Plane grating spectrometer system based on lens array and pinhole filter

Abstract

The present invention discloses a plane grating spectrometer system based on a lens array and pinhole filtering, belonging to the field of optical instrument technology. The purpose is to solve the problems of complex optical and mechanical design, high coating requirements, and difficult assembly and adjustment in the prior art. In the present invention, incident polychromatic light is introduced through an SMA905 optical fiber interface, passes through an off-axis parabolic mirror, and becomes parallel polychromatic light. Light of different wavelengths in the parallel polychromatic light is converged by a lens array focusing system and then focused at different positions. The light focused at different positions is spatially filtered by a pinhole array filter system composed of pinholes located at different positions. The polychromatic light emitted by the pinhole array filter system is collimated by a lens array collimation system. The collimated parallel light is incident on the surface of a digital micromirror device for channel selection. Light from the selected channel is reflected by the digital micromirror device and incident on a plane reflection grating for diffraction and spectral separation. The light is then converged onto a linear array detector after passing through a focusing reflector.

Description

Technical Field

[0001] The invention belongs to the technical field of optical instruments, and in particular relates to a plane grating spectrometer system based on a lens array and pinhole filtering. Background Art

[0002] The most common plane grating spectrometer today is Figure 1 It is mainly composed of a light source, an incident slit 1, a collimating mirror 2, a plane grating 3, a focusing mirror 4, a linear array detector 5, a partitioned coated filter 6 for filtering out high-order diffraction, the corresponding mechanical structure and data acquisition system. Compared with other spectrometers, the plane grating spectrometer has the advantages of wider band coverage, high resolution, high stability and high flexibility. In terms of structure, the plane grating spectrometer can also further optimize performance by adjusting the focusing system and collimation system, and support multiple detectors and multi-grating switching to meet different experimental needs. In terms of design, resolution, signal-to-noise ratio and monochromaticity are important indicators for optimizing the plane grating spectrometer.

[0003] Multi-order diffraction superposition means that in a plane grating spectrometer, 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. Multi-order 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 today is to add a partitioned coated filter 6 at the focal plane of the spectrometer, which only allows light of a specific wavelength range to pass through in a specific area and blocks light incident from other bands. Suppressing stray light and high-order diffraction through filters can effectively improve spectral resolution and signal-to-noise ratio, but the partitioned filters require additional processing. Different spectrometers require the use of partitioned coated filters with different parameters, and the optical and mechanical design is relatively complex.

[0004] The spectral splitting of a plane grating spectrometer is mainly determined by the grating equation of the plane grating. The plane grating spectrometer system will output the first-order target wavelength light that satisfies the grating equation and the higher-order light of different wavelengths on the detector at the same time, so there will be spectral aliasing. For example, the order used in the design of the spectrometer is 1. Taking the target wavelength as 600nm as an example, in addition to the 1st-order diffraction light of 600nm appearing at the specified position of the detector, the 2nd-order diffraction light of 300nm and the 3rd-order diffraction light of 200nm will also appear at the convergence focus of 600nm. Therefore, the light at the target wavelength is superimposed on other higher-order lights of shorter wavelengths. This superposition will confuse the spectral information and reduce the measurement accuracy. The main solution at present is to suppress the short-wavelength light by adding a partition filter in front of the spectral focal plane. The wider the working wavelength, the higher the requirements for zone coating. Different parameters need to be coated at different positions on the filter substrate to meet the requirements. During installation and adjustment, the position of the filter in the optical path needs to be ensured, which neither blocks the light of the working wavelength nor blocks the higher-order diffracted light of other wavelengths. The coating requirements are high and the installation and adjustment are difficult. Summary of the Invention

[0005] The present invention aims to propose a planar grating spectrometer system based on a lens array and pinhole filtering, addressing the existing challenges of complex optical and mechanical design, high coating requirements, and difficult assembly and adjustment. The system optimizes the filtering mechanism, replacing the zoned coated filter with a pre-pinhole filter. By utilizing pinhole filters of different channels in conjunction with a digital micromirror array (DMD), and leveraging the regional gating and high-frequency switching capabilities of the DMD, the system achieves time-sharing convergence of spectra from different wavelength bands at the linear array detector, eliminating multi-level spectra while improving spectral resolution.

