spatiotemporal joint modulation fourier transform stokes polarimetric imaging spectrometer

Abstract

The application provides a kind of spatiotemporal modulation Fourier transform stokes polarization imaging spectrometer, including in turn along the direction of propagation of light beam: telescope system, polarization modulation system, converging system, polarization interference system and imaging system;Target scene emitted target light field is collimated into parallel light field in telescope system and is incident;Linearly polarized light field is obtained after collimated parallel light field is incident to polarization modulation system and is incident to converging system;Converging system is used to image linearly polarized light field to polarization interference system and produce superposition interference, form polarization interference imaging light field with specific optical path difference distribution characteristics and are incident to imaging system to obtain polarization interference image;By step scanning to target scene, obtain polarization interference image cube, by extracting each field of view corresponding interference order interference map, carry out stokes channel filtering and fourier transform, and then demodulate the spectral information of each stokes parameter of target light field.

Description

Technical Field

[0001] This invention relates to the field of spectroscopy, and in particular to a spatiotemporally coupled modulated 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, 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 conducted in the infrared band. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to propose a spatiotemporally joint modulated Fourier transform Stokes polarization imaging spectrometer. Utilizing the higher-order phase delay characteristics of birefringent crystals, all Stokes parameters of the incident light field are modulated into the light intensity signal, achieving synchronous detection of Stokes parameters. Simultaneously, multi-stage micromirrors are employed to perform distributed phase modulation on the imaging light field, resulting in specific optical path difference distributions for the imaging light fields of different fields of view. By performing a step-scan of the target scene to obtain polarization interferograms corresponding to each field of view, and by performing Stokes channel filtering and Fourier transform on the polarization interferograms, synchronous demodulation of the Stokes parameter spectrum is achieved.

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

[0006] This invention provides a spatiotemporally coupled modulated Fourier transform Stokes polarization imaging spectrometer, which, along the beam propagation direction, sequentially comprises: a telescope system, a polarization modulation system, a convergence system, a polarization interferometry system, and an imaging system;

[0007] The target light field emitted by the target scene is collimated into a parallel light field when it is incident on the telescope system; the collimated parallel light field is then incident on the polarization modulation system.

[0008] The polarization modulation system includes: a first higher-order phase retarder, a second higher-order phase retarder, 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] Converging systems are used to image linearly polarized light fields onto polarization interferometers;

[0011] The polarization interferometer system includes: a beam splitter, a plane mirror, and a multi-stage micromirror; the beam splitter is used to decompose the imaging light field of the linearly polarized light field into a reflected imaging light field and a transmitted imaging light field;

[0012] The reflected and transmitted imaging light fields are incident on the plane mirror and the multi-stage micro-mirrors, and after reflection and distributed phase modulation, they return to the beam splitter along the original path. At the exit position of the beam splitter, superimposed interference is generated to form a polarization interference imaging light field with specific optical path difference distribution characteristics. The polarization interference image is obtained by incident on the imaging system.

[0013] By performing a step-by-step scan of the target scene, the target light field sequentially traverses each step of the multi-level micro-mirrors to obtain a polarization interference image cube. By extracting the interferograms of each interference level corresponding to each field of view, performing Stokes channel filtering and Fourier transform, the spectral information of each Stokes parameter of the target light field is simultaneously demodulated.

[0014] Preferably, the telescope system includes: a telescope objective lens, a field stop, and a collimating lens;

[0015] 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 at 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 and is located on the object-side focal plane of the converging system.

[0016] The imaging light field passing through the field stop is collimated into a parallel light field by the collimating lens.

[0017] Preferably, the fast axis direction 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°.

[0018] The crystal materials of the first and second higher-order phase retarders are quartz, calcite, magnesium fluoride, yttrium vanadate, or barium metaborate, which are used to adjust the phase difference between the emitted light.

[0019] The angle between the transmission axis of the polarizer polarizer and the x-axis is 0°.

