A MEMS-based spectral imaging system and method

Abstract

The present invention discloses a MEMS-based spectral imaging system and method, belonging to the field of spectral imaging, mainly involving microelectromechanical system technology, optical system design technology, hyperspectral imaging technology, etc. By introducing a MEMS scanning grating mirror array between the collimation subsystem and the detector, the present invention enables the light that is reflected by each micromirror scanning unit of the DMD and then processed by the collimation subsystem to be dispersed on each MEMS scanning grating mirror unit to obtain the corresponding dispersion spectrum. At the same time, by controlling the deflection angle of each unit in the MEMS scanning grating mirror array, the dispersion spectrum corresponding to each micromirror scanning unit in the DMD is incident on the detector working surface at the same position. Therefore, the dispersion spectra generated after the DMD micromirrors are scanned column by column no longer shift along one direction, but are distributed at the same position on the detector working surface, thereby greatly reducing the total length of the dispersion spectra and reducing the system's requirement for a detector working surface with a large aspect ratio.

Description

Technical Field

[0001] The present invention belongs to the field of spectral imaging, and mainly relates to microelectromechanical system technology, optical system design technology, hyperspectral imaging technology, etc. Prior Art

[0002] Spectral resolution refers to the minimum width recorded by a detector in the wavelength direction and is one of the important performance indicators of a spectral imaging system. Generally speaking, the higher the spectral resolution, the more spectral bands the system can obtain, the narrower the width of the divided spectral bands, the easier it is to distinguish and identify the information of the target, and the stronger the pertinence. With a high enough spectral resolution, it is relatively easy to distinguish targets with diagnostic spectral characteristics. Data with high spectral resolution can especially depict the spectral details of ground objects, support waveform analysis technology, and is widely used in fields such as atmospheric remote sensing, vegetation detection, geological archaeology, military reconnaissance, and pathological tissue identification. Subdividing the spectrum and improving the spectral resolution can improve the system's ability to automatically distinguish and identify the nature and composition of targets. Therefore, it is very important for a spectral imaging system to obtain high spectral resolution.

[0003] Slit push-broom is a commonly used method for obtaining spectral data. Compared with methods such as staring and snapshot methods, it can obtain higher spectral resolution, and the principle of constructing a three-dimensional data cube of the target is also simpler. However, this method needs to rely on mechanical movement to push and scan the spatial scene, and then collect the spectral data of the spatial scene, which results in a large system volume and mass and high energy consumption.

[0004] With the rapid development of Micro - electro - mechanical systems (MEMS) technology, its representative product, the Digital Micromirror Device (DMD), has the advantages of small size, light weight, low energy consumption, and customization, and can overcome many limitations in traditional spectral imaging methods. The working surface of the DMD usually consists of up to 500,000 to 2 million micromirrors. The size of each micromirror unit is about 10 μm, and each can deflect the same angle around the articulated skew axis, and can be programmed to achieve two opposite deflection states in the positive and negative directions. The column - by - column scanning of the micromirrors can replace the mechanical slit push - sweep motion in the traditional spectral imaging system (such as CN105527021A, CN110132412A, etc.). This DMD - based scanning spectral imaging method can reduce the mass and volume of the system, making the system more compact and portable. However, the column - by - column scanning of the DMD micromirrors will cause the corresponding dispersion spectrum to shift in one direction on the detector. Therefore, in order to collect all the dispersion spectra and obtain a higher spectral resolution, a detector with a relatively large aspect ratio of the working surface length to width is required. This expensive detector greatly increases the system cost and is not conducive to the popularization and application of the DMD - based scanning spectral imaging system in the civilian field. To address this problem, a new DMD - based spectral imaging system divides the micromirror array on the DMD working surface into upper and lower parts (CN112484857A). By adding an image - transfer subsystem to change the position of the optical axis of the light emitted from each part, the dispersion spectrum on the detector no longer shifts only in one direction but in two directions, as Figure 1 shown. Compared with the DMD - based scanning spectral imaging system (CN105527021A and CN110132412A), this method can reduce the system's requirement for the detector surface type with a large aspect ratio; at the same time, under the condition of using the same detector, this method allows the dispersion spectrum generated by the deflection of each column of micromirrors to be spread wider, and the spectral resolution provided by the system also increases accordingly. However, this method only reduces the total length of the dispersion spectrum by 50% and does not fundamentally solve the problem of dispersion spectrum shift. A special - surface - type detector still needs to be selected, and the improvement of the spectral resolution is limited.

[0005] In addition to DMD, the rapid development of optical MEMS technology has opened up an imaginative space for the development of new spectral imaging systems. Integrating the grating structure with the MEMS scanning mirror structure can achieve the function of dynamic spectral scanning, promising to greatly reduce the volume and weight of the spectral imaging system, and having a flexible and adjustable diverse scene adaptation ability and a higher degree of intelligence. Summary of the Invention

[0006] Object of the Invention

[0007] The present invention provides a spectral imaging system and method based on a DMD and a MEMS scanning grating mirror array. By introducing a MEMS scanning grating mirror array between the collimation subsystem and the detector, the light reflected by each micromirror scanning unit of the DMD and then processed by the collimation subsystem can be spectrally separated on each MEMS scanning grating mirror unit to obtain the corresponding dispersed spectrum. At the same time, by controlling the deflection angle of each unit in the MEMS scanning grating mirror array, the dispersed spectrum corresponding to each micromirror scanning unit in the DMD is incident on the detector working surface at the same position. Therefore, the dispersed spectra generated after the DMD micromirrors are scanned column by column are no longer offset in one direction, but are distributed at the same position on the detector working surface, thereby greatly reducing the total length of the dispersed spectra and reducing the requirement of the system for a detector working surface with a large aspect ratio. Under the condition of using the same detector, compared with the existing DMD-based scanning spectral imaging method, this method helps to obtain a wider dispersed spectrum and higher spectral resolution. The present invention does not require spectroscopic elements such as blazed gratings and prisms, effectively reduces the mass and volume of the system, greatly improves the integration of the system, and can obtain a high spectral resolution only by using a common detector surface type, which can effectively reduce the system cost and solve the problems of the existing DMD-based scanning spectral imaging system being overly dependent on a detector surface type with a large aspect ratio and insufficient integration level, etc.

[0008] Technical solution

[0009] The technical solution adopted by the present invention is a MEMS-based spectral imaging system and method. Refer to Figure 2, the system mainly includes a target 1, an imaging subsystem 2, a DMD working surface 3, the first micromirror scanning unit 3-1 on the DMD working surface, the middle micromirror scanning unit 3-2 on the DMD working surface, the last micromirror scanning unit 3-3 on the DMD working surface, a collimating subsystem 4, a working surface 5 of the MEMS scanning grating mirror array, the first MEMS scanning grating mirror unit 5-1 on the working surface of the MEMS scanning grating mirror array, the middle MEMS scanning grating mirror unit 5-2 on the working surface of the MEMS scanning grating mirror array, the last MEMS scanning grating mirror unit 5-3 on the working surface of the MEMS scanning grating mirror array, a detector working surface 6, a light ray 7 passing through the center of the first micromirror scanning unit on the DMD working surface, a light ray 8 passing through the center of the middle micromirror scanning unit on the DMD working surface, and a light ray 9 passing through the center of the last micromirror scanning unit on the DMD working surface. The target 1 and the DMD working surface 3 are respectively placed at the object surface and the image surface of the imaging subsystem 2. The target image formed by the target 1 passing through the imaging subsystem 2 is divided by columns by the micromirror scanning units on the DMD working surface 3. The collimating subsystem 4 makes the light reflected from the DMD working surface 3 into parallel light. The working surface 5 of the MEMS scanning grating mirror array is located in the light exit direction of the collimating subsystem 4. The number of MEMS scanning grating mirror units in the working surface 5 of the MEMS scanning grating mirror array is the same as the number of micromirror scanning units in the DMD working surface 3. It is required that when each micromirror scanning unit on the DMD working surface 3 is in the deflection working state, it must reflect the target image of the corresponding column into the collimating subsystem 4 for collimation. The obtained parallel light is then incident on the corresponding MEMS scanning grating mirror unit in the working surface 5 of the MEMS scanning grating mirror array for beam splitting. At the same time, it is required that the light rays passing through the centers of each micromirror scanning unit on the DMD working surface 3 also pass through the centers of the corresponding MEMS scanning grating mirror units in the working surface 5 of the MEMS scanning grating mirror array. For example, the light ray 7 passing through the center of the first micromirror scanning unit on the DMD working surface, the light ray 8 passing through the center of the middle micromirror scanning unit on the DMD working surface, and the light ray 9 passing through the center of the last micromirror scanning unit on the DMD working surface respectively pass through the centers of the first MEMS scanning grating mirror unit 5-1, the middle MEMS scanning grating mirror unit 5-2, and the last MEMS scanning grating mirror unit 5-3 on the working surface 5 of the MEMS scanning grating mirror array. By changing the deflection angle of each MEMS scanning grating mirror unit in the working surface 5 of the MEMS scanning grating mirror array, the dispersed spectra that are split and emitted by each MEMS scanning grating mirror unit are incident on the same area of the detector, that is, the minimum wavelength λ 1 and the maximum wavelength λ 2 of the light rays are incident on the starting and ending fixed points M and N of the dispersed spectrum area, and all the finally obtained dispersed spectra will be imaged at the same position on the detector working surface 6.

