CN103868596A - Large-aperture space heterodyne interference spectral imaging method and spectrometer - Google Patents

Abstract

The invention discloses a large-aperture space heterodyne interference spectral imaging method and a spectrometer. The method comprises the steps that one part of compound light is reflected to obtain reflected light, the other part of the compound light is transmitted to obtain transmitted light after the compound light passes through a beam splitter; the reflected light is reflected by the beam splitter to reach an imaging mirror after passing through a reflecting mirror group and a blazed grating group, and the transmitted light reaches the imaging mirror along an optical path opposite to the reflected light after passing the reflecting mirror group and the blazed grating group, wherein the blazed grating group comprises a first blazed grating and a second blazed grating which are in parallel arrangement, the compound light entering the blazed grating group is diffracted into multiple beams of mutually parallel emergent light which are parallel to the incident light, and interference light with lateral shear amount is obtained from the imaging mirror, so that interference information can be obtained from a detector. A pair of parallel blazed gratings is added, so that the characteristic of heterodyning is realized, the number of samples is reduced, and the signal to noise ratio is improved.

Description

A Large Aperture Spatial Heterodyne Interference Spectral Imaging Method and Spectrometer

technical field

The invention relates to the technical field of optical imaging, in particular to a large-aperture spatial heterodyne interference spectral imaging method and a spectrometer.

Background technique

Interferometric spectral imaging technology can be divided into three types of modulation methods: (1) time modulation, (2) space modulation and (3) space-time joint modulation.

(1) The time-modulated interferometric spectroscopy imaging technology has moving parts, which is less stable than the spatially modulated interferometric spectroscopy technique, but it is easier to achieve a large optical path difference through the moving mechanism.

(2) Spatial modulation interferometric imaging technology has no moving parts, so it has good stability. A typical example of spatial modulation interferometric imaging technology is Sagnac interferometric spectrometer. As shown in Figure 1, the Sagnac interference spectrometer acquires the image of the target on the primary image plane 12 through the front optical system 11, and places a slit 13 on the primary image plane 12, meanwhile, the slit is also located at the Fourier mirror 15 (imaging The optical system includes a Fourier mirror and a cylindrical mirror) on the front focal plane, the slit will be cut into a pair of virtual images after passing through the transverse shearer 14, and the shearing distance between these two virtual images is d, and the Fourier mirror The focal length of is f, and the interferogram expression obtained on the pixel whose distance from the optical axis is y on the detector 16 is: $I\left(\mathrm{the\; y}\right)=\underset{{\mathrm{\σ}}_{\max }}{\overset{{\mathrm{\σ}}_{\max }}{\∫}}B\left(\mathrm{\σ}\right)\cos (2\mathrm{\π\σ}\&Center\; Dot;\mathrm{OPD}\left(\mathrm{the\; y}\right))\mathrm{d\σ},$ In the formula $\mathrm{OPD}\left(\mathrm{the\; y}\right)=d\&Center\; Dot;\sin \mathrm{\θ}=d\&Center\; Dot;\frac{\mathrm{the\; y}}{f}$ is the expression of the optical path difference at the distance y from the optical axis on the detector.

由乃奎斯特定理来决定，采样点数与最大波数成正比、与波数分辨率成反比，当最大波数而波数分辨率高，则采样点数巨大，另一方面，Sagnac干涉光谱仪一次成像获得所有光程差的干涉信息，单个像素（通道）上的探测强度与采样点数成反比，当全部能量为E，则每一个像素的所接收的能量大致为

，当波数分辨率越高则单个通道的能量越小，探测器的灵敏度要求则越高。However, the Sagnac interferometer needs to achieve small wavenumber range and high-resolution detection, and the number of sampling points

Determined by the Nyquist theorem, the number of sampling points is proportional to the maximum wave number and inversely proportional to the wave number resolution. When the maximum wave number and the wave number resolution are high, the number of sampling points is huge. On the other hand, the Sagnac interferometric spectrometer obtains all optical paths in one imaging For poor interference information, the detection intensity on a single pixel (channel) is inversely proportional to the number of sampling points. When the total energy is E, the received energy of each pixel is roughly

, when the wavenumber resolution is higher, the energy of a single channel is smaller, and the sensitivity requirement of the detector is higher.

，γ是光线经过光栅23和光栅24后出射波面的夹角，该角也是σ波数的光出射方向与σ₀波数光出射方向之间的夹角。在探测距离光轴距离为x处，干涉图的表达式为： $I\left(x\right)=\underset{0}{\overset{\∞}{\∫}}B\left(\mathrm{\σ}\right)\cos \left(2\mathrm{\π}\left(4({\mathrm{\σ}}_0-\mathrm{\σ})\mathrm{tg\θ}\right)\right)\mathrm{xd\σ}.$ Another special form of spatially modulated interferometric spectral imaging technology is spatial heterodyne interferometric spectral imaging technology. Spatial heterodyne interferometric spectral imaging technology adopts the principle of heterodyne, so that the initial wave number of the interferogram does not need to start from 0 wave number when sampling , and can start from the set minimum wavenumber σ _min , which can greatly reduce the number of sampling points, achieve high spectral resolution through fewer sampling points, and reduce data redundancy. As shown in FIG. 2 , the spatial heterodyne spectrometer (SHS) includes a collimator 21 , a grating 22 , a grating 23 , a beam splitter 24 , a lens 25 , a lens 26 and a detector 27 . Other symbols in FIG. 2 are: object plane 20 , incident wavefront 201 , Cotterrow angle 202 , outgoing wavefront 203 , and interferogram 204 . SHS uses a pair of gratings (23, 24) with the same parameters to replace the mirror in the Michelson interferometer, and makes a certain angle between the grating and the optical axis. The angle between the grating and the optical axis satisfies the set The light with wave number σ ₀ passes through the grating, and the diffracted light will return to the original path. At this time, the grating equation between the incident light and the diffracted light satisfies , where θ is the angle of incidence and also the angle between the grating 23 and the horizontal direction and the grating 24 and the horizontal direction, which is called the Littrow angle 202, m is the diffraction order, generally m=1, and d is the grating density constant, When the incident wavenumber becomes σ, the grating equation becomes

