Snapshot Fourier Transform Stokes Polarization Imaging Spectrometer

Abstract

This invention provides a snapshot-type Fourier transform Stokes polarization imaging spectrometer, comprising, in sequence along the beam propagation direction: a telescope system, a polarization modulation system, a converging system, a polarization interferometer system, and an imaging system. A target light field emitted from a target scene is incident on the telescope system. After passing through the telescope system, the target light field is collimated into a parallel light field and incident on the polarization modulation system. The parallel light field passes through the polarization modulation system sequentially to obtain a linearly polarized light field, which is then incident on the converging system. The converging system is used to perform multi-array imaging of the linearly polarized light field, resulting in multiple imaging light fields that are incident on the polarization interferometer system. The multiple imaging light fields generate superimposed interference at the light exit position of the polarization interferometer system, forming a polarization interferometric image field with specific optical path difference distribution characteristics. This image field is then incident on the imaging system to obtain an interferometric image array. Based on the aforementioned interferometric image array, the spectral information of each Stokes parameter of the target light field under each field of view is demodulated.

Description

Technical Field

[0001] This invention relates to the field of spectroscopy, and in particular to a snapshot Fourier transform Stokes polarization imaging spectrometer. Background Technology

[0002] With the development of science and technology, high-tech fields such as space exploration, military reconnaissance, medical engineering, and resource remote sensing are placing increasingly higher demands on the accuracy and real-time performance of target detection and identification. Imaging can acquire information about the entire target scene, spectroscopy can reflect the composition and content information of each point within the target scene, and polarization can obtain detailed target features and suppress the influence of complex environments. Therefore, combining imaging spectroscopy with infrared polarization technology to construct a multi-dimensional real-time detection system has become a pressing application requirement. Infrared polarization spectral information is characterized by its all-weather capability and independence from day-night variations, offering unique advantages in complex environment applications. Fourier transform spectroscopy, with its advantages of multi-channel operation, high throughput, high wavenumber accuracy, and low stray light, can achieve high-resolution detection and analysis of weak radiators, making it the most powerful spectral detection technology in the infrared band. However, traditional Fourier transform infrared spectroscopy is limited in reliability, stability, and real-time performance due to its moving mirror scanning mechanism. Therefore, infrared polarization imaging spectroscopy based on static interferometry systems has greater development potential and significant application value.

[0003] Current polarization imaging spectral detection technology is in a phase of rapid development. Most polarization imaging spectral detection systems employ time-division or amplitude-division detection methods, splitting the system into multiple polarization detection channels through polarizer rotation or beam splitters. Time-division detection cannot acquire transient information in all dimensions in real time, limiting its ability to detect moving scenes or rapidly changing targets; while amplitude-division detection results in a very large system size and weight. Furthermore, current research primarily focuses on the visible light band, with relatively little research on the infrared band. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to propose a snapshot-type Fourier transform Stokes polarization imaging spectrometer. By employing a high-order phase retarder based on a birefringent crystal for polarization modulation, all Stokes parameters of the incident light field are modulated into the light intensity signal. Simultaneously, by employing multi-lens array-based multiple imaging technology and multi-level micromirror spatial phase modulation technology, synchronous acquisition of light intensity information at all interference orders of the target scene is achieved, resulting in a three-dimensional data cube of the interferometric image array. Through interferogram extraction, channel filtering, and Fourier transform, snapshot measurements of the target image, spectrum, and polarization are realized, expanding the dimensions of information detection and improving the real-time performance of information detection. The system has a compact structure and features static and high stability, making it easy to miniaturize and integrate. Furthermore, the effective fusion of image, polarization, and spectral information can reconstruct a higher-quality target scene, highlighting the detailed features of the target, enhancing the target recognition effect, and improving the accuracy of target detection. This invention solves the problem of static, real-time, and integrated measurement of multiple dimensions of information, including image, spectrum, and polarization.

[0005] To achieve the above objectives, the present invention adopts the following specific technical solution:

[0006] This invention provides a snapshot Fourier transform Stokes polarization imaging spectrometer, which includes, in sequence along the beam propagation direction: a telescope system, a polarization modulation system, a convergence system, a polarization interferometry system, and an imaging system;

[0007] The target light field emitted from the target scene is incident on the telescope system. After passing through the telescope system, the target light field is collimated into a parallel light field and incident on the polarization modulation system.

[0008] The polarization modulation system includes: a first higher-order phase delayer, a second higher-order phase delayer, and a polarizer polarizer;

[0009] The parallel light field is polarized by passing through the first higher-order phase retarder and the second higher-order phase retarder in sequence to obtain the modulated light field. The modulated light field then passes through the polarizer polarizer to obtain the linearly polarized light field, which is then incident on the converging system.

[0010] The converging system is used to perform multi-array imaging of linearly polarized light fields, resulting in multiple imaging light fields incident on the polarization interferometer system.

