A multi-channel simultaneous polarization imager system

Abstract

The application belongs to the technical field of astronomy, and provides a multi-channel synchronous polarization imager system for a night astronomical observation scene. The system cooperates with key components such as a relay optical system, a polarization calibration unit rotating wheel, a broadband optical filter, a zero-polarization beam splitter prism, a super-achromatic half-wave plate and a polarization beam splitter prism to realize synchronous measurement of the polarization state of celestial bodies in the whole field of view through one exposure. The relay optical system is responsible for collimation and imaging functions; the polarization calibration unit rotating wheel is used for polarization calibration; the zero-polarization beam splitter prism divides the incident light beam into a transmitted light beam and a reflected light beam; and the super-achromatic half-wave plate and the polarization beam splitter prism are used for polarization modulation. The system solves the problem of dispersion effect in wide-band measurement, improves the detection capability of dark and weak targets, and is suitable for high-precision synchronous polarization measurement of a large field of view.

Description

Technical Field

[0001] This application belongs to the field of astronomical telescope imaging technology, and in particular relates to a multi-channel synchronous polarization imager system. Background Technology

[0002] Traditional single-channel synchronous polarization imagers have a small field of view and can only measure point source targets, unable to perform synchronous polarization measurements on area sources or targets with a large field of view. Modern four-channel synchronous polarization imagers, due to their extremely complex optical systems, have achieved synchronous polarization measurement capabilities with a large field of view, but have reduced their ability to detect faint targets, which is not conducive to applications in night astronomy. Modern dual-channel synchronous polarization imagers have both a large field of view and high-efficiency detection capabilities, but they place stringent requirements on the bandwidth of the observation band, and the dispersion effect restricts the specific application of this type of imager in wide-band night astronomy scenarios.

[0003] Existing synchronous polarization imagers are mainly divided into two categories. The first category is single-channel synchronous polarization imagers, whose main drawback is a narrow field of view, typically only capable of polarization measurements on a single celestial object. The second category is multi-channel synchronous polarization imagers, which are further divided into dual-channel and four-channel types. Dual-channel synchronous polarization imagers suffer from significant dispersion effects when the O and E beams are output separately at large angles in the same direction, severely limiting their observation bandwidth and making it impossible to conduct wide-band measurements in night astronomy. On the other hand, four-channel synchronous polarization imagers have extremely complex optical systems and low optical efficiency for polarization measurements, making them unsuitable for measuring faint targets in night astronomy. Summary of the Invention

[0004] This application provides a multi-channel synchronous polarization imager system designed to address the technical challenges of wide-field-of-view, broad-band synchronous polarization measurement in nighttime astronomical scenarios. The multi-channel synchronous polarization imager (MSPI) not only overcomes the bandwidth limitation of the observation band in the dual-separation synchronous polarization imager (SIP-DSWP) scheme but also doubles the observation field of view. Furthermore, its optical system complexity is significantly lower than that of the four-channel WALOP scheme, improving the overall observation efficiency and polarization detection capability for faint targets.

[0005] The technical solution adopted in this invention is: A multi-channel synchronous polarization imager system, comprising: The relay optical system includes a collimating optical system and an imaging optical system, which are used to convert diverging beams into parallel beams, realize the focusing function of the telescope optical system, and achieve good imaging on the camera target surface. The polarization calibration unit wheel is used for polarization calibration. It can be rotated to the empty position during polarization observation and to the position of the linear polarizer during calibration. Broadband optical filters are used to select light in specific wavelengths; Zero-polarization beam splitter (NPBS): Used to split an incident parallel beam into a mutually perpendicular transmitted beam (T) and a reflected beam (R); Two sets of super achromatic half-wave plates: respectively set in the optical paths of the transmitted beam and the reflected beam, with the fast axis angle of the half-wave plate for the transmitted beam being 0 degrees and the fast axis angle of the half-wave plate for the reflected beam being 22.5 degrees; Two sets of polarizing beam splitters (PBS): used to polarize and split the beam modulated by the half-wave plate, outputting mutually perpendicular polarized light O-beam and E-beam; Imaging optical system: Connected to polarizing beam splitters, used to image polarized beams onto the detector; The detector is used to receive the imaging beam and generate image signals; A single exposure enables simultaneous measurement of the polarization state of celestial bodies across the entire field of view.