, γ is the angle between the light exiting the wave surface after passing through the grating 23 and the grating 24, and this angle is also the included angle between the light exit direction of the σ wavenumber and the light exit direction of the σ ₀ wavenumber. At the distance x from the detection distance to the optical axis, the expression of the interferogram is: $I\left(x\right)=\underset{0}{\overset{\∞}{\∫}}B\left(\mathrm{\σ}\right)\cos \left(2\mathrm{\π}\left(4({\mathrm{\σ}}_0-\mathrm{\σ})\mathrm{tg\θ}\right)\right)\mathrm{xd\σ}.$

，当波数分辨率越高则单个通道所接收的能量越小，探测器的灵敏度要求则越高。However, the detection intensity of a single detection point (channel) of the spatial heterodyne interference spectrometer SHS is inversely proportional to the number of sampling points. When the total energy is E, the energy of each channel is roughly

, when the wavenumber resolution is higher, the energy received by a single channel is smaller, and the sensitivity requirement of the detector is higher.

(3) Space-time joint modulation interference spectrum imaging technology combines the characteristics of time modulation and space modulation, and can obtain the interference information of a certain object point under a specific optical path at a certain moment. The imaging relationship of the point, all the energy is concentrated on one point, and its signal-to-noise ratio is higher than that of the spatially modulated interferometer. The spectral information can be obtained by extracting and combining the interferograms and then performing Fourier transform. The typical representative is the Large Aperture Static Interferometric Spectral Imager (LASIS). As shown in FIG. 3 , the LASIS interference spectrum imager includes a front optical system 31 , a primary image plane 32 , a collimator mirror 33 , a transverse shearer 34 , an imaging mirror 35 and a detector 36 . The LASIS interferometric imager adds a transverse shearer to an ordinary photographic system. At a certain moment, the space image of the same object point is obtained, and at the same time, the interference information of the object point under a specific optical path difference is obtained. The role of the collimator The primary image plane is collimated, and then the primary image plane is cut into a pair of coherent virtual images by the transverse shearer, and the pair of virtual images are obtained on the detector through the imaging mirror to obtain a spatial image containing interference information; Compared with the spectrometer, there is no slit on the primary image plane in the LASIS system, and there is no cylindrical mirror in the system. At a certain moment, what is obtained on the detector is a spatial image containing interference information. The expression of the interferogram is for $I\left(\mathrm{the\; y}\right)=\underset{{\mathrm{\&sigma;}}_{\max }}{\overset{{\mathrm{\&sigma;}}_{\max }}{\&Integral;}}B\left(\mathrm{\&sigma;}\right)\cos (2\mathrm{\&pi;\&sigma;}\&Center\; Dot;\mathrm{OPD}\left(\mathrm{the\; y}\right))\mathrm{d\&sigma;},$ In the formula $\mathrm{OPD}\left(\mathrm{the\; y}\right)=d\&Center\; Dot;\sin \mathrm{\&theta;}=d\&CenterDot;\frac{\mathrm{the\; <figure-callout\; id="1"\; label="y\; f"\; filenames="HDA0000468251700000011.png"\; state="\{\{state\}\}">y</figure-callout>}}{f_{}}$ , d is the shear amount, y is the distance between the pixel on the detector and the optical axis, and f1 is the focal length of the imaging system.

However, when the LASIS interferometric spectrometer obtains the interferogram of a single point, it uses push-broom to obtain complete interference information. A single imaging only obtains the interference information of a certain point with a fixed optical path difference. Compared with the Sagna interferometer, the interference information of the optical path difference has the biggest advantage that each pixel of a single detection receives all the energy E of the same object point, and its signal-to-noise ratio is improved. However, when it is required to achieve high-resolution detection in the small wavenumber range, the number of sampling points is still limited by the Nyquist theorem. When the maximum wavenumber is large and the wavenumber resolution is high, the number of sampling points is huge, which further makes the system structure complex and the signal detection and storage. more demanding.

Contents of the invention

The purpose of the embodiments of the present invention is to provide a large-aperture spatial heterodyne interference spectral imaging method and a spectrometer, which can reduce the number of sampling points and improve the signal-to-noise ratio.

The purpose of the embodiments of the present invention is achieved through the following technical solutions:

A large-aperture spatial heterodyne interference spectrometer, comprising:

It includes a beam splitter, a reflector group, and a blazed grating group, wherein the blazed grating group includes a first blazed grating and a second blazed grating arranged in parallel, and the reflector group includes a first reflector and a blazed grating arranged at an angle. Second mirror:

After passing through the beam splitter, part of the composite light is reflected to obtain reflected light, and the other part is transmitted to obtain transmitted light;

The reflected light passes through the mirror group and the blazed grating group, and then is reflected by the beam splitter to reach the imaging mirror, and the transmitted light passes through the mirror group and the mirror group along the opposite optical path to the reflected light. The blazed grating group then reaches the imaging mirror, wherein the composite light incident on the blazed grating group is diffracted into multiple beams of outgoing light parallel to each other, and the multiple beams of outgoing light are parallel to the incident light;

Interfering light with a transverse shear amount is obtained on the imaging mirror, so that interference information is obtained on the detector.