[0011] The polarization interference system includes: a beam splitter, a transverse multi-stage micromirror, and a longitudinal multi-stage micromirror;

[0012] The multiple imaging light fields are decomposed into reflected imaging light fields and transmitted imaging light fields with equal amplitude by a beam splitter.

[0013] The reflected imaging light field and the transmitted imaging light field are respectively incident into the transverse multi-stage micro-reflector and the longitudinal multi-stage micro-reflector, and the transverse phase modulation and longitudinal phase modulation are generated respectively. After returning to the beam splitter along the original path, the reflected imaging light field and the transmitted imaging light field are emitted from the beam splitter. The two beams emitted from the beam splitter are superimposed and interfered at the emission position of the beam splitter to form a polarization interference image field with specific optical path difference distribution characteristics. The light field is incident on the imaging system to obtain the interference image array.

[0014] An interferometric image data cube is obtained by extracting and rearranging image units from the interferometric image array. The interferogram sequence of each field of view in the interferometric image data cube is extracted sequentially along the optical path difference direction. The interferogram sequence is then subjected to Stokes channel filtering and Fourier transform, and the spectral information of each Stokes parameter of the target light field under each field of view is demodulated.

[0015] Preferably, the telescope system includes: a telescope objective lens, a field stop, and a collimating lens;

[0016] The target light field is imaged at the field stop after passing through the telescope objective. The field stop is located on the image-side focal plane of the telescope objective and simultaneously on the object-side focal plane of the collimating lens. It is used to limit the field of view of the image of the target scene formed by the telescope objective. The imaged light field through the field stop is collimated into a parallel light field by the collimating lens and then incident on the polarization modulation system.

[0017] Preferably, the fast axis direction of the first higher-order phase delay is along the positive x-axis;

[0018] The fast axis direction of the second higher-order phase delay makes an angle of 45° with the positive x-axis;

[0019] The first and second higher-order phase retarders are birefringent crystals used to adjust the phase difference of the outgoing light; their materials are quartz, calcite, magnesium fluoride, yttrium vanadate, or barium metaborate.

[0020] The polarizer polarizer has a transmission axis that makes a 0° angle with the positive x-axis, and is used to transmit linearly polarized light with a specific vibration direction.

[0021] Preferably, after the parallel light field passes through the polarization modulation system, all of its Stokes parameters S0, S1, S2, and S3 are modulated into the intensity parameter S0 component, thereby enabling the polarization state of the target light field to be detected.

[0022] set up:

[0023] The Stokes vector of the target light field is S in The Mueller matrix of the first higher-order phase delay is M. R1 The Mueller matrix of the second higher-order phase delay is M. R2 The Mueller matrix of the polarizer polarizer is M. P;

[0024] set up:

[0025] The wavenumber of the target optical field is ν, and the refractive indices of the o-ray and e-ray of the higher-order phase retarder crystal are n and n, respectively. o and n e The thickness of the first higher-order phase delay is d1, and the thickness of the second higher-order phase delay is d2;

[0026] Then the optical path difference between the o-ray and e-ray emitted from the first higher-order phase retarder is L1 = (n e -n o )d1, the phase delay is

[0027] The optical path difference between the emitted o-light and e-light from the second higher-order phase retarder 5 is L2 = (n e -n o )d2, the phase delay is

[0028] Stokes parameter S of the linearly polarized light field obtained after the target light field passes through the polarization modulation system out for:

[0029]

[0030] Therefore, the S0' parameter in the linearly polarized optical field contains all the Stokes parameters of the target optical field, and each parameter is modulated by a different modulation function, that is:

[0031]

[0032] Preferably, the converging system includes a microlens array;

[0033] The microlens array is composed of the same number of rows and columns of microlens units, which perform multiple array imaging on the incident linearly polarized light field to obtain multiple imaging light fields incident on the polarization interference system.

[0034] Preferably, the reflected imaging light field is imaged onto a transverse multi-stage micromirror after being reflected by a beam splitter.

[0035] The transmitted imaging light field is imaged onto the longitudinal multi-stage micro-reflective mirror after being transmitted through the beam splitter.

[0036] The horizontal and vertical multi-stage micromirrors have a stepped structure and are located on the image-side focal plane of the microlens array. They are placed in mirror image with respect to the beam-splitting surface of the beam splitter, and the step directions are orthogonal to each other.

[0037] Each step of the horizontal multi-level micromirror corresponds to a row of microlens units in the microlens array.

[0038] Each step of the longitudinal multi-stage micromirror corresponds to a column of microlens units in the microlens array;

[0039] The interference channel formed by the horizontal multi-level micromirror row ladder and the vertical multi-level micromirror column ladder corresponds one-to-one with the imaging channel formed by the microlens units in the microlens array.

[0040] Preferably, the imaging system includes: a relay imaging system and an area array detector;

[0041] The relay imaging system is a telecentric optical path structure used to image the polarization interference image field onto the area array detector;

[0042] The area array detector is located on the image plane of the relay imaging system and is used to receive polarization interferometric image arrays;

[0043] The polarization interference image field light field passes through the relay imaging system and forms an interference image array on the area array detector.

