Polarization modulation module adjustment method and polarization spectral imaging system

Abstract

The invention discloses a polarization modulation module adjustment method and a polarization spectral imaging system. The system comprises a polarization modulation module, a telescopic module and a spectral imaging module. After a target light beam passes through the polarization modulation module, the target light beam is received by the telescopic module and imaged, and then the target light beam is transmitted to two external entity planes through the spectral imaging module. The method comprises the following steps: respectively adjusting an optical axis of a polarization spectral imaging system and a long edge of a slit in a spectral imaging module to be horizontal; a high-precision angle relation is established between the fast axis direction of the polarization modulation module and the long edge direction of the slit in sequence by using the adjustment auxiliary tool and image data of the polarization spectral imaging system; according to the characteristics of each optical element of the polarization modulation module, a fast axis characterization method of each optical element is established, and high-precision adjustment of the polarization modulation module is realized.

Description

Technical Field

[0001] The invention relates to the technical field of remote sensor assembly and adjustment, and in particular to a polarization modulation module assembly and adjustment method and a polarization spectrum imaging system. Background Art

[0002] Compared with non-biased detection, polarization imaging technology can effectively enhance the detection and identification capabilities of targets, and has broad application prospects in the field of atmospheric aerosol detection. Spectral modulation polarization imaging technology is one of the important development directions of polarization imaging technology. Compared with traditional polarization detection technology, it has irreplaceable advantages, including: 1) snapshot detection, avoiding the generation of false polarization signals, theoretically with higher polarization measurement accuracy, and no moving parts make the detection system more reliable; 2) rich observation information, which is conducive to obtaining more and more accurate target parameters; 3) compact structure, reducing platform resource occupation, etc.

[0003] The polarization modulation module is a key module for realizing polarization information spectral modulation in spectral modulation polarization imaging technology. It is composed of multiple polarization elements. The fast axis angle relationship between them and the relationship with the spectrometer slit will significantly affect the measurement equation, measurement error and subsequent stray light measurement of the spectral modulation polarization imaging system. Therefore, the adjustment accuracy of the polarization modulation module is crucial to the performance and subsequent application of the spectral modulation polarization imaging system.

[0004] In the prior art, such as the invention patents with patent publication numbers CN108957781A, CN108732780A, CN104007560A, CN115598854A, CN118688974A, CN116400513A, CN106526884A and CN116381886A, the installation and adjustment technology of the optical module is usually aimed at the optical lens, and usually an external measuring device is used to measure and adjust the interval between lenses of the optical lens and the center deviation error of each lens, so as to achieve a satisfactory imaging quality of the optical lens.

[0005] However, there are obvious problems when the traditional optical module assembly method is applied to the polarization modulation module assembly of the polarization spectral imaging system:

[0006] 1. The measurement object during traditional optical lens adjustment is a lens with focus, while the optical elements of the polarization modulation module are mostly optical prisms or flat plates without focus. Therefore, the traditional optical lens adjustment technology is not suitable for the measurement of the optical elements of the polarization modulation module in principle.

[0007] 2. Traditional optical lens adjustment technology does not have the fast-axis measurement function of the polarization element, and cannot assist the optical elements of the polarization modulation module to establish the fast-axis angle relationship, nor can it establish the relationship between the optical elements of the polarization modulation module and the slit.

[0008] 3. Relying solely on external measurement devices, it is impossible to directly establish the relationship between the polarization modulation module and the slit, and the debugging efficiency is low.

[0009] Therefore, how to provide a suitable adjustment method for the polarization modulation module of the polarization spectral imaging system is a technical problem that urgently needs to be solved in this field. Summary of the invention

[0010] The technical problem to be solved by the present invention is to provide a method for assembling and adjusting a polarization modulation module of a polarization spectrum imaging system.

