Plane grating spectrometer system based on lens array and aperture filtering

Abstract

The invention discloses a plane grating spectrometer system based on a lens array and pinhole filtering, belongs to the technical field of optical instruments, and aims to solve the problems of complex optical machine design, high coating requirement and high installation and adjustment difficulty in the prior art. In the invention, incident polychromatic light is introduced through an SMA905 optical fiber interface and becomes parallel polychromatic light after passing through an off-axis parabolic mirror, and light with different wavelengths in the parallel polychromatic light is focused at different positions after being converged by a lens array focusing system; light focused at different positions is subjected to spatial filtering through a small hole array filtering system formed by small holes located at different positions, polychromatic light emitted by the small hole array filtering system is collimated by a lens array collimation system, and collimated parallel light enters the surface of a digital micromirror device for channel gating; the light of the selected channel is reflected by the digital micromirror device, then is incident on the plane reflection grating for diffraction light splitting, and then is converged on the linear array detector after passing through the focusing mirror.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical instruments, and particularly relates to a flat grating spectrometer system based on a lens array and small hole filtering. Background Technique

[0002] The commonly used flat grating spectrometers nowadays, as shown in Figure 1 , mainly consist of a light source, an incident slit 1, a collimating mirror 2, a flat grating 3, a focusing mirror 4, a linear array detector 5, a partition-coated filter 6 for filtering out high-order diffraction, corresponding mechanical structures, a data acquisition system, etc. Compared with other spectrometers, the flat grating spectrometer has advantages such as a wider wavelength band coverage range, high resolution, high stability, and high flexibility. In terms of structure, the performance of the flat grating spectrometer can be further optimized by adjusting the focusing system and the collimating system, and it supports multiple detectors and multi-grating switching to meet different experimental requirements. In terms of design, resolution, signal-to-noise ratio, and monochromaticity are important indicators for optimizing the flat grating spectrometer.

[0003] Multilevel diffraction superposition refers to the situation in a flat grating spectrometer where when the grating diffracts, spectra of different orders may appear at the same angle, resulting in the overlap of different wavelengths of light of different orders. Multilevel diffraction superposition will cause spectral measurement errors, reduce the signal-to-noise ratio, and affect subsequent spectral analysis. Therefore, eliminating high-order diffraction is crucial in the application of spectrometers. The main method to solve high-order diffraction nowadays is to add a partition-coated filter 6 at the focal plane of the spectrometer, allowing only light within a specific wavelength range to pass through in a specific area and blocking the light incident in other wavelength bands. Suppressing stray light and high-order diffraction through the filter can effectively improve the spectral resolution and signal-to-noise ratio. However, the partition filter needs to be processed additionally, and different spectrometers need to use partition-coated filters with different parameters, and the opto-mechanical design is relatively complex.

[0004] The spectral splitting of a planar grating spectrometer is mainly determined by the grating equation of the planar grating. The planar grating spectrometer system outputs the light of the target wavelength that satisfies the first order of the grating equation and the light of different wavelengths of higher orders onto the detector simultaneously, so spectral aliasing will occur. For example, when the order used in the spectrometer design is 1, taking the target wavelength of 600 nm as an example, in addition to the 1st order diffracted light of 600 nm appearing at the designated position on the detector, the 2nd order diffracted light of 300 nm and the 3rd order diffracted light of 200 nm will also appear at the convergent focus of 600 nm simultaneously. Therefore, the light at the target wavelength is superimposed with the higher order light of other short wavelengths, and this superimposition will confuse the spectral information and reduce the measurement accuracy. The main current solution is to suppress the short wavelength light by adding a partitioned filter in front of the spectral focal plane. The wider the working wavelength, the higher the requirement for partitioned coating. Different parameters need to be coated at different positions on the filter substrate to meet the requirements. During alignment, it is necessary to ensure the position of the filter in the optical path, which neither blocks the light of the working wavelength nor blocks the higher order diffracted light of other wavelengths. The coating requirement is high and the alignment difficulty is great. Summary of the Invention

[0005] The purpose of the present invention is to propose a planar grating spectrometer system based on a lens array and a small hole filter, which solves the problems of complex optomechanical design, high coating requirements and great alignment difficulty existing in the prior art. The filter mechanism is optimized, the partitioned coating filter is replaced by a front small hole filter, and the small hole filter of different channels is used in cooperation with a digital micromirror device (DMD). By utilizing the region selection and high-frequency switching characteristics of the digital micromirror array, the spectral convergence of different bands is realized at the linear array detector in a time-sharing manner. While eliminating the multi-level spectrum, the spectral resolution is improved.