[0006] To achieve the above-mentioned object, the plane grating spectrometer system based on lens array and pinhole filtering of the present invention comprises an SMA905 optical fiber interface, an off-axis parabolic mirror for collimation, a lens array focusing system, a pinhole array filtering system, a lens array collimating system, a digital micromirror device, a plane reflection grating, a focusing reflector, and a linear array detector;

[0007] The lens array focusing system includes a plurality of identical focusing lenses, the pinhole array filtering system includes a plurality of pinholes corresponding one-to-one to the plurality of focusing lenses, the plurality of pinholes being located at different focusing positions behind the corresponding plurality of focusing lenses, and the lens array collimating system includes a plurality of collimating lenses corresponding one-to-one to the plurality of pinholes;

[0008] Incident polychromatic light is introduced through the SMA905 fiber optic interface and becomes parallel polychromatic light after passing through the off-axis parabolic mirror. Light of different wavelengths in the parallel polychromatic light is 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. The polychromatic light emitted by the pinhole array filter system is collimated by the lens array collimation system. 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 separation, and then converged onto the linear array detector after passing through the focusing reflector.

[0009] The focusing lens in the lens array focusing system is a lens with an Abbe number lower than 35.

[0010] The focusing lens in the mirror array focusing system is a double convex lens made of ZF6 material.

[0011] The digital micromirror device individually controls each micromirror thereon to rotate to two working states, a specific positive angle and a specific negative angle, so that the micromirror rotates at a specific positive angle as a working angle and rotates at a specific negative angle as a non-working angle; the digital micromirror device adjusts each micromirror so that the micromirror corresponds to the light-transmitting area of the lens filtering system composed of the front-end lens array focusing system and the 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.

[0012] The beneficial effects of the present invention are as follows: the plane grating spectrometer system based on a lens array and pinhole filtering uses pinhole filtering to reduce high-order diffraction and performs different optical path gating, converging light from different wavelength bands onto a linear array detector in a time-sharing manner, thereby improving the signal-to-noise ratio and spectral resolution. To this end, multiple systems have been established: a collimation system based on an off-axis parabolic mirror, a spectral filtering system based on a lens and pinhole combination, 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 parabolic mirror as a collimation system to collimate the incident polychromatic light. Since the off-axis parabolic mirror is a reflector, theoretically, it has no chromatic aberration and can therefore produce relatively good polychromatic collimated light. The polychromatic collimated light is focused by a lens array focusing system composed of multiple identical small lenses. The light emitted after pinhole filtering is polychromatic light with a certain spectral bandwidth. It then passes through the lens array collimation system to become parallel light, which 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 a 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 a focusing mirror.

[0013] In the present invention, the dispersion lenses in the lens array focusing system, the pinholes in the pinhole array filtering system, the lenses in the lens array collimation system, and the individual reflective channels in the digital micromirror device all correspond to each other. The deflection of the different reflective mirror surfaces of the digital micromirror device can be controlled to quickly select the wavelength band of a particular channel as the operating wavelength band. Light emitted from the corresponding region of the digital micromirror device is subsequently dispersed and focused, ultimately converging on a linear array detector. Compared to conventional CT-type plane grating spectrometers, the present invention allows spatial filtering to be performed on each of the different pinhole channels. Light reflected by the digital micromirror device and reaching the plane grating exhibits no higher-order diffraction, effectively preventing overlap of different-order light. Therefore, no zoned coated filters are required in the spectrum to eliminate higher-order diffraction, thereby reducing the difficulty of assembly and adjustment. Furthermore, light in non-operating wavelengths is filtered at the pinholes. Combined with the channel selection of the digital micromirror system, light in the non-operating wavelength band that could enter the plane grating is effectively suppressed, significantly improving the signal-to-noise ratio.