[0044] Preferably, let:

[0045] The number of steps in the transverse and longitudinal multi-stage micromirrors is N, and the step height of one multi-stage micromirror is h1; then the step height of the other multi-stage micromirror is h2 = N × h1; therefore, the optical path difference Δ and phase difference φ of the interference image field unit corresponding to the m-th step of the first multi-stage micromirror and the n-th step of the other multi-stage micromirror are respectively:

[0046] Δ(m,n)=2nh2-2mh1=2(nN-m)h1

[0047]

[0048] By extracting each interferometric image field unit from the interferometric image array and rearranging them according to the optical path difference, an interferometric image data cube is formed.

[0049] By selecting a field of view within the interferometric image unit and extracting the interferogram signal along the direction of the optical path difference, the interferogram signal I can be obtained as follows:

[0050]

[0051] Preferably, the interferogram signal I is expanded using Euler's formula, then the interferogram signal I of the target light field is:

[0052]

[0053] The Stokes parametric interferogram of the target light field was modulated to be 0, and The seven parts centered on the center will form an interference pattern with seven channels;

[0054] Each channel's interferogram contains one or two Stokes parameter information, where channel C0 contains only the S0 parameter, and C... ±1 The channel contains only the S1 parameter, C ±2 and C ±3 The channel contains parameters S2 and S3, and the center positions of the interferogram channels are located at 0, ±L2, ±(L2-L1), and ±(L2+L1), respectively.

[0055] The Stokes parametric spectral demodulation process is as follows:

[0056] The C0 interferogram channel is bandpass filtered, with the passband located at Δ = [-(L2-L1) / 2, (L2-L1) / 2]. After Fourier transform, the spectrum of the S0 parameter is obtained as S0(ν) = 2FT[C0(Δ)].

[0057] The C1 interferogram channel is bandpass filtered, with the passband located at Δ=[(2L2-L1) / 2,(2L2+L1) / 2]. After Fourier transform, the spectrum of the S1 parameter is obtained as S1(ν)=4FT[C1(Δ)]exp(j2πνL2);

[0058] The C2 interferogram channel is bandpass filtered, with the passband located at Δ = [(L2-L1) / 2, (2L2-L1) / 2]. After Fourier transform, the spectra of parameters S2 and S3 are obtained as follows:

[0059] S2(ν)=8Re{FT[C2(Δ)]exp[j2πν(L2-L1)]}

[0060] S3(ν)=-8Im{FT[C2(Δ)]exp[j2πν(L2-L1)]}.

[0061] Preferably, when the thickness ratio of the first higher-order phase retarder and the second higher-order phase retarder is d1:d2 = 1:2, the seven channels C0, C1, C2, and C3 of the interferogram are... ±1 C ±2 C ±3 Separating the signals, three independent channels were selected to perform Fourier transforms on the interferogram signals, thereby obtaining the spectral information of the four Stokes parameters of the target light field:

[0062] S0(ν)=2FT[C0(Δ)]

[0063]

[0064]

[0065]

[0066] Compared with existing technologies, the present invention has the following advantages:

[0067] 1. This invention uses an interference system based on multi-level micromirrors for phase modulation, with no moving parts, which improves the reliability of the system and the real-time nature of information acquisition.

[0068] 2. This invention uses a high-order phase delayer and a microlens array for polarization imaging modulation, eliminating the need for amplitude division and reducing the size and weight of the system.

[0069] 3. This invention can achieve integrated acquisition of imaging, spectral, and polarization multidimensional information, and has the advantages of miniaturization, multi-parameter, static, and snapshot detection. Attached Figure Description

[0070] Figure 1 This is a schematic diagram of the structure of a snapshot Fourier transform Stokes polarization imaging spectrometer provided in an embodiment of the present invention.

[0071] Figure 2 This is a schematic diagram of the crystal optical features of a first higher-order phase delayer provided according to an embodiment of the present invention.

[0072] Figure 3 This is a schematic diagram of the crystal optical features of a second higher-order phase delayer provided according to an embodiment of the present invention.

[0073] Figure 4 This is a schematic diagram of the crystal optical characteristics of a polarizer polarizer provided according to an embodiment of the present invention.

[0074] Figure 5 This is a schematic diagram of the structure of a multi-level micromirror provided according to an embodiment of the present invention.

[0075] Figure 6 This is a schematic diagram of the imaging optical path of a microlens array for multiple micromirrors according to an embodiment of the present invention.

[0076] Figure 7 This is a schematic diagram of the optical path difference modulation process of each interference imaging channel, provided by an embodiment of the present invention.

[0077] Figure 8 This is a schematic diagram of the Stokes channel interference provided according to an embodiment of the present invention.

[0078] Figure 9 This is a schematic diagram of the Stokes parametric spectral demodulation process provided in an embodiment of the present invention.