[0006] Preferably, the zero-polarization beam splitter (NPBS) achieves stable beam splitting in the 400-700 nm wavelength range, with a residual polarization amount of less than 6%.

[0007] Preferably, the polarizing beam splitters of the transmitted beam channel and the reflected beam channel output polarization modulated images of 0° and 90°, and 135° and 45°, respectively.

[0008] Preferably, the system is suitable for nighttime astronomical observation scenarios, and is especially suitable for high-precision synchronous polarization measurement with a wide field of view and a wide band.

[0009] Preferably, the system utilizes a non-polarizing beam splitter prism and a super achromatic half-wave plate to eliminate the dispersion effect during wide-band measurements.

[0010] Preferably, the system compensates for the polarization error introduced by the non-polarized beam splitter by calibration measurements using a zero-polarization standard star.

[0011] Preferably, the system is suitable for installation on an astronomical telescope with an axisymmetric optical system, which is an RC optical system.

[0012] Preferably, the system can complete the synchronous measurement of the linear polarization state (I, Q, U) of the target across the entire field of view with a single exposure.

[0013] Preferably, the imaging optics of the relay optical system has a zoom function to improve the detection capability of dark targets; the imaging optical system also includes optical elements for converging the beam and imaging it well on the camera target surface.

[0014] The present invention also provides a method for operating a multi-channel synchronous polarization imager system, comprising the following steps: 1) Light Acquisition and Collimation Telescope acquisition: Light from point or surface sources in the night sky is initially collected using an astronomical telescope; Collimation process: The light collected by the telescope enters the collimation optical system in the relay optical system of MSPI, which converts the diverging beam into a parallel beam, preparing it for subsequent polarization modulation. 2) Polarization calibration Calibration preparation: If polarization calibration of the system is required, the polarization calibration unit wheel will rotate to the position of the linear polarizer; Calibration procedure: The incident light is polarized using a linear polarizer to ensure the accuracy of subsequent measurements.

[0015] Observation mode switching: During normal polarization observation, the polarization calibration unit wheel is rotated to the empty position, allowing light to pass through directly without calibration. 3) Filtering and spectral dispersion Filter selection: Parallel beams pass through broadband optical filters to select light in a specific wavelength band to meet observation requirements; Beam splitting: The filtered parallel beam is incident on the zero-polarization beam splitter NPBS and splits into a mutually perpendicular transmitted beam T and a reflected beam R; ensuring that the polarization states of the two beams are consistent with the incident beam, and that the intensity of each beam is 50% of that of the incident beam; 4) Polarization modulation Transmitted beam channel T modulation: The transmitted beam undergoes polarization modulation after passing through a super achromatic half-wave plate with a fast axis of 0 degrees. The modulated beam passes through the polarizing beam splitter PBS, outputting beams with polarization directions of 0° and 90°; Reflected beam channel R modulation: The reflected beam undergoes polarization modulation after passing through a super achromatic half-wave plate with a fast axis of 22.5 degrees. The modulated beam passes through the polarizing beam splitter PBS and outputs beams with polarization directions of 45° and 135°. 5) Imaging and Detection Imaging Processing: The four modulated polarized beams at 0°, 45°, 90°, and 135° pass through their respective imaging optical systems and are imaged on four detectors, which are either sCMOS or CCD. Detection and recording: The detector receives the imaging beam and generates image signals, recording polarization-modulated images of the entire field of view; 6) Data processing and polarization state calculation Synchronization control: By synchronously controlling the exposure of the four detectors, four polarization-modulated images are acquired simultaneously.

[0016] Data calculation: Using data from four images, the linear polarization state parameters (I, Q, U) of celestial bodies are calculated, enabling high-precision polarization measurement of targets across the entire field of view.

[0017] The beneficial effects of the embodiments in this application compared with the prior art are: The characteristics of nighttime astronomical observation targets necessitate the design of a synchronous polarization imaging instrument with a relatively simple optical system, a large field of view, and adaptability to wide-band measurements.