[0010] The imaging subsystem 2 described above can be a telescopic lens, a microscopic lens, etc., and is responsible for converging the reduced or magnified image of the target 1 onto the DMD working surface 3.

[0011] The DMD working surface 3 is rectangular. Refer to Figure 3 , which is composed of a micromirror array. The number of columns and rows of the micromirror array are a and b respectively, the width of each micromirror is u, the image of the target 1 is divided into 2K + 1 columns (K is a positive integer) by the micromirror scanning unit of the DMD working surface 3, each micromirror scanning unit contains x columns of micromirrors, the width of each micromirror scanning unit is xu, and x(2K + 1) ≤ a is satisfied. The deflection angle of each micromirror has only two types, positive and negative, mostly ±12°, and there are also ±10°, ±17°, etc. One of the deflection states is selected as the "ON" working state, and the micromirror scanning unit in this state will reflect the selected target image to the collimation subsystem 4; the other deflection state is the "OFF" state, and the micromirror scanning unit in this state is responsible for reflecting the selected target image outside the system.

[0012] The collimation subsystem 4 described above can be composed of components such as a lens group or a concave spherical mirror, and is responsible for collimating the light reflected from the DMD working surface 3 so that it is incident parallel to the MEMS scanning grating mirror array working surface 5.

[0013] The MEMS scanning grating mirror array working surface 5 uses MEMS technology to perform grating ruling on a long strip-shaped scanning micromirror array, and can simultaneously realize two functions of chromatic dispersion spectroscopy and scanning deflection. Refer to Figure 4 , the MEMS scanning grating mirror array working surface 5 includes 2K + 1 MEMS scanning grating mirror units, the grating ruling width is d, the diffraction order is m, the width of each MEMS scanning grating mirror unit is t, and the center point of the i-th MEMS scanning grating mirror unit is O i (i is a positive integer, i ∈ [1, 2K + 1]). Refer to Figure 5 , the spectral dispersion length on the detector working surface 6 is MN, the wavelength λ ∈ [λ 1 , λ 2 , it is required that the MEMS scanning grating mirror array working surface 5 and the detector working surface 6 are parallel to each other, the extension line of the cross-section of the MEMS scanning grating mirror array working surface 5 intersects the perpendicular line of the detector working surface 6 at point N at point O, the length of ON is h, the length of MN is s, the length of OO 2K+1 is l, it is required that l >> s, it is required that each MEMS scanning grating mirror unit can only deflect clockwise, when the i-th MEMS scanning grating mirror unit is in the working state "ON", its deflection angle is β i , β i = 0, the incident angle of the corresponding MEMS scanning grating mirror unit is α 0, the dispersion wavelength is λ 1 and λ 2 The diffraction angles corresponding to the light rays are θ i1 and θ i2 , respectively. They are incident on the fixed points M and N respectively. By reasonably selecting the values of h, s, l, t, d, λ 1 , λ 2 , so that the dispersion spectra obtained by splitting and reflecting through the i-th MEMS scanning grating mirror unit can all be incident on the fixed area MN on the detector, that is, β i has a solution. According to the above known parameters, introduce the intermediate variable ∠NO i O = γ i , ∠MO i O = δ i , and give the solution method of β i :

[0014] β i Satisfies the following formula:

[0015]

[0016]

[0017] Where:

[0018]

[0019]

[0020] d(sin(α 0 +β i ) + sinθ i1 ) = mλ 1 (3)

[0021] d(sin(α 0 +β i ) + sinθ i2 ) = mλ 2 (4)

[0022] (4) - (3) and substituting (1), (2) into it gives:

[0023]

[0024] Expand formula (5) and substitute it into the equation cos 2 β i +sin 2 β i = 1, to obtain a quadratic equation:

[0025] 2(1 - sinγ i sinδ i-cosγ i cosδ i )sin 2 β i +2c(sinγ i -sinδ i )sinβ i

[0026] +c 2 -(cosγ i -cosδ i ) 2 =0

[0027] Solve to get That is

[0028] If there are two solutions, take the smaller value, where

[0029] A = 2(1 - sinγ i sinδ i -cosγ i cosδ i )

[0030] B = 2c(sinγ i -sinδ i )

[0031] D = c 2 -(cosγ i -cosδ i ) 2

[0032] The working surface 6 of the detector is responsible for collecting the dispersed spectrum emitted from the working surface 5 of the MEMS scanning grating mirror array, and the surface shape of the working surface 6 of the detector is a common detector surface shape on the market.

[0033] The light ray 7 passing through the center of the first micromirror scanning unit of the DMD working surface 3 passes through the center of the first micromirror scanning unit 3-1 of the DMD working surface 3, the collimation subsystem 4, and the center of the first MEMS scanning grating mirror unit 5-1 of the MEMS scanning grating mirror array working surface 5. After being dispersed and deflected by the first MEMS scanning grating mirror unit 5-1 of the MEMS scanning grating mirror array working surface 5, the light rays with wavelengths of λ 1 、λ 2 are respectively incident on the fixed points M and N.

[0034] The light ray 8 passing through the center of the middle micromirror scanning unit of the DMD working surface 3 passes through the center of the middle micromirror scanning unit 3-2 of the DMD working surface 3, the collimation subsystem 4, and the center of the middle MEMS scanning grating mirror unit 5-2 of the MEMS scanning grating mirror array working surface 5 respectively. After being dispersed and deflected by the middle MEMS scanning grating mirror unit 5-2 of the MEMS scanning grating mirror array working surface 5, the light rays with wavelengths of λ 1 and λ 2 are incident on the fixed points M and N respectively.

[0035] The light ray 9 passing through the center of the last micromirror scanning unit of the DMD working surface 3 passes through the center of the last micromirror scanning unit 3-3 of the DMD working surface 3, the collimation subsystem 4, and the center of the last MEMS scanning grating mirror unit 5-3 of the MEMS scanning grating mirror array working surface 5 respectively. After being dispersed and deflected by the last MEMS scanning grating mirror unit 5-3 of the MEMS scanning grating mirror array working surface 5, the light rays with wavelengths of λ 1 and λ 2 are incident on the fixed points M and N respectively.