[0006] To achieve the above purpose, the planar grating spectrometer system based on a lens array and a small hole filter of the present invention includes an SMA905 fiber optic interface, an off-axis parabolic mirror for collimation, a lens array focusing system, a small hole array filter system, a lens array collimation system, a digital micromirror device, a planar reflection grating, a focusing mirror, and a linear array detector; The lens array focusing system includes a plurality of identical focusing lenses. The small hole array filter system includes a plurality of small holes corresponding one-to-one to the plurality of focusing lenses. The plurality of small holes are located at different focusing positions behind the corresponding plurality of focusing lenses. The lens array collimation system includes a plurality of collimation lenses corresponding one-to-one to the plurality of small holes; The incident polychromatic light is introduced through the SMA905 optical fiber interface, and becomes parallel polychromatic light after passing through the off-axis parabolic mirror. Lights of different wavelengths in the parallel polychromatic light are converged by the lens array focusing system and then focused at different positions; the light focused at different positions is spatially filtered by the pinhole array filter system composed of pinholes located at different positions, and the polychromatic light emitted by the pinhole array filter system is collimated by the lens array collimation system, and the collimated parallel light is incident on the surface of the digital micromirror device for channel selection; the light of the selected channel is reflected by the digital micromirror device and incident on the plane reflection grating for diffraction and spectral splitting, and then converged onto the linear array detector after passing through the focusing reflector.

[0007] The focusing lens in the lens array focusing system is a lens with an Abbe number lower than 35.

[0008] The focusing lens in the mirror array focusing system is a double convex lens made of ZF6 material.

[0009] The digital micromirror device individually controls each micromirror thereon to rotate to two working states, a specific positive angle or a specific negative angle, so that the micromirror rotates to a working angle at a specific positive angle and rotates to a non-working angle at a specific negative angle; the digital micromirror device adjusts each micromirror so that the micromirror corresponds to a light-transmitting area of a lens filtering system composed of a front-end lens array focusing system and a pinhole array filtering system, so that the micromirror corresponding to the lens of the selected channel is at a working angle, and the micromirrors corresponding to other channels are at a non-working angle.

[0010] The beneficial effects of the present invention are as follows: the plane grating spectrometer system based on lens array and pinhole filtering of the present invention uses pinhole filtering to reduce high-order diffraction, and performs different optical path gating, and converges light of different bands on the linear array detector in a time-sharing manner, thereby improving the signal-to-noise ratio and spectral resolution. For this purpose, multiple systems are established: a collimation system based on an off-axis parabola, a spectral filtering system based on a combination of lenses and pinholes, a digital micromirror system capable of high-speed channel gating, a plane grating spectrometer, a focusing reflector and a linear array detector. The present invention uses an off-axis parabola as a collimation system to collimate the incident polychromatic light. Since the off-axis parabola is a reflector, there is no chromatic aberration in theory, so better polychromatic collimated light can be formed. The polychromatic collimated light is focused by a lens array focusing system composed of a plurality of identical small lenses. The light emitted after pinhole filtering is polychromatic light with a certain spectral bandwidth, and then passes through the lens array collimation system to become parallel light, and the parallel light is incident on the corresponding area on the surface of the digital micromirror device. The digital micromirror device can adjust the deflection of the micromirrors in the specified area of the reflective surface of the working surface, thereby selecting a specific channel. Light with a certain spectral bandwidth is reflected by the digital micromirror device to the plane grating. After the plane grating splits the light, the spectrum corresponding to the channel selected by the digital micromirror is converged onto the linear array detector through the focusing mirror.