[0018] This method enables dual-channel spectral splitting and four-channel imaging, allowing MSPI to simultaneously measure the polarization state of celestial objects across the entire field of view in a single exposure. It is suitable for nighttime astronomical observation scenarios and is particularly well-suited for observing wide-band, large-field-of-view, and faint targets. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 These are schematic diagrams and measured figures of three types of synchronous polarization imagers provided by the prior art of this application; Figure 2 It is the O1 channel optical system of the WALOP instrument provided in this application; Figure 3 This is the O2 channel optical system of the WALOP instrument provided in this application; Figure 4 This application provides a dual-separation Wollaston prism simultaneous polarization imaging system; Figure 5 This application provides the SALT-RSS dual-channel polarimeter for O and E light imaging, which exhibits chromatic aberration characteristics (4′x8′ field of view). Figure 6 This is a schematic diagram of the MOPTOP dual-beam asynchronous polarization imager for the Liverpool Telescope in the UK, provided in this application. Figure 7 This is a schematic diagram of the MSPI (Multi-channel Synchronous Polarization Imager) provided in this application; Figure 8 This is the transmittance curve of the Johnson series filters for astronomical use provided in this application; Figure 9 This is a schematic diagram illustrating the implementation principle of the synchronous polarization imager and telescope provided in this application; Figure 10 shows the beam splitting process and beam splitting efficiency of the non-polarized beam splitter provided in this application: (a) beam splitting by the non-polarized prism; (b) transmission (TP, TS) and reflection efficiency (RP, RS) of P- and S-polarized light. Figure 11 is a schematic diagram of the polarization modulation and imaging optical path of the transmitted beam and reflected beam provided in this application, (a) the optical path of the transmitted beam, and (b) the optical path of the reflected beam.

[0021] Figure 12 This is a system structure diagram provided in this application, wherein 1 is a collimating lens, 2 is a filter, 3 is an unpolarized beam splitter, 4 is a super achromatic half-wave plate with a fast axis angle of 0 degrees, 5 is a polarizing beam splitter, 6 is an imaging mirror, 7 is an imaging camera, 8 is a super achromatic half-wave plate with a fast axis angle of 22.5 degrees, 9 is a polarizing beam splitter, 10 is an imaging mirror, and 11 is an imaging camera. Detailed Implementation

[0022] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0023] The operation of a multi-channel synchronous polarization imager system (MSPI) can be divided into the following key steps: 1. Light Acquisition and Collimation Telescope acquisition: Point or surface light from the night sky is initially collected using an astronomical telescope.

[0024] Collimation process: The light collected by the telescope enters the collimation optical system in the relay optical system of MSPI, which converts the divergent beam into a parallel beam, preparing it for subsequent polarization modulation.

[0025] 2. Polarization calibration (optional) Calibration preparation: If polarization calibration of the system is required, the polarization calibration unit wheel will rotate to the position of the linear polarizer.

[0026] Calibration procedure: The incident light is polarized using a linear polarizer to ensure the accuracy of subsequent measurements.

[0027] Observation mode switching: During normal polarization observation, the polarization calibration unit wheel is rotated to the empty position, allowing light to pass through directly without calibration.

[0028] 3. Filtering and Spectroscopy Filter selection: Parallel beams pass through broadband optical filters to select light in a specific wavelength band to meet observation requirements.

[0029] Beam splitting: The filtered parallel beam is incident on a zero-polarization beam splitter (NPBS) and splits into a transmitted beam (T) and a reflected beam (R) that are perpendicular to each other. The NPBS ensures that the polarization states of the two beams are consistent with the incident beam, and that the intensity of each beam is 50% of that of the incident beam.

[0030] 4. Polarization modulation Transmitted beam channel (T) modulation: The transmitted beam is polarized by passing through a super achromatic half-wave plate with a fast axis of 0 degrees.

[0031] The modulated beam passes through a polarizing beam splitter (PBS) and outputs beams with polarization directions of 0° and 90°.

[0032] Reflected beam channel (R) modulation: The reflected beam is polarized by passing through a super achromatic half-wave plate with a fast axis of 22.5 degrees.

[0033] The modulated beam passes through a polarizing beam splitter (PBS) and outputs beams with polarization directions of 45° and 135°.

[0034] 5. Imaging and Detection Imaging processing: The four modulated polarized beams (0°, 45°, 90°, 135°) are imaged on four detectors (such as sCMOS or CCD) through their respective imaging optical systems.

[0035] Detection and recording: The detector receives the imaging beam and generates image signals, recording polarization-modulated images of the entire field of view.

[0036] 6. Data Processing and Polarization State Calculation Synchronization control: By synchronously controlling the exposure of the four detectors, four polarization-modulated images are acquired simultaneously.