[0036] The spectral acquisition principle of a MEMS-based spectral imaging system and method proposed by the present invention is as Figure 6 shown. By controlling 2K + 1 micromirror scanning units and 2K + 1 MEMS scanning grating mirror units to be simultaneously in the "ON" working state in sequence, column scanning of the target image is realized, and then 2K + 1 dispersion spectral images are obtained on the same area of the detector working surface 6, completing the acquisition of the target three-dimensional data cube. The spectral acquisition principle process of a MEMS-based spectral imaging system and method proposed by the present invention specifically includes the following steps:

[0037] Step 1: Refer to Figure 6 , control the first micromirror scanning unit of the DMD working surface 3 and the first MEMS scanning grating mirror unit of the MEMS scanning grating mirror array 5 to be simultaneously in the "ON" working state, and other micromirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light rays of the first column of the target image are first reflected by the first micromirror scanning unit and enter the collimation subsystem 4. After being collimated by the collimation subsystem 4, they are parallelly emitted to the MEMS scanning grating mirror array working surface 5, and then are dispersed and reflected by the first MEMS scanning grating mirror unit. The obtained outgoing dispersion spectrum is imaged on the detector working surface 6. Refer to Figure 7, define the direction of spectral dispersion as the X-axis direction, and the Y-axis direction perpendicular to this direction as the spatial position direction. The spectra of the target images in the first column are sequentially expanded according to different wavelengths along the X-axis direction, and the spectral components corresponding to different spatial positions are obtained in the Y-axis direction. The detector working surface 6 records and stores the dispersion spectrogram of the target images in the first column. After the reflection operation of the first micromirror scanning unit and the dispersion deflection operation of the first MEMS scanning grating mirror unit are completed, the spectral imaging of the target images in the first column is finished;

[0038] Step 2: Refer to Figure 6 , control the second micromirror scanning unit on the DMD working surface 3 and the second MEMS scanning grating mirror unit on the MEMS scanning grating mirror array working surface 5 to be simultaneously in the "ON" working state, and other micromirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light of the target images in the second column is first reflected by the second micromirror scanning unit into the collimation subsystem 4, collimated by the collimation subsystem 4 and then emitted parallel to the MEMS scanning grating mirror array working surface 5, and then dispersed and reflected by the second MEMS scanning grating mirror unit. The obtained outgoing dispersion spectrum is imaged on the detector working surface 6. Refer to Figure 7 , although the target images are offset in the horizontal direction, the positions of their dispersion spectra on the detector working surface 6 do not change. The detector working surface 6 records and stores the dispersion spectrogram at this time. After the reflection operation of the second micromirror scanning unit and the dispersion deflection operation of the second MEMS scanning grating mirror unit are completed, the spectral imaging of the target images in the second column is finished;

[0039] Step 3: Control the 3rd, 4th... 2Kth micromirror scanning units on the DMD working surface 3 and the 3rd, 4th... 2Kth MEMS scanning grating mirror units on the MEMS scanning grating mirror array working surface 5 to be simultaneously in the "ON" working state in sequence. The detector working surface 6 synchronously records and stores the corresponding dispersion spectrograms to complete the spectral imaging of the target images in the 3rd, 4th... 2Kth columns;

[0040] Step 4: Refer to Figure 6 , control the (2K + 1)th micromirror scanning unit on the DMD working surface 3 and the (2K + 1)th MEMS scanning grating mirror unit on the MEMS scanning grating mirror array working surface 5 to be simultaneously in the "ON" working state, and other micromirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light of the target images in the (2K + 1)th column is first reflected by the (2K + 1)th micromirror scanning unit into the collimation subsystem 4, collimated by the collimation subsystem 4 and then emitted parallel to the MEMS scanning grating mirror array working surface 5, and then dispersed and reflected by the (2K + 1)th MEMS scanning grating mirror unit. The obtained outgoing dispersion spectrum is imaged on the detector working surface 6. Refer to Figure 7, since the spectral positions of the target images in different columns remain unchanged in the X-axis direction, as long as it is ensured that the detector working surface 6 can completely collect the dispersed spectra of any column of target images, the spectral imaging of the entire target can be completed. The detector working surface 6 records and stores the dispersed spectrum diagram at this time. The reflection work of the (2K + 1)-th micromirror scanning unit and the dispersion deflection work of the (2K + 1)-th MEMS scanning grating mirror unit are completed, and the spectral imaging of the (2K + 1)-th column of target images is completed;

[0041] Step 5: Perform data processing on the 2K + 1 dispersed spectrum diagrams collected by the detector working surface 6 to obtain the two-dimensional spatial scene and one-dimensional spectral information of the target 1, that is, a complete three-dimensional data cube, and the spectral acquisition process of a spectral imaging system and method based on MEMS proposed by the present invention ends.

[0042] Beneficial effects

[0043] 1. Eliminate the phenomenon of dispersed spectrum offset caused by the deflection of DMD micromirrors by columns. Compared with the existing DMD-based scanning spectral imaging method, within the working cycle of the DMD and the MEMS scanning grating mirror array, the dispersed spectrum position obtained by the present invention remains fixed;

[0044] 2. The system has a smaller mass and volume and a higher degree of integration. Compared with the existing DMD-based scanning spectral imaging method, the MEMS scanning grating mirror array has both the functions of dispersion spectroscopy and deflection, and does not require additional spectroscopic elements such as blazed gratings.

[0045] 3. There is no need to select a special surface type detector, nor to customize a detector with a large aspect ratio surface type, effectively reducing the system cost and improving the system spectral resolution. The present invention can greatly reduce the total length of the dispersed spectrum. The length of the detector working surface only needs to accommodate the dispersed spectrum generated by a certain micromirror scanning unit of the DMD. Therefore, it is allowed to expand the dispersed spectrum wider, and the obtained spectral resolution will also be higher. Description of the drawings

[0046] Figure 1 : Comparison diagram of the change in the dispersed spectrum position in two existing DMD-based scanning spectral imaging methods

[0047] Figure 2 : Schematic diagram of the composition of a spectral imaging system based on MEMS

[0048] Figure 3 : Schematic diagram of the division of the target image by the micromirror scanning unit of the DMD working surface by columns

[0049] Figure 4 : Schematic diagram of the composition of the MEMS scanning grating mirror array

[0050] Figure 5: Schematic diagram of the relative position distribution of the MEMS scanning grating mirror array and the fixed points M and N

[0051] Figure 6 : Schematic diagram of the spectral acquisition principle of a MEMS-based spectral imaging system and method

[0052] Figure 7 : Schematic diagram of the spectral acquisition principle of the target image

[0053] Wherein: 1. Target; 2. Imaging subsystem; 3. DMD working surface; 3-1. The first micromirror scanning unit of the DMD working surface; 3-2. The middle micromirror scanning unit of the DMD working surface; 3-3. The last micromirror scanning unit of the DMD working surface; 4. Collimation subsystem; 5. MEMS scanning grating mirror array working surface; 5-1. The first MEMS scanning grating mirror unit of the MEMS scanning grating mirror array working surface; 5-2. The middle MEMS scanning grating mirror unit of the MEMS scanning grating mirror array working surface; 5-3. The last MEMS scanning grating mirror unit of the MEMS scanning grating mirror array working surface; 6. Detector working surface; 7. Light passing through the center of the first micromirror scanning unit of the DMD working surface; 8. Light passing through the center of the middle micromirror scanning unit of the DMD working surface; 9. Light passing through the center of the last micromirror scanning unit of the DMD working surface. Specific implementation manners