[0079] The reference numerals in the figures include: telescope objective 1, field stop 2, collimating lens 3, first higher-order phase retarder 4, second higher-order phase retarder 5, polarizer 6, microlens array 7, beam splitter 8, lateral multi-stage micromirror 9, longitudinal multi-stage micromirror 10, relay imaging system 11, and area array detector 12. Detailed Implementation

[0080] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0081] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0082] Figure 1 The structure of a snapshot Fourier transform Stokes polarization imaging spectrometer provided according to an embodiment of the present invention is shown.

[0083] like Figure 1 As shown, the snapshot Fourier transform Stokes polarization imaging spectrometer provided in this embodiment of the invention includes, in sequence along the beam propagation direction, a telescope system, a polarization modulation system, a convergence system, a polarization interferometry system, and an imaging system.

[0084] The target light field emitted from a distant target scene first enters the telescope system. The polarization state of the target light field is determined by the polarization characteristics of the target scene. Target light fields emitted from different target scenes have different polarization characteristics. After passing through the telescope system, the target light field is collimated into a parallel light field.

[0085] The telescope system includes: a telescope objective lens 1, a field stop 2, and a collimating lens 3. The target light field, after passing through the telescope objective lens 1, is imaged at the field stop 2. The field stop 2 is located on the image-side focal plane of the telescope objective lens 1 and simultaneously on the object-side focal plane of the collimating lens 3. It is used to limit the field of view of the image of the target scene formed by the telescope objective lens 1. The imaged light field through the field stop 2 is collimated into a parallel light field by the collimating lens 3. The collimated parallel light field is then incident on the polarization modulation system.

[0086] The polarization modulation system includes: a first higher-order phase delayer 4, a second higher-order phase delayer 5, and a polarizer polarizer 6;

[0087] Figure 2 The crystal optical features of a first high-order phase delayer provided according to an embodiment of the present invention are shown.

[0088] Figure 3 The crystal optical features of a second higher-order phase delayer provided according to an embodiment of the present invention are shown.

[0089] Figure 4 The crystal optical features of a polarizer polarizer provided according to an embodiment of the present invention are shown.

[0090] like Figure 2-4 As shown, the fast axis (e-axis) of the first higher-order phase retarder 4 is along the positive x-axis, and the slow axis (o-axis) is along the positive y-axis. It is a birefringent crystal, and the optical axis of the crystal is parallel to the surface.

[0091] The second higher-order phase retarder 5 has a fast axis (e-axis) direction with an angle of 45° to the positive x-axis and a slow axis (o-axis) direction with an angle of 135° to the positive x-axis. It is a birefringent crystal, and the optical axis of the crystal is parallel to the surface.

[0092] The crystal materials of the first higher-order phase retarder 4 and the second higher-order phase retarder 5 are quartz, calcite, magnesium fluoride, yttrium vanadate, barium metaborate (α-BBO), etc., which are used to adjust the phase difference between the emitted o-light and e-light.

[0093] The polarizer polarizer 6 is located after the second higher-order phase retarder. Its transmission axis forms a 0° angle with the positive x-axis, allowing light to pass through only in the 0° vibration direction. It is constructed by depositing a layer of micro / nano-structured metal grating on the surface of a substrate. The substrate material can be a dielectric such as calcium fluoride, zinc selenide, zinc sulfide, silicon, or germanium, while the grating material can be a metal such as gold or aluminum. Light with a polarization direction perpendicular to the grating direction can pass through, while light with a polarization direction parallel to the grating direction is blocked; that is, the grating direction is along the y-axis.

[0094] The parallel light field is polarized and modulated by passing through the first higher-order phase delayer 4 and the second higher-order phase delayer 5 in sequence to obtain the modulated light field.

[0095] The modulated light field is then passed through polarizer 6 to obtain a linearly polarized light field. The vibration direction of the linearly polarized light field makes an angle of 0° with the positive x-axis.

[0096] After the parallel light field passes through the polarization modulation system, all of its Stokes parameters (S0, S1, S2, S3) are modulated into the intensity parameter S0 component, thereby enabling the polarization state of the target light field to be detected.

[0097] set up:

[0098] The Stokes vector of the target light field is S in The Mueller matrix of the first higher-order phase delayer 4 is M. R1 The Mueller matrix of the second higher-order phase delayer 5 is M. R2 The Mueller matrix of polarizer 6 is M. P .

[0099] set up:

[0100] The wavenumber of the target optical field is ν, and the refractive indices of the o-ray and e-ray of the higher-order phase retarder crystal are n and n, respectively. o and n e The thickness of the first higher-order phase delay 4 is d1, and the thickness of the second higher-order phase delay 5 is d2.

[0101] Then the optical path difference between the emitted o-ray and e-ray from the first higher-order phase retarder 4 is L1 = (n e -n o )d1, the phase delay is

[0102] The optical path difference between the emitted o-light and e-light from the second higher-order phase retarder 5 is L2 = (n e -n o )d2, the phase delay is

[0103] After the target light field passes through the polarization modulation system, the Stokes parameter of the linearly polarized light field can be expressed as:

[0104]

[0105] Therefore, the S0' parameter in the polarized beam exiting the polarization modulation system contains all the Stokes parameters of the target optical field, and each parameter is modulated by a different modulation function, that is:

[0106]

[0107] The parallel light field is modulated by the polarization modulation system and exits from the polarizer polarizer 6 as a linearly polarized light field with a polarization direction at an angle of 0° to the positive x-axis, which is then incident on the converging system.