A large-aperture spatial heterodyne interference spectral imaging method, comprising:

After the composite light passes through the beam splitter, part of it is reflected to obtain reflected light, and the other part is transmitted to obtain transmitted light;

The reflected light passes through the mirror group and the blazed grating group, and then is reflected by the beam splitter to reach the imaging mirror, and the transmitted light passes through the mirror group and the mirror group along the opposite optical path to the reflected light. The blazed grating group then reaches the imaging mirror, wherein the blazed grating group includes a first blazed grating and a second blazed grating arranged in parallel, and the mirror group includes a first mirror and a second mirror arranged at an angle. Two reflecting mirrors, the composite light incident on the blazed grating group is diffracted into multiple beams of outgoing light parallel to each other, and the multiple beams of outgoing light are parallel to the incident light;

Interfering light with a transverse shear amount is obtained on the imaging mirror, so that interference information is obtained on the detector.

It can be seen from the technical solutions provided by the above-mentioned embodiments of the present invention that by adding a pair of parallel blazed gratings to the large-aperture static interference spectroscopic imager LASIS to realize the heterodyne characteristics, the high wavenumber (spectral ) resolution detection, the number of sampling points can be greatly reduced, and with the characteristics of LASIS interferometer, the signal-to-noise ratio can be greatly improved, resulting in higher detection sensitivity and better data quality.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For Those of ordinary skill in the art can also obtain other drawings based on these drawings on the premise of not paying creative work.

Fig. 1 is a schematic diagram of an existing Sagnac interferometric spectrometer.

Fig. 2 is a schematic diagram of an existing spatial heterodyne interference spectrometer.

Fig. 3 is a schematic diagram of the existing LASIS interferometric spectrometer.

Fig. 4 is a schematic flow chart of a large-aperture spatial heterodyne interference spectral imaging method according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of the composition of a large-aperture spatial heterodyne interference spectrometer according to an embodiment of the present invention.

Fig. 6 is a block diagram of a large-aperture spatial heterodyne interference spectrometer according to an embodiment of the present invention.

Fig. 7 is a schematic diagram of application of a large-aperture spatial heterodyne interference spectrometer according to an embodiment of the present invention.

Fig. 8 is a schematic diagram of the relationship between wavenumber and diffraction angle of a large-aperture spatial heterodyne interference spectrometer according to an embodiment of the present invention.

FIG. 9 is a second application schematic diagram of a large-aperture spatial heterodyne interference spectrometer according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

As shown in Figure 4, an embodiment of the present invention provides a large-aperture spatial heterodyne interference imaging method, including:

Step 41, after passing through the beam splitter, part of the composite light is reflected to obtain reflected light, and the other part is transmitted to obtain transmitted light;

Step 42: The reflected light passes through the reflector group and the blazed grating group, and then is reflected by the beam splitter to reach the imaging mirror, and the transmitted light passes through the reflected light along the optical path opposite to the reflected light After the mirror group and the blazed grating group reach the imaging mirror, the blazed grating group includes a first blazed grating and a second blazed grating arranged in parallel, and the reflective mirror group includes first reflectors arranged at an angle. mirror and a second reflector, the composite light incident on the blazed grating group is diffracted into multiple beams of outgoing light parallel to each other, and the multiple beams of outgoing light are parallel to the incident light;

Step 43: Obtain interference light with a transverse shear amount on the imaging mirror, so as to obtain interference information on the detector.

The large-aperture spatial heterodyne spectral imaging method of the embodiment of the present invention adds a pair of blazed gratings parallel to each other in the LASIS interferometer. The addition of the blazed grating will make the LASIS interferometer have heterodyne characteristics. When detecting with high wavenumber (spectrum) resolution, the number of sampling points can be greatly reduced; compared with the traditional spatial heterodyne interferometric spectrometer, the signal-to-noise ratio can be greatly improved, making the detection sensitivity higher and the data quality Better; can better meet various application fields.

即可。In the large-aperture spatial heterodyne spectral imaging method of the embodiment of the present invention, when the target wavenumber range to be detected is σ _min to σ _max , the wavenumber resolution to be realized is Δσ, and the number of sampling points only needs to satisfy

That's it.

The large-aperture spatial heterodyne spectral imaging method of the embodiment of the present invention is suitable for the detection of high spectral resolution in the small wavenumber range, such as the detection of gases with characteristic wavelengths such as CO2 and O3 in the atmosphere, and can also be used for the monitoring of regional chemical smog, etc. wait.

In the large-aperture spatial heterodyne spectral imaging method of the embodiment of the present invention, the angle between the first mirror and the second mirror can be set with reference to the angle between the two mirrors of the LASIS interferometer in the prior art. Exemplarily, the first The included angle between the first reflector and the second reflector may be 45°, which will not be described in detail here.

In the large-aperture spatial heterodyne spectral imaging method of the embodiment of the present invention, the first reflector and the second reflector can be plane reflectors, which can be set with reference to the two reflectors of the LASIS interferometer in the prior art, and will not be described in detail here.