[0054] Example 1

[0055] A MEMS-based spectral imaging system and method proposed in this example, refer to Figure 2, the system mainly includes a target 1, an imaging subsystem 2, a DMD working surface 3, the first micromirror scanning unit 3-1 of the DMD working surface, the middle micromirror scanning unit 3-2 of the DMD working surface, the last micromirror scanning unit 3-3 of the DMD working surface, a collimation subsystem 4, a working surface 5 of the MEMS scanning grating mirror array, the first MEMS scanning grating mirror unit 5-1 of the working surface 5 of the MEMS scanning grating mirror array, the middle MEMS scanning grating mirror unit 5-2 of the working surface 5 of the MEMS scanning grating mirror array, the last MEMS scanning grating mirror unit 5-3 of the working surface 5 of the MEMS scanning grating mirror array, a detector working surface 6, a light ray 7 passing through the center of the first micromirror scanning unit of the DMD working surface, a light ray 8 passing through the center of the middle micromirror scanning unit of the DMD working surface, and a light ray 9 passing through the center of the last micromirror scanning unit of the DMD working surface. The target 1 and the DMD working surface 3 are respectively placed at the object surface and the image surface of the imaging subsystem 2. The target image formed by the target 1 through the imaging subsystem 2 is divided by columns by the micromirror scanning units of the DMD working surface 3. The collimation subsystem 4 makes the light reflected from the DMD working surface 3 into parallel light. The working surface 5 of the MEMS scanning grating mirror array is located in the light exit direction of the collimation subsystem 4. The number of MEMS scanning grating mirror units in the working surface 5 of the MEMS scanning grating mirror array is the same as the number of micromirror scanning units in the DMD working surface 3. It is required that when each micromirror scanning unit in the DMD working surface 3 is in the deflection working state, it must reflect the corresponding column of the target image into the collimation subsystem 4 for collimation. The obtained parallel light is then incident on the corresponding MEMS scanning grating mirror unit in the working surface 5 of the MEMS scanning grating mirror array for spectral splitting. At the same time, it is required that the light rays passing through the centers of each micromirror scanning unit of the DMD working surface 3 also pass through the centers of the corresponding MEMS scanning grating mirror units in the working surface 5 of the MEMS scanning grating mirror array. For example, the light ray 7 passing through the center of the first micromirror scanning unit of the DMD working surface, the light ray 8 passing through the center of the middle micromirror scanning unit of the DMD working surface, and the light ray 9 passing through the center of the last micromirror scanning unit of the DMD working surface respectively pass through the centers of the first MEMS scanning grating mirror unit 5-1, the middle MEMS scanning grating mirror unit 5-2, and the last MEMS scanning grating mirror unit 5-3 of the working surface 5 of the MEMS scanning grating mirror array. By changing the deflection angles of each MEMS scanning grating mirror unit in the working surface 5 of the MEMS scanning grating mirror array, the dispersed spectra that are spectrally split and emitted from each MEMS scanning grating mirror unit are incident on the same area of the detector, that is, the minimum wavelength λ 1 and the maximum wavelength λ 2 of the light rays are incident on the starting and ending fixed points M and N of the dispersed spectral region, and all the finally obtained dispersed spectra will be imaged at the same position on the detector working surface 6.

[0056] The imaging subsystem 2 described above is a telescopic lens, which is responsible for converging the reduced image of the target 1 onto the DMD working surface 3.

[0057] The DMD working surface 3 is rectangular. Refer to Figure 3 , which is composed of a micromirror array. The number of columns and rows of the micromirror array are a = 1024 and b = 768 respectively. The width of each micromirror is u = 13.68 μm. The image of the target 1 is divided into 251 columns by the micromirror scanning unit of the DMD working surface 3. K = 125. Each micromirror scanning unit contains x = 4 columns of micromirrors. The width of each micromirror scanning unit is xu = 54.72 μm, satisfying x(2K + 1) ≤ a. The deflection angle of each micromirror is ±12°. The deflection state with a deflection angle of 12° is selected as the "ON" working state. The micromirror scanning unit in this state will reflect the selected target image to the collimation subsystem 4; the other deflection state is the "OFF" state. The micromirror scanning unit in this state is responsible for reflecting the selected target image outside the system.

[0058] The collimation subsystem 4 described above is composed of a lens group, which is responsible for collimating the light reflected from the DMD working surface 3 and making it incident parallel to the MEMS scanning grating mirror array working surface 5.

[0059] The MEMS scanning grating mirror array working surface 5 uses MEMS technology to perform grating ruling on a long strip scanning micromirror array, and can simultaneously realize two functions of dispersion spectroscopy and scanning deflection. Refer to Figure 4 , the MEMS scanning grating mirror array working surface 5 contains 251 MEMS scanning grating mirror units. The grating ruling width is d = 3.5 μm, the diffraction order is m = 1, the width of each MEMS scanning grating mirror unit is t = 100 μm, and the center point of the i-th MEMS scanning grating mirror unit is O i (i is a positive integer, i ∈ [1, 251]). Refer to Figure 5 , the spectral dispersion length on the detector working surface 6 is MN, the wavelength λ ∈ [400 nm, 600 nm]. It is required that the MEMS scanning grating mirror array working surface 5 and the detector working surface 6 are parallel to each other. The extension line of the cross-section of the MEMS scanning grating mirror array working surface 5 intersects the perpendicular line of the detector working surface 6 at point N at point O. The length of ON is h = 100 mm, the length of MN is s = 30 mm, and the length of OO 251 is l = 200 mm, satisfying l >> s. It is required that each MEMS scanning grating mirror unit can only deflect clockwise. When the i-th MEMS scanning grating mirror unit is in the working state "ON", its deflection angle is β i , β i = 0 corresponds to the incident angle α of the MEMS scanning grating mirror unit 0= 20°, the diffraction angles corresponding to the light with dispersion wavelengths of 400 nm and 600 nm are θ i1 and θ i2 , respectively, and they are incident on the fixed points M and N. According to the above known parameters, introduce the intermediate variable ∠NO i O = γ i , ∠MO i O = δ i , and the solution method of β i is as follows:

[0060] β i satisfies the following equation:

[0061]

[0062]

[0063] where:

[0064]

[0065]

[0066] d(sin(α 0 + β i ) + sinθ i1 ) = mλ 1 (3)

[0067] d(sin(α 0 + β i ) + sinθ i2 ) = mλ 2 (4)

[0068] (4) - (3) and substituting equations (1) and (2) gives:

[0069]

[0070] Expanding equation (5) and substituting the equation cos 2 β i + sin 2 β i = 1, we get a quadratic equation:

[0071] 2(1 - sinγ i sinδ i - cosγ i cosδ i )sin 2 β i + 2c(sinγ i - sinδ i )sinβ i

[0072] +c 2 -(cosγ i -cosδ i ) 2 =0

[0073] Solve to get That is

[0074] If there are two solutions, take the smaller value, where:

[0075] A = 2(1 - sinγ i sinδ i -cosγ i cosδ i )

[0076] B = 2c(sinγ i -sinδ i )

[0077] D = c 2 -(cosγ i -cosδ i ) 2

[0078] The working surface 6 of the detector is responsible for collecting the dispersed spectrum emitted from the working surface 5 of the MEMS scanning grating mirror array, and the surface shape of the working surface 6 of the detector is a common detector surface shape on the market.

[0079] The light ray 7 passing through the center of the first micromirror scanning unit of the DMD working surface 3 passes through the center of the first micromirror scanning unit 3-1 of the DMD working surface 3, the collimation subsystem 4, and the center of the first MEMS scanning grating mirror unit 5-1 of the MEMS scanning grating mirror array working surface 5. After being dispersed and deflected by the first MEMS scanning grating mirror unit 5-1 of the MEMS scanning grating mirror array working surface 5, the light rays with wavelengths of 400 nm and 600 nm in the obtained dispersed spectrum are incident on the fixed points M and N respectively.

[0080] The light ray 8 passing through the center of the middle micromirror scanning unit of the DMD working surface 3 passes through the center of the middle micromirror scanning unit 3-2 of the DMD working surface 3, the collimation subsystem 4, and the center of the middle MEMS scanning grating mirror unit 5-2 of the MEMS scanning grating mirror array working surface 5. After being dispersed and deflected by the middle MEMS scanning grating mirror unit 5-2 of the MEMS scanning grating mirror array working surface 5, the light rays with wavelengths of 400 nm and 600 nm in the obtained dispersed spectrum are incident on the fixed points M and N respectively.