[0108] The converging system includes a microlens array 7;

[0109] The microlens array 7 is composed of many rows and columns of microlens units, which perform multiple array imaging on the incident linearly polarized light field to obtain multiple imaging light fields incident on the polarization interference system.

[0110] The polarization interference system includes: a beam splitter 8, a transverse multi-stage micromirror 9, and a longitudinal multi-stage micromirror 10;

[0111] The multiple imaging light field is decomposed into two parts of the multiple imaging light field with equal amplitude by the beam splitter 8, namely the reflected imaging light field and the transmitted imaging light field.

[0112] in,

[0113] The reflected imaging light field is imaged onto the transverse multi-stage micro-reflector 9 after being reflected by the beam splitter 8, and the transmitted imaging light field is imaged onto the longitudinal multi-stage micro-reflector 10 after being transmitted by the beam splitter 9.

[0114] Figure 5 The structure of a multi-stage micromirror provided according to an embodiment of the present invention is shown.

[0115] like Figure 5 As shown, the transverse multi-stage micromirror 9 and the longitudinal multi-stage micromirror 10 have a stepped structure, both located on the image-side focal plane of the microlens array 7, mirror-image positioned relative to the beam-splitting plane of the beam splitter 9, and the step directions are orthogonal to each other. Each step of the transverse multi-stage micromirror 9 corresponds to a row of microlens units in the microlens array 7, and each step of the longitudinal multi-stage micromirror 10 corresponds to a column of microlens units in the microlens array 7. This allows for aperture segmentation of the multiple imaging light fields, forming multiple interference channels.

[0116] Figure 6 This illustrates the imaging optical path of a microlens array for multiple micromirrors according to an embodiment of the present invention.

[0117] like Figure 6 As shown, the interference channel formed by the specific row steps of the horizontal multi-level micro-reflector 9 and the specific column steps of the vertical multi-level micro-reflector 1 corresponds one-to-one with the imaging channel formed by the microlens units in the microlens array 7.

[0118] The transverse multi-stage micro-reflector 9 and the longitudinal multi-stage micro-reflector 10 use their stepped structures to modulate each imaging unit in the reflected imaging light field and the transmitted imaging light field with different phase delays. The modulated reflected imaging light field and transmitted imaging light field return to the beam splitter 9 along the original path, and superposition interference is generated at the exit position of the beam splitter 9.

[0119] The imaging channel O1 corresponding to the first microlens unit ultimately corresponds to the interferometric imaging channel O4;

[0120] The imaging channel O2 corresponding to the second microlens unit ultimately corresponds to the interferometric imaging channel O5;

[0121] The imaging channel O3 corresponding to the third microlens unit ultimately corresponds to the interferometric imaging channel O6;

[0122] Figure 7 The optical path difference modulation process of each interferometric imaging channel is illustrated in the schematic diagram of the main ray provided according to an embodiment of the present invention.

[0123] like Figure 7 As shown, the specific modulation process of the polarization interference optical field is as follows:

[0124] R1 is the interference imaging channel corresponding to the first step of the transverse multi-stage micro-reflector 9 and the first step of the longitudinal multi-stage micro-reflector 10, forming an interference image unit (1).

[0125] R2 is the interference imaging channel corresponding to the third step of the transverse multi-stage micro-reflector 9 and the first step of the longitudinal multi-stage micro-reflector 10, forming an interference image unit (3).

[0126] R3 is the interference imaging channel corresponding to the fifth step of the transverse multi-stage micro-reflector 9 and the first step of the longitudinal multi-stage micro-reflector 10, forming an interference image unit (5).

[0127] R4 is the interference imaging channel formed by the first step of the transverse multi-stage micro-reflector 9 and the third step of the longitudinal multi-stage micro-reflector 10, forming an interference image unit (11).

[0128] R5 is the interference imaging channel corresponding to the third step of the transverse multi-stage micro-reflector 9 and the third step of the longitudinal multi-stage micro-reflector 10, forming an interference image unit (13).

[0129] R6 is the interference imaging channel corresponding to the 5th step of the transverse multi-stage micro-reflector 9 and the 3rd step of the longitudinal multi-stage micro-reflector 10, forming an interference image unit (15).

[0130] R7 is the interference imaging channel corresponding to the first step of the transverse multi-stage micro-reflector 9 and the fifth step of the longitudinal multi-stage micro-reflector 10, forming an interference image unit (21).

[0131] R8 is the interference imaging channel corresponding to the third step of the transverse multi-stage micro-reflector 9 and the fifth step of the longitudinal multi-stage micro-reflector 10, forming an interference image unit (23).