[0011] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0012] A polarization modulation module installation method, a polarization spectrum imaging system includes a polarization modulation module 10, a telescope module 20 and a spectrum imaging module 30; after a target light beam passes through the polarization modulation module 10, it is received and imaged by the telescope module 20, and then forms an image through the spectrum imaging module 30; the polarization modulation module 10 includes a Fresnel prism 11, a multi-stage phase retarder 12 and a polarization beam splitter 13 arranged in sequence along the emission direction of the target light beam;

[0013] Define the coordinate system: the optical axis direction of the polarization spectrum imaging system is the Z axis, the vertical direction is the Y axis, and the horizontal direction perpendicular to the YOZ plane is the X axis; the installation and adjustment methods include:

[0014] S10, positioning the optical axis of the polarization spectrum imaging system: adjusting the optical axis of the polarization spectrum imaging system and the long side of the slit 31 in the spectrum imaging module 30 to be horizontal respectively;

[0015] S20, adjustment of the polarization modulation module 10: using adjustment auxiliary tools and image data of the polarization spectrum imaging system, the fast axis directions of the polarization beam splitter 13, the Fresnel prism 11 and the multi-stage phase retarder 12 are sequentially established with a high-precision angle relationship with the long side direction of the slit 31.

[0016] Beneficial effects: The present invention establishes a fast axis characterization method for each optical element according to the performance characteristics of each optical element of the polarization modulation module, thereby realizing the assembly and adjustment of the polarization modulation module with high precision and high efficiency.

[0017] In one embodiment of the present invention, the optical axis positioning of the polarization spectrum imaging system includes:

[0018] S11, the spectral imaging module 30 is mounted on a multi-dimensional adjustment platform 40 with horizontal direction angle and pitch angle adjustment functions, and the long side of the slit 31 is in the horizontal direction; a monochromatic light source 51 and an integrating sphere 52 are arranged before the telescope module 20; the monochromatic light source 51 emits monochromatic light which is introduced into the integrating sphere 52 and then enters the telescope module 20 and the spectral imaging module 30 in sequence, the image formed by the spectral imaging module 30 is checked, and the pixel coordinates corresponding to the maximum signal of the image are obtained;

[0019] S12, replace the integrating sphere 52 with the collimator 53, set the theodolite 60 behind the collimator 53, and use the theodolite 60 to adjust the monochromatic light beam emitted by the collimator 53 to be in the horizontal direction; adjust the pitch angle of the multi-dimensional adjustment platform 40 to obtain the maximum signal sequence of a series of images formed by the spectral imaging module 30 at different pitch angles, fit different pitch angles and the maximum signal sequence, and obtain the pitch angle φ corresponding to the peak value of the maximum signal at different pitch angles max,0 , and adjust the pitch angle of the multi-dimensional adjustment stage 40 to φ max,0 ;

[0020] S13, adjusting the horizontal direction angle of the multi-dimensional adjustment platform 40, obtaining a pixel coordinate sequence corresponding to the maximum signal of a series of images formed by the spectral imaging module 30 at different horizontal direction angles, fitting the horizontal direction angle and the pixel coordinate sequence corresponding to the maximum signal, and interpolating to obtain the horizontal azimuth angle θ corresponding to the pixel coordinate corresponding to the maximum signal max,0 , and adjust the horizontal angle of the multi-dimensional adjustment stage 40 to φ max,0 .

[0021] In one embodiment of the present invention, the polarization modulation module 10 is installed and adjusted, including:

[0022] S21, pre-installing the polarization beam splitter 13 before the telescope module 20, ensuring that the two light beams emitted by the polarization beam splitter 13 pass through the telescope module 20 and fall beside the slit 31;

[0023] S22, a wide-band light source 54 and a collimator 53 are arranged before the polarization beam splitter 13; the wide-band light source 54 forms a wide-band parallel light beam after passing through the collimator 53, and then passes through the polarization beam splitter 13, the telescope module 20 and the spectral imaging module 30 in sequence; the polarization beam splitter 13 is adjusted to rotate in the XOY plane, and the image formed by the spectral imaging module 30 is checked under different rotation angle conditions, and the consistency of the signals of the two thin lines on the image in the spatial dimension is compared. When the peak signals of the two thin lines in the spatial dimension are consistent, the rotation in the XOY plane is stopped, and the adjustment of the spectral imaging module 30 is completed;

[0024] S23, pre-install the multi-stage phase retarder 12 before the polarization beam splitter 13, so that the fast axis of the multi-stage phase retarder 12 is close to the angle of 45° with the X axis in the XOY plane; pre-install the Fresnel prism 11 before the multi-stage phase retarder 12; close the front end face and the side face of the Fresnel prism 11 to the reflector respectively, and observe the reflector by using the theodolite 60 at the same time, adjust the posture of the Fresnel prism 11, so that the reflection surface of the Fresnel prism 11 is parallel to the YOZ plane, and then adjust the front end face of the Fresnel prism 11 to be parallel to the XOY plane, and complete the installation and adjustment of the Fresnel prism 11;