[0020] 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 allowing the polarization state of the target light field to be detected.

[0021] set up:

[0022] The Stokes parameter 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 ;

[0023] set up:

[0024] The wavenumber of the target light field is ν, and the refractive indices of the o-ray and e-ray of the first and second higher-order phase retarder crystals 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;

[0025] Then the optical path difference of the emitted light from the first higher-order phase retarder is L1 = (n e -n o )d1, the phase delay is

[0026] The optical path difference of the emitted light from the second higher-order phase retarder 5 is L2 = (n e -n o )d2, the phase delay is

[0027] Stokes parameter S of the linearly polarized light field obtained by the polarization modulation system of the target light field out for:

[0028]

[0029] Therefore, the S0' parameter of 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, i.e.

[0030]

[0031] Preferably, the converging system includes an imaging objective; the imaging objective has an image-side telecentric optical path structure and is used to image the linearly polarized light field into the polarization interferometry system.

[0032] Preferably, the plane mirror is located at the image-side focal plane of the imaging objective lens in the beam splitter's reflected optical path;

[0033] The multi-stage micromirror is located at the image-side focal plane of the imaging objective in the beam splitter's transmission optical path, and is in a mirror-symmetrical position with the plane mirror relative to the beam splitter. It has a stepped structure, and the multi-stage micromirror uses its stepped structure to perform distributed phase modulation of the transmitted imaging light field.

[0034] Preferably, the imaging system includes: a relay imaging mirror and an area array detector; the relay imaging mirror has an object-side telecentric optical path structure and is used to image the polarization interference imaging light field onto the area array detector; the area array detector is located on the image plane of the relay imaging mirror and is used to receive the polarization interference image.

[0035] The polarization interferometric imaging light field passes through a relay imaging mirror and forms an interferometric image on the area array detector.

[0036] Preferably, let:

[0037] If the number of steps in a multi-stage micromirror is N and the step height is h, then the optical path difference of the interference image field corresponding to the field of view (x,y) of the nth step of the multi-stage micromirror is Δ(n) = 2nh, and the phase difference is...

[0038] By sequentially stitching together interferometric image units of different interference orders corresponding to the same field of view, the interferogram signal I corresponding to the above field of view is obtained as follows:

[0039]

[0040] Preferably, the interferogram signal I is expanded using Euler's formula to obtain:

[0041]

[0042] After modulation by the polarization modulation system, the Stokes parametric interferograms corresponding to each field of view in the target optical field are modulated into polarization patterns with 0, ... and The seven parts centered on the center form an interference pattern with seven channels;

[0043] Each channel contains one or two Stokes parameters, where channel C0 contains only the S0 parameter, and C... ±1 The channel contains only the S1 parameter, C ±2 and C ±3The 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.

[0044] The Stokes parametric spectral demodulation process is as follows:

[0045] 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)];

[0046] 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);

[0047] 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:

[0048] S2(ν)=8Re{FT[C2(Δ)]exp[j2πν(L2-L1)]};

[0049] S3(ν)=-8Im{FT[C2(Δ)]exp[j2πν(L2-L1)]}.

[0050] 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 The signals are separated, and then three independent channels are selected to perform Fourier transform on the interferogram signals, thereby obtaining the spectral information of the target light field corresponding to the four Stokes parameters in each field of view:

[0051] S0(ν)=2FT[C0(Δ)]

[0052]

[0053]

[0054]

[0055] Compared with existing technologies, this invention combines Fourier transform imaging spectroscopy with infrared polarization modulation technology to simultaneously acquire infrared image information, spectral information, and polarization information of the target. Phase modulation is achieved using a polarization interferometry system based on multi-stage micromirrors, eliminating moving parts and improving system reliability and real-time information acquisition. Polarization modulation is performed using a high-order phase delayer, eliminating the need for amplitude division and reducing system size and weight. This allows for integrated acquisition of multi-dimensional information including imaging, spectroscopy, and polarization, while also offering advantages in miniaturization and lightweight design. Attached Figure Description

[0056] Figure 1 This is a schematic diagram of the optical path of a spatiotemporally coupled modulated Fourier transform Stokes polarization imaging spectrometer provided according to an embodiment of the present invention.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] Figure 5 This is a schematic diagram of the structure of a multi-stage micromirror provided according to an embodiment of the present invention.