[0132] R9 is the interference imaging channel corresponding to the fifth step of the transverse multi-stage micro-reflector 9 and the fifth step of the longitudinal multi-stage micro-reflector 10, forming an interference image unit (25).

[0133] Due to the distributed phase modulation effect of the transverse multi-stage micro-reflector 9 and the longitudinal multi-stage micro-reflector 10 on the above two parts of the multiple imaging light fields, the superimposed interference of the two imaging light field arrays forms a polarization interference image field light field with specific optical path difference distribution characteristics, which is incident on the imaging system.

[0134] The imaging system includes a relay imaging system 11 and an area array detector 12. The relay imaging system 11 has a telecentric optical path structure and is used to image the polarization interference image field onto the area array detector 12. The area array detector 12 is located on the image plane of the relay imaging system 11 and is used to receive the polarization interference image array.

[0135] The polarization interference image field light field passes through the relay imaging system 11 and forms an interference image array on the area array detector 12.

[0136] Image cells are extracted and rearranged from the polarization interferometric image array to obtain an interferometric image data cube. Interferogram sequences of each field of view in the interferometric image data cube are extracted sequentially along the optical path difference direction. By performing Stokes channel filtering and Fourier transform on the interferogram sequences, the spectral information of each Stokes parameter of the target light field emitted by the target scene in each field of view can be demodulated simultaneously.

[0137] set up:

[0138] Both the transverse multi-stage micromirror 9 and the longitudinal multi-stage micromirror 10 have N steps, with one of the multi-stage micromirrors having a step height of h1. Then the step height of the other multi-stage micromirror is h2 = N × h1;

[0139] Therefore, the optical path difference Δ and phase difference φ between the interference image field units corresponding to the m-th step of the first multi-stage micromirror and the n-th step of another multi-stage micromirror are respectively:

[0140] Δ(m,n)=2nh2-2mh1=2(nN-m)h1

[0141]

[0142] By extracting each interferometric image field unit from the interferometric image array and rearranging them according to the optical path difference, an interferometric image data cube is formed.

[0143] By selecting a field of view within the interferometric image unit and extracting the interferogram signal along the direction of the optical path difference, we can obtain:

[0144]

[0145] Expanding it using Euler's formula, the interferogram signal is represented as:

[0146]

[0147] Therefore, after modulation by the polarization imaging spectrometer provided by this invention, the Stokes parametric interferogram of the target light field is modulated to be 0, and The seven parts centered on the center will form an interference pattern with seven channels.

[0148] Figure 8 A tox channel interferogram provided according to an embodiment of the present invention is shown.

[0149] like Figure 8As shown, the interferograms for the 7 channels include:

[0150] The C0 interferogram channel, centered at Δ = 0, contains only the S0 parameter;

[0151] The C1 interferogram channel, centered at Δ = L2, contains only the S1 parameter;

[0152] The C2 interferogram channel is centered at Δ = L2 - L1 and includes parameters S2 and S3.

[0153] The C3 interferogram channel is centered at Δ = L2 + L1 and contains parameters S2 and S3.

[0154] C -1 The interferogram channel, centered at Δ = -L2, contains only the S1 parameter;

[0155] C -2 The interferogram channel, centered at Δ = -(L2 - L1), contains parameters S2 and S3;

[0156] C -3 The interferogram channel, centered at Δ = -(L2 + L1), contains parameters S2 and S3;

[0157] Each channel contains one or two Stokes parameters; the C0 channel contains only the S0 parameter. ±1 The channel contains only the S1 parameter, C ±2 and C ±3 The channel contains parameters S2 and S3, and the center positions of the interferogram channels are located at 0, ±L2, ±(L2-L1), and ±(L2+L1), respectively.

[0158] Figure 9 The Stokes parametric spectral demodulation process provided according to an embodiment of the present invention is illustrated.

[0159] like Figure 9 As shown, the Stokes parametric spectral demodulation process is as follows:

[0160] The C0 interferogram channel is bandpass filtered, with the passband located at Δ = [-(L2-L1) / 2, (L2-L1) / 2]. After Fourier transform, the spectrum of the S0 parameter is obtained as S0(ν) = 2FT[C0(Δ)].

[0161] The C1 interferogram channel is bandpass filtered, with the passband located at Δ=[(2L2-L1) / 2,(2L2+L1) / 2]. After Fourier transform, the spectrum of the S1 parameter is obtained as S1(ν)=4FT[C1(Δ)]exp(j2πνL2);

[0162] The C2 interferogram channel is bandpass filtered, with the passband located at Δ = [(L2-L1) / 2, (2L2-L1) / 2]. After Fourier transform, the spectra of parameters S2 and S3 are obtained as follows:

[0163] S2(ν)=8Re{FT[C2(Δ)]exp[j2πν(L2-L1)]}

[0164] S3(ν)=-8Im{FT[C2(Δ)]exp[j2πν(L2-L1)]}

[0165] By rationally designing the thickness ratio of the first higher-order phase delay unit 4 and the second higher-order phase delay unit 5, for example, by designing the thickness ratio to d1:d2 = 1:2, the thickness ratio of the seven channels (C0, C1, C2, C3, C4, C5, C6, C7, C8, C9 ... ±1 C ±2 C ±3 The interferograms are separated from each other. Then, three independent channels are selected, and a Fourier transform is performed on the interferogram to obtain the spectral information of the four Stokes parameters corresponding to the target light field in each field of view.