[0014] The present invention establishes a multi-channel spectral filtering system using lenses and pinholes for filtering, utilizes the regional selection of a digital micromirror device as channel selection, realizes filtering before spectral dispersion, ensures that the spectral bands in each channel do not have a multiple relationship, and thus eliminates the need to use partitioned filters in the spectrometer system to filter high-order diffracted light, thereby improving the resolution of the system based on plane grating spectroscopy; uses a digital microlens device for time-sharing multiplexing of different channels, and most of the energy of light in non-working channels does not enter the subsequent spectroscopic system, thereby significantly improving the signal-to-noise ratio of the spectrometer system. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the working principle of a plane grating spectrometer in the prior art;

[0016] Figure 2 This is a working principle diagram of the plane grating spectrometer system based on lens array and pinhole filtering of the present invention;

[0017] Figure 3 Schematic diagram of chromatic aberration of the focusing lens in the present invention;

[0018] Figure 4 This is a front view schematic diagram of the lens array focusing system of the present invention;

[0019] Figure 5 Schematic side view of the lens array focusing system of the present invention;

[0020] Figure 6 This is a front view of the digital micromirror device in the present invention;

[0021] Figure 7 A side view of a digital micromirror device in the present invention;

[0022] Figure 8 is the intercept distance of the rear surface of the focusing lens at different wavelengths of 400nm-1000nm in the present invention;

[0023] Figure 9 Schematic diagram of light of different wavelengths passing through a small hole at the working wavelength in the present invention;

[0024] Figure 10 The energy ratio of each wavelength passing through when the position of the third pinhole in the present invention coincides with the focus position of the 570nm wavelength light;

[0025] Figure 11 is the energy ratio of each wavelength passing through when the position of the seventh aperture in the present invention coincides with the focus position of the 830nm wavelength light;

[0026] Among them: 1. Pre-slit, 2. Collimating lens, 3. Plane grating, 4. Focusing lens, 5. Linear array detector, 6. Partitioned coated 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, pinhole array filtering system, 1001, first pinhole, 1002, second pinhole, 1003, third pinhole, 1004, fourth pinhole, 1005, fifth pinhole, 1006, sixth pinhole, 1007, seventh pinhole, 1008, eighth pinhole, 1009, ninth pinhole, 11, lens array collimation system, 12, digital micromirror device, 13, plane reflection grating, 14, focusing mirror. DETAILED DESCRIPTION

[0027] The embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0028] See also Figure 2 The plane grating spectrometer system based on lens array and pinhole filtering of the present invention includes an SMA905 optical fiber interface 7, an off-axis parabolic mirror 8 for collimation, a lens array focusing system 9, a pinhole array filtering system 10, a lens array collimating system 11, a digital micromirror device 12, a plane reflection grating 13, a focusing reflector 14, and a linear array detector 5;

[0029] The lens array focusing system 9 includes a plurality of identical focusing lenses, the pinhole array filtering system includes a plurality of pinholes corresponding one-to-one to the plurality of focusing lenses, the plurality of pinholes being located at different focusing positions behind the corresponding plurality of focusing lenses, and the lens array collimating system 11 includes a plurality of collimating lenses corresponding one-to-one to the plurality of pinholes; the focusing lenses in the lens array focusing system are lenses having an Abbe number lower than 35;

[0030] The incident polychromatic light is introduced through the SMA905 optical fiber interface 7, and becomes parallel polychromatic light after passing through the off-axis parabolic mirror. The reason for selecting the off-axis parabolic mirror as the collimator is that the off-axis parabolic mirror theoretically does not introduce chromatic aberration, and can obtain relatively ideal parallel polychromatic light. The parallel polychromatic light is converged 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 focus positions of light of different wavelengths after passing through the lens array focusing system 9 are different. The same pinholes with the same number of lenses are placed at the focus positions of the working wavelengths of different channels. The pinholes at different positions form a pinhole array filter system 10. After the light is emitted from the pinhole array filter system 10, due to the spatial filtering effect of the pinholes, the spectral bandwidth of the emitted polychromatic light becomes smaller. Therefore, only the light of the corresponding wavelength bands in different channels can pass through and enter the subsequent optical path. The light after the pinhole filtering is emitted by the lens array. The collimation system 11 performs collimation, and 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: +12° or -12°. The micromirrors are designed to rotate at a +12° angle as the working angle, and at a -12° angle as the non-working angle. The digital micromirror device 12 can set any micromirror to an operating angle or a non-working angle by parameter setting. The micromirrors are matched with the light-passing areas of the front-end lens filter system, so that the micromirrors corresponding to the lens group of the selected channel are at the working angle, and the micromirrors corresponding to the other channels are at the non-working angle, thereby achieving channel selection. The light from the selected channel is reflected by the digital micromirror device 12 and incident on the plane reflection grating 13 for diffraction and spectral separation. After passing through the focusing system, it is focused onto the linear array detector.