[0037] Data calculation: Using data from four images, the linear polarization state parameters (I, Q, U) of celestial bodies are calculated, enabling high-precision polarization measurement of targets across the entire field of view.

[0038] This working method enables MSPI to simultaneously measure the polarization state of celestial objects across the entire field of view in a single exposure, making it suitable for nighttime astronomical observation scenarios, and particularly well-suited for observing wide-band, large-field-of-view, and faint targets. like Figure 1As shown, synchronous polarization measurement technology is a technology that has been developing for nearly 50 years. From the initial proposal of amplitude-splitting simultaneous (synchronous) polarization measurement scheme by American Garlick in 1976, to the synchronous polarization modulation technology based on the double Wollaston prism scheme proposed by German astronomer Geyer in 1996 to study continuously rotating small celestial bodies (comets, asteroids) in the solar system, and now to the three types of synchronous polarization modulation schemes: WeDoWo (Ernesto Oliva, 1997), Robopol (Ramaprakash AN, 2019), and WALOP (Siddharth Maharana, 2021), the core idea is to simultaneously modulate the image of the target object into four polarization angles (0°, 45°, 90°, 135°). This allows for the measurement of the linear polarization state (I, Q, U) of the target object in a single exposure.

[0039] To prevent the four polarization-modulated images from overlapping on the camera's target surface, the field of view must be narrowed. WeDoWo achieves high-precision synchronous polarization measurement of the slit field of view by placing a slit at the front focal plane; therefore, its field of view is limited by the slit width, typically allowing measurement of only a single or two targets in the sky. Robopol, by placing a single-target mask at the front focal plane, can only perform high-precision synchronous polarization measurement of one target in the field of view; the polarization results of other targets within the field of view can only be used as a reference. WALOP, to achieve synchronous polarization measurement across the entire field of view, employs a four-channel synchronous measurement method with independent imaging on four cameras; however, the optical system design for these four polarization modulation channels (O1, O2, P1, P2) is also exceptionally complex. Figure 2-3 As shown, the O1 and O2 beam channels of the WALOP instrument cause severe light loss in the entire system, reduce optical efficiency, and decrease the ability to observe faint targets in nighttime astronomy.

[0040] In recent years, synchronous polarization measurement technology has been fully developed and practically applied in other fields in my country. For example, the Dual-Separated Wollaston Prism Simultaneous Polarization Imaging System (SIP-DSWP) at Beijing Institute of Technology (Liu Jing et al., 2015) pioneered the use of a zero-polarization beam splitter prism to split the incident beam into two perpendicular beams. Then, the polarization modulation of the two beams was achieved separately through a half-wave plate and a Wollaston prism, ultimately obtaining four polarization-modulated images on two cameras, such as... Figure 4 As shown, synchronous polarization imaging measurement with a large field of view was achieved.

[0041] However, the biggest difference between this type of synchronous polarization imaging system and traditional synchronous polarization imagers (WeDoWo, Robopol) is the significantly increased requirement for the opening angles of the O and E beams. Traditional systems require opening angles of several arcseconds to tens of arcseconds, while this system needs to expand to several arcminutes. If the observation bandwidth reaches 100-150 nm, severe chromatic aberration will occur in the star images. The SALT-RSS dual-channel polarimeter on the South African telescope uses the same design, obtaining O and E beam images from the upper and lower parts of a single CCD, respectively. However, the star images in these images are no longer symmetrical bell-shaped structures, but rather conical structures due to the dispersion effect of different wavelengths. Furthermore, the dispersion directions of the stars in the O and E beam images are symmetrically distributed, such as... Figure 5 As shown.

[0042] In summary, traditional single-channel synchronous polarization imagers have a small field of view and can only measure point source targets, unable to perform synchronous polarization measurements on area sources or targets with a large field of view. Modern four-channel synchronous polarization imagers, due to their extremely complex optical systems, achieve synchronous polarization measurement capabilities with a large field of view, but reduce their ability to detect faint targets, which is not conducive to applications in night astronomy. Modern dual-channel synchronous polarization imagers combine a large field of view and high-efficiency detection capabilities, but impose stringent requirements on the bandwidth of the observation band, and the dispersion effect restricts the specific application of this type of imager in wide-band night astronomy scenarios.

[0043] In view of the characteristics of nighttime astronomical observation targets, it is necessary to design a synchronous polarization imaging instrument with a relatively simple optical system, a large field of view, and adaptability to wide-band measurements. This invention proposes a synchronous polarization imaging instrument solution that meets the above requirements.