[0025] S24, placing a wide-band light source 54, an integrating sphere 52 and a linear polarizer 70 in front of the polarization spectral imaging system; the wide-band light source 54 is introduced into the integrating sphere 52 and then passes through the linear polarizer 70 to form a wide-band linear polarized light that enters the polarization spectral imaging system; the polarization spectral imaging system observes the wide-band linear polarized light to form a high-contrast modulated image; the multi-stage phase retarder 12 is adjusted to rotate in the XOY plane, and the minimum signal of the spectral dimension modulation curve is checked under different rotation angles. When the minimum signal reaches the minimum, the adjustment of the multi-stage phase retarder 12 is completed.

[0026] In one embodiment of the present invention, the adjustment method further comprises:

[0027] S30, reference transfer: transferring the optical axis direction of the polarization spectrum imaging system and the long side direction of the slit 31 to the physical plane outside the polarization spectrum imaging system respectively.

[0028] In one embodiment of the present invention, the benchmark transfer includes:

[0029] S31, select a plane P1 parallel to the XOY plane on the spectral imaging module 30, attach the reflector M1, and select a plane P2 parallel to the YOZ plane, attach the reflector M2;

[0030] S32, using the reflected light of the reflector M1, aligning the theodolite 60 with the reflector M1, checking the elevation angle displayed by the theodolite 60 and recording it as α1, checking the horizontal azimuth displayed by the theodolite 60 and recording it as β1; using the theodolite 60 to check the reflected light of the reflector M2, aligning the theodolite 60 with the reflector M2, checking the elevation angle displayed by the theodolite 60 and recording it as α2.

[0031] In one embodiment of the present invention, the benchmark transfer includes:

[0032] A cubic prism is arranged on the stable surface of the outer shell of the spectral imaging module 30, and two planes of the cubic prism are set as A surface and B surface, which are parallel to the XOY plane and the YOZ plane respectively. Two theodolites 60 are used to simultaneously check the reflected light of the A surface and the B surface of the cubic prism, and the posture of the cubic prism is adjusted until the A surface is parallel to the XOY plane and the B surface is parallel to the YOZ plane.

[0033] The present invention also provides a polarization spectrum imaging system, which uses the polarization modulation module assembly method described above.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] Using the spectral imaging module as a measurement method, according to the change law of image data when the fast axis direction of each component changes, the image data of the spectral imaging module can more intuitively judge whether the fast axis direction of the optical component has reached a satisfactory position, which solves the problem that traditional optical lens adjustment technology is not suitable for the measurement of optical components of the polarization modulation module.

[0036] The optical components of the polarization modulation module are directly installed before the telescope module and the spectral imaging module, which can easily establish the relationship between the optical components of the polarization modulation module and the slits of the spectral imaging module. While meeting the installation and adjustment requirements, each component is directly in place. After the polarization modulation module is installed and adjusted, the polarization spectral imaging system can be put into use, which significantly improves efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 The present invention is a flowchart of a polarization modulation module assembly method according to an embodiment of the present invention.

[0038] Figure 2 Schematic diagram of a polarization spectral imaging system according to an embodiment of the present invention.

[0039] Figure 3 This is a schematic diagram of the preliminary adjustment of the spectral imaging module according to an embodiment of the present invention.

[0040] Figure 4 This is an image formed by the preliminary adjustment of the spectral imaging module in an embodiment of the present invention.

[0041] Figure 5 Schematic diagram of the pitch angle of the multi-dimensional adjustment platform according to an embodiment of the present invention.

[0042] Figure 6 This is an image formed by the spectral imaging module at a pitch angle according to an embodiment of the present invention.

[0043] Figure 7 Schematic diagram of the installation and adjustment of the polarization beam splitter according to an embodiment of the present invention.

[0044] Figure 8 The polarization beam splitter is adjusted for different rotation angle conditions of the embodiment of the present invention, and the image formed by the spectral imaging module is adjusted.

[0045] Fig. 9 It is a schematic diagram of adjusting the Fresnel prism according to an embodiment of the present invention.

[0046] Fig.10Schematic diagram of the adjustment of a multi-stage phase delay device according to an embodiment of the present invention.

[0047] Fig.11 Schematic diagram of a minimum signal of a spectral dimension modulation curve according to an embodiment of the present invention. DETAILED DESCRIPTION

[0048] In order to facilitate those skilled in the art to understand the technical solution of the present invention, the technical solution of the present invention is further described in conjunction with the accompanying drawings of the specification.