[0166] S0(ν)=2FT[C0(Δ)]

[0167]

[0168]

[0169]

[0170] This invention utilizes high-order phase delay technology with birefringent crystals to modulate all Stokes parameters of the incident light field into the light intensity signal, achieving synchronous detection of Stokes parameters. Simultaneously, a microlens array and multi-stage micromirrors are employed to perform multiple imaging of the polarized light field, and distributed phase modulation is applied to these multiple image fields. A polarization interferometric image array is obtained through optical field coupling between the imaging and interference channels, achieving synchronous acquisition of interferometric imaging information. By extracting images and rearranging data from the polarization interferometric image array, polarization interferograms corresponding to each field of view of the target scene are obtained. Stokes channel filtering and Fourier transform are then performed on the polarization interferograms to achieve synchronous demodulation of the Stokes parameter spectrum. This invention solves the problem of static, real-time, and integrated measurement of multiple dimensions of information, including image, spectrum, and polarization.

[0171] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

[0172] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A snapshot Fourier transform Stokes polarization imaging spectrometer, characterized in that, Along the beam propagation direction, it includes, in sequence: telescope system, polarization modulation system, convergence system, polarization interferometry system, and imaging system; The target light field emitted from the target scene is incident on the telescope system, and after passing through the telescope system, the target light field is collimated into a parallel light field and incident on the polarization modulation system; The polarization modulation system includes: a first higher-order phase retarder, a second higher-order phase retarder, and a polarizer polarizer; The parallel light field is polarized and modulated by passing through the first higher-order phase retarder and the second higher-order phase retarder in sequence to obtain a modulated light field. The modulated light field then passes through the polarizer polarizer to obtain a linearly polarized light field that is incident on the converging system. The converging system is used to perform multi-array imaging of the linearly polarized light field, resulting in multiple imaging light fields incident on the polarization interference system; after the parallel light field passes through the polarization modulation system, all of its Stokes parameters S0, S1, S2, and S3 are modulated into the intensity parameter S0 component, thereby enabling the polarization state of the target light field to be detected. set up: The Stokes vector of the target light field is S in The Mueller matrix of the first higher-order phase delay is: M R1 The Mueller matrix of the second higher-order phase delay is M R2 The Mueller matrix of the polarizer polarizer is: M P ; set up: The wavenumber of the target optical field is ν, and the refractive indices of the o-ray and e-ray of the higher-order phase retarder crystal are respectively... n o and n e The thickness of the first higher-order phase delay is d 1. The thickness of the second higher-order phase delay is d 2; The optical path difference between the o-ray and e-ray emitted from the first higher-order phase retarder is: The phase delay is ; The optical path difference between the emitted o-ray and e-ray from the second higher-order phase retarder (5) is: The phase delay is ; Stokes parameters of the linearly polarized light field obtained after the target light field passes through the polarization modulation system S out for: Therefore, in the linearly polarized light field S The 0' parameter contains all the Stokes parameters of the target optical field, and each parameter is modulated by a different modulation function, i.e.: ； Therefore, in the linearly polarized light field S The 0' parameter contains all the Stokes parameters of the target optical field, and each parameter is modulated by a different modulation function, i.e.: ； The polarization interference system includes: a beam splitter, a transverse multi-stage micromirror, and a longitudinal multi-stage micromirror; The multiple imaging light fields are decomposed into reflected imaging light fields and transmitted imaging light fields with equal amplitude by the beam splitter. The reflected imaging light field and the transmitted imaging light field are respectively incident into the horizontal multi-stage micro-reflector and the vertical multi-stage micro-reflector, respectively, and generate horizontal phase modulation and vertical phase modulation. After returning to the beam splitter along the original path, the two beams emitted from the reflected imaging light field and the transmitted imaging light field through the beam splitter generate superimposed interference at the emission position of the beam splitter to form a polarization interference image field with specific optical path difference distribution characteristics. The light field is incident on the imaging system to obtain an interference image array. By extracting and rearranging image units from the interferometric image array, an interferometric image data cube is obtained; the interferogram sequence of each field of view in the interferometric image data cube is extracted sequentially along the optical path difference direction; the interferogram sequence is then subjected to Stokes channel filtering and Fourier transform, and the spectral information of each Stokes parameter of the target light field in each field of view is demodulated. set up: The number of steps in the horizontal and vertical multi-stage micromirrors is: N The step height of one of the multi-stage micromirrors is h 1; then the step height of the other multi-stage micromirror is h 2= N × h 1; thus the first multi-stage micromirror m The first step and another multi-stage micromirror n The optical path difference Δ and phase difference φ of the interference image field units corresponding to each step are as follows: ； By extracting each interference image field unit from the interference image array and rearranging them according to the optical path difference, an interference image data cube is formed. By selecting a field of view within the interferometric image unit and extracting the interferogram signal along the direction of the optical path difference, the interferogram signal I can be obtained as follows: ； Expanding the interferogram signal I using Euler's formula, the interferogram signal I of the target light field is: ； The Stokes parametric interferogram of the target light field was modulated with 0, ± φ 2. ±( φ 2- φ 1) and ±( φ 2+ φ 1) The seven parts centered on the center will form an interference pattern of seven channels; The interferogram for each channel contains one or two Stokes parametric information, where C Channel 0 contains only S 0 parameters C ±1 The channel only contains S 1 parameter, C ±2 and C ±3 Channel contains S 2 and S 3 parameters, the center positions of the interferogram channels are located at 0, ± L 2. ±( L 2- L 1) and ±( L 2+ L 1); The Stokes parametric spectral demodulation process is as follows: C 0 interferogram channel bandpass filtering, the passband is located at Δ=[-( L 2- L 1) / 2, ( L 2- L [1) / 2], obtained after Fourier transform S The spectrum of 0 parameters is ; C 1. Interferogram channel bandpass filtering, the passband is located at Δ=[ (2 L 2- L 1) / 2, (2 L 2+ L [1) / 2], obtained after Fourier transform S The spectrum of parameter 1 is ; C 2. Interferogram channel bandpass filtering, the passband is located at Δ=[ ( L 2- L 1) / 2, (2 L 2- L [1) / 2], obtained after Fourier transform S 2 and S The spectrum of the 3 parameters is as follows: ； When the thickness ratio of the first higher-order phase delay unit to the second higher-order phase delay unit is d 1: d When 2=1:2, the 7 channels of the interferogram C 0、 C ±1 , C ±2 , C ±3 Separating the signals from each other, three independent channels are selected to perform Fourier transforms on the interferogram signals, thereby obtaining the spectral information of the four Stokes parameters of the target light field: 。 2. The snapshot Fourier transform Stokes polarization imaging spectrometer according to claim 1, characterized in that, The telescope system includes: a telescope objective lens, a field stop, and a collimating lens; The target light field is imaged at the field stop after passing through the telescope objective. The field stop is located on the image-side focal plane of the telescope objective and simultaneously on the object-side focal plane of the collimating lens. It is used to limit the field of view of the image of the target scene formed by the telescope objective. The imaged light field through the field stop is collimated into a parallel light field by the collimating lens and then incident on the polarization modulation system.