[0011] In the present invention, the dispersive lenses in the lens array focusing system, the small holes in the small hole array filtering system, the lenses in the lens array collimating system, and the respective reflection channels in the digital micromirror device are in one-to-one correspondence. By controlling the deflection of different reflecting mirrors of the digital micromirror device, a certain channel band can be quickly selected as the working band, and the light exiting from the corresponding area of the digital micromirror device is dispersed and focused by the subsequent optical components and finally converges on the linear array detector. Compared with the conventional CT-type plane grating spectrometer, in the present invention, spatial filtering can be performed on different small hole channels, and there is no high-order diffraction of the light reaching the plane grating after being reflected by the digital micromirror device, effectively avoiding the overlap of different-order lights. Therefore, it is not necessary to use a partition-coated filter in the spectrum to eliminate high-order diffraction, thereby reducing the alignment difficulty; moreover, the light in the non-working band is filtered at the small holes, and combined with the channel selection of the digital micromirror system, the light in the non-working band that can enter the plane grating is effectively suppressed, thereby significantly improving the signal-to-noise ratio.

[0012] The present invention establishes a multi-channel spectral filtering system that uses lenses and small holes for filtering, and uses the area selection of the digital micromirror device as channel selection to achieve filtering before spectral dispersion, ensuring that there is no multiple relationship between the spectral bands in each channel. Therefore, it is no longer necessary to use partition filters in the spectrometer system to filter high-order diffracted light, improving the resolution of the system based on plane grating spectroscopy; using a digital microlens device for time-division multiplexing of different channels, most of the energy of the light in the non-working channels will not enter the subsequent spectroscopic system, thereby significantly improving the signal-to-noise ratio of the spectrometer system. Description of the Drawings

[0013] Figure 1 Schematic diagram of the working principle of a plane grating spectrometer in the prior art; Figure 2 Schematic diagram of the working principle of the plane grating spectrometer system based on lens array and small hole filtering of the present invention; Figure 3 Schematic diagram of the chromatic aberration of the focusing lens in the present invention; Figure 4 Front view schematic diagram of the lens array focusing system in the present invention; Figure 5 Side view schematic diagram of the lens array focusing system in the present invention; Figure 6 Front view schematic diagram of the digital micromirror device in the present invention; Figure 7 Side view schematic diagram of the digital micromirror device in the present invention; Figure 8 Intercept of the back surface of the focusing lens for different wavelengths from 400nm to 1000nm in the present invention; Figure 9Schematic diagram of different wavelength lights passing through the small hole at the working wavelength in the present invention; Figure 10 Energy ratio of each wavelength passing through when the position of the third small hole coincides with the focusing position of the 570nm wavelength light in the present invention; Figure 11 Energy ratio of each wavelength passing through when the position of the seventh small hole coincides with the focusing position of the 830nm wavelength light in the present invention; Wherein: 1. Pre - slit, 2. Collimating mirror, 3. Plane grating, 4. Focusing mirror, 5. Linear array detector, 6. Partitioned coating filter, 7. SMA905 fiber optic interface, 8. Off - axis parabolic mirror for collimation, 9. Lens array focusing system, 901. First focusing lens, 902. Second focusing lens, 903. Third focusing lens, 904. Fourth focusing lens, 905. Fifth focusing lens, 906. Sixth focusing lens, 907. Seventh focusing lens, 908. Eighth focusing lens, 909. Ninth focusing lens, 10. Small - hole array filtering system, 1001. First small hole, 1002. Second small hole, 1003. Third small hole, 1004. Fourth small hole, 1005. Fifth small hole, 1006. Sixth small hole, 1007. Seventh small hole, 1008. Eighth small hole, 1009. Ninth small hole, 11. Lens array collimation system, 12. Digital micromirror device, 13. Plane reflection grating, 14. Focusing reflector. Detailed implementation mode