[0049] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0050] See also Figure 1 and Figure 2 As shown, the present invention discloses a polarization modulation module installation method. Before describing the installation method, the polarization spectrum imaging system of the installation object is described first. The polarization spectrum imaging system includes a polarization modulation module 10, a telescope module 20 and a spectrum imaging module 30.

[0051] In this embodiment, the polarization modulation module 10 includes a Fresnel prism 11 with a fast axis direction of 0°, a multi-stage phase retarder 12 with a fast axis direction of 45°, and a polarization beam splitter 13 with polarization analysis directions of 0° and 90°, which are sequentially arranged along the emission direction of the target light beam. Among them, the Fresnel prism 11 is an achromatic 1 / 4 wave plate realized by total internal reflection. The spectral imaging module 30 includes a slit 31, a grating dispersion component 32, and a planar array detector component 33. After the target light beam passes through the Fresnel prism 11, the multi-stage phase retarder 12, and the polarization beam splitter 13 in sequence, two light beams with a certain separation angle, whose vibration directions are perpendicular to each other and whose amplitudes are complementary, are formed, called S light and P light, which are received by the telescope module 20 and imaged on the slit 31 of the spectral imaging module 30. After the two light beams passing through the slit 31 are dispersed by the grating dispersion component 32, they are received by the array detector component 33 and form an image. The two dimensions of the image are the spatial dimension and the spectral dimension. There are two independent areas on the image, corresponding to the S light area and the P light area, respectively. In this embodiment, the slit 31 and the grating dispersion component 32 are designed as offner type, which is conducive to the miniaturization of the components.

[0052] See also Figure 1 and Figure 2As shown, in one embodiment of the present invention, a coordinate system is defined: the optical axis direction of the polarization spectrum imaging system is the Z axis, the vertical direction is the Y axis, and the horizontal direction perpendicular to the YOZ plane is the X axis. The adjustment method includes the following steps:

[0053] S10, positioning the optical axis of the polarization spectrum imaging system: adjusting the optical axis of the polarization spectrum imaging system and the long side of the slit 31 in the spectrum imaging module 30 to be horizontal.

[0054] In one embodiment of the present invention, the optical axis positioning of the polarization spectrum imaging system specifically includes:

[0055] S11, installing the spectral imaging module 30 on a multi-dimensional adjustment platform 40 with horizontal direction angle and pitch angle adjustment functions, with the long side of the slit 31 in the horizontal direction.

[0056] A monochromatic light source 51 and an integrating sphere 52 are arranged before the telescope module 20. The monochromatic light source 51 emits monochromatic light which is introduced into the integrating sphere 52 and then enters the telescope module 20 and the spectral imaging module 30 in sequence to view the image formed by the spectral imaging module 30 and obtain the pixel coordinates corresponding to the maximum signal of the image.

[0057] See also Figure 3 and Figure 4 As shown, in this embodiment, the multi-dimensional adjustment stage 40 can also perform translation in the X-axis direction and lifting in the Y-axis direction. The long side of the slit 31 is horizontal, that is, parallel to the X-axis. The telescope module 20 is fixedly connected to the spectral imaging module 30, and the monochromatic light source 51 is introduced into the uniform surface light source of the integrating sphere 52. In this embodiment, the monochromatic light source 51 can be a monochromatic light beam output by a monochromator or a laser, such as Figure 3 As shown. The image formed by the spectral imaging module 30 is shown Figure 4 As shown, in this embodiment, the row direction of the image is the spatial dimension direction parallel to the slit 31, and the column direction of the image is the spectral dimension direction. The pixel coordinate P corresponding to the maximum signal of the image is obtained. max,0 =(i max,0 ,j max,0 ), where i max,0 represents the row number of the pixel corresponding to the maximum signal of the image, where j max,0 Represents the column number of the pixel corresponding to the maximum signal of the image.

[0058] S12, replace the integrating sphere 52 with the collimator 53, set the theodolite 60 behind the collimator 53, and use the theodolite 60 to adjust the monochromatic light beam emitted by the collimator 53 to be in the horizontal direction. Adjust the pitch angle of the multi-dimensional adjustment platform 40, obtain the maximum signal sequence of a series of images formed by the spectral imaging module 30 at different pitch angles, fit different pitch angles and the maximum signal sequence, and obtain the pitch angle φ corresponding to the peak value of the maximum signal at different pitch angles max,0 , and adjust the pitch angle of the multi-dimensional adjustment stage 40 to φ max,0 .