[0044] like Figure 4 and Figure 6 As shown in the figure, this embodiment proposes a large field-of-view synchronous polarization measurement solution suitable for nighttime astronomical observation scenarios. Specifically, it combines the zero-polarization beam splitting scheme of the dual-separation synchronous polarization imager SIP-DSWP with the O and E light dual-channel independent imaging scheme of the MOPTOP polarization imager (Manisha Shrestha, 2020), thus realizing a multi-channel synchronous polarization imager (MSPI) with dual-channel beam splitting and four-channel imaging.

[0045] like Figure 7As shown, the basic principle of the Multi-channel Synchronous Polarization Imager (MSPI) is as follows: The light beam from the telescope first passes through a collimating lens to achieve parallel transmission. Then, the parallel beam passes through the polarization calibration unit wheel (rotated to an empty position during polarization observation and to the position of the linear polarizer during polarization calibration), and then through a broadband optical filter before being incident on an ultra-wideband zero-polarization beam splitter (NPBS). The NPBS splits the incident beam into two mutually perpendicular beams: a transmitted beam T and a reflected beam R. The transmitted beam T passes through a super achromatic beam with a fast axis of 0 degrees. Modulation by a half-wave plate and a polarizing beam splitter produces O-light and E-light in two perpendicular directions, respectively. These are then imaged on two detectors (sCMOS or CCD) through their respective imaging mirror systems, yielding full-field-of-view polarization-modulated images at 0 degrees and 90 degrees. The reflected beam R, modulated by a super-achromatic half-wave plate with a fast axis of 22.5 degrees and a polarizing beam splitter, also produces O-light and E-light in two perpendicular directions. These are then imaged on two detectors (sCMOS or CCD) through their respective imaging systems, yielding full-field-of-view polarization-modulated images at 135 degrees and 45 degrees. This achieves the goal of obtaining the polarization state of celestial objects across the entire field of view in a single exposure, and enables broadband polarization measurements throughout the visible light spectrum, making it more advantageous for synchronous polarization measurements of surface-source targets or faint targets.

[0046] Before the improvement, synchronous polarization imagers were mainly divided into two categories. The first category was single-channel synchronous polarization imagers, whose main drawback was a narrow field of view, typically only capable of polarization measurements on a single celestial target. The second category was multi-channel synchronous polarization imagers, which were further divided into dual-channel and four-channel types. Among them, dual-channel synchronous polarization imagers suffered from significant dispersion effects when the O and E beams were output separately at large angles in the same direction, severely limiting their observation bandwidth and making it impossible to conduct wide-band measurements in night astronomy. On the other hand, four-channel synchronous polarization imagers had extremely complex optical systems and low optical efficiency for polarization measurements, which was not conducive to measuring faint targets in night astronomy.

[0047] The improved Multi-channel Synchronous Polarization Imager (MSPI) not only solves the bandwidth limitation problem of the observation band in the dual-separation synchronous polarization imager (SIP-DSWP) scheme, but also doubles the field of view. At the same time, its optical system complexity is far lower than that of the WALOP four-channel scheme, improving the overall observation efficiency and polarization detection capability of faint targets.

[0048] like Figure 8As shown below, taking the optical system of the Lijiang 2.4-meter telescope as an example, the effective field of view of the Cajoler is 10×10 arcminutes. If the dual-separation synchronous polarization imager (SIP-DSWP) scheme is directly used, the O and E rays must be separated by an angle of at least 5 arcminutes on the camera target surface to ensure that the two images do not overlap. If Johnson's B-band is selected for observation, its optical band range is 368nm~500nm. Under atmospheric seeing conditions where the half-width of a normal star is 1 arcsecond, the stars in the polarization image will be stretched by tens of arcseconds due to the dispersion effect. Such synchronous polarization modulated images cannot be used for high-precision polarization measurements. However, if the multi-channel synchronous imager (MSPI) scheme proposed in this patent is used, this dispersion effect that occurs in wide-band measurements can be avoided, resulting in four high-quality polarization modulated images, thereby achieving high-precision synchronous polarization measurements of the entire field of view of 10×10 arcminutes.

