. 1 shows an embodiment of a fabry-perot cavity based imaging system.

The band-pass filter and the Fabry-Perot cavity are mutually separated elements and are arranged in an upstream light path of the monochromatic imaging chip, the band-pass filter is arranged in the upstream light path of the Fabry-Perot cavity, incident light firstly passes through the band-pass filter and enters the Fabry-Perot cavity after passing through a first optical response range, the Fabry-Perot cavity is adjustable so that an optical response peak of the Fabry-Perot cavity can be within the first optical response range or completely outside the first optical response range, and the incident light enters the monochromatic imaging chip after being emitted from the adjustable Fabry-Perot cavity to be imaged.

In a particular embodiment, the bandpass filter is configured to have a first optical response range including from 430nm to 760nm, and the fabry-perot cavity is tunable such that its optical response peak may be within or completely outside the first optical response range.

In a specific embodiment, the reflecting mirror in the Fabry-Perot cavity is made of a broad-spectrum reflecting material. For example, a mirror surface made of silver can operate over the entire response range of a typical imaging device from 380nm to 1050 nm.

In a specific embodiment, the optical distance d between the two mirror surfaces of the fabry-perot cavity is adjustable between 300-1125nm, and the position of the filtered peak of the fabry-perot cavity can be adjusted by decreasing or increasing the optical distance d, so as to achieve the adjustability of the spectral response.

In a specific embodiment, the monochromatic imaging chip adopts a silicon-based optical imaging chip, and monochromatic imaging is realized, namely, an RGB filter film is not arranged on a single imaging unit (pixel), so that the spectral response range of the monochromatic imaging chip can be 380nm-1050nm, and the response capability of the monochromatic imaging chip to light with any wavelength is determined by the quantum efficiency of the monochromatic imaging chip. As shown in the quantum efficiency curve of fig. 2, it can be seen that the quantum efficiency of the monochrome imaging chip is higher than that of the RGB imaging chip, so that the responsivity to light of any wavelength is higher than that of the RGB imaging chip.

In a specific embodiment, the imaging system further includes a collimating lens group, which is disposed at an upstream optical path position of the bandpass filter, and collimates incident light with a large angle into incident light with a small angle, where the incident light mainly includes ambient light and object reflected light, the light is complex, and the light angle is generally greater than 60 °, and the incident light passing through the collimating lens group is collimated into incident light with a light angle less than 30 °, which is beneficial to light collection.

Fig. 3 shows a control curve of the fabry-perot cavity modulated by the voltage control in this embodiment. The optical distance d between the two mirrors of the fabry-perot cavity is reduced or increased by increasing or decreasing the driving voltage, and specifically, the relationship between the driving voltage V and the optical distance d between the mirrors is as follows: wherein V represents the driving voltage, d represents the current optical distance between the mirrors, d₀Representing the initial optical distance between the mirrors, k representing the elastic coefficient of the Fabry-Perot cavity, ε₀Which represents the dielectric constant in vacuum. And the position of the filtered wave peak of the Fabry-Perot cavity can be adjusted by reducing or increasing the optical distance d, so that the spectral response can be adjusted. But when V is greater than a certain value V₂When the Fabry-Perot cavity is failed, the Fabry-Perot cavity can not work continuously.

Fig. 4 is a table for calculating spectral response data of an imaging system, where the peak order m of incident light is adjusted by a fabry-perot cavity through a voltage change, an optical distance between two mirrors of the fabry-perot cavity is d, a wavelength of an optical response of a bandpass filter is λ, and a relationship between the three is simplified to m ═ 2d/λ.

As can be seen from the data of fig. 4, when the optical response wavelength λ of the bandpass filter is set to 450nm to 750nm, the peak order m in the optical response wavelength range appears to be 3 at an optical distance d of 1125 nm; when the optical distance d is 900nm, the number m of the peak steps in the optical response wavelength range is 2; when the optical distance d is 825nm, 600nm, 500nm and 450nm, the wave crest order m in the optical response wavelength range is 1; when the optical distance between two mirror surfaces of different Fabry-Perot cavities is larger, the acquired image corresponds to 1-3 wavelengths of response, and RGB imaging and IR imaging can be met. On the other hand, a spectral image of an arbitrary wavelength in the optical response range from 450nm to 750nm can be calculated from a combination of these images.

When the optical distance d is 380nm-440nm, the 1 st order peak (m is 1) of the Fabry-Perot cavity appears at the position where λ is more than 750nm, and the 2 nd order peak (m is 2) appears at the position where λ is less than 450nm, namely, the number of peaks of the band-pass filter with the optical response wavelength λ is 0 in the range of 450nm-750nm, so the optical response of the imaging system is OFF (OFF). That is, the optical distance d between the two mirrors of the fabry-perot cavity is such that a 1-order peak (m ═ 1) occurs at λ > 750nm and a 2-order peak (m ═ 2) occurs at λ < 450nm, and the imaging system is OFF (OFF).

In a specific embodiment, the half-wave width of the peak of the fabry-perot cavity may reach 20-30nm, and the bottom width of the peak may even be larger than 50nm, so the above margin should be added when selecting the spectral range and the off position of the bandpass filter. In the data in the table of fig. 3, the spectral range of the bandpass filter at 450nm to 750nm can satisfy the spectral response requirements of RGB imaging, IR imaging, and turn-off at the same time, but in consideration of the above margin, the spectral range of the bandpass filter at 430nm to 760nm is selected to meet the actual requirement, i.e., the first optical response range of the bandpass filter.

It can also be derived from the table in fig. 4 that when the optical distance d is 200nm and the wavelength λ of the fabry-perot cavity response is 400nm, the peak order m is 1, so that an optical distance below 200nm can be considered as another OFF position in theory. However, in practical applications, the optical distance of the fp cavity is usually difficult to be stabilized to 200nm or less, and when the driving voltage is greater than a certain value, an absorption effect is generated, while the distance below 200nm is generally regarded as a distance that can generate the absorption effect, so the optical distance of the fp cavity needs to be maintained above 200 nm.

Fig. 5 is a graph of a spectral response of the fp cavity according to an embodiment of the present invention, and positions 1 to 4 correspond to optical distance ranges in the table in fig. 4, it can be seen that, when the cutoff wavelength of the bandpass filter is in a range from 450nm to 750nm, the fp cavity has only 1 peak at position 1, 2 peaks at position 2, 3 peaks at position 3, and all peaks at position 4 appear outside 450nm to 750nm, and an optical response of the imaging system is OFF (OFF).

The invention utilizes the adjustable Fabry-Perot cavity with wide spectrum coverage and the band-pass filter with the first optical response range from 430nm to 760nm, and can realize an imaging system of RGB imaging, IR imaging and ON-OFF imaging through a monochromatic imaging chip, and can analyze the spectrum image of any waveband. Therefore, the imaging system and the method for obtaining the spectrum imaging range capable of covering RGB and IR by using the single Fabry-Perot cavity and the single imaging chip and simultaneously realizing off-effect imaging are realized.

It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present invention without departing from the spirit and scope of the invention. In this way, if these modifications and changes are within the scope of the claims of the present invention and their equivalents, the present invention is also intended to cover these modifications and changes. The word "comprising" does not exclude the presence of other elements or steps than those listed in a claim. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims shall not be construed as limiting the scope.