[0059] In one embodiment of the present invention, Figure 5 , set up a multi-dimensional adjustment platform 40 to translate the spectral imaging module 30 and the telescope module 20 along the X-axis until they are outside the light beam emitted by the collimator 53, use the theodolite 60 to adjust the light beam emitted by the collimator 53 to be in the horizontal direction, set up a multi-dimensional adjustment platform 40 to translate the spectral imaging module 30 and the telescope module 20 along the X-axis until the telescope module 20 is in the center area of ​​the light beam emitted by the collimator 53, adjust the pitch angle of the multi-dimensional adjustment platform 40, and obtain the maximum signal sequence of a series of images formed by the spectral imaging module 30 at different pitch angles. At this time, the image is a single bright spot such as Figure 6 As shown, the different pitch angles and the maximum signal sequence are fitted to obtain the pitch angle φ corresponding to the peak value of the maximum signal at different pitch angles. max,0 , and adjust the pitch angle of the multi-dimensional adjustment stage 40 to φ max,0 .

[0060] S13, adjusting the horizontal direction angle of the multi-dimensional adjustment platform 40, obtaining a pixel coordinate sequence corresponding to the maximum signal of a series of images formed by the spectral imaging module 30 at different horizontal direction angles, fitting the horizontal direction angle and the pixel coordinate sequence corresponding to the maximum signal, and interpolating to obtain the horizontal azimuth angle θ corresponding to the pixel coordinate corresponding to the maximum signal max,0 , and adjust the horizontal angle of the multi-dimensional adjustment stage 40 to θ max,0 .

[0061] In one embodiment of the present invention, at this time, the optical axis direction of the polarization spectrum imaging system and the length direction of the slit 31 are both horizontal, and the light beams emitted by the collimator 53 are all in the Z-axis direction.

[0062] S20, adjustment of the polarization modulation module 10: using adjustment auxiliary tools and image data of the polarization spectrum imaging system, the fast axis directions of the polarization beam splitter 13, the Fresnel prism 11 and the multi-stage phase retarder 12 are sequentially established with a high-precision angle relationship with the long side direction of the slit 31.

[0063] In one embodiment of the present invention, the adjustment of the polarization modulation module 10 specifically includes:

[0064] S21 , pre-installing the polarization beam splitter 13 before the telescope module 20 , ensuring that the two light beams emitted by the polarization beam splitter 13 pass through the telescope module 20 and both fall beside the slit 31 .

[0065] In this embodiment, it is ensured that the two light beams emitted from the polarization beam splitter 13 are both in the vicinity of the horizontal direction, or in other words, the two light spots corresponding to the two light beams emitted from the polarization beam splitter 13 are both located near the slit 31 .

[0066] S22, a wide-band light source 54 and a collimator 53 are arranged before the polarization beam splitter 13; the wide-band light source 54 forms a wide-band parallel light beam after passing through the collimator 53, and then passes through the polarization beam splitter 13, the telescope module 20 and the spectral imaging module 30 in sequence. The polarization beam splitter 13 is adjusted to rotate in the XOY plane, and the image formed by the spectral imaging module 30 is checked under different rotation angle conditions, and the consistency of the signals of the two thin lines on the image in the spatial dimension is compared. When the peak signals of the two thin lines in the spatial dimension are consistent, the rotation in the XOY plane is stopped, and the adjustment of the spectral imaging module 30 is completed.

[0067] In this embodiment, if Figure 7 As shown, the wide-spectrum parallel light beam enters the spectral imaging module 30 via the polarization beam splitter 13 and the telescope module 20. The image obtained by the spectral imaging module 30 will show a pair of thin bright lines, such as Figure 8 As shown. The polarization beam splitter 13 is adjusted to rotate in the XOY plane, and the positions of the two light spots corresponding to the two light beams emitted by the polarization beam splitter 13 on the slit 31 change accordingly, and the relative sizes of the two signal peaks of the two thin lines on the image in the spatial dimension change accordingly. Under different rotation angle conditions, the consistency of the two signal peaks of the two thin lines on the image in the spatial dimension is observed. When the signal peaks of the two thin lines in the spatial dimension are consistent, the rotation in the XOY plane is stopped, and the adjustment of the polarization beam splitter 13 is completed.

