Spectral polarization integrated imaging system based on spatial dimension coding and design method thereof

A design method of a spectral polarization integrated imaging system based on spatial dimension coding, comprising:

• step 1:
• determining indicators and components of the spectral polarization integrated imaging system based on spatial dimension coding, which comprises:
• analyzing a working scene of the spectral polarization integrated imaging system based on spatial dimension coding;
• determining spatial resolution, spectral resolution, a number of spectral channels and a number of polarization channels of the spectral polarization integrated imaging system based on spatial dimension coding, based on an initial imaging structure of the spectral polarization integrated imaging system;
• and preliminarily determining a digital mirror device (DMD), a grating, and a micro polarizer array detector as the components of the spectral polarization integrated imaging system based on spatial dimension coding;
• step 2:
• determining the micro polarizer array detector, which comprises:
• determining resolution and an indicator of a pixel size of the micro polarizer array detector based on the spatial resolution, the spectral resolution, and the number of the spectral channels;
• and returning to step 1 to re-determine the spatial resolution, the spectral resolution, the number of the spectral channels and the number of the polarization channels of the spectral polarization integrated imaging system based on spatial dimension coding when the resolution of the micro polarizer array detector does not meet requirements for the spatial resolution and the number of the spectral channels of the spectral polarization integrated imaging system based on spatial dimension coding;
• step 3:
• analyzing an aliasing model, which comprises:
• designing an encoding matrix;
• establishing a multi-dimensional discretization energy transmission model of each component of the spectral polarization integrated imaging system based on spatial dimension coding, and a two-dimensional aliasing model of spatial information, spectral information and polarization information obtained on a target surface of the micro polarizer array detector;
• analyzing whether aliasing of the spectral information and the polarization information in the multi-dimensional discretization energy transmission model of each component of the spectral polarization integrated imaging system based on spatial dimension coding is independent, and whether encoded two-dimensional aliasing information of space, spectrum and polarization conforms to restricted isometry property of compressed sensing;
• and modifying the encoding matrix or returning to step 1 to re-determine the spatial resolution, the number of the spectral channels and the number of the polarization channels of the spectral polarization integrated imaging system based on spatial dimension coding when the multi-dimensional discretization energy transmission model is not independent or the aliasing information obtained on the target surface of the micro polarizer array detector does not conform to a restricted isometry property (RIP) criterion;
• step 4:
• during an unmixing process, extracting the polarization information in a same direction from the encoded two-dimensional aliasing information of space, spectrum and polarization information to form four (0°, 45°, 90°, 135°) polarization images;
• during a reconstruction process, setting an independent Bernoulli random matrix as a measurement matrix and the encoding matrix, setting a sparse matrix, selecting a Two-Step Iterative Shrinkage Thresholding (TwIST) algorithm as a reconstruction algorithm;
• and based on the four (0°, 45°, 90°, 135°) polarization images, the measurement matrix, the encoding matrix, and the sparse matrix, restoring a spectral image of each polarization direction by using the Two-Step Iterative Shrinkage Thresholding (TwIST) algorithm to finally generate a data cube;
• wherein according to a corresponding relationship between a polarization array, the encoding matrix and the grating, each group of polarization spectral images differs from an adjacent group of polarization spectral images by 2t(t∈N*) pixels on the micro polarizer array detector;
• and optical design is guided by such a result as priori knowledge of a focal length design of a third mirror in a subsequent optical system;
• and
• when an indicator of optical system design is not derived from the corresponding relationship between the polarization array, the encoding matrix and the grating or the spectral image of each polarization direction is not restored based on the TwIST algorithm, returning to step 1 to re-determine the spatial resolution, the spectral resolution, the number of the spectral channels and the number of the polarization channels of the spectral polarization integrated imaging system based on spatial dimension coding, or returning to step 3 to redesign the encoding matrix;
• step 5:
• selecting an encoding component, which comprises:
• determining DMD resolution based on a corresponding relationship between the encoding matrix, the polarization array of the micro polarizer array detector and the spatial resolution of the spectral polarization integrated imaging system based on spatial dimension coding;