[0081] The light ray 9 passing through the center of the last micromirror scanning unit of the DMD working surface 3 passes through the center of the last micromirror scanning unit 3-3 of the DMD working surface 3, the collimation subsystem 4, and the center of the last MEMS scanning grating mirror unit 5-3 of the MEMS scanning grating mirror array working surface 5. After being dispersed and deflected by the last MEMS scanning grating mirror unit 5-3 of the MEMS scanning grating mirror array working surface 5, the light rays with wavelengths of 400 nm and 600 nm in the obtained dispersed spectrum are incident on the fixed points M and N respectively.

[0082] The spectral acquisition principle of a spectral imaging system and method based on MEMS proposed by the present invention is as Figure 6 shown. By controlling 251 micromirror scanning units and 251 MEMS scanning grating mirror units to be simultaneously in the "ON" working state in sequence, column scanning of the target image is realized, and then 251 dispersed spectrograms are obtained on the same area of the detector working surface 6, completing the acquisition of the target three-dimensional data cube. The spectral acquisition principle process of a spectral imaging system and method based on MEMS proposed by the present invention specifically includes the following steps:

[0083] Step 1: Refer to Figure 6 , control the first micromirror scanning unit of the DMD working surface 3 and the first MEMS scanning grating mirror unit of the MEMS scanning grating mirror array 5 to be simultaneously in the "ON" working state, and other micromirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light ray of the first column of the target image is first reflected by the first micromirror scanning unit and enters the collimation subsystem 4. After being collimated by the collimation subsystem 4, it exits parallel to the MEMS scanning grating mirror array working surface 5, and then is dispersed and reflected by the first MEMS scanning grating mirror unit. The obtained output dispersed spectrum is imaged on the detector working surface 6. Refer to Figure 7 , define the direction of spectral dispersion as the X-axis direction, and the Y-axis direction perpendicular to this direction as the spatial position direction. The spectrum of the first column of the target image is sequentially unfolded along the X-axis direction according to different wavelengths, and spectral components corresponding to different spatial positions are obtained in the Y-axis direction. The detector working surface 6 records and stores the dispersed spectrogram of the first column of the target image. The reflection work of the first micromirror scanning unit and the dispersion deflection work of the first MEMS scanning grating mirror unit are completed, and the spectral imaging of the first column of the target image is completed;

[0084] Step 2: Refer to Figure 6, control the second micromirror scanning unit on the DMD working surface 3 and the second MEMS scanning grating mirror unit on the MEMS scanning grating mirror array working surface 5 to be in the "ON" working state simultaneously, and other micromirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light of the target image in the second column is first reflected by the second micromirror scanning unit into the collimation subsystem 4, collimated by the collimation subsystem 4 and then emitted parallel to the MEMS scanning grating mirror array working surface 5, and then dispersed and reflected by the second MEMS scanning grating mirror unit. The obtained emitted dispersed spectrum is imaged on the detector working surface 6. Refer to Figure 7 , although the target image is shifted in the horizontal direction, its position of the dispersed spectrum on the detector working surface 6 does not change. The detector working surface 6 records and stores the dispersed spectrum diagram at this time. The reflection work of the second micromirror scanning unit and the dispersion deflection work of the second MEMS scanning grating mirror unit are completed, and the spectral imaging of the target image in the second column is completed;

[0085] Step 3: Control the 3rd, 4th... 250th micromirror scanning units on the DMD working surface 3 and the 3rd, 4th... 250th MEMS scanning grating mirror units on the MEMS scanning grating mirror array working surface 5 to be in the "ON" working state simultaneously in sequence. The detector working surface 6 synchronously records and stores the corresponding dispersed spectrum diagrams to complete the spectral imaging of the target images in the 3rd, 4th... 250th columns;

[0086] Step 4: Refer to Figure 6 , control the 251st micromirror scanning unit on the DMD working surface 3 and the 251st MEMS scanning grating mirror unit on the linear MEMS scanning grating mirror array working surface 5 to be in the "ON" working state simultaneously, and other micromirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light of the target image in the 251st column is first reflected by the 251st micromirror scanning unit into the collimation subsystem 4, collimated by the collimation subsystem 4 and then emitted parallel to the MEMS scanning grating mirror array working surface 5, and then dispersed and reflected by the 251st MEMS scanning grating mirror unit. The obtained emitted dispersed spectrum is imaged on the detector working surface 6. Refer to Figure 7 , since the spectral positions of the spatial positions of the target images in different columns are unchanged in the X-axis direction, as long as it is ensured that the detector working surface 6 can completely collect the dispersed spectrum of any column of the target image, the spectral imaging of the entire target can be completed. The detector working surface 6 records and stores the dispersed spectrum diagram at this time. The reflection work of the 251st micromirror scanning unit and the dispersion deflection work of the 251st MEMS scanning grating mirror unit are completed, and the spectral imaging of the target image in the 251st column is completed;

[0087] Step 5: Process the 251 dispersion spectrograms collected by the detector working surface 6 to obtain the two-dimensional spatial image and one-dimensional spectral information of the target 1, that is, the complete three-dimensional data cube, and the spectral acquisition process of a spectral imaging system and method based on MEMS proposed by the present invention ends.

[0088] Embodiment 2

[0089] A spectral imaging system and method based on MEMS proposed in this embodiment are referred to Figure 2, the system mainly includes a target 1, an imaging subsystem 2, a DMD working surface 3, the first micromirror scanning unit 3-1 on the DMD working surface, the middle micromirror scanning unit 3-2 on the DMD working surface, the last micromirror scanning unit 3-3 on the DMD working surface, a collimation subsystem 4, a working surface 5 of the MEMS scanning grating mirror array, the first MEMS scanning grating mirror unit 5-1 on the working surface of the MEMS scanning grating mirror array, the middle MEMS scanning grating mirror unit 5-2 on the working surface of the MEMS scanning grating mirror array, the last MEMS scanning grating mirror unit 5-3 on the working surface of the MEMS scanning grating mirror array, a detector working surface 6, a light ray 7 passing through the center of the first micromirror scanning unit on the DMD working surface, a light ray 8 passing through the center of the middle micromirror scanning unit on the DMD working surface, and a light ray 9 passing through the center of the last micromirror scanning unit on the DMD working surface. The target 1 and the DMD working surface 3 are respectively placed at the object surface and the image surface of the imaging subsystem 2. The target image formed by the target 1 through the imaging subsystem 2 is divided by columns by the micromirror scanning units on the DMD working surface 3. The collimation subsystem 4 makes the light reflected from the DMD working surface 3 into parallel light. The working surface 5 of the MEMS scanning grating mirror array is located in the light exit direction of the collimation subsystem 4. The number of MEMS scanning grating mirror units in the working surface 5 of the MEMS scanning grating mirror array is the same as the number of micromirror scanning units in the DMD working surface 3. It is required that when each micromirror scanning unit on the DMD working surface 3 is in the deflection working state, it must reflect the corresponding column of the target image into the collimation subsystem 4 for collimation. The obtained parallel light is then incident on the corresponding MEMS scanning grating mirror unit in the working surface 5 of the MEMS scanning grating mirror array for spectral splitting. At the same time, it is required that the light rays passing through the centers of each micromirror scanning unit on the DMD working surface 3 also pass through the centers of the corresponding MEMS scanning grating mirror units in the working surface 5 of the MEMS scanning grating mirror array. For example, the light ray 7 passing through the center of the first micromirror scanning unit on the DMD working surface, the light ray 8 passing through the center of the middle micromirror scanning unit on the DMD working surface, and the light ray 9 passing through the center of the last micromirror scanning unit on the DMD working surface respectively pass through the centers of the first MEMS scanning grating mirror unit 5-1, the middle MEMS scanning grating mirror unit 5-2, and the last MEMS scanning grating mirror unit 5-3 on the working surface 5 of the MEMS scanning grating mirror array. By changing the deflection angle of each MEMS scanning grating mirror unit in the working surface 5 of the MEMS scanning grating mirror array, the dispersed spectra that are split and emitted by each MEMS scanning grating mirror unit are incident on the same area of the detector, that is, the minimum wavelength λ 1 and the maximum wavelength λ 2 of the light rays are incident on the starting and ending fixed points M and N of the dispersed spectral region. All the finally obtained dispersed spectra will be imaged at the same position on the detector working surface 6.