[0068] S23, pre-install the multi-stage phase retarder 12 before the polarization beam splitter 13, so that the fast axis of the multi-stage phase retarder 12 is close to the angle of 45° with the X-axis in the XOY plane; pre-install the Fresnel prism 11 before the multi-stage phase retarder 12; close the reflector to the front end face and the side face of the Fresnel prism 11 respectively, and observe the reflector by using the theodolite 60 at the same time, adjust the posture of the Fresnel prism 11, make the reflecting surface of the Fresnel prism 11 parallel to the YOZ plane, and then adjust the front end face of the Fresnel prism 11 to be parallel to the XOY plane, and complete the installation and adjustment of the Fresnel prism 11.

[0069] In one embodiment of the present invention, Fig. 9As shown, the reflection surface of the Fresnel prism 11 is the reflection plane when the light beam incident on the front face is totally reflected inside, and is parallel to the side surface of the Fresnel prism 11. In this embodiment, the front face of the fixed structure of the Fresnel prism 11 is parallel to the front face of the Fresnel prism 11, and the side surface of the fixed structure of the Fresnel prism 11 is parallel to the side surface of the Fresnel prism 11. The front face and side surface of the fixed structure of the Fresnel prism 11 are respectively close to the reflector. The reflector is observed by the theodolite 60, and the posture of the Fresnel prism 11 is adjusted so that the side surface of the fixed structure of the Fresnel prism 11 is parallel to the YOZ plane, and then the front face of the fixed structure of the Fresnel prism 11 is adjusted to be parallel to the XOY plane, and the adjustment of the Fresnel prism 11 is completed. At this time, the front face of the Fresnel prism 11 is perpendicular to the Z-axis direction, and the side surface of the Fresnel prism 11 is perpendicular to the length direction of the slit 31.

[0070] S24, placing a wide-band light source 54, an integrating sphere 52 and a linear polarizer 70 in front of the polarization spectral imaging system; the wide-band light source 54 is introduced into the integrating sphere 52 and then passes through the linear polarizer 70 to form a wide-band linear polarized light that enters the polarization spectral imaging system; the polarization spectral imaging system observes the wide-band linear polarized light to form a high-contrast modulated image; the multi-stage phase retarder 12 is adjusted to rotate in the XOY plane, and the minimum signal of the spectral dimension modulation curve is checked under different rotation angles. When the minimum signal reaches the minimum, the adjustment of the multi-stage phase retarder 12 is completed.

[0071] In this embodiment, if Fig.10 As shown, the broadband light source 54 is introduced into the uniform surface light source of the integrating sphere 52 and the linear polarizer 70 to form broadband linear polarized light. The polarization spectrum imaging system observes the broadband linear polarized light to form a high-contrast modulated image, such as Fig.11 As shown, the multi-stage phase retarder 12 is adjusted to rotate in the XOY plane, and the minimum signal of the spectral dimension modulation curve is checked under different rotation angle conditions. When the minimum signal reaches the minimum, the adjustment of the multi-stage phase retarder 12 is completed. At this time, the fast axis direction of the multi-stage phase retarder 12 and the length direction of the slit 31 are at an angle of 45°.

[0072] The above is the completion of the adjustment of the polarization spectrum imaging system. However, after the adjustment is completed, the external structure is not clear about the optical axis of the polarization spectrum imaging system and the long side direction of the slit 31. Therefore, the adjustment method of the present invention also includes step S30, which is used to transmit the optical axis direction of the polarization spectrum imaging system and the long side direction of the slit 31 to facilitate the adjustment of the external structure. Specifically, it includes:

[0073] S30, reference transfer: the optical axis direction of the polarization spectrum imaging system and the long side direction of the slit 31 are respectively transferred to the physical plane outside the spectrum imaging module 30. The spectrum imaging module 30 is used for reference transfer mainly because the structure flatness of the spectrum imaging module 30 is relatively good, which is convenient for assembling and adjusting auxiliary tools.

[0074] In one embodiment of the present invention, the benchmark transfer specifically includes:

[0075] S31, select a plane P1 parallel to the XOY plane on the spectral imaging module 30, attach the reflector M1, and select a plane P2 parallel to the YOZ plane, attach the reflector M2.