[0031] See also Figure 3-Figure 5The lens array focusing system 9 constructed in the present invention is composed of multiple identical focusing lenses. This utilizes the axial chromatic aberration characteristic of lenses, resulting in different wavelengths of light being focused at different locations after passing through the lens array focusing system 9. For this purpose, biconvex lenses made of ZF6 are used, which feature large axial chromatic aberration, making the lateral intercepts of the focus positions of light of different wavelengths easily distinguishable after passing through the focusing lenses. Each pinhole forms a pinhole array filtering system 10 to achieve spatial multi-channel filtering. In the pinhole array filtering 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 after the target wavelength light passes 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 focus 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, as an optical path channel, can effectively filter light of non-working wavelengths. A lens array collimating system 11 is placed after the pinhole array filtering system 10. The lens array collimating system 11 includes multiple identical collimating lenses, which are symmetrical with the corresponding focusing lenses in the front-end lens focusing system about the pinhole. Its purpose is to collimate the light emitted from the pinhole. The parallel light emitted from the lens array collimating 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 (MEMS) whose surface is composed of multiple small reflective mirrors. Each mirror can independently deflect a certain positive or negative angle. In this embodiment, +12° or -12° is selected. The deflection of one or more small reflective mirrors can be controlled simultaneously. Due to the filtering effect of the pinhole array system and the deflection state of the designated reflective surface of the digital micromirror device 12, other higher-order diffracted light is effectively removed at the output position after diffraction by the plane reflection grating 13. Therefore, in the present invention, different optical paths can be selected 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 operating wavelengths. Because the digital micromirror device 12 can select different areas in a time-sharing manner, light from different optical path channels can be converged on the linear array detector 5 in a time-sharing manner. Compared with ordinary grating spectrometers, the number of spectral channels is increased by the lens array system. The use of the micromirror array device to select different optical paths achieves time-sharing multiplexing of the detector without using a partitioned filter, and improves the spectral resolution and signal-to-noise ratio of the spectrometer system.

[0032] The focusing lens in the lens array focusing system 9 of the present invention can be replaced with lenses of other materials, focal lengths, apertures, and thicknesses. This is primarily to make the intercepts of the focus positions of different wavelengths more distinct and to match the array combination of multiple focusing lenses with 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 of other materials, focal lengths, and apertures. This is primarily to match the focal length of the collimating lens with the focal length of the light emitted from the front aperture.

[0033] Based on the principle of axial chromatic aberration of a single lens, the present invention establishes a lens array focusing system 9, which integrates multiple focusing lenses to achieve convergence of different wavelengths. Pinholes are placed at the different wavelength convergence positions as filters, creating a pinhole array filtering system 10, which integrates multiple pinholes. Each pinhole can only pass light of the wavelength corresponding to the overlap between the focus position and the pinhole position. The output wavelength band of each pinhole is highly concentrated. A digital micromirror device 12 is introduced to select different optical paths, ensuring that the bandwidth of light incident on the planar reflection grating 13 is narrow, avoiding the influence of higher-order diffracted light. After diffraction by the planar reflection grating 13, no higher-order diffracted light enters the linear array detector 5. Pinhole filtering also filters out most of the light in the wavelength band of the non-selected channel, effectively improving the signal-to-noise ratio. Because the wavelength band of a single channel is smaller than the overall effective operating 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, effectively improving it.

