Multichannel dispersive polarization spectrometer and method for demodulating polarization spectral data

Abstract

This invention relates to the field of polarization optical remote sensing, specifically providing a multi-channel dispersive polarization spectrometer, comprising a front mirror group, a polarization modulation module matrix, an imaging mirror group, and a channel dispersive spectrometer arranged sequentially along the optical path. The front mirror group is used to acquire parallel light and incident the parallel light onto the polarization modulation module matrix. The polarization modulation module matrix is ​​used to generate multiple modulation spectral curves to demodulate the polarization spectral data. The polarization modulation module matrix includes phase retarders with different thickness ratios and multiple linear polarizers. The imaging mirror group is used to image the modulated light onto a detector. The channel dispersive spectrometer detector is used to receive the modulated light from multiple channels. This invention also provides a method for demodulating multi-channel dispersive polarization spectral data. This invention can avoid the impact of channel crosstalk caused by Fourier frequency domain demodulation of polarization spectral information on the accuracy and resolution of polarization spectral detection.

Description

Technical Field

[0001] This invention relates to the field of polarization optical remote sensing, specifically to a multi-channel dispersive polarization spectrometer and a method for demodulating polarization spectral data in channel dispersive polarization spectral imaging technology. In particular, it relates to the structure of a multi-channel dispersive polarization spectrometer and a method for demodulating spatial polarization spectral data. Background Technology

[0002] With the continuous development of the times, people's needs for remote sensing data are no longer satisfied with qualitative or semi-quantitative descriptions of the basic characteristics of ground targets. Higher requirements are placed on space optical remote sensors to achieve quantitative interpretation of geophysical parameters. In the field of polarization optical remote sensing, Channeled Dispersive Imaging Spectropolarimetry (CDISP), as an advanced polarization spectral measurement technique, requires only a simple optical structure and its internal polarization components do not need to rotate, enabling the simultaneous acquisition of polarization, spectral, and spatial intensity information. To realize the quantitative application of this instrument, accurate data demodulation is required. However, current Fourier frequency domain polarization spectral data demodulation methods typically introduce the following problems: 1) Channel propagation; 2) Windowing of the experimental data is required each time. These problems significantly affect the polarization spectral resolution of the demodulated data.

[0003] Therefore, optimizing the structure and data demodulation method of channel-dispersive polarization spectral imagers to achieve high-precision polarization spectral information detection and quantitative applications is a technical problem that researchers in this field urgently need to solve. Among the existing technologies, the following publicly available documents relate to polarization spectral measurement technology:

[0004] 1. The journal article "Design of a Four-Channel Array Polarization Imaging Adaptive Optical System" (Optoelectronic Technology and Systems, Vol. 46, No. 6, June 2016) discloses a four-channel array polarization imaging adaptive optical system. Specifically, it discloses an adaptive compensation system including a wavefront sensor, a wavefront controller, and a wavefront corrector; the polarization imaging system employs a common-aperture symmetrical array structure composed of four eccentric subsystems, and also discloses an imaging detector. However, it does not address the structure of a multi-channel dispersive polarization spectrometer, nor does it disclose a method for demodulating polarization spectral data in a multi-channel dispersive polarization spectrometer.

[0005] 2. Patent publication number "CN112284541A", entitled "A Calibration Method and Apparatus for Combined Absolute Radiation and Polarization", enables high-precision absolute radiation calibration of channel dispersive polarization spectral imagers, improving the polarization detection accuracy of channel dispersive polarization spectral imagers and achieving uniformity in polarization detection accuracy across different fields of view. Patent publication number "CN113375790A", entitled "A Rapid Measurement Method and System for the Cross-Spectral Density Function of Partially Coherent Vector Light Fields", enables rapid measurement of the cross-spectral density function of partially coherent vector light fields without introducing a reference arm, a lens, or requiring knowledge of the light source information. It is applicable to partially coherent vector fields with complex real and imaginary structures. Both patents relate to the field of polarization spectral measurement, but their polarization detection accuracy remains limited, the polarization spectral data resolution is low, and they do not disclose the multi-channel dispersive polarization spectral data demodulation method involved in this invention.

[0006] In summary, designing a multi-channel dispersive polarization spectrometer and a polarization spectral data demodulation method to solve the problems of channel crosstalk and low polarization spectral data resolution caused by Fourier data demodulation in current polarization spectral imagers is an urgent issue that needs to be addressed. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a multi-channel dispersive polarization spectrum.