[0014] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0015] See Figure 2 , the plane grating spectrometer system based on lens array and small - hole filtering of the present invention includes SMA905 fiber optic interface 7, off - axis parabolic mirror 8 for collimation, lens array focusing system 9, small - hole array filtering system 10, lens array collimation system 11, digital micromirror device 12, plane reflection grating 13, focusing reflector 14, and linear array detector 5; The lens array focusing system 9 includes a plurality of identical focusing lenses, the small - hole array filtering system includes a plurality of small holes corresponding one - to - one to the plurality of focusing lenses, the plurality of small holes are located at different focusing positions behind the corresponding plurality of focusing lenses, and the lens array collimation system 11 includes a plurality of collimating lenses corresponding one - to - one to the plurality of small holes; the focusing lenses in the lens array focusing system are selected as lenses with an Abbe number less than 35; The incident polychromatic light is introduced through the SMA905 fiber optic interface 7 and becomes parallel polychromatic light after passing through the off-axis parabolic mirror. The reason for choosing the off-axis parabolic mirror for collimation is that the off-axis parabolic mirror theoretically does not introduce chromatic aberration, and relatively ideal parallel polychromatic light can be obtained. The parallel polychromatic light converges after passing through the lens array focusing system 9. The focusing lens is a high-dispersion lens. Due to the axial chromatic aberration of the lens, the focusing positions of lights with different wavelengths are different after passing through the lens array focusing system 9. Identical small holes equal in number to the lenses are respectively placed at the focusing positions of the working wavelengths of different channels. The small holes at different positions form the small hole array filtering system 10. After the light exits from the small hole array filtering system 10, due to the spatial filtering effect of the small holes, the spectral bandwidth of the exiting polychromatic light becomes smaller. Therefore, only the light of the corresponding wavelength band in different channels can pass through and enter the subsequent optical path; the light filtered by the small holes is collimated by the lens array collimation system 11. The collimated parallel light is incident on the surface of the digital micromirror device 12. The digital micromirror device 12 can control the micromirrors on it to rotate to two working states of +12° or -12°. It is designed that the rotation of the micromirror by +12° is the working angle, and the micromirror at -12° is the non-working angle. The digital micromirror device 12 can make any micromirror be in the working angle or the non-working angle through parameter setting; the micromirrors are corresponded to the light passing areas of the front-end lens filtering system, so that the micromirrors corresponding to the lens groups of the selected channels are in the working angle, and the micromirrors corresponding to other channels are in the non-working angle, thus realizing the channel selection. The light of the selected channel is reflected by the digital micromirror device 12 and then incident on the planar reflection grating 13 for diffraction spectroscopy, and converges on the linear array detector after passing through the focusing system.

[0016] See Figures 3 - 5The lens array focusing system 9 established in the present invention is composed of a plurality of identical focusing lenses, and utilizes the characteristic of axial chromatic aberration of the lens, so that different wavelengths of light are focused at different positions after passing through the lens array focusing system 9. For this purpose, a double convex lens made of ZF6 material is selected, which is characterized by large axial chromatic aberration, and the lateral intercepts of the focusing positions of different wavelengths of light after passing through the focusing lens are easy to distinguish. Each pinhole forms a pinhole array filter system 10 to achieve spatial multi-channel filtering. In the pinhole array filter system 10, each pinhole is at a different distance from the corresponding small lens in the lens array focusing system 9. The distance between the corresponding pinhole and the small lens depends on the position of the image formed by the target wavelength light after passing through the lens. For a single focusing lens in the lens array focusing system 9, only the light of the central wavelength represented by the coincidence of the focal position and the pinhole position can pass through the pinhole. Light of other wavelengths is a diffuse spot at the pinhole position. The farther away from the pinhole position, the more obvious the diffusion. Therefore, a single pinhole becomes a small filter. Each pinhole can effectively filter non-working wavelength light as an optical path channel. A lens array collimation system 11 is placed behind the pinhole array filter system 10. The lens array collimation system 11 includes a plurality of identical collimating lenses, which are symmetrical with the corresponding focusing lenses in the front-end lens focusing system about the pinhole. The purpose is to collimate the light emitted from the pinhole until the parallel light emitted from the lens array collimation system 11 is incident on the surface of the digital micromirror device 12, see Figure 6 and Figure 7 The digital micromirror device 12 is a micro-electromechanical system whose surface is composed of multiple small reflective mirrors. Each mirror can independently deflect a positive or negative angle. In this embodiment, +12° or -12° is selected. At the same time, the deflection of one or more small reflective mirrors can be controlled. Due to the filtering effect of the pinhole array system and the deflection state of the specified reflective surface of the digital micromirror device 12, other high-order diffracted lights are effectively removed at the output position after the plane reflection grating 13 is diffracted. Therefore, in the present invention, the gating of different optical paths can be achieved by controlling the deflection of the small reflective mirrors in different areas of the digital micromirror device 12, thereby achieving the emission of light of different working wavelengths. Since the digital micromirror device 12 can perform gating of different areas in time-sharing, the light in different optical path channels can be converged on the linear array detector 5 in time-sharing. Compared with the ordinary grating spectrometer, the number of spectral channels is increased by the lens array system, and the gating of different optical paths is achieved by using the micromirror array device. Without using a partition filter, the time-sharing multiplexing of the detector is achieved, and the spectral resolution and signal-to-noise ratio of the spectrometer system are improved.