[0034] In this embodiment, taking a 3×3 lens array focusing system 9 as an example, the system has a total of 9 focusing lenses, namely a first focusing lens 901, a second focusing lens 902, a third focusing lens 903, a fourth focusing lens 904, a fifth focusing lens 905, a sixth focusing lens 906, a seventh focusing lens 907, an eighth focusing lens 908, and a ninth focusing lens 909. Parallel polychromatic light passing through the system can be regarded as a collection of 9 optical paths. Each focusing lens in the lens array focusing system 9 is made of a high dispersion lens of ZF6. According to the following example, Figure 3 The principle of axial dispersion is shown in the figure. When light of different wavelengths passes through a high dispersion lens, the positions of the different wavelengths of light focused on the central optical axis of the lens are different. Taking the wavelength of 400-1000nm as an example, the material used for the 9 small lenses in the lens array focusing system 9 is ZF6, the lens thickness is 3mm, the lens diameter is 12mm, and the focal length is 50mm. When the wavelength of 400-1000nm passes through the lens, the position of the focus of the different wavelengths of light is different from the position of the rear surface of the lens. 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 from the rear surface of the lens, and the light with a wavelength of 1000 nm focuses at 68.10 mm from the rear surface. The lateral intercept within the wavelength band is 6.69 mm, and the focal length change is 6.69 mm.

[0035] Behind each of the nine lenses in the lens array focusing system 9 are nine corresponding apertures. These apertures are designated as a first aperture 1001, a second aperture 1002, a third aperture 1003, a fourth aperture 1004, a fifth aperture 1005, a sixth aperture 1006, a seventh aperture 1007, an eighth aperture 1008, and a ninth aperture 1009. These apertures are used to filter light at non-operating wavelengths and improve the signal-to-noise ratio. In this embodiment, the wavelength range is 400-1000 nm. A small aperture is placed behind each of the 3×3 lens array focusing system 9. The center 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, with a spectral bandwidth of 80 nm. The position of the first pinhole 1001 is the focal position of the first focusing lens 901 at a central wavelength of 440nm, the position of the second pinhole 1002 is the focal position of the second focusing lens 902 at a central wavelength of 505nm, and so on. The position of the ninth pinhole 1009 is the focal position of the ninth focusing lens 909 at a central wavelength of 960nm. Taking the third focusing lens 903 in the lens array focusing system 9 and the corresponding third pinhole 1003 in the pinhole array filtering system 10 as an example, when the parallel polychromatic light passes through the third focusing lens 903, since the position of the third pinhole 1003 coincides with the position where the 570nm wavelength light is focused, the 570nm wavelength light will almost completely pass through the third pinhole 1003, and the remaining wavelengths will be lost in large quantities due to the deviation between the focusing position and the position of the third pinhole 1003, and the light passing through the third pinhole 1003 can be ignored. Figure 9 As shown, when the working wavelength is selected as 570nm, the third focusing lens 903 in the lens array focusing system 9 and the third pinhole 1003 in the pinhole array filtering system 10 are corresponding. The third pinhole 1003 with a diameter of 0.03mm is set at the focus of the 570nm wavelength. Figure 3 It can be seen that the intercept of the rear surface of the third focusing lens 903 is 65.52 mm. Due to the different focal points of different wavelengths, light of other wavelengths forms a diffuse spot at the third aperture 1003. For light with a wavelength of λ+Δλ, refer to formula (1). The diameter of the diffuse spot at the third aperture 1003 is for:

[0036] (one)

[0037] Refer to formula (2), the inclination angle of light with wavelength λ+Δλ relative to the horizontal axis for:

[0038] (two)

[0039] Refer to formula (3), substitute formula (2) into formula (1), and the diffuse spot diameter of light with a wavelength of λ+Δλ is for:

[0040] (three)

[0041] Where: λ is the wavelength of the light focused at the position of the third aperture 1003;

[0042] D is the lens aperture, which is 12mm;

[0043] is the focus offset;

[0044] is the focal length corresponding to the wavelength λ.

[0045] Assuming that the light intensity is uniformly distributed, refer to formula (4), the energy passing through the third aperture 1003 is for:

[0046] (Four)

[0047] Where: is the diameter of the small hole at the focus of the λ wavelength light, which is 0.03mm here.