[0090] The imaging subsystem 2 described above is a telephoto lens, which is responsible for converging the reduced image of the target 1 onto the DMD working surface 3.

[0091] The DMD working surface 3 is rectangular. Refer to Figure 3 , which is composed of a micromirror array. The number of columns and rows of the micromirror array are a = 1024 and b = 768 respectively. The width of each micromirror is u = 13.68 μm. The image of the target 1 is divided into 169 columns by the micromirror scanning unit of the DMD working surface 3. K = 84, and each micromirror scanning unit contains x = 6 columns of micromirrors. The width of each micromirror scanning unit is xu = 82.08 μm, satisfying x(2K + 1) ≤ a. The deflection angle of each micromirror is ±12°. The deflection state with a deflection angle of 12° is selected as the "ON" working state. The micromirror scanning unit in this state will reflect the selected target image to the collimation subsystem 4; the other deflection state is the "OFF" state, and the micromirror scanning unit in this state is responsible for reflecting the selected target image outside the system.

[0092] The collimation subsystem 4 described above is composed of a lens group, which is responsible for collimating the light reflected from the DMD working surface 3 so that it is incident parallel to the MEMS scanning grating mirror array working surface 5.

[0093] The MEMS scanning grating mirror array working surface 5 uses MEMS technology to perform grating rulings on a long strip scanning micromirror array, which can simultaneously achieve two functions of dispersion spectroscopy and scanning deflection. Refer to Figure 4 , the MEMS scanning grating mirror array working surface 5 contains 169 MEMS scanning grating mirror units. The grating ruling width is d = 4 μm, the diffraction order is m = 1, the width of each MEMS scanning grating mirror unit is t = 160 μm, and the center point of the i-th MEMS scanning grating mirror unit is O i (i is a positive integer, i ∈ [1, 169]). Refer to Figure 5 , the spectral dispersion length on the detector working surface 6 is MN, and the wavelength λ ∈ [650 nm, 780 nm]. It is required that the MEMS scanning grating mirror array working surface 5 and the detector working surface 6 are parallel to each other. The extension line of the cross-section of the MEMS scanning grating mirror array working surface 5 intersects the perpendicular line of the detector working surface 6 at point N at point O. The length of ON is h = 50 mm, the length of MN is s = 30 mm, and the length of OO 169 is l = 200 mm, satisfying l >> s. It is required that each MEMS scanning grating mirror unit can only deflect clockwise. When the i-th MEMS scanning grating mirror unit is in the working state "ON", its deflection angle is β i , β i = 0 corresponds to the incident angle α of the MEMS scanning grating mirror unit 0= 20°, the diffraction angles corresponding to the light with dispersion wavelengths of 650 nm and 780 nm are θ i1 and θ i2 , respectively, and they are incident on the fixed points M and N. According to the above known parameters, introduce the intermediate variable ∠NO i O = γ i , ∠MO i O = δ i , and the solution method of β i is as follows:

[0094] β i satisfies the following formula:

[0095]

[0096]

[0097] where:

[0098]

[0099]

[0100] d(sin(α 0 + β i ) + sinθ i1 ) = mλ 1 (3)

[0101] d(sin(α 0 + β i ) + sinθ i2 ) = mλ 2 (4)

[0102] (4) - (3) and substituting equations (1) and (2) gives:

[0103]

[0104] Expanding equation (5) and substituting the equation cos 2 β i + sin 2 β i = 1, we get a quadratic equation:

[0105] 2(1 - sinγ i sinδ i - cosγ i cosδ i )sin 2 β i + 2c(sinγ i - sinδ i )sinβ i

[0106] +c 2 -(cosγ i -cosδ i ) 2 =0

[0107] Solve to get That is

[0108] If there are two solutions, take the smaller value, where:

[0109] A = 2(1 - sinγ i sinδ i -cosγ i cosδ i )

[0110] B = 2c(sinγ i -sinδ i )

[0111] D = c 2 -(cosγ i -cosδ i ) 2

[0112] The working surface 6 of the detector is responsible for collecting the dispersed spectrum emitted from the working surface 5 of the MEMS scanning grating mirror array, and the surface shape of the working surface 6 of the detector is a common detector surface shape in the market.

[0113] The light ray 7 passing through the center of the first micromirror scanning unit of the DMD working surface 3 passes through the center of the first micromirror scanning unit 3-1 of the DMD working surface 3, the collimation subsystem 4, and the center of the first MEMS scanning grating mirror unit 5-1 of the MEMS scanning grating mirror array working surface 5. After being dispersed and deflected by the first MEMS scanning grating mirror unit 5-1 of the MEMS scanning grating mirror array working surface 5, the light rays with wavelengths of 650 nm and 780 nm in the obtained dispersed spectrum are incident on the fixed points M and N respectively.

[0114] The light ray 8 passing through the center of the middle micromirror scanning unit of the DMD working surface 3 passes through the center of the middle micromirror scanning unit 3-2 of the DMD working surface 3, the collimation subsystem 4, and the center of the middle MEMS scanning grating mirror unit 5-2 of the MEMS scanning grating mirror array working surface 5. After being dispersed and deflected by the middle MEMS scanning grating mirror unit 5-2 of the MEMS scanning grating mirror array working surface 5, the light rays with wavelengths of 650 nm and 780 nm in the obtained dispersed spectrum are incident on the fixed points M and N respectively.

[0115] The light ray 9 passing through the center of the last micromirror scanning unit of the DMD working surface 3 passes through the center of the last micromirror scanning unit 3-3 of the DMD working surface 3, the collimation subsystem 4, and the center of the last MEMS scanning grating mirror unit 5-3 of the MEMS scanning grating mirror array working surface 5 respectively. After being dispersed and deflected by the last MEMS scanning grating mirror unit 5-3 of the MEMS scanning grating mirror array working surface 5, the light rays with wavelengths of 650 nm and 780 nm in the obtained dispersed spectrum are incident on the fixed points M and N respectively.

[0116] The spectral acquisition principle of a spectral imaging system and method based on MEMS proposed by the present invention is as Figure 6 shown. By controlling 169 micromirror scanning units and 169 MEMS scanning grating mirror units to be simultaneously in the "ON" working state in sequence, column-by-column scanning of the target image is realized, and then 169 dispersed spectrum images are obtained on the same area of the detector working surface 6, completing the acquisition of the target three-dimensional data cube. The spectral acquisition principle process of a spectral imaging system and method based on MEMS proposed by the present invention specifically includes the following steps:

[0117] Step 1: Refer to Figure 6 , control the first micromirror scanning unit of the DMD working surface 3 and the first MEMS scanning grating mirror unit of the MEMS scanning grating mirror array 5 to be simultaneously in the "ON" working state, and other micromirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light rays of the first column of the target image are first reflected by the first micromirror scanning unit and enter the collimation subsystem 4. After being collimated by the collimation subsystem 4, they are parallelly emitted to the MEMS scanning grating mirror array working surface 5, and then are dispersed and reflected by the first MEMS scanning grating mirror unit. The obtained emitted dispersed spectrum is imaged on the detector working surface 6. Refer to Figure 7 , define the direction of spectral dispersion as the X-axis direction, and the Y-axis direction perpendicular to this direction as the spatial position direction. The spectrum of the first column of the target image is sequentially expanded along the X-axis direction according to different wavelengths, and the spectral components corresponding to different spatial positions are obtained in the Y-axis direction. The detector working surface 6 records and stores the dispersed spectrum image of the first column of the target image. The reflection work of the first micromirror scanning unit and the dispersion deflection work of the first MEMS scanning grating mirror unit are completed, and the spectral imaging of the first column of the target image is completed;