[0017] In the present invention, the focusing lens in the lens array focusing system 9 can be replaced with lenses made of other materials, having other focal lengths, other apertures, and other thicknesses. The main purpose is to make the intercepts of the focusing positions of different wavelengths more obvious and to make the array combination of multiple focusing lenses match the aperture of the off-axis parabolic mirror at the front end. The collimating lens in the lens array collimating system 11 can also be replaced with lenses made of other materials, having other focal lengths, and other apertures. The main purpose is to make the collimating lens match the focal length of the light emitted from the small hole at the front end.

[0018] Based on the principle of axial chromatic aberration of a single lens, the present invention establishes a lens array focusing system 9 composed of multiple focusing lenses to achieve the convergence of different wavelengths. Small holes are placed at the convergence positions of different wavelengths as filters, and a small hole array filtering system 10 composed of multiple small holes is established, so that each small hole can only pass the light of the wavelength corresponding to the coincidence of the focusing position and the position of its own small hole. The outgoing wavelength band of each small hole is highly concentrated. At the same time, a digital micromirror device 12 is introduced to select different optical paths, ensuring that the optical bandwidth incident on the planar reflection grating 13 is narrow, avoiding the influence of high-order diffracted light. After diffraction by the planar reflection grating 13, no high-order diffracted light enters the linear array detector 5, and the small hole filtering will filter most of the light in the bands of non-selected channels, thereby effectively improving the signal-to-noise ratio. Since the wavelength band of a single channel is smaller than the overall effective working wavelength band of the system, the linear array detector 5 effectively performs time-division multiplexing. Therefore, the spectral resolution of the system is proportional to the number of channels and is effectively improved.

[0019] In this embodiment, taking the 3×3 lens array focusing system 9 as an example, the system has a total of 9 focusing lenses, namely the first focusing lens 901, the second focusing lens 902, the third focusing lens 903, the fourth focusing lens 904, the fifth focusing lens 905, the sixth focusing lens 906, the seventh focusing lens 907, the eighth focusing lens 908, and the ninth focusing lens 909. The parallel polychromatic light passing through this system can be regarded as a set of 9 optical path channels. The materials of the respective focusing lenses in the lens array focusing system 9 are selected as high-dispersion lenses of ZF6. According to the Figure 3 axial dispersion principle shown, when light of different wavelengths passes through a high-dispersion lens, the focusing positions of light rays of different wavelengths on the central optical axis of the lens are different. Taking the wavelength range of 400 - 1000 nm as an example, the materials of the 9 small lenses in the lens array focusing system 9 are ZF6, the lens thickness is 3 mm, the lens diameter is 12 mm, and the focal length is 50 mm. When light with a wavelength of 400 - 1000 nm passes through the lens, the focusing positions of light of different wavelengths from the rear surface of the lens are as Figure 8As shown in the figure. After the polychromatic light passes through the lens array focusing system 9, the position where the light with a wavelength of 400 nm converges is 61.41 mm away from the rear surface of the lens, and the light with a wavelength of 1000 nm is focused at 68.10 mm from the rear surface. The lateral intercept within the wavelength band is 6.69 mm, and the focal length variation is 6.69 mm.