[0049] The Multichannel Synchronous Polarization Imager (MSPI) is a polarization measurement system mounted on an astronomical optical telescope. Its implementation requires a telescope with an axisymmetric optical system (e.g., an RC optical system). A block diagram of the entire system is shown below. Figure 9 As shown, light from point or surface sources in the night sky passes through the telescope's optical system and the MSPI's relay optical system, polarization modulation system, and camera synchronization control system. With a single exposure, the linear polarization state of the target across the entire field of view can be synchronously measured.

[0050] The relay optics system of MSPI includes a collimating optics system and an imaging optics system, and mainly has three functions: first, to convert diverging beams into collimated beams for polarization modulation at the back end; second, to realize the focusing function of the telescope optics system, thereby improving MSPI's ability to detect faint targets; and third, to converge the beams for good imaging on the camera target surface, which requires the imaging optics part of the relay optics system to have focusing function.

[0051] The polarization modulation system of MSPI is a beam-splitting dual-channel polarization modulation system. This part requires the use of a broadband non-polarizing beam splitter (NPBS). Theoretically, the two beams separated by the non-polarizing beam splitter should have the same polarization state as the incident beam, and their intensities should be equal, both equal to 50% of the incident beam's intensity. However, in reality, it is impossible to perfectly split a beam. Currently available non-polarizing beam splitters can achieve stable beam splitting within a specified wavelength range (400~700nm). The transmission and reflection efficiencies of P-polarized and S-polarized light are as follows: Figure 10a , Figure 10bAs shown, the residual polarization is less than 6% (|Rs-Rp|<6%). In actual observations, we usually use a single filter from the Johnson or SDSS series, such as Johnson's V filter (bandwidth: 490nm~580nm). In this case, the residual polarization introduced by the non-polarizing beam splitter will be less than 3%. We can subtract this polarization error introduced by the non-polarizing beam splitter through calibration measurements using a zero-polarization standard star.

[0052] After collimation, filtering, and beam splitting of the incident beam, it is divided into two beams: a transmitted beam T containing the original polarization states and a reflected beam R. The transmitted beam T and the reflected beam R then pass through a super achromatic half-wave plate (HWP) and a polarizing beam splitter (PBS, e.g., a Wollaston beam splitter), respectively, to obtain two mutually perpendicular polarized beams (P-beam and S-beam). These beams are then imaged on two optical detectors (sCMOS or CCD) by an imaging optical system. The difference between the transmitted and reflected beam channels lies in the fast-axis azimuth angle of the half-wave plate. To achieve a 45-degree polarization modulation difference between the two channels, the transmitted beam T channel uses a half-wave plate with a 0-degree fast-axis azimuth angle, and then uses the PBS to achieve full-field imaging with 0-degree and 90-degree polarization modulation, as shown below. Figure 11a As shown; the reflected beam R channel uses a half-wave plate with a fast axis azimuth angle of 22.5 degrees, and then uses a PBS to achieve full-field imaging with 135-degree and 45-degree polarization modulation. Due to the mirror effect produced by the beam splitter prism reflection, the 45-degree and 135-degree polarization images are located at... Figure 11b The positional relationship is shown.

[0053] The system schematic diagram of the Multi-channel Synchronous Polarization Imager (MSPI) is as follows: Figure 7 As shown, the system structure diagram is as follows: Figure 12 As shown.

[0054] It should be noted that the information interaction and execution process between the above-mentioned devices / units are based on the same concept as the method embodiments of this application. For details on their specific functions and technical effects, please refer to the method embodiments section, and they will not be repeated here.

[0055] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0056] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0057] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0058] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A multi-channel synchronous polarization imager system, characterized in that, include: The relay optical system includes a collimating optical system and an imaging optical system, which are used to convert diverging beams into parallel beams, realize the focusing function of the telescope optical system, and achieve good imaging on the camera target surface. The polarization calibration unit wheel is used for polarization calibration. It can be rotated to the empty position during polarization observation and to the position of the linear polarizer during calibration. Broadband optical filters are used to select light in specific wavelength bands; Zero-polarization beam splitter (NPBS): Used to split an incident parallel beam into a mutually perpendicular transmitted beam (T) and a reflected beam (R); Two sets of super achromatic half-wave plates: respectively set in the optical paths of the transmitted beam and the reflected beam, with the fast axis angle of the half-wave plate for the transmitted beam being 0 degrees and the fast axis angle of the half-wave plate for the reflected beam being 22.5 degrees; Two sets of polarizing beam splitters (PBS): used to polarize and split the beam modulated by the half-wave plate, outputting mutually perpendicular polarized light O-beam and E-beam; Imaging optical system: Connected to polarizing beam splitters, used to image polarized beams onto the detector; The detector is used to receive the imaging beam and generate image signals; A single exposure enables simultaneous measurement of the polarization state of celestial bodies across the entire field of view; The zero-polarization beam splitter prism (NPBS) achieves stable beam splitting in the 400-700 nm wavelength range with a residual polarization of less than 6%. The polarization beam splitters in the transmitted beam channel and the reflected beam channel output polarization modulated images at 0° and 90°, and 135° and 45°, respectively.