3. The snapshot Fourier transform Stokes polarization imaging spectrometer according to claim 2, characterized in that, The fast axis of the first higher-order phase delay is along the positive x-axis; The angle between the fast axis direction of the second higher-order phase delay and the positive x-axis is 45°; The first and second higher-order phase retarders are birefringent crystals used to adjust the phase difference of the outgoing light; their materials are quartz, calcite, magnesium fluoride, yttrium vanadate, or barium metaborate. The polarizer polarizer has a transmission axis that makes a 0° angle with the positive x-axis, and is used to transmit linearly polarized light with a specific vibration direction.

4. The snapshot Fourier transform Stokes polarization imaging spectrometer according to claim 1, characterized in that, The convergence system includes a microlens array; The microlens array is composed of the same number of rows and columns of microlens units, which perform multiple array imaging on the incident linearly polarized light field to obtain multiple imaging light fields incident on the polarization interference system.

5. The snapshot Fourier transform Stokes polarization imaging spectrometer according to claim 4, characterized in that, The reflected imaging light field is imaged onto the lateral multi-stage micromirror after being reflected by the beam splitter. The transmitted imaging light field is imaged onto the longitudinal multi-stage micro-reflective mirror after being transmitted through the beam splitter. The horizontal multi-stage micromirrors and the vertical multi-stage micromirrors have a stepped structure and are both located on the image-side focal plane of the microlens array. They are placed in a mirror image relative to the beam-splitting surface of the beam splitter, and the step directions are orthogonal to each other. Each step of the horizontal multi-stage micro-reflector corresponds to a row of microlens units in the microlens array. Each step of the longitudinal multi-stage micro-reflector corresponds to a column of microlens units in the microlens array; The interference channel formed by the horizontal multi-level micro-reflector row steps and the vertical multi-level micro-reflector column steps corresponds one-to-one with the imaging channel formed by the microlens units in the microlens array.

6. The snapshot Fourier transform Stokes polarization imaging spectrometer according to claim 5, characterized in that, The imaging system includes: a relay imaging system and an area array detector; The relay imaging system is a telecentric optical path structure, used to image the polarization interference image field onto the area array detector; The area array detector is located on the image plane of the relay imaging system and is used to receive the polarization interferometric image array; The polarization interference image field light field passes through the relay imaging system and forms an interference image array on the area array detector.

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