[0076] S32, using the reflected light of the reflector M1, aligning the theodolite 60 with the reflector M1, checking the elevation angle displayed by the theodolite 60 and recording it as α1, checking the horizontal azimuth displayed by the theodolite 60 and recording it as β1; using the theodolite 60 to check the reflected light of the reflector M2, aligning the theodolite 60 with the reflector M2, checking the elevation angle displayed by the theodolite 60 and recording it as α2. According to the recorded angles α1, β1 and α2, the optical axis direction of the polarization spectrum imaging system and the long side direction of the slit 31 are determined.

[0077] In another embodiment of the present invention, alternatively, a cubic prism is set on the stable surface of the housing of the spectral imaging module 30, and two planes of the cubic prism are set as A surface and B surface, which are parallel to the XOY surface and the YOZ surface respectively. Two theodolites 60 are used to simultaneously check the reflected light of the A surface and the B surface of the cubic prism, and adjust the posture of the cubic prism until the A surface is parallel to the XOY surface and the B surface is parallel to the YOZ surface. Similarly, the final posture of the cubic prism determines the optical axis direction of the polarization spectral imaging system and the long side direction of the slit 31.

[0078] In one embodiment of the present invention, the above-mentioned auxiliary adjustment tools include a monochromatic light source 51, an integrating sphere 52, a collimator 53, a broadband light source 54, a theodolite 60, a linear polarizer 70, a reflector and a cubic prism.

[0079] See also Figures 1 to 11 As shown, the present invention also provides a polarization spectrum imaging system, which uses the polarization modulation module assembly method described above.

[0080] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0081] The above-described embodiments merely represent implementation methods of the invention. The protection scope of the present invention is not limited to the above-described embodiments. For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A polarization modulation module installation method, characterized in that: The polarization spectrum imaging system comprises a polarization modulation module (10), a telescope module (20) and a spectrum imaging module (30); after a target light beam passes through the polarization modulation module (10), it is received and imaged by the telescope module (20), and then an image is formed by the spectrum imaging module (30); the polarization modulation module (10) comprises a Fresnel prism (11), a multi-stage phase retarder (12) and a polarization beam splitter (13) which are sequentially arranged along the emission direction of the target light beam; Define the coordinate system: the optical axis direction of the polarization spectrum imaging system is the Z axis, the vertical direction is the Y axis, and the horizontal direction perpendicular to the YOZ plane is the X axis; the installation and adjustment methods include: S10, positioning the optical axis of the polarization spectral imaging system: adjusting the optical axis of the polarization spectral imaging system and the long side of the slit (31) in the spectral imaging module (30) to be horizontal; S20, adjustment of the polarization modulation module (10): using adjustment auxiliary tools and image data from a polarization spectrum imaging system, the fast axis directions of the polarization beam splitter (13), the Fresnel prism (11) and the multi-stage phase retarder (12) are sequentially established with a high-precision angular relationship with the long side direction of the slit (31).

2. The polarization modulation module assembly and adjustment method according to claim 1, characterized in that: Optical axis positioning of polarization spectral imaging system, including: S11, installing the spectral imaging module (30) on a multi-dimensional adjustment platform (40) having horizontal direction angle and pitch angle adjustment functions, with the long side of the slit (31) being in the horizontal direction; arranging a monochromatic light source (51) and an integrating sphere (52) before the telescope module (20); the monochromatic light emitted by the monochromatic light source (51) is introduced into the integrating sphere (52) and then enters the telescope module (20) and the spectral imaging module (30) in sequence, checking an image formed by the spectral imaging module (30), and obtaining pixel coordinates corresponding to the maximum signal of the image; S12, replacing the integrating sphere (52) with a collimator (53), placing the theodolite (60) behind the collimator (53), and using the theodolite (60) to adjust the monochromatic light beam emitted by the collimator (53) to a horizontal direction; adjusting the elevation angle of the multi-dimensional adjustment platform (40) to obtain a maximum signal sequence of a series of images formed by the spectral imaging module (30) at different elevation angles, fitting different elevation angles and the maximum signal sequence, and obtaining the elevation angle φ corresponding to the peak value of the maximum signal at different elevation angles. max,0 , and adjust the pitch angle of the multi-dimensional adjustment platform (40) to φ max,0 ; S13, adjusting the horizontal direction angle of the multi-dimensional adjustment platform (40) to obtain a pixel coordinate sequence corresponding to the maximum signal of a series of images formed by the spectral imaging module (30) at different horizontal direction angles, fitting the horizontal direction angle and the pixel coordinate sequence corresponding to the maximum signal, and interpolating to obtain a horizontal azimuth angle θ corresponding to the pixel coordinate corresponding to the maximum signal max,0 , and adjust the horizontal angle of the multi-dimensional adjustment platform (40) to φ max,0 .