[0008] The proposed method for demodulating polarization spectral data avoids the impact of channel crosstalk caused by Fourier frequency domain demodulation on the accuracy and resolution of polarization spectral detection, thereby improving the polarization detection accuracy of the instrument and the resolution of polarization spectral data demodulation.

[0009] A multi-channel dispersive polarization spectrometer includes a front mirror group, a polarization modulation module matrix, an imaging mirror group, and a channel dispersive spectrometer arranged sequentially along the optical path. The front mirror group is used to acquire parallel light and incident the parallel light onto the polarization modulation module matrix. The polarization modulation module matrix is ​​used to generate multiple modulation spectral curves to demodulate the polarization spectral data. The polarization modulation module matrix includes a phase retarder group I with a thickness ratio of 2:1, a phase retarder group II with a thickness ratio of 1:2, and linear polarizer groups located in different directions. The total thickness of the phase retarder group I and the phase retarder group II is consistent. The phase retarder group I includes phase retarders R3 and R4 horizontally stacked along the beam direction. The phase retarder group II includes phase retarders R1 and R2 horizontally stacked along the beam direction. The linear polarizer group includes linear polarizers P1, P2, P3, and P4 stacked perpendicular to the beam direction. The first channel of the four-channel optical path passes through the phase retarder group. The first channel consists of a phase retarder R3, a phase retarder R4, and a linear polarizer P1; the second channel passes through phase retarder R1, phase retarder R2, and linear polarizer P2; the third channel passes through phase retarder R1, phase retarder R2, and linear polarizer P3; the fourth channel passes through phase retarder R1, phase retarder R2, and linear polarizer P4; the two fast axis directions of phase retarder R3 and phase retarder R4 are 0° and 45° respectively; the two fast axis directions of phase retarder R1 and phase retarder R2 are 0° and 45° respectively; the fast axis directions of linear polarizer P1, linear polarizer P2, linear polarizer P3, and linear polarizer P4 are 0°, 90°, 45°, and 0° respectively; the imaging mirror group is used to image the modulated light onto the detector of the channel dispersive spectrometer; the detector of the channel dispersive spectrometer is used to receive the modulated light from the four channels; a slit is set between the imaging mirror group and the channel dispersive spectrometer, and the incident target light passing through the polarization modulation module matrix is ​​imaged onto the channel dispersive spectrometer by the imaging mirror group and the slit.

[0010] A method for demodulating multi-channel dispersive polarization spectral data, comprising the following steps, based on a multi-channel dispersive polarization spectrometer:

[0011] S1: Align the assembled channel dispersive spectrometer with the target and obtain four sets of modulated curves on the detector of the channel dispersive spectrometer.

[0012] The four modulated curves in S1 are represented by formulas (1), (2), (3), and (4), respectively:

[0013] (1)

[0014] (2)

[0015] (3)

[0016] (4)

[0017] in, , , , Characterizing the four modulation curves obtained on the detector of the channel dispersive spectrometer. The superscript indicates the angle of the linear polarizer. The subscript indicates the thickness ratio of the phase delayer group. The amount of phase delay introduced for phase delay unit group one and phase delay unit group two; , , and The target's polarization spectrum Stokes vector represents the target's polarization spectrum information.

[0018] S2: Spatial processing is performed on the four modulated curves obtained, and the polarization spectrum data of the target is calculated using a formula;

[0019] S2 includes the following sub-steps:

[0020] S21: Convert the four sets of modulated curves into matrix multiplication and form a matrix equation expression (5):

[0021] (5)

[0022] Among them, the square matrix in the matrix equation expression (5) For full rank;

[0023] S22: Opponent's formation Perform inverse multiplication operations to obtain the polarization spectrum information of the target;

[0024] In S22, the square matrix is ​​solved by the matrix equation expression (6). Perform the inverse multiplication operation:

[0025] (6)

[0026] Among them, the square matrix in the matrix equation expression (6) It is full rank.

[0027] The beneficial effects of this invention are as follows: The multi-channel dispersive polarization spectrometer of this invention includes a polarization modulation module matrix. The multi-channel dispersive polarization spectral data demodulation method of this invention obtains four sets of modulated curves through the detector of the channel dispersive spectrometer, performs spatial processing on the four modulated curves, and calculates the polarization spectral data of the target through matrix multiplication. This avoids the influence of channel crosstalk caused by traditional Fourier frequency domain demodulation of polarization spectral information on the accuracy and resolution of polarization spectral detection. It can improve the polarization detection accuracy of the instrument and improve the resolution of polarization spectral data demodulation. It plays an important role in the data demodulation of channel dispersive polarization spectral imagers and has broad engineering application value. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of the multi-channel dispersive polarization spectrometer provided in an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram of the structure of the polarization modulation module matrix provided in an embodiment of the present invention.