[0061] Figure 6 This is a schematic diagram of the telecentric imaging optical path on a multi-stage micromirror with different fields of view according to an embodiment of the present invention.

[0062] Figure 7 This is a schematic diagram of the optical path difference modulation process of a multi-stage micromirror according to an embodiment of the present invention.

[0063] Figure 8 This is a schematic diagram of Stokes channel interference provided according to an embodiment of the present invention.

[0064] Figure 9 This is a schematic diagram of the Stokes parametric spectral demodulation process provided in an embodiment of the present invention.

[0065] The reference numerals in the accompanying drawings include: telescope objective 1, field stop 2, collimating lens 3, first higher-order phase retarder 4, second higher-order phase retarder 5, polarizer 6, imaging objective 7, beam splitter 8, plane mirror 9, multi-stage micromirrors 10, relay imaging mirror 11, and area array detector 12. Detailed Implementation

[0066] 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.

[0067] 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.

[0068] Figure 1 The optical path of a spatiotemporally modulated Fourier transform Stokes polarization imaging spectrometer provided according to an embodiment of the present invention is shown.

[0069] like Figure 1 As shown, the spatiotemporal joint modulation 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.

[0070] 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.

[0071] The telescope system includes: telescope objective lens 1, field stop 2, and collimating lens 3; the target light field is imaged at field stop 2 after passing through telescope objective lens 1. Field stop 2 is located on the image-side focal plane of telescope objective lens 1 and also on the object-side focal plane of collimating lens 3. It is used to limit the field of view of the image of the target scene formed by telescope objective lens 1. At the same time, it serves as the aperture stop of the system and is located on the object-side focal plane of imaging objective lens 7.

[0072] The imaging light field passing through field stop 2 is collimated into a parallel light field by collimating lens 3. The collimated parallel light field is then incident on the polarization modulation system.

[0073] The polarization modulation system includes: a first higher-order phase delayer 4, a second higher-order phase delayer 5, and a polarizer polarizer 6;

[0074] Figure 2 The crystal optical features of a first high-order phase delayer provided according to an embodiment of the present invention are shown.

[0075] Figure 3 The crystal optical features of a second higher-order phase delayer provided according to an embodiment of the present invention are shown.

[0076] Figure 4The crystal optical features of a polarizer polarizer provided according to an embodiment of the present invention are shown.

[0077] like Figure 2-4 As shown, the first higher-order phase retarder 4 is located in the parallel optical path of the collimating mirror 3. It is a birefringent crystal with the optical axis of the crystal parallel to the surface. The fast axis (e-axis) is along the positive x-axis and the slow axis (o-axis) is along the positive y-axis.

[0078] The second higher-order phase retarder 5 is located after the first higher-order phase retarder 4. It is a birefringent crystal with its optical axis parallel to the surface. The angle between the fast axis (e-axis) and the positive x-axis is 45°, and the angle between the slow axis (o-axis) and the positive x-axis is 135°.

[0079] The crystal materials of the first higher-order phase retarder 4 and the second higher-order phase retarder 5 are quartz, calcite, magnesium fluoride (MgF2), yttrium vanadate (YVO4), barium metaborate (α-BBO), etc., which are used to adjust the phase difference between the emitted o-light and e-light.