The large-aperture spatial heterodyne spectral imaging method in the embodiment of the present invention may further include: imaging the composite light on the primary image plane through the front optical system, and entering the beam splitter after being collimated by the collimation system;

The reflected light passes through the mirror group and the blazed grating group, and then is reflected by the beam splitter to reach the imaging mirror, and the transmitted light passes through the mirror group and the mirror group along the opposite optical path to the reflected light. After the blazed grating group reaches the imaging mirror, it specifically includes:

The reflected light reflected by the beam splitter reaches the second reflector and is reflected to the second blazed grating, and the diffracted light of the second blazed grating reaches the first blazed grating and is diffracted into multiple beams The mutually parallel light rays reach the first reflecting mirror, the parallel light rays are reflected by the first reflecting mirror and then reach the beam splitter, and after being reflected by the beam splitter, reach the imaging mirror, and are imaged by the imaging mirror on the on said detector;

The transmitted light transmitted by the beam splitter reaches the first reflector and is reflected to the first blazed grating, and the diffracted light of the first blazed grating reaches the second blazed grating and is diffracted into multiple beams The mutually parallel light rays reach the second reflection mirror, and the parallel light rays are reflected by the second reflection mirror and then reach the imaging mirror, and are imaged by the imaging mirror on the detector.

Or, as an optional method, the large-aperture spatial heterodyne spectral imaging method in the embodiment of the present invention may also include:

The composite light is imaged on the primary image plane by the front optical system, and enters the beam splitter after being collimated by the collimation system;

The reflected light passes through the mirror group and the blazed grating group, and then is reflected by the beam splitter to reach the imaging mirror, and the transmitted light passes through the mirror group and the mirror group along the opposite optical path to the reflected light. After the blazed grating group reaches the imaging mirror, it specifically includes:

The reflected light reflected by the beam splitter reaches the first blazed grating, and the diffracted light of the first blazed grating reaches the second blazed grating, and is diffracted into multiple parallel beams of light to reach the second reflector mirror, the parallel light rays are reflected by the second reflector and reach the first reflector, and the first reflector reflects and reaches the beam splitter, and the beam splitter reaches the imaging mirror after being reflected, and being imaged on the detector by the imaging mirror;

The transmitted light transmitted by the beam splitter reaches the first reflector and is reflected to the second reflector, and is reflected by the second reflector to the second blazed grating, and the second blazed grating The diffracted light reaches the first blazed grating, is diffracted into multiple parallel beams of light, reaches the imaging mirror, and is imaged by the imaging mirror on the detector.

The large-aperture spatial heterodyne spectral imaging method of the embodiment of the present invention, the pre-optical system, the primary image plane imaging, the collimation system, the beam splitter, the imaging mirror and the detector can be understood by referring to the prior art, and will not be described in detail here.

In the large-aperture spatial heterodyne spectral imaging method in the embodiment of the present invention, the composite light incident on the blazed grating group is diffracted into multiple beams of outgoing light parallel to each other, which may include:

Different wave numbers of the composite light incident on the blazed grating group correspond to different diffraction angles. When the diffraction order m=1, the larger the wave number σ, the larger the diffraction angle.

The wave number σ is the reciprocal of the wavelength λ, that is,

In the large-aperture spatial heterodyne spectral imaging method of the embodiment of the present invention,

Transverse shear volume:

（公式1）

(Formula 1)

Optical path difference:

（公式2）

(Formula 2)

Wherein, a represents the horizontal distance between the symmetrical position of the second reflector and the first reflector, L represents the vertical distance between the first blazed grating and the second blazed grating, and θ represents the compound incident The incident angle of light, β ₁ represents the diffraction angle of wavenumber σ ₁ , and β ₂ represents the diffraction angle of σ ₂ .

The large-aperture spatial heterodyne spectral imaging method of the embodiment of the present invention can obtain the interference information under a certain optical path difference of an object point at a certain moment, and can obtain all the optical path differences of a certain object point by flying push-broom The interference information of different images can be combined to obtain a complete interference curve, and the spectral information of the object point can be obtained by Fourier transforming the interference curve.

As shown in Figure 5, corresponding to the large-aperture spatial heterodyne spectral imaging method of the above-mentioned embodiment, the embodiment of the present invention provides a large-aperture spatial heterodyne interference spectrometer, including a beam splitter 51, a mirror group 52, and a blazed grating group 53, Wherein, the blazed grating group includes a first blazed grating and a second blazed grating arranged in parallel, and the reflector group includes a first reflector and a second reflector arranged at an angle:

After passing through the beam splitter, part of the composite light is reflected to obtain reflected light, and the other part is transmitted to obtain transmitted light;

The reflected light passes through the mirror group and the blazed grating group, and then is reflected by the beam splitter to reach the imaging mirror, and the transmitted light passes through the mirror group and the mirror group along the opposite optical path to the reflected light. The blazed grating group then reaches the imaging mirror, wherein the composite light incident on the blazed grating group is diffracted into multiple beams of outgoing light parallel to each other, and the multiple beams of outgoing light are parallel to the incident light;

Interfering light with a transverse shear amount is obtained on the imaging mirror, so that interference information is obtained on the detector.

The large-aperture spatial heterodyne interference spectrometer in the embodiment of the present invention adds a pair of blazed gratings parallel to each other in the LASIS interferometer. The addition of the blazed grating will make the LASIS interferometer have heterodyne characteristics. When detecting with high wavenumber (spectrum) resolution, the number of sampling points can be greatly reduced; compared with the traditional spatial heterodyne interferometric spectrometer, it can greatly improve the signal-to-noise ratio, making the detection sensitivity higher and the data quality better. Good; can better meet various application fields.