[0020] Nine small holes are placed one by one behind the nine lenses in the lens array focusing system 9. The nine small holes are the first small hole 1001, the second small hole 1002, the third small hole 1003, the fourth small hole 1004, the fifth small hole 1005, the sixth small hole 1006, the seventh small hole 1007, the eighth small hole 1008, and the ninth small hole 1009, which are used to filter the light with non-working wavelengths and improve the signal-to-noise ratio. In this embodiment, the wavelength band is 400 - 1000 nm, and small holes are placed behind the 3×3 lens array focusing system 9. The central wavelengths of the nine focusing lenses are 440 nm, 505 nm, 570 nm, 635 nm, 700 nm, 765 nm, 830 nm, 895 nm, and 960 nm respectively, and the spectral bandwidth is 80 nm. The position of the first small hole 1001 is the focal position of the first focusing lens 901 at the central wavelength of 440 nm, the position of the second small hole 1002 is the focal position of the second focusing lens 902 at the central wavelength of 505 nm, and so on. The position of the ninth small hole 1009 is the focal position of the ninth focusing lens 909 at the central wavelength of 960 nm. Taking the third focusing lens 903 in the lens array focusing system 9 and the corresponding third small hole 1003 in the small hole array filtering system 10 as an example, when the parallel polychromatic light passes through the third focusing lens 903, since the position where the third small hole 1003 is placed coincides with the focusing position of the 570 nm wavelength light, the 570 nm light will almost completely pass through the third small hole 1003, and the light of the remaining wavelengths will be greatly lost due to the deviation between the focusing position and the position of the third small hole 1003. Thus, the light passing through the third small hole 1003 can be ignored. As Figure 9 shown in the figure, when the working wavelength is selected as 570 nm, corresponding to the third focusing lens 903 in the lens array focusing system 9 and the third small hole 1003 in the small hole array filtering system 10, a third small hole 1003 with a diameter of 0.03 mm is set at the focal point of the 570 nm wavelength. From Figure 3 it can be known that the rear surface intercept of the third focusing lens 903 is 65.52 mm. Due to the different focal points of different wavelengths, the light of other wavelengths forms a diffuse spot at the third small hole 1003. For the light with a wavelength of λ + Δλ, referring to formula (1), the diameter of its diffuse spot at the third small hole 1003 is: (1) Referring to formula (2), the inclination angle of the light with a wavelength of λ + Δλ relative to the horizontal axis is: (2) Refer to Equation (3), substitute Equation (2) into Equation (1), the diameter of the light diffusion spot with wavelength λ + Δλ is:[[]] (3) Where: λ is the wavelength of the light with the focus at the position of the third small hole 1003; D is the lens aperture, taking 12 mm; is the focus offset; is the focal length corresponding to the wavelength λ.

[0021] Assuming that the light intensity is evenly distributed, refer to Equation (4), the energy ratio passing through the third small hole 1003 is:[[]] (4) Where: is the diameter of the small hole at the focus of the light with wavelength λ, taking 0.03 mm here.

[0022] The energy passing rate of light with different wavelengths through the third small hole 1003 is as Figure 10 shown. It can be seen that the wavelength range in which more light beams can pass through the third small hole 1003 is about 530 - 610 nm. For the wavelengths that differ greatly from the target wavelength of 570 nm, the energy passing through the third small hole 1003 is very small. The farther away from 570 nm, the lower the passing rate of the light. In this embodiment, the spatial filter composed of the third focusing lens 903 and the third small hole 1003 can effectively filter the light with non-working wavelengths. Therefore, the spatial filters composed of the 9 focusing lenses and the corresponding 9 small holes in the 3×3 array can all effectively filter the non-working wavelength light in their respective channels, improving the signal-to-noise ratio.

[0023] Taking the wavelength of 830 nm as an example again, the position where the seventh small hole 1007 is placed is at the position where the light with a wavelength of 830 nm converges after passing through the seventh focusing lens 907. For a traditional planar grating spectrometer, when the first-order diffracted light of 830 nm after grating spectroscopy also contains the second-order diffracted light of 415 nm, there is spectral aliasing. In the present invention, by placing the small reflection mirror area of the digital micromirror device 12 corresponding to the seventh focusing lens 907 and the seventh small hole 1007 in the working deflection state and other areas in the non-working deflection state, the light emitted from the seventh small hole 1007 is collimated by the lens array collimation system 11 and then reaches the digital micromirror device 12 for reflection. When reaching the planar reflection grating 13, according to Figure 11From the energy ratio of each wavelength passing through the seventh small hole 1007, it can be seen that the spectral bandwidth that can effectively pass through the seventh small hole 1007 is 790 - 870 nm. When the 415 nm light of high-order diffraction passes through the seventh small hole 1007, the transmittance is as low as 0.1%, and the transmittance is negligible compared to the target wavelength of 830 nm. Therefore, after the parallel polychromatic light passes through the seventh focusing lens 907 of the lens array group focusing system, the seventh small hole 1007 of the small hole array filter system 10, the corresponding collimating lens of the lens array collimating system 11, and the corresponding small reflecting mirror surface of the digital micromirror device 12 in sequence, when it reaches the plane reflection grating 13, most of the high-order diffracted light of short waves in non-current channels has been filtered due to the filtering of the seventh small hole 1007.