[0030] Figure reference numerals: 1. Front mirror group; 2. Polarization modulation module matrix; 3. Imaging mirror group; 4. Slit; 5. Channel dispersive spectrometer; 6. Phase retarder group one; 7. Phase retarder group two; 8. Linear polarizer group. Detailed Implementation

[0031] The appendix will be referenced below. Figure 1-2 Embodiments of the present invention are described below. In the following description, 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.

[0032] To make the objectives, technical solutions, and advantages of this invention clearer, the following description is provided in conjunction with the appendix. Figure 1-2 The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and do not constitute a limitation thereof.

[0033] like Figure 1-2As shown, a multi-channel dispersive polarization spectrometer includes a front mirror group 1, a polarization modulation module matrix 2, an imaging mirror group 3, and a channel dispersive spectrometer 5 arranged sequentially along the optical path. The front mirror group 1 is used to acquire parallel light and incident the parallel light onto the polarization modulation module matrix 2. The polarization modulation module matrix 2 is used to generate multiple modulation spectral curves to demodulate the polarization spectral data. The polarization modulation module matrix 2 includes a phase retarder group 1 6 with a thickness ratio of 2:1, a phase retarder group 2 7 with a thickness ratio of 1:2, and linear polarizer groups 8 located in different directions. The total thickness of the phase retarder group 1 6 and the phase retarder group 2 7 is consistent. The phase retarder group 1 6 includes phase retarders R3 and R4 horizontally stacked along the beam direction. The phase retarder group 2 7 includes phase retarders R1 and R2 horizontally stacked along the beam direction. The linear polarizer group 8 includes linear polarizers P1, P2, P3, and P4 stacked perpendicular to the beam direction. The first channel of the four-channel optical path passes through... The first channel passes through phase delayers R3 and R4 and linear polarizer P1; the second channel passes through phase delayers R1 and R2 and linear polarizer P2; the third channel passes through phase delayers R1 and R2 and linear polarizer P3; the fourth channel passes through phase delayers R1 and R2 and linear polarizer P4; the two fast axis directions of phase delayers R3 and R4 are 0° and 45° respectively; the two fast axis directions of phase delayers R1 and R2 are 0° respectively. The fast axis directions of linear polarizers P1, P2, P3, and P4 are 0°, 90°, 45°, and 0°, respectively; the imaging mirror group 3 is used to image the modulated light onto the detector of the channel dispersive spectrometer 5; the detector of the channel dispersive spectrometer 5 is used to receive the four channel modulated light; a slit 4 is set between the imaging mirror group 3 and the channel dispersive spectrometer 5, and the incident target light passing through the polarization modulation module matrix 2 is imaged onto the channel dispersive spectrometer 5 by the imaging mirror group 3 and the slit 4.

[0034] A method for demodulating multi-channel dispersive polarization spectral data, using the aforementioned multi-channel dispersive polarization spectrometer for polarization spectral data demodulation, includes the following steps:

[0035] S1: Align the assembled four-channel dispersive spectrometer 5 with the target and obtain four sets of modulated curves on the detector of the four-channel dispersive spectrometer 5; the four sets of modulated curves are represented by formula (1), formula (2), formula (3) and formula (4) respectively:

[0036] (1)

[0037] (2)

[0038] (3)

[0039] (4)

[0040] in, , , , The four modulation curves obtained on the detector of channel dispersive spectrometer 5 characterize the spectrum. The superscript indicates the angle of the linear polarizer. The subscript indicates the thickness ratio of the phase delayer group. The phase delay introduced by phase delay group 6 and phase delay group 7 is the same because the total thickness of phase delay group 6 and phase delay group 7 is the same. , , and The target's polarization spectrum Stokes vector is the target's polarization spectrum Stokes vector, which represents the target's polarization spectrum information.

[0041] S2: Spatial processing is performed on the four modulated curves obtained, and the polarization spectrum data of the target is calculated using a formula. S2 includes the following sub-steps:

[0042] S21: Convert the four sets of modulated curves into matrix multiplication and form a matrix equation expression (5):

[0043] (5)

[0044] In the matrix equation expression (5), Obtained through a detector Obtained through the parameters of the instrument itself.