[0080] The polarizer polarizer 6 is located after the second higher-order phase retarder 5. Its transmission axis makes a 0° angle with the 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 wire grids 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 wire grid material can be a metal such as gold or aluminum. Light with a polarization direction perpendicular to the wire grid direction can pass through, while light with a polarization direction parallel to the wire grid direction is blocked; that is, the wire grid direction is along the y-axis.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] set up:

[0085] The Stokes parameter 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 ;

[0086] set up:

[0087] The wavenumber of the target light field is ν, and the refractive indices of the o-ray and e-ray of the crystals of the first higher-order phase retarder 4 and the second higher-order phase retarder 5 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.

[0088] 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

[0089] 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

[0090] The Stokes parameter S of the linearly polarized light field obtained after the target light field passes through the polarization modulation system. out It can be represented as:

[0091]

[0092] Therefore, the S0' parameter of the linearly polarized light field emitted from the polarization modulation system contains all the Stokes parameters of the target light field, and each parameter is modulated by a different modulation function, i.e.

[0093]

[0094] The aforementioned linearly polarized beam is imaged into the polarization interferometer system via a converging system.

[0095] The converging system includes: an imaging objective 7; the imaging objective 7 is an image-side telecentric optical path structure that images the linearly polarized beam after polarization modulation onto the polarization interferometer system.

[0096] The polarization interference system includes a beam splitter 8, a plane mirror 9, and a multi-stage micro-mirror 10. The beam splitter 8 is located after the imaging objective lens 7 and is used to decompose the imaging light field of the linearly polarized light field into two beams of light with equal amplitude. One beam of light is reflected by the beam splitter to form a reflected imaging light field, and the other beam of light is transmitted through the beam splitter to form a transmitted imaging light field.

[0097] The plane mirror 9 is located at the image-side focal plane of the imaging objective lens 7 in the reflected light path of the beam splitter 8; the reflected imaging light field is incident on the plane mirror 9 and, after being reflected by the plane mirror 9, returns to the beam splitter 8 along the original path.

[0098] Figure 5 A schematic diagram of the structure of a multi-stage micromirror provided according to an embodiment of the present invention is shown.

[0099] Figure 6 The telecentric imaging optical path on a multi-stage micromirror with different fields of view provided by embodiments of the present invention is illustrated.

[0100] Figure 7 The optical path difference modulation process of a multi-stage micromirror provided according to an embodiment of the present invention is illustrated.

[0101] like Figure 5-7 As shown, the multi-stage micromirror 10 is located at the image-side focal plane of the imaging objective lens 7 in the transmission optical path of the beam splitter 8, and is in a mirror-symmetrical position with the plane mirror 9 relative to the beam splitter 8. It has a stepped structure with N steps and a step height of [missing information].

[0102] The field of view O1 corresponding to the first step of the multi-level micro-mirror ultimately corresponds to the interference image field O4, and the interference image field O4 ultimately corresponds to the interference image unit (5);

[0103] The field of view O2 corresponding to the third step of the multi-level micro-mirror ultimately corresponds to the interference image field O5; the interference image field O5 ultimately corresponds to the interference image unit (3);

[0104] The field of view O3 corresponding to the fifth step of the multi-level micro-mirror ultimately corresponds to the interference image field O6; the interference image field O6 ultimately corresponds to the interference image unit (1);

[0105] The multi-stage micro-mirror 10 uses its stepped structure to perform distributed phase modulation on the transmitted imaging light field, and then the transmitted imaging light field returns to the beam splitter 8 along the original path.

[0106] The transmitted imaging light field reflected back by the multi-stage micro-mirrors 10 and the reflected imaging light field reflected back by the plane mirror 9 superimpose and interfere at the exit position of the beam splitter 8. Due to the distributed phase modulation effect of the multi-stage micro-mirrors 10 on the imaging light field, the superimposed interference of the two beams forms a polarization interference imaging light field with specific optical path difference distribution characteristics, which is incident on the imaging system.

[0107] The imaging system includes a relay imaging mirror 11 and an area array detector 12. The relay imaging mirror 11 has an object-side telecentric optical path structure, which images the primary image fields from the plane mirror 9 and the multi-stage micro-mirrors 10 onto the area array detector 12. The area array detector 12 is located on the image plane of the relay imaging mirror 11 and is used to receive polarization interference images.