[0118] Step 2: Refer to Figure 6, control the 2nd micromirror scanning unit on the DMD working surface 3 and the 2nd MEMS scanning grating mirror unit on the MEMS scanning grating mirror array working surface 5 to be in the "ON" working state simultaneously, and other micromirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light of the target image in the 2nd column is first reflected by the 2nd micromirror scanning unit into the collimation subsystem 4, collimated by the collimation subsystem 4 and then emitted parallel to the MEMS scanning grating mirror array working surface 5, and then dispersed and reflected by the 2nd MEMS scanning grating mirror unit. The obtained emitted dispersed spectrum is imaged on the detector working surface 6. Refer to Figure 7 , although the target image is shifted in the horizontal direction, its position of the dispersed spectrum on the detector working surface 6 does not change. The detector working surface 6 records and stores the dispersed spectrum image at this time. The reflection work of the 2nd micromirror scanning unit and the dispersion deflection work of the 2nd MEMS scanning grating mirror unit are completed, and the spectral imaging of the target image in the 2nd column is completed;

[0119] Step 3: Control the 3rd, 4th... 168th micromirror scanning units on the DMD working surface 3 and the 3rd, 4th... 168th MEMS scanning grating mirror units on the MEMS scanning grating mirror array working surface 5 to be in the "ON" working state simultaneously in sequence. The detector working surface 6 synchronously records and stores the corresponding dispersed spectrum images, and completes the spectral imaging of the target images in the 3rd, 4th... 168th columns;

[0120] Step 4: Refer to Figure 6 , control the 169th micromirror scanning unit on the DMD working surface 3 and the 169th MEMS scanning grating mirror unit on the linear MEMS scanning grating mirror array working surface 5 to be in the "ON" working state simultaneously, and other micromirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light of the target image in the 169th column is first reflected by the 169th micromirror scanning unit into the collimation subsystem 4, collimated by the collimation subsystem 4 and then emitted parallel to the MEMS scanning grating mirror array working surface 5, and then dispersed and reflected by the 169th MEMS scanning grating mirror unit. The obtained emitted dispersed spectrum is imaged on the detector working surface 6. Refer to Figure 7 , since the spectral positions of the spatial positions of the target images in different columns are unchanged in the X-axis direction, as long as it is ensured that the detector working surface 6 can completely collect the dispersed spectrum of any column of the target image, the spectral imaging of the entire target can be completed. The detector working surface 6 records and stores the dispersed spectrum image at this time. The reflection work of the 169th micromirror scanning unit and the dispersion deflection work of the 169th MEMS scanning grating mirror unit are completed, and the spectral imaging of the target image in the 169th column is completed;

[0121] Step 5: Process the 169 dispersion spectrograms collected by the detector working surface 6 to obtain the two-dimensional spatial image and one-dimensional spectral information of the target 1, that is, a complete three-dimensional data cube, and the spectral acquisition process of a spectral imaging system and method based on MEMS proposed by the present invention ends.

Claims

1. A MEMS-based spectral imaging system, characterized in that, It mainly includes a target (1), an imaging subsystem (2), a DMD working surface (3), the first micromirror scanning unit (3-1) of the DMD working surface, the middle micromirror scanning unit (3-2) of the DMD working surface, the last micromirror scanning unit (3-3) of the DMD working surface, a collimation subsystem (4), a working surface of a MEMS scanning grating mirror array (5), the first MEMS scanning grating mirror unit (5-1) of the working surface of the MEMS scanning grating mirror array, the middle MEMS scanning grating mirror unit (5-2) of the working surface of the MEMS scanning grating mirror array, the last MEMS scanning grating mirror unit (5-3) of the working surface of the MEMS scanning grating mirror array, a detector working surface (6), the light ray (7) passing through the center of the first micromirror scanning unit of the DMD working surface, the light ray (8) passing through the center of the middle micromirror scanning unit of the DMD working surface, and the light ray (9) passing through the center of the last micromirror scanning unit of the DMD working surface; the target (1) and the DMD working surface (3) are respectively placed at the object surface and the image surface of the imaging subsystem (2), and the target image formed by the target (1) through the imaging subsystem (2) is divided by columns by the micromirror scanning units of the DMD working surface (3); the collimation subsystem (4) makes the light reflected from the DMD working surface (3) become parallel light, the working surface of the MEMS scanning grating mirror array (5) is located in the light exit direction of the collimation subsystem (4), and the number of MEMS scanning grating mirror units in the working surface of the MEMS scanning grating mirror array (5) is the same as the number of micromirror scanning units in the DMD working surface (3). It is required that when each micromirror scanning unit in the DMD working surface (3) is in the deflection working state, it must reflect the target image of the corresponding column into the collimation subsystem (4) for collimation, and the obtained parallel light is then incident on the corresponding MEMS scanning grating mirror unit in the working surface of the MEMS scanning grating mirror array (5) for beam splitting. At the same time, it is required that the light rays passing through the centers of each micromirror scanning unit of the DMD working surface (3) also pass through the centers of the corresponding MEMS scanning grating mirror units in the working surface of the MEMS scanning grating mirror array (5). The light ray (7) passing through the center of the first micromirror scanning unit of the DMD working surface, the light ray (8) passing through the center of the middle micromirror scanning unit of the DMD working surface, and the light ray (9) passing through the center of the last micromirror scanning unit of the DMD working surface respectively pass through the centers of the first MEMS scanning grating mirror unit (5-1), the middle MEMS scanning grating mirror unit (5-2), and the last MEMS scanning grating mirror unit (5-3) of the working surface of the MEMS scanning grating mirror array (5); by changing the deflection angle of each MEMS scanning grating mirror unit in the working surface of the MEMS scanning grating mirror array (5), the dispersed spectra split and emitted by each MEMS scanning grating mirror unit are incident on the same area of the detector, that is, the minimum wavelength λ 1 and the maximum wavelength λ 2 The light rays are incident on the starting and ending fixed points M and N of the dispersion spectrum region, and all the finally obtained dispersion spectra will be imaged at the same position on the working surface (6) of the detector; the imaging subsystem (2) is responsible for converging the reduced or magnified image of the target (1) onto the DMD working surface (3); the DMD working surface (3) is rectangular and consists of a micro-mirror array. The number of columns and rows of the micro-mirror array are a and b respectively. The width of each micro-mirror is u. The image of the target (1) is divided into 2K + 1 columns by the micro-mirror scanning unit of the DMD working surface (3), where K is a positive integer. Each micro-mirror scanning unit contains x columns of micro-mirrors, and the width of each micro-mirror scanning unit is xu, and x(2K + 1) ≤ a. Each micro-mirror has only two deflection angles, positive and negative. One of the deflection states is selected as the "ON" working state. The micro-mirror scanning unit in this state will reflect the selected target image to the collimation subsystem (4); the other deflection state is the "OFF" state, and the micro-mirror scanning unit in this state is responsible for reflecting the selected target image out of the system; the collimation subsystem (4) can be composed of components such as a lens group or a concave spherical mirror, and is responsible for collimating the light reflected from the DMD working surface (3) so that it is incident parallel to the MEMS scanning grating mirror array working surface (5); The working surface (5) of the MEMS scanning grating mirror array is fabricated by using MEMS technology to engrave grating lines on a long strip-shaped scanning mirror array, which can simultaneously achieve two functions of dispersion spectroscopy and scanning deflection. The working surface (5) of the MEMS scanning grating mirror array contains 2K + 1 MEMS scanning grating mirror units. The grating line width is d, the diffraction order is m, the width of each MEMS scanning grating mirror unit is t, and the center point of the i-th MEMS scanning grating mirror unit is O i , where i is a positive integer and i ∈ [1, 2K + 1]. The spectral dispersion length on the detector working surface (6) is MN, and the wavelength λ ∈ [λ 1 , λ 2 . It is required that the working surface (5) of the MEMS scanning grating mirror array is parallel to the detector working surface (6). The extension line of the cross-section of the working surface (5) of the MEMS scanning grating mirror array intersects the perpendicular line of the detector working surface (6) at point N at point O. The length of ON is h, the length of MN is s, and the length of OO 2K+1 is l. It is required that l >> s. It is required that each MEMS scanning grating mirror unit can only deflect clockwise. When the i-th MEMS scanning grating mirror unit is in the working state "ON", its deflection angle is β i , β i = 0, the incident angle of the MEMS scanning grating mirror unit is α 0 , and the diffraction angles corresponding to the light with dispersion wavelengths of λ 1 and λ 2 are θ i1 and θ i2 respectively, and they are incident on the fixed points M and N respectively. By reasonably selecting the values of h, s, l, t, d, λ 1 , λ 2 , it is ensured that the dispersion spectra obtained by splitting and reflecting through the i-th MEMS scanning grating mirror unit can all be incident on the fixed area MN on the detector, that is, β i has a solution. According to the above known parameters, an intermediate variable ∠NO i O = γ i , ∠MO i O = δ i is introduced, and a solution method for β i is given: β i satisfies the following formula: where: d(sin(α 0 +β i )+sinθ i1 ) = mλ 1 (3) d(sin(α 0 +β i )+sinθ i2 ) = mλ 2 (4) (4)-(3) and substituting (1) and (2) into it gives: Expand Equation (5) and substitute it into the equation cos 2 β i +sin 2 β i = 1 to obtain a quadratic equation: 2(1 - sinγ i sinδ i -cosγ i cosδ i )sin 2 β i + 2c(sinγ i - sinδ i )sinβ i + c 2 -(cosγ i - cosδ i ) 2 =0 Solve to obtain That is If there are two solutions, take the smaller value, where: A = 2(1 - sinγ i sinδ i - cosγ i cosδ i ) B = 2c(sinγ i - sinδ i ) D = c 2 -(cosγ i -cosδ i ) 2 the detector working surface (6) is responsible for collecting the dispersed spectrum emitted from the MEMS scanning grating mirror array working surface (5), and the surface type of the detector working surface (6) is a common detector surface type on the market; The light ray (7) passing through the center of the first micromirror scanning unit of the DMD working surface (3) passes through the center of the first micromirror scanning unit (3-1) of the DMD working surface (3), the collimation subsystem (4), and the center of the first MEMS scanning grating mirror unit (5-1) of the MEMS scanning grating mirror array working surface (5). After being dispersed and deflected by the first MEMS scanning grating mirror unit (5-1) of the MEMS scanning grating mirror array working surface (5), the light rays with wavelengths of λ 1 , λ 2 respectively enter the fixed points M and N; The light beam (8) passing through the center of the middle micromirror scanning unit on the DMD working surface (3) passes through the center of the middle micromirror scanning unit (3-2) on the DMD working surface (3), the collimation subsystem (4), and the center of the middle MEMS scanning grating mirror unit (5-2) on the MEMS scanning grating mirror array working surface (5). After dispersion and deflection by the middle MEMS scanning grating mirror unit (5-2) on the MEMS scanning grating mirror array working surface (5), the light rays with wavelengths of λ 1 , λ 2 in the obtained dispersion spectrum are respectively incident on the fixed points M and N; The light ray (9) passing through the center of the last micromirror scanning unit on the DMD working surface (3) passes through the center of the last micromirror scanning unit (3-3) on the DMD working surface (3), the collimation subsystem (4), and the center of the last MEMS scanning grating mirror unit (5-3) on the MEMS scanning grating mirror array working surface (5). After dispersion and deflection by the last MEMS scanning grating mirror unit (5-3) on the MEMS scanning grating mirror array working surface (5), the light rays with wavelengths of λ 1 , λ 2 in the obtained dispersion spectrum are respectively incident on the fixed points M and N.