即可。In the large-aperture spatial heterodyne interference spectrometer in the embodiment of the present invention, when the target wavenumber range to be detected is σ _min ~ σ _max , the wavenumber resolution to be realized is Δσ, and the number of sampling points only needs to satisfy

That's it.

The large-aperture spatial heterodyne interference spectrometer in the embodiment of the present invention is suitable for the detection of high spectral resolution in the small wavenumber range, such as the detection of gases with characteristic wavelengths such as CO2 and O3 in the atmosphere, and can also be used for the monitoring of regional chemical smog, etc. .

In the large-aperture spatial heterodyne interference spectrometer in the embodiment of the present invention, the angle between the first reflector and the second reflector can be set with reference to the angle between the two reflectors of the prior art LASIS interferometer. Exemplarily, the first The included angle between the reflecting mirror and the second reflecting mirror may be 45°, which will not be described in detail here.

The large-aperture spatial heterodyne interferometric spectrometer of the embodiment of the present invention, the large-aperture spatial heterodyne spectral imaging method of the embodiment of the present invention, the angle between the first reflector and the second reflector can refer to the two reflections of the prior art LASIS interferometer The setting of the included angle between the mirrors will not be repeated here.

In the large-aperture spatial heterodyne interference spectrometer in the embodiment of the present invention, the first reflector and the second reflector may be planar reflectors, and reference may be made to the arrangement of two reflectors in the prior art LASIS interferometer, which will not be repeated here.

The large-aperture spatial heterodyne interference spectrometer in the embodiment of the present invention may also include a front optical system and a collimation system:

The composite light is imaged on the primary image plane by the front optical system, and enters the beam splitter after being collimated by the collimation system;

The reflected light reflected by the beam splitter reaches the second reflector and is reflected to the second blazed grating, and the diffracted light of the second blazed grating reaches the first blazed grating and is diffracted into multiple beams The mutually parallel light rays reach the first reflecting mirror, the parallel light rays are reflected by the first reflecting mirror and then reach the beam splitter, and after being reflected by the beam splitter, reach the imaging mirror, and are imaged by the imaging mirror on the on said detector;

The transmitted light transmitted by the beam splitter reaches the first reflector and is reflected to the first blazed grating, and the diffracted light of the first blazed grating reaches the second blazed grating and is diffracted into multiple beams The mutually parallel light rays reach the second reflection mirror, and the parallel light rays are reflected by the second reflection mirror and then reach the imaging mirror, and are imaged by the imaging mirror on the detector.

Or, as an option, the large-aperture spatial heterodyne interference spectrometer in the embodiment of the present invention may also include a front optical system and a collimation system:

The composite light is imaged on the primary image plane by the front optical system, and enters the beam splitter after being collimated by the collimation system;

The reflected light reflected by the beam splitter reaches the first blazed grating, and the diffracted light of the first blazed grating reaches the second blazed grating, and is diffracted into multiple parallel beams of light to reach the second reflector mirror, the parallel light rays are reflected by the second reflector and reach the first reflector, and the first reflector reflects and reaches the beam splitter, and the beam splitter reaches the imaging mirror after being reflected, and being imaged on the detector by the imaging mirror;

The transmitted light transmitted by the beam splitter reaches the first reflector and is reflected to the second reflector, and is reflected by the second reflector to the second blazed grating, and the second blazed grating The diffracted light reaches the first blazed grating, is diffracted into multiple parallel beams of light, reaches the imaging mirror, and is imaged by the imaging mirror on the detector.

The large-aperture spatial heterodyne interference spectrometer in the embodiment of the present invention, the pre-optical system, the primary image plane imaging, the collimation system, the beam splitter, the imaging mirror and the detector can be understood by referring to the prior art, and will not be described in detail here.

In the large-aperture spatial heterodyne interference spectrometer according to the embodiment of the present invention, different wave numbers of the composite light incident on the blazed grating group correspond to different diffraction angles. When the diffraction order m=1, the larger the wave number σ, the larger the diffraction angle.

The wave number is the reciprocal of the wavelength λ, that is,

The large-aperture spatial heterodyne spectroscopic interference spectrometer of the embodiment of the present invention,

Transverse shear volume:

（公式1）

(Formula 1)

Optical path difference:

（公式2）

(Formula 2)

Wherein, a represents the horizontal distance between the symmetrical position of the second reflector and the first reflector, L represents the vertical distance between the first blazed grating and the second blazed grating, and θ represents the compound incident The incident angle of light, β ₁ represents the diffraction angle of wavenumber σ ₁ , and β ₂ represents the diffraction angle of σ ₂ .

The large-aperture spatial heterodyne interference spectrometer in the embodiment of the present invention can obtain the interference information under a certain optical path difference of an object point at a certain moment, and can obtain the interference information under all optical path differences of a certain object point by flying push-broom Interference information, a complete interference curve is obtained by combining the interference information of different images, and the spectral information of the object point can be obtained by Fourier transforming the interference curve.

The large-aperture spatial heterodyne interference spectrometer according to the embodiment of the present invention will be described below in combination with specific embodiments.

As shown in Fig. 6, the principle block diagram of the large-aperture spatial heterodyne interference spectrometer according to the embodiment of the present invention, the incident light 60 is imaged on the primary image plane 62 through the pre-optical system 61, the collimated light is obtained through the collimation system 63, and after including the blaze The interferometer 64 of the grating reaches the imaging mirror 65 and is imaged on the detector by the imaging mirror 65 to obtain an image 66 containing interference information.