[0024] After the light wave filtered by the small hole is collimated by the lens array collimating system 11, the spectral bandwidth is narrow, which is 80 nm. Then, the small reflecting mirror surface area of the digital micromirror device 12 corresponding to the small hole is selected and gated to be in the deflection working state. Only the light in the gated channel can be dispersed and spectroscopically analyzed by the subsequent system, and finally converge on the linear array detector 5.

[0025] For each small reflecting mirror surface of the digital micromirror device 12, a certain area in the digital micromirror device 12 can be selectively deflected to the working state to match the front-end lens and the small hole to form a spatial filter, so that the light of the wavelength corresponding to the specified channel enters the subsequent spectroscopic system. Due to the filtering effect, the energy of the other light entering the subsequent system can be ignored. In the present invention, the 3×3 array lens system and the 3×3 array small hole system can set the channels of the spectrometer to 9 channels. The light of each channel can be detected by the linear array detector 5 in a time-sharing manner, so that the spectral resolution can be increased by 9 times. And due to the filtering effect, the light of non-working wavelengths basically does not enter the subsequent system, so the signal-to-noise ratio of the spectrometer is significantly improved.

Claims

1. A planar grating spectrometer system based on a lens array and a pinhole filter, characterized in that, It includes an SMA905 fiber optic interface (7), an off-axis parabolic mirror for collimation (8), a lens array focusing system (9), a small hole array filtering system (10), a lens array collimation system (11), a digital micromirror device (12), a planar reflection grating (13), a focusing mirror (14), and a linear array detector (5); The lens array focusing system (9) includes a plurality of identical focusing lenses. The small hole array filtering system includes a plurality of small holes corresponding one-to-one to the plurality of focusing lenses. The plurality of small holes are located at different focusing positions behind the corresponding plurality of focusing lenses. The lens array collimation system (11) includes a plurality of collimating lenses corresponding one-to-one to the plurality of small holes; The incident polychromatic light is introduced through the SMA905 fiber optic interface (7) and becomes parallel polychromatic light after passing through the off-axis parabolic mirror. The light of different wavelengths in the parallel polychromatic light is focused at different positions after being converged by the lens array focusing system (9); The light focused at different positions is spatially filtered by the small hole array filtering system (10) composed of small holes located at different positions. The polychromatic light emitted from the small hole array filtering system (10) is collimated by the lens array collimation system (11). The collimated parallel light is incident on the surface of the digital micromirror device (12) for channel gating; The light of the selected channel is reflected by the digital micromirror device (12) and then incident on the planar reflection grating (13) for diffraction spectroscopy, and then converged onto the linear array detector (5) after passing through the focusing mirror (14).

2. The planar grating spectrometer system based on a lens array and pinhole filtering according to claim 1, wherein The focusing lenses in the lens array focusing system (9) are selected as lenses with an Abbe number lower than 35.

3. The planar grating spectrometer system based on a lens array and small hole filtering according to claim 2, wherein The focusing lenses in the mirror array focusing system are biconvex lenses made of ZF6 material.

4. The planar grating spectrometer system based on a lens array and a pinhole filter according to claim 1, characterized in that, The digital micromirror device (12) individually controls each micromirror on it to rotate to two working states: a specific positive angle or a specific negative angle. Rotating a specific positive angle is the working angle, and rotating a specific negative angle is the non-working angle; The digital micromirror device (12) adjusts each micromirror so that the micromirror corresponds to the light passing area of the lens filtering system composed of the front-end lens array focusing system (9) and the small hole array filtering system (10), so that the micromirrors corresponding to the lenses of the selected channel are in the working angle, and the micromirrors corresponding to other channels are in the non-working angle.

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