[0108] The polarization interference imaging light field passes through the relay imaging mirror 11 and forms an interference image on the area array detector 12.

[0109] set up:

[0110] The multi-stage micromirror has N steps and h steps. Therefore, the optical path difference of the interference image field corresponding to the nth step of the multi-stage micromirror is Δ(n) = 2nh, and the phase difference is...

[0111] The polarization imaging spectrometer provided by this invention performs a step scan along a direction perpendicular to the step length, stepping one step at a time, so that each field of view in the target scene sequentially traverses each step, obtaining a polarization interferometric image cube, and thus obtaining the interferometric image unit of each field of view at each interference order. The interferometric image units of different interference orders corresponding to the same field of view are sequentially stitched together to obtain the interferogram signal I corresponding to the above field of view:

[0112]

[0113] Expanding the above interferogram signal I using Euler's formula, the interferogram signal I is expressed as:

[0114]

[0115] Therefore, through modulation by the polarization imaging spectrometer provided by this invention, the Stokes parametric interferograms corresponding to each field of view in the target light field are modulated into a waveform with 0, and The seven parts centered on the center will form an interference pattern with seven channels.

[0116] Figure 8 A Stokes channel interferogram provided according to an embodiment of the present invention is shown.

[0117] like Figure 8 As shown, the interferograms for the 7 channels include:

[0118] The C0 interferogram channel, centered at Δ = 0, contains only the S0 parameter;

[0119] The C1 interferogram channel, centered at Δ = L2, contains only the S1 parameter;

[0120] The C2 interferogram channel is centered at Δ = L2 - L1 and includes parameters S2 and S3.

[0121] The C3 interferogram channel is centered at Δ = L2 + L1 and contains parameters S2 and S3.

[0122] C -1 The interferogram channel, centered at Δ = -L2, contains only the S1 parameter;

[0123] C -2 The interferogram channel, centered at Δ = -(L2 - L1), contains parameters S2 and S3;

[0124] C -3 The interferogram channel, centered at Δ = -(L2 + L1), contains parameters S2 and S3;

[0125] 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.

[0126] Figure 9 The Stokes parametric spectral demodulation process provided according to an embodiment of the present invention is illustrated.

[0127] 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)];

[0128] 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);

[0129] 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:

[0130] S2(ν)=8Re{FT[C2(Δ)]exp[j2πν(L2-L1)]}

[0131] S3(ν)=-8Im{FT[C2(Δ)]exp[j2πν(L2-L1)]}

[0132] 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.

[0133] S0(ν)=2FT[C0(Δ)]

[0134]

[0135]

[0136]

[0137] This invention employs a high-order phase retarder based on a birefringent crystal for polarization modulation, ensuring that all Stokes parameters of the incident light field are modulated into the light intensity signal. Simultaneously, it utilizes phase modulation technology based on multi-level micromirrors to achieve distributed modulation of different interference orders in the imaging light field. Combined with step scanning, it obtains interferometric image data cubes for each field of view of the target scene. The combination of Stokes polarization modulation and imaging light field phase modulation synchronously acquires Stokes channel interferograms for each imaging field of view. By performing channel filtering and Fourier transform, it achieves synchronous detection of the target image, spectrum, and polarization, expanding the dimensions of information detection and improving real-time performance. The system has a compact structure and features static and high stability, facilitating miniaturization and integration. Furthermore, the effective fusion of image, polarization, and spectral information allows for the reconstruction of a higher-quality target scene, highlighting detailed target features, enhancing target recognition, and improving target detection accuracy.

[0138] 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.