As shown in Figure 7, the large-aperture spatial heterodyne interference spectrometer according to the embodiment of the present invention includes a front optical system 71, a collimation system 72, a beam splitter 73, a first reflector 74 (also referred to as M1), a second reflector A mirror 75 (M2), a first blazed grating 76, a second blazed grating 77, an imaging mirror 78, and a detector 79.

Specifically, the front optical system 71 images the target on the primary image plane 70 , and the primary image plane 70 is collimated by the collimation system 72 and enters the beam splitter 73 . The function of the beam splitter 73 is to allow 50% of the light to pass through and the other 50% to be reflected.

On the one hand, the transmitted light is reflected after reaching the first mirror 74, and then reaches the first blazed grating 76. The nature of the blazed grating is that when the light is incident perpendicular to the groove surface of the grating, the first-order diffracted light of its blazed wavelength will return to the original path.

After the light reaches the first blazed grating 76, the light of different wavelengths will be diffracted by the grating, and the diffraction angle will vary with the wavelength. The grating equation is satisfied between the diffracted light and the incident light:

，其中σ为入射光波数，θ₁为透射光相对于第一闪耀光栅的入射角，β₁为其衍射角，不同波数σ的光其衍射角β₁不同。

, where σ is the wave number of incident light, θ ₁ is the incident angle of transmitted light relative to the first blazed grating, β ₁ is its diffraction angle, and the diffraction angle β ₁ of light with different wave numbers σ is different.

When the diffracted light reaches the second blazed grating 77, the second blazed grating 77 and the first blazed grating 76 are parallel to each other, and the transmitted light will be diffracted again at this time, and the grating equation is also satisfied between the diffracted light and the incident light at this time:

$\mathrm{<span\; class="notranslate">\; \&sigma;</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&theta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&beta;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; m</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; ,</span>$

It can be seen from the geometrical relationship that θ ₁ ^' = β ₁ , in order to ensure that the light exits parallel to the incident light after passing through the first blazed grating 76 and the second blazed grating 77, m=-m ^' must be made, at this time, β ₁ ^' = θ ₁ .

Therefore, after passing through a pair of blazed gratings placed parallel to each other, the composite light with a certain wavenumber range will be diffracted into multiple beams of light parallel to each other.

After reaching the second reflection mirror 75, it is reflected again and then reaches the imaging mirror 78, and is imaged by the imaging mirror 78 on the detector 79.

As shown in Figure 8, after passing through a pair of blazed gratings placed parallel to each other, the composite light with a certain wavenumber range will be diffracted into multiple beams of parallel light rays, and the exit position is related to the wavenumber σ, the larger the σ, the more the diffraction angle big.

θ is the angle of incidence of incident light relative to the first blazed grating 81, _β1 is the diffraction angle of the wave number σ1, _β2 is the diffraction angle of σ2, and L is the vertical distance between the first blazed grating 81 and the second blazed grating 82 , according to h=L×tgβ, then h ₁ =L×tgβ ₁ , the emission position 83 of wave number σ ₁ , h ₂ =L×tgβ ₂ , and the emission position 84 of wave number σ ₂ is obtained.

On the other hand, the light reflected by the beam splitter 73 first reaches the second reflector 75, and the light reflected by the second reflector 75 reaches the second blazed grating 77 and is diffracted. Like the transmitted light, the diffraction angle of the diffracted light is related to the wavenumber σ and satisfies the grating equation The reflected light after passing through the first blazed grating 76 and the second blazed grating 77 is also diffracted into multiple bundles of parallel light rays. This group of rays generated by the diffraction of reflected light reaches the first reflector 74 and is reflected, and finally reaches the On the beam splitter 73 , after being reflected by the beam splitter 73 , it reaches the imaging mirror 78 and is imaged by the imaging mirror 78 on the detector 79 .

It can be seen that this group of light reflected by the beam splitter 73 will exit parallel to the previous group of transmitted light reflected by the second reflector 75, but the reflected light and the transmitted light will be separated by a distance, which is called the transverse direction. shear amount D.

The transverse shear amount D is related to the horizontal distance a between the symmetrical position 710 of the second reflector 75 with respect to the beam splitter 73 and the first reflector 74 and the wavenumber of the diffracted light:

（公式1）

(Formula 1)

Among them, a represents the horizontal distance between the symmetrical position of the second reflector and the first reflector, L represents the vertical distance between the first blazed grating and the second blazed grating, θ represents the incident angle, and _β1 represents the wave number _σ1 Diffraction angle, _β2 represents the diffraction angle of _σ2 .

It can be seen that the smaller the wavenumber of the incident light at the same object point, the larger the shear amount D will be.

Finally, after the reflected light and the transmitted light pass through the imaging mirror 78, an image containing interference information is obtained on the detector 79, and the interference intensity is determined by $I\left(\mathrm{the\; y}\right)=\underset{{\mathrm{\&sigma;}}_{\min }}{\overset{{\mathrm{\&sigma;}}_{\max }}{\&Integral;}}B\left(\mathrm{\&sigma;}\right)\cos (2\mathrm{\&pi;\&sigma;}.\mathrm{OPD}(\mathrm{the\; y},\mathrm{\&sigma;}))\mathrm{d\&sigma;}$ , where OPD(y,σ) is not only related to the position on the detector but also related to the wave number.

Specifically, the optical path difference:

（公式2）

(Formula 2)

Among them, a represents the horizontal distance between the symmetrical position of the second reflector and the first reflector, L represents the vertical distance between the first blazed grating and the second blazed grating, θ represents the incident angle, and _β1 represents the wave number _σ1 Diffraction angle, _β2 represents the diffraction angle of _σ2 .