[0045] Because the phase delay structures used, phase delay group 6 and phase delay group 7, have different thickness ratios, the square matrix in matrix equation expression (5) It is at full capacity.

[0046] S22: Opponent's formation Perform inverse multiplication to obtain the polarization spectrum information of the target. Specifically, perform inverse multiplication using the matrix equation expression (6):

[0047] (6).

[0048] Because the thickness ratios of phase retarder group 6 and phase retarder group 7 are different, and the azimuth angles of the fast axis direction of the linear polarizer group are different, the matrix equation expression (6) in the data demodulation process is as follows: To achieve full rank, therefore, the square formation There must be an inverse.

[0049] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0050] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A multi-channel dispersive polarization spectrometer, characterized in that, The system includes a front mirror group (1), a polarization modulation module matrix (2), an imaging mirror group (3), and a channel dispersive spectrometer (5) arranged sequentially along the optical path. The front mirror group (1) is used to acquire parallel light and incident the parallel light onto the polarization modulation module matrix (2). The polarization modulation module matrix (2) is used to generate multiple modulation spectral curves to demodulate the polarization spectral data. The polarization modulation module matrix (2) includes a phase retarder group one (6) with a thickness ratio of 2:1, a phase retarder group two (7) with a thickness ratio of 1:2, and phase retarder groups located in different directions. The linear polarizer group (8) has the same total thickness as the phase retarder group one (6) and the phase retarder group two (7); the phase retarder group one (6) includes phase retarder R3 and phase retarder R4 stacked horizontally along the beam direction; the phase retarder group two (7) includes phase retarder R1 and phase retarder R2 stacked horizontally along the beam direction; the linear polarizer group (8) includes linear polarizer P1, linear polarizer P2, linear polarizer P3 and linear polarizer P4 stacked perpendicularly to the beam direction; the first channel of the four-channel optical path passes through The first channel passes through phase delayers R3 and R4 and linear polarizer P1; the second channel passes through phase delayers R1 and R2 and linear polarizer P2; the third channel passes through phase delayers R1 and R2 and linear polarizer P3; the fourth channel passes through phase delayers R1 and R2 and linear polarizer P4; the two fast axis directions of phase delayers R3 and R4 are 0° and 45° respectively; the two fast axis directions of phase delayers R1 and R2 are 0° and 45° respectively; linear polarizer P1, The fast axis directions of linear polarizers P2, P3, and P4 are 0°, 90°, 45°, and 0°, respectively; the imaging mirror group (3) is used to image the modulated light onto the detector of the channel dispersive spectrometer (5); the detector of the channel dispersive spectrometer (5) is used to receive the four channel modulated light; a slit (4) is provided between the imaging mirror group (3) and the channel dispersive spectrometer (5), and the incident target light passing through the polarization modulation module matrix (2) is imaged onto the channel dispersive spectrometer (5) by the imaging mirror group (3) and the slit (4).

2. A method for demodulating multi-channel dispersive polarization spectral data, characterized in that, Demodulating polarization spectral data using the multi-channel dispersive polarization spectrometer according to claim 1 includes the following steps: S1: Align the calibrated channel dispersive spectrometer (5) with the target and obtain four sets of modulated curves on the detector of the channel dispersive spectrometer (5); The four modulated curves in S1 are represented by formulas (1), (2), (3), and (4), respectively: （1） （2） （3） （4） in, , , , The four modulation curves obtained on the detector of the channel dispersive spectrometer (5) characterize the four modulation curves. The superscript indicates the angle of the linear polarizer. The subscript indicates the thickness ratio of the phase delayer group. The amount of phase delay introduced for phase delay unit group one (6) and phase delay unit group two (7); , , and The target's polarization spectrum Stokes vector represents the target's polarization spectrum information. S2: Spatial processing is performed on the four modulated curves obtained, and the polarization spectrum data of the target is calculated using a formula; S2 includes the following sub-steps: S21: Convert the four sets of modulated curves into matrix multiplication and form a matrix equation expression (5): （5） Among them, the square matrix in the matrix equation expression (5) For full rank; S22: Opponent's formation Perform inverse multiplication operations to obtain the polarization spectrum information of the target; In S22, the square matrix is ​​solved by the matrix equation expression (6). Perform the inverse multiplication operation: （6） Among them, the square matrix in the matrix equation expression (6) It is full rank.

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