[0139] 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 spatiotemporally joint modulated 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 collimated into a parallel light field when it is incident into the telescope system; the collimated parallel light field is then incident into 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 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, which is then incident on the converging system. After passing through the polarization modulation system, all of the Stokes parameters S0, S1, S2, and S3 of the parallel light field are modulated into the intensity parameter S0 component, thereby allowing the polarization state of the target light field to be detected. set up: The Stokes parameter 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 first and second higher-order phase retarder crystals 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 of the emitted light from the first higher-order phase retarder is: The phase delay is ; The optical path difference of the emitted light from the second higher-order phase retarder (5) is The phase delay is ; Stokes parameters of the linearly polarized light field obtained by the polarization modulation system for the target light field S out for: ； Therefore, 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 convergence system is used to image the linearly polarized light field onto the polarization interferometry system; The polarization interferometry system includes: a beam splitter, a plane mirror, and a multi-stage micro-mirror; the beam splitter is used to decompose the imaging light field of the linearly polarized light field into a reflected imaging light field and a transmitted imaging light field. The reflected and transmitted imaging light fields are incident on the plane mirror and the multi-stage micro-mirrors, and after reflection and distributed phase modulation, they return to the beam splitter along the original path. At the exit position of the beam splitter, superimposed interference is generated to form a polarization interference imaging light field with specific optical path difference distribution characteristics. The polarization interference image is then incident on the imaging system. By performing a step scan on the target scene, the field of view of the target light field sequentially traverses each step of the multi-level micro-reflectors to obtain a polarization interference image cube. By extracting the interference map of each interference level corresponding to each field of view, Stokes channel filtering is performed on it, and Fourier transform is performed, thereby simultaneously demodulating the spectral information of each Stokes parameter of the target light field. set up: The number of steps in the multi-stage micromirror is: N The height of the steps is h , Then the multi-stage micromirror n The field of view corresponding to each step ( x , y The optical path difference of the interference image field is The phase difference is ; By sequentially stitching together interferometric image units of different interference orders corresponding to the same field of view, the interferogram signal I corresponding to the above field of view is obtained as follows: ； Expanding the interferogram signal I using Euler's formula yields: After modulation by the polarization modulation system, the Stokes parametric interferograms corresponding to each field of view in the target optical field are modulated into polarizations with 0, ± φ 2. ±( φ 2- φ 1) and ±( φ 2+ φ 1) The seven parts centered on the center form an interference pattern with seven channels; Each channel contains one or two Stokes parameter 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 with zero 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 The signals are separated, and then three independent channels are selected to perform Fourier transform on the interferogram signal, thereby obtaining the spectral information of the target light field corresponding to the four Stokes parameters in each field of view: 。 2. The spatiotemporal joint modulation 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 onto 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 also 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 and is located on the object-side focal plane of the converging system. The imaging light field passing through the field stop is collimated into a parallel light field by the collimating lens.

3. The spatiotemporal joint modulation 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 fast axis of the second higher-order phase delay makes an angle of 45° with the positive x-axis. The crystal materials of the first and second higher-order phase retarders are quartz, calcite, magnesium fluoride, yttrium vanadate, or barium metaborate, which are used to adjust the phase difference between the emitted light. The polarizer polarizer has a transmission axis that makes a 0° angle with the x-axis.

4. The spatiotemporal joint modulation Fourier transform Stokes polarization imaging spectrometer according to claim 1, characterized in that, The converging system includes an imaging objective lens; the imaging objective lens has an image-side telecentric optical path structure and is used to image the linearly polarized light field onto the polarization interference system.

5. The spatiotemporal joint modulation Fourier transform Stokes polarization imaging spectrometer according to claim 4, characterized in that, The plane mirror is located at the image-side focal plane of the imaging objective lens in the beam splitter's reflected optical path; The multi-stage micro-mirrors are located at the image-side focal plane of the imaging objective in the beam splitter's transmission optical path, and are mirror-symmetrical with respect to the beam splitter to the planar mirror. They have a stepped structure, and the multi-stage micro-mirrors use their stepped structure to perform distributed phase modulation on the transmitted imaging light field.

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

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