3. The polarization modulation module assembly and adjustment method according to claim 1, characterized in that: The assembly and adjustment of the polarization modulation module (10) comprises: S21, pre-installing the polarization beam splitter (13) before the telescope module (20), ensuring that the two light beams emitted by the polarization beam splitter (13) pass through the telescope module (20) and both fall beside the slit (31); S22, a wide-band light source (54) and a collimator (53) are arranged before the polarization beam splitter (13); the wide-band light source (54) forms a wide-band parallel light beam after passing through the collimator (53), and then passes through the polarization beam splitter (13), the telescope module (20) and the spectral imaging module (30) in sequence; the polarization beam splitter (13) is adjusted to rotate in the XOY plane, and under different rotation angle conditions, an image formed by the spectral imaging module (30) is checked, and the consistency of the signals of two thin lines on the image in the spatial dimension is compared; when the peak signals of the two thin lines in the spatial dimension are consistent, the rotation in the XOY plane is stopped, and the adjustment of the spectral imaging module (30) is completed; S23, pre-installing the multi-stage phase retarder (12) before the polarization beam splitter (13), so that the fast axis of the multi-stage phase retarder (12) is close to the angle of 45° with the X axis in the XOY plane; pre-installing the Fresnel prism (11) before the multi-stage phase retarder (12); placing the front end face and the side face of the Fresnel prism (11) close to the reflector respectively, and using the theodolite (60) to observe the reflector, adjusting the posture of the Fresnel prism (11), so that the reflection surface of the Fresnel prism (11) is parallel to the YOZ plane, and then adjusting the front end face of the Fresnel prism (11) is parallel to the XOY plane, and completing the installation and adjustment of the Fresnel prism (11); S24, placing a wide-band light source (54), an integrating sphere (52) and a linear polarizer (70) in front of the polarization spectrum imaging system; the wide-band light source (54) is introduced into the integrating sphere (52) and then passes through the linear polarizer (70) to form a wide-band linear polarized light that enters the polarization spectrum imaging system; the polarization spectrum imaging system observes the wide-band linear polarized light to form a high-contrast modulated image; the multi-stage phase retarder (12) is adjusted to rotate in the XOY plane, and the minimum signal of the spectral dimension modulation curve is checked under different rotation angle conditions. When the minimum signal reaches the minimum, the multi-stage phase retarder (12) is installed and adjusted.

4. The polarization modulation module assembly and adjustment method according to claim 1, characterized in that: The installation method also includes: S30, reference transfer: transferring the optical axis direction of the polarization spectrum imaging system and the long side direction of the slit (31) to a physical plane outside the polarization spectrum imaging system respectively.

5. The polarization modulation module assembly and adjustment method according to claim 4, characterized in that: Benchmark transfer, including: S31, select a plane P1 on the spectral imaging module (30) parallel to the XOY plane, attach the reflector M1, and select a plane P2 parallel to the YOZ plane, attach the reflector M2; S32, using the reflected light of the reflector M1, aligning the theodolite (60) with the reflector M1, checking the elevation angle displayed by the theodolite (60) and recording it as α1, and checking the horizontal azimuth displayed by the theodolite (60) and recording it as β1; using the theodolite (60) to check the reflected light of the reflector M2, aligning the theodolite (60) with the reflector M2, checking the elevation angle displayed by the theodolite (60) and recording it as α2.

6. The polarization modulation module assembly and adjustment method according to claim 4, characterized in that: Benchmark transfer, including: A cubic prism is arranged on a stable surface of the outer shell of the spectral imaging module (30), and two planes of the cubic prism are set as A surface and B surface, which are parallel to the XOY surface and the YOZ surface respectively. Two theodolites (60) are used to simultaneously check the reflected light of the A surface and the B surface of the cubic prism, and the posture of the cubic prism is adjusted until the A surface is parallel to the XOY surface, and the B surface is parallel to the YOZ surface.

7. A polarization spectrum imaging system, characterized in that: A polarization modulation module assembly and adjustment method according to any one of claims 1 to 6 is used.

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