[0048] The energy transmission rate of light of different wavelengths passing through the third aperture 1003 is as follows: Figure 10 As shown, it can be seen that the wavelength range in which more light beams can pass through the third pinhole 1003 is approximately 530-610 nm, and the energy of other wavelengths that are significantly different from the target wavelength of 570 nm passing through the third pinhole 1003 is very small. The further away from 570 nm, the lower the light transmission rate. In this embodiment, the spatial filter composed of the third focusing lens 903 and the third pinhole 1003 can effectively filter out light of non-working wavelengths. Therefore, the spatial filters composed of the 9 focusing lenses and the corresponding 9 pinholes in the 3×3 array can effectively filter out light of non-working wavelengths in their respective channels, thereby improving the signal-to-noise ratio.

[0049] Taking the wavelength of 830nm as an example, the seventh aperture 1007 is placed at the position where the 830nm wavelength light converges after passing through the seventh focusing lens 907. For a traditional plane grating spectrometer, the 830nm first-order diffraction light after grating splitting also contains 415nm second-order diffraction light, resulting in spectral aliasing. The present invention places the small reflective mirror area of the digital micromirror device 12 corresponding to the seventh focusing lens 907 and the seventh aperture 1007 in a working deflection state, and the other areas in a non-working deflection state. The light emitted from the seventh aperture 1007 is collimated by the lens array collimation system 11 and then reaches the digital micromirror device 12 for reflection. When it reaches the plane reflection grating 13, according to the Figure 11 The energy ratios of the various wavelengths shown when passing through the seventh aperture 1007 indicate that the spectral bandwidth that can effectively pass through the seventh aperture 1007 is 790-870 nm. The transmittance of the higher-order diffracted 415 nm light is as low as 0.1% when passing through the seventh aperture 1007, a negligible transmittance compared to the target wavelength of 830 nm. Therefore, after the parallel polychromatic light sequentially passes through the seventh focusing lens 907 of the lens array focusing system, the seventh aperture 1007 of the aperture array filtering system 10, the corresponding collimating lens of the lens array collimating system 11, and the corresponding small reflective mirror of the digital micromirror device 12, by the time it reaches the planar reflection grating 13, the filtering by the seventh aperture 1007 has already filtered out most of the short-wavelength, higher-order diffracted light not belonging to the current channel.

[0050] After the light waves are filtered by the pinhole and then collimated by the lens array collimation system 11, the spectral bandwidth is relatively narrow, at 80nm. Then, the small reflective mirror area of the digital micromirror device 12 corresponding to the pinhole is selected, so that it is in a deflection working state. Only the light from the selected channel can be dispersed and split by the subsequent system and finally converged on the linear array detector 5.

[0051] Each small reflective mirror surface of the digital micromirror device 12 can be selectively deflected into a specific region within the digital micromirror device 12 to operate, thereby matching the front-end lens and pinhole to form a spatial filter. This allows light of the wavelength corresponding to the designated channel to enter the subsequent spectroscopic system, while the energy of other light entering the subsequent system is negligible due to the filtering effect. The 3×3 array lens system and 3×3 array pinhole system of the present invention can set the channels of the spectrometer to 9 channels. The light of each channel can be detected using the linear array detector 5 in a time-sharing manner, thereby increasing the spectral resolution by 9 times. Moreover, due to the filtering effect, light of non-operating wavelengths basically does not enter the subsequent system, thereby significantly improving the signal-to-noise ratio of the spectrometer.

Claims

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

2. The plane grating spectrometer system based on lens array and pinhole filtering according to claim 1, characterized in that: The focusing lens in the lens array focusing system (9) is a lens with an Abbe number lower than 35.

3. The plane grating spectrometer system based on lens array and pinhole filtering according to claim 2, characterized in that: The focusing lens in the mirror array focusing system is a double convex lens made of ZF6 material.

4. The plane grating spectrometer system based on lens array and pinhole filtering according to claim 1, characterized in that: The digital micromirror device (12) 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 (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 pinhole array filtering system (10), 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.

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