In Formula 2, when the incident angle θ is constant, the diffraction angles β ₁ and β ₂ will change with the change of the wave number, and the distance L between the two blazed gratings and the horizontal offset distance a of the two mirrors are both constant.

At a certain moment, the interference information under a certain optical path difference of an object point can be obtained, and the interference information under all optical path differences of a certain object point can be obtained by flying push-broom, and the combination of interference information of different images The complete interference curve is obtained, and the spectral information of the object point can be obtained by Fourier transforming the interference curve.

As shown in Figure 9, the large-aperture spatial heterodyne interference spectrometer according to the embodiment of the present invention includes a front optical system 91, a collimation system 92, a beam splitter 93, a first mirror 94 (also referred to as M1), a second reflector A mirror 95 (M2), a first blazed grating 96, a second blazed grating 97, an imaging mirror 98, and a detector 99.

The difference between the large-aperture spatial heterodyne interference spectrometer in the embodiment of the present invention and the large-aperture spatial heterodyne interference spectrometer shown in FIG. 7 above is that:

The positions where the first blazed grating 96 and the second blazed grating 97 are placed are changed. Placing the two blazed gratings at different positions can increase the distance between the blazed gratings, which in turn can cause a large change in the transverse shear amount D and change the optical path difference. In this way, at a certain moment, the interference information under a certain optical path difference of an object point can be obtained, and the interference information under all optical path differences of a certain object point can be obtained by flying push-broom, and the interference information of different images can be obtained A complete interference curve can be obtained through the combination, and the spectral information of the object point can be obtained by Fourier transforming the interference curve.

The large-aperture spatial heterodyne interference spectrum imaging method and spectrometer in the embodiment of the present invention mainly solve the problem that when the traditional interference spectrum imager obtains spectral information through Fourier transform, the number of sampling points needs to satisfy the Nyquist theorem, which leads to sampling Huge problem with points. On the other hand, in order to solve the problem that the energy of a single channel of SHS is too low, the present invention realizes point-to-point imaging detection in a single detection, that is, all the energy E of a certain object point is concentrated in the detector during one imaging process On the same pixel point, the signal-to-noise ratio of detection can be improved, and all the interference information of the same target point can be obtained by means of push-broom.

The invention also solves the problem of low signal-to-noise ratio in the traditional spatial heterodyne interference spectrum imaging technology. The characteristics of the present invention are particularly suitable for the detection of high spectral resolution in the small wavenumber range, such as the detection of gases with characteristic wavelengths such as CO2 and O3 in the atmosphere, and can also be used for the monitoring of regional chemical smog and the like.

The above is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person familiar with the technical field can easily conceive of changes or changes within the technical scope disclosed in the present invention. Replacement should be covered within the protection scope of the present invention. Therefore, the protection scope of the present invention should be determined by the protection scope of the claims.

Claims (10)

1. A large-aperture spatial heterodyne interference spectrometer, characterized in that it comprises a beam splitter, a mirror group, and a blazed grating group, wherein the blazed grating group includes a first blazed grating and a second blazed grating arranged in parallel, The reflector group includes a first reflector and a second reflector arranged at an angle: After passing through the beam splitter, part of the composite light is reflected to obtain reflected light, and the other part is transmitted to obtain transmitted light; The reflected light passes through the mirror group and the blazed grating group, and then is reflected by the beam splitter to reach the imaging mirror, and the transmitted light passes through the mirror group and the mirror group along the opposite optical path to the reflected light. The blazed grating group then reaches the imaging mirror, wherein the composite light incident on the blazed grating group is diffracted into multiple beams of outgoing light parallel to each other, and the multiple beams of outgoing light are parallel to the incident light; Interfering light with a transverse shear amount is obtained on the imaging mirror, so that interference information is obtained on the detector. 2. The large-aperture spatial heterodyne interference spectrometer according to claim 1, wherein the large-aperture spatial heterodyne interference spectrometer also includes a front optical system and a collimation system: The composite light is imaged on the primary image plane by the front optical system, and enters the beam splitter after being collimated by the collimation system; The reflected light reflected by the beam splitter reaches the second reflector and is reflected to the second blazed grating, and the diffracted light of the second blazed grating reaches the first blazed grating and is diffracted into multiple beams The mutually parallel light rays reach the first reflecting mirror, the parallel light rays are reflected by the first reflecting mirror and then reach the beam splitter, and after being reflected by the beam splitter, reach the imaging mirror, and are imaged by the imaging mirror on the on said detector; The transmitted light transmitted by the beam splitter reaches the first reflector and is reflected to the first blazed grating, and the diffracted light of the first blazed grating reaches the second blazed grating and is diffracted into multiple beams The mutually parallel light rays reach the second reflection mirror, and the parallel light rays are reflected by the second reflection mirror and then reach the imaging mirror, and are imaged by the imaging mirror on the detector. 3. The large-aperture spatial heterodyne interference spectrometer according to claim 1, wherein the large-aperture spatial heterodyne interference spectrometer also includes a front optical system and a collimation system: The composite light is imaged on the primary image plane by the front optical system, and enters the beam splitter after being collimated by the collimation system; The reflected light reflected by the beam splitter reaches the first blazed grating, and the diffracted light of the first blazed grating reaches the second blazed grating, and is diffracted into multiple parallel beams of light to reach the second reflector mirror, the parallel light rays are reflected by the second reflector and reach the first reflector, and the first reflector reflects and reaches the beam splitter, and the beam splitter reaches the imaging mirror after being reflected, and being imaged on the detector by the imaging mirror; The transmitted light transmitted by the beam splitter reaches the first reflector and is reflected to the second reflector, and is reflected by the second reflector to the second blazed grating, and the second blazed grating The diffracted light reaches the first blazed grating, is diffracted into multiple parallel beams of light, reaches the imaging mirror, and is imaged by the imaging mirror on the detector. 4. according to claim 1 or 2 or 3 described large-aperture spatial heterodyne interference spectrometers, it is characterized in that, the different wavenumbers of the composite light of the incident described blazed grating group correspond to different diffraction angles, when the diffraction order m= 1. The larger the wave number σ, the larger the diffraction angle. 5. according to claim 1 or 2 or 3 described large-aperture spatial heterodyne interference spectrometers, it is characterized in that, Transverse shear