• and returning to step 3 to modify the encoding matrix when the DMD resolution does not meet an encoding requirement and a zoom ratio of design in the aliasing model;
• step 6:
• designing a beam-splitting element, which comprises:
• selecting the grating as a beam-splitting element, wherein a grating equation is d sin(α±β)=Mλ, α is an incident angle, β is a diffraction angle, d is a grating constant, M is a diffraction order, and λ is a wavelength, a plus sign indicates that a diffracted light and an incident light are on a same side of a grating normal line, and a minus sign indicates that the diffracted light and the incident light are on an opposite side of a grating normal line;
• selecting a type and an indicator of the grating based on an aliasing model of a space, a spectrum and a polarization obtained on the target surface of the micro polarizer array detector;
• and returning to step 1 to re-determine the spatial resolution, the number of the spectral channels, and the number of the polarization channels of the spectral polarization integrated imaging system based on spatial dimension coding when the beam-splitting element does not meet a beam-splitting requirement of the aliasing model;
• step 7:
• designing an Offner system, which comprises:
• designing a primary mirror and the third mirror, wherein the third mirror and grating constant determine a multi-dimensional aliasing information state on the target surface of the detector of the spectral polarization integrated imaging system based on spatial dimension coding;
• when an interval between adjacent spectral images on the detector is 2t(t∈N*) pixels based on the aliasing model and the reconstruction algorithm, a formula
• 2
• ⁢
• t
• ×
• p
• CCD
• =
• {
• f
• I
• [
• arcsin
• ⁡
• (
• M
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• λ
• /
• d
• )
• -
• α
• ]
• ⁢
• same
• ⁢
• side
• f
• I
• [
• α
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• arcsin
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• is obtained, wherein PCCD is the pixel size of the micro polarizer array detector;
• a focal length fthird of the third mirror is analyzed based on the formula, a focal length ffirst=fthird/c of the primary mirror is determined based on an analysis result of the aliasing model analyzed by the spectral polarization integrated imaging system, wherein c is a zoom ratio of the primary mirror to the third mirror, c=PDMD/e×PCCD, e is a positive even number, and PDMD is a mirror size of the DMD;
• and when design of the Offner system does not meet a requirement of the aliasing model for beam-splitting, imaging indicator or zoom ratio, returning to step 1 to re-determine the spatial resolution, the spectral resolution, the number of spectral channels and the number of the polarization channels of the spectral polarization integrated imaging system based on spatial dimension coding, or returning to step 5 to re-determine the DMD resolution, or returning to step 6 to re-select a grating index;
• step 8:
• designing an objective lens, which comprises:
• designing the objective lens based on an application environment and an imaging indicator of the spectral polarization integrated imaging system based on spatial dimension coding;
• step 9:
• manufacturing the spectral polarization integrated imaging system based on spatial dimension coding comprising:
• an objective lens, a filter, a target DMD, a target primary mirror, a target convex grating, a target third mirror, a target micro polarizer array detector, and a computer;
• wherein, the target micro polarizer array detector is selected based on the determined resolution and indicator of the pixel size of the micro polarizer array detector, the target DMD is selected based on the determined DMD resolution, the target convex grating is selected based on the selected type and indicator of the grating, the target third mirror is selected based on the analyzed focal length of the third mirror, and the target primary mirror is selected based on the determined focal length of the primary mirror;
• wherein the Offner system comprises the target primary mirror, the target convex grating, and the target third mirror;
• and the objective lens generates an image of a target on the target DMD;
• the filter filters out light in a non-working band before the light enters into the target DMD;
• the target DMD is disposed on a focal plane of the objective lens;
• the target DMD is connected to the computer;
• the computer controls an encoding matrix loaded on the target DMD to encode information;
• the light is reflected to the target primary mirror after being encoded by the target DMD, and then the light is reflected by the target primary mirror to the target convex grating for dispersion;
• the light subjected to the dispersion is then reflected to the target third mirror;
• an encoded image is produced on the target micro polarizer array detector;
• polarization channel coding is completed by using a micro polarizer array on the target micro polarizer array detector;
• the target micro polarizer array detector is connected to the computer;
• and the computer performs calculation on spectral polarization coding data cube obtained on a target surface of the target micro polarizer array detector to obtain a compressive spectral polarization image.