2. A spectral imaging method for the system according to claim 1, characterized in that, it includes the following steps: Step 1: Control the first micro-mirror scanning unit of the DMD working surface (3) and the first MEMS scanning grating mirror unit of the MEMS scanning grating mirror array (5) to be in the "ON" working state at the same time, and other micro-mirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light of the first column of the target image is first reflected by the first micro-mirror scanning unit into the collimation subsystem (4), collimated by the collimation subsystem (4) and then emitted parallel to the MEMS scanning grating mirror array working surface (5), and then dispersed and reflected by the first MEMS scanning grating mirror unit. The obtained emitted dispersed spectrum is imaged on the detector working surface (6). Define the direction of spectral dispersion as the X-axis direction, and the Y-axis direction perpendicular to this direction as the spatial position direction. The spectrum of the first column of the target image is sequentially unfolded along the X-axis direction according to different wavelengths, and the spectral components corresponding to different spatial positions are obtained in the Y-axis direction. The detector working surface (6) records and stores the dispersed spectrum diagram of the first column of the target image. The reflection work of the first micro-mirror scanning unit and the dispersion deflection work of the first MEMS scanning grating mirror unit are completed, and the spectral imaging of the first column of the target image is completed; Step 2: Control the second micromirror scanning unit of the DMD working surface (3) and the second MEMS scanning grating mirror unit of the MEMS scanning grating mirror array working surface (5) to be in the "ON" working state at the same time, and the other micromirror scanning units and other MEMS scanning grating mirror units to be in the "OFF" state, the light of the second column of target images is first reflected by the second micromirror scanning unit and enters the collimation subsystem (4), and then collimated by the collimation subsystem (4) and emitted in parallel to the MEMS scanning grating mirror array working surface (5), and then dispersed and reflected by the second MEMS scanning grating mirror unit, and the obtained emission dispersion spectrum is imaged on the detector working surface (6); although the target image is offset in the horizontal direction, the position of its dispersion spectrum on the detector working surface (6) does not change; the detector working surface (6) records and stores the dispersion spectrum diagram at this time, the reflection work of the second micromirror scanning unit and the dispersion deflection work of the second MEMS scanning grating mirror unit are completed, and the spectrum imaging of the second column of target images is completed; Step 3: Control the 3rd, 4th, ... 2K micromirror scanning units of the DMD working surface (3) and the 3rd, 4th, ... 2K MEMS scanning grating mirror units of the MEMS scanning grating mirror array working surface (5) to be in the "ON" working state in sequence and at the same time, and the detector working surface (6) synchronously records and stores the corresponding dispersion spectrum diagram to complete the spectral imaging of the 3rd, 4th, ... 2K columns of target images; Step 4: Control the 2K+1th micromirror scanning unit of the DMD working surface (3) and the 2K+1th MEMS scanning grating mirror unit of the MEMS scanning grating mirror array working surface (5) to be in the "ON" working state at the same time, and the other micromirror scanning units and other MEMS scanning grating mirror units are in the "OFF" state. The light of the 2K+1th column of the target image is first reflected by the 2K+1th micromirror scanning unit and enters the collimation subsystem (4). After being collimated by the collimation subsystem (4), it is emitted in parallel to the MEMS scanning grating mirror array working surface (5), and then is reflected by the 2K+1th MEMS scanning unit. The grating mirror unit performs dispersion and reflection, and the obtained outgoing dispersion spectrum is imaged on the detector working surface (6); since the spectral positions of the spatial positions of different columns of target images in the X-axis direction remain unchanged, as long as the detector working surface (6) can completely collect the dispersion spectrum of any column of target images, the spectral imaging of the entire target can be completed; the detector working surface (6) records and stores the dispersion spectrum diagram at this time, the reflection work of the 2K+1th micromirror scanning unit and the dispersion deflection work of the 2K+1th MEMS scanning grating mirror unit are completed, and the spectral imaging of the 2K+1th column of target images is completed; Step 5: Data processing is performed on the 2K+1 dispersion spectra collected by the detector working surface (6) to obtain the two-dimensional spatial scene and one-dimensional spectral information of the target (1), that is, a complete three-dimensional data cube. At this point, the spectrum collection process of a MEMS-based spectral imaging system and method is completed.

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