Optical path difference

Wherein, a represents the horizontal distance between the symmetrical position of the second reflector and the first reflector, L represents the vertical distance between the first blazed grating and the second blazed grating, and θ represents the compound incident The incident angle of light, β ₁ represents the diffraction angle of wavenumber σ ₁ , and β ₂ represents the diffraction angle of σ ₂ . 6. A large-aperture spatial heterodyne interference imaging method, characterized in that it comprises: After the composite light passes through the beam splitter, part of it is reflected to obtain reflected light, and the other part is transmitted to obtain transmitted light; The reflected light passes through the mirror group and the blazed grating group, and then is reflected by the beam splitter to reach the imaging mirror, and the transmitted light passes through the mirror group and the mirror group along the opposite optical path to the reflected light. The blazed grating group then reaches the imaging mirror, wherein the blazed grating group includes a first blazed grating and a second blazed grating arranged in parallel, and the mirror group includes a first mirror and a second mirror arranged at an angle. Two reflecting mirrors, the composite light incident on the blazed grating group is diffracted into multiple beams of outgoing light parallel to each other, and the multiple beams of outgoing light are parallel to the incident light; Interfering light with a transverse shear amount is obtained on the imaging mirror, so that interference information is obtained on the detector. 7. The large-aperture spatial heterodyne interference imaging method according to claim 6, characterized in that, the method further comprises: the composite light is imaged on the primary image plane through the front optical system, and the collimation system collimates directly into the beam splitter; The reflected light passes through the mirror group and the blazed grating group, and then is reflected by the beam splitter to reach the imaging mirror, and the transmitted light passes through the mirror group and the mirror group along the opposite optical path to the reflected light. After the blazed grating group reaches the imaging mirror, it specifically includes: The reflected light reflected by the beam splitter reaches the second reflector and is reflected to the second blazed grating, and the diffracted light of the second blazed grating reaches the first blazed grating and is diffracted into multiple beams The mutually parallel light rays reach the first reflecting mirror, the parallel light rays are reflected by the first reflecting mirror and then reach the beam splitter, and after being reflected by the beam splitter, reach the imaging mirror, and are imaged by the imaging mirror on the on said detector; The transmitted light transmitted by the beam splitter reaches the first reflector and is reflected to the first blazed grating, and the diffracted light of the first blazed grating reaches the second blazed grating and is diffracted into multiple beams The mutually parallel light rays reach the second reflection mirror, and the parallel light rays are reflected by the second reflection mirror and then reach the imaging mirror, and are imaged by the imaging mirror on the detector. 8. The large-aperture spatial heterodyne interference imaging method according to claim 7, characterized in that, the method further comprises: the composite light is imaged on the primary image plane through the front optical system, and the collimation system collimates directly into the beam splitter; The reflected light passes through the mirror group and the blazed grating group, and then is reflected by the beam splitter to reach the imaging mirror, and the transmitted light passes through the mirror group and the mirror group along the opposite optical path to the reflected light. After the blazed grating group reaches the imaging mirror, it specifically includes: The reflected light reflected by the beam splitter reaches the first blazed grating, and the diffracted light of the first blazed grating reaches the second blazed grating, and is diffracted into multiple parallel beams of light to reach the second reflector mirror, the parallel light rays are reflected by the second reflector and reach the first reflector, and the first reflector reflects and reaches the beam splitter, and the beam splitter reaches the imaging mirror after being reflected, and being imaged on the detector by the imaging mirror; The transmitted light transmitted by the beam splitter reaches the first reflector and is reflected to the second reflector, and is reflected by the second reflector to the second blazed grating, and the second blazed grating The diffracted light reaches the first blazed grating, is diffracted into multiple parallel beams of light, reaches the imaging mirror, and is imaged by the imaging mirror on the detector. 9. The large-aperture spatial heterodyne interference imaging method according to claim 6, 7 or 8, wherein the composite light incident on the blazed grating group is diffracted into multiple beams of outgoing light parallel to each other, including: Different wave numbers of the composite light incident on the blazed grating group correspond to different diffraction angles. When the diffraction order m=1, the larger the wave number σ, the larger the diffraction angle. 10. The large-aperture spatial heterodyne interference imaging method according to claim 6 or 7 or 8, characterized in that, Transverse shear

Optical path difference

Wherein, a represents the horizontal distance between the symmetrical position of the second reflector and the first reflector, L represents the vertical distance between the first blazed grating and the second blazed grating, and θ represents the compound incident The incident angle of light, β ₁ represents the diffraction angle of wavenumber σ ₁ , and β ₂ represents the diffraction angle of σ ₂ .

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