2. The multi-channel synchronous polarization imager system according to claim 1, characterized in that, The system is suitable for nighttime astronomical observation scenarios and is used for high-precision synchronous polarization measurement of 10×10 arcminutes across the entire field of view.

3. The multi-channel synchronous polarization imager system according to claim 1, characterized in that, The system utilizes a non-polarizing beam splitter prism and a super achromatic half-wave plate to eliminate dispersion effects during wide-band measurements.

4. The multi-channel synchronous polarization imager system according to claim 1, characterized in that, The system compensates for polarization errors introduced by the unpolarized beam splitter by calibration measurements using a zero-polarization standard star.

5. The multi-channel synchronous polarization imager system according to claim 1, characterized in that, The system is suitable for installation on astronomical telescopes with an axisymmetric optical system, which is an RC optical system.

6. The multi-channel synchronous polarization imager system according to claim 1, characterized in that, The system can simultaneously measure the linear polarization states (I, Q, U) of targets across the entire field of view with a single exposure.

7. The multi-channel synchronous polarization imager system according to claim 1, characterized in that, The imaging optics section of the relay optics system has a zoom function to improve the detection capability of dark and weak targets; the imaging optics system also includes optical elements for focusing the beam and imaging it well on the camera target surface.

8. The operating method of the multi-channel synchronous polarization imager system according to any one of claims 1-7, characterized in that, Includes the following steps: 1) Light Acquisition and Collimation Telescope acquisition: Light from point or surface sources in the night sky is initially collected using an astronomical telescope; Collimation process: The light collected by the telescope enters the collimation optical system in the relay optical system of MSPI, which converts the diverging beam into a parallel beam, preparing it for subsequent polarization modulation. 2) Polarization calibration Calibration preparation: If polarization calibration of the system is required, the polarization calibration unit wheel will rotate to the position of the linear polarizer; Calibration procedure: The incident light is polarized using a linear polarizer to ensure the accuracy of subsequent measurements; Observation mode switching: During normal polarization observation, the polarization calibration unit wheel is rotated to the empty position, allowing light to pass through directly without calibration. 3) Filtering and spectral dispersion Filter selection: Parallel beams pass through broadband optical filters to select light in a specific wavelength band to meet observation requirements; Beam splitting: The filtered parallel beam is incident on the zero-polarization beam splitter NPBS and splits into a mutually perpendicular transmitted beam T and a reflected beam R; ensuring that the polarization states of the two beams are consistent with the incident beam, and that the intensity of each beam is 50% of that of the incident beam; 4) Polarization modulation Transmitted beam channel T modulation: The transmitted beam undergoes polarization modulation after passing through a super achromatic half-wave plate with a fast axis of 0 degrees. The modulated beam passes through the polarizing beam splitter PBS, outputting beams with polarization directions of 0° and 90°; Reflected beam channel R modulation: The reflected beam undergoes polarization modulation after passing through a super achromatic half-wave plate with a fast axis of 22.5 degrees. The modulated beam passes through the polarizing beam splitter PBS and outputs beams with polarization directions of 45° and 135°. 5) Imaging and Detection Imaging Processing: The four modulated polarized beams at 0°, 45°, 90°, and 135° pass through their respective imaging optical systems and are imaged on four detectors, which are either sCMOS or CCD. Detection and recording: The detector receives the imaging beam and generates image signals, recording polarization-modulated images of the entire field of view; 6) Data processing and polarization state calculation Synchronization control: By synchronously controlling the exposure of the four detectors, four polarization-modulated images are acquired simultaneously; Data calculation: Using data from four images, the linear polarization state parameters (I, Q, U) of celestial bodies are calculated, enabling high-precision polarization measurement of targets across the entire field of view.

Images