Daman grating-based binocular off-axis multi-reflection space camera calibration system and method

Abstract

The application belongs to the technical field of space optics, and particularly relates to a binocular off-axis multi-reflection space camera calibration system and method based on a Dammam grating. After the first laser beam output by a first laser emission module is diffracted by a first Dammam grating, a first shaped laser beam is obtained, and at the same time, after the second laser beam output by a second laser emission module is diffracted by a second Dammam grating, a second shaped laser beam is obtained. After the first and second shaped laser beams are processed by a binocular off-axis multi-reflection space camera, corresponding imaging is formed on the target surface of the double CMOS of the binocular off-axis multi-reflection space camera, and first and second Dammam grating image point pictures are obtained. A data processing module calculates the distortion parameters of the binocular off-axis multi-reflection space camera based on the first and second Dammam grating image point pictures, and the calibration of the binocular off-axis multi-reflection space camera is realized. The application provides a relatively inexpensive, practical and accurate and fast calibration scheme for sub-pixel level precision.

Description

Technical Field

[0001] This invention belongs to the field of space optics technology, and particularly relates to a calibration system and method for a binocular off-axis multi-lens space camera based on a Damman grating. Background Technology

[0002] Star sensors are attitude measurement devices widely used in aerospace, ship navigation, and astronomical observation. Their core mechanism involves: imaging with an optical lens and image sensor; extracting star points and locating their centers of mass to obtain the position and brightness data of the stars on the target surface; then identifying stars by matching them with star catalogs; finally, combining the star catalog data with attitude calculations to obtain the three-axis attitude of the star sensor, providing attitude data for the carrier control system. The accuracy of single-star measurement determines the attitude accuracy; therefore, the focal length, distortion, principal point, and principal distance of the star sensor need to be calibrated to improve accuracy.

[0003] For star sensor calibration, traditional ground-based static calibration uses a high-precision turntable to collect target points on the star sensor's image plane. However, this method requires expensive equipment and is complex and time-consuming. Dynamic calibration uses a star simulator to simulate stars in the sky to calibrate the star sensor. However, this method has lower accuracy and is difficult to meet the accuracy requirements of star sensors with high precision requirements. When using a calibration checkerboard, the checkerboard must be perfectly flat; any slight bending, wrinkles, or deformation will directly lead to calibration errors. The contrast between the black and white squares must be sufficiently high; failure to meet these requirements will affect the accuracy of corner detection, leading to problems such as blurred corner extraction and edge noise interference. Summary of the Invention

[0004] In view of this, the present invention aims to provide a calibration system and method for a binocular off-axis multi-reflector space camera based on a damman grating. The present invention uses a damman grating as a calibration plate. The damman grating has the characteristics of accurate diffraction angle and accurate extraction of diffraction spot centroid, providing a relatively inexpensive, practical and accurate and fast calibration scheme for sub-pixel level accuracy.

[0005] To achieve the above objectives, the technical solution created by this invention is implemented as follows:

[0006] A calibration system for a binocular off-axis multi-reflector space camera based on a Damman grating includes a first laser emitting module, a second laser emitting module, a first Damman grating, a second Damman grating, and a data processing module. The system comprises a first laser beam output from the first laser emitting module, which is diffracted by the first Damman grating to obtain a first shaped laser beam; simultaneously, a second laser beam output from the second laser emitting module is diffracted by the second Damman grating to obtain a second shaped laser beam. The first and second shaped laser beams are processed by the binocular off-axis multi-reflector space camera and imaged on the target surface of the camera's dual CMOS sensors, resulting in first and second Damman grating image point images. The data processing module calculates the distortion parameters of the binocular off-axis multi-reflector space camera based on these images, thereby calibrating the camera.

[0007] Furthermore, both the first and second laser emitting modules emit collimated 632.8nm helium-neon lasers.

[0008] Furthermore, after the first shaped laser beam is processed by the binocular off-axis multi-reflector space camera, it is imaged on the target surface of the first CMOS of the binocular off-axis multi-reflector space camera to obtain a first Dammann grating image point image; after the second shaped laser beam is processed by the binocular off-axis multi-reflector space camera, it is imaged on the target surface of the second CMOS of the binocular off-axis multi-reflector space camera to obtain a second Dammann grating image point image.

[0009] A calibration method for a binocular off-axis multi-lens spatial camera based on a Damman grating is implemented using a Damman grating-based binocular off-axis multi-lens spatial camera calibration system, and specifically includes the following steps:

[0010] S1: Acquire images of the first and second Damman gratings;

[0011] S2: Extract the actual pixel coordinates on the target surface of the first CMOS corresponding to the centroid of each spot on the first Damman grating image point;

[0012] S3: Based on the period length of the first Damman grating, calculate the diffraction angle of the first Damman grating at different diffraction orders;

[0013] S4: Let the coordinates of the principal point of the first camera on the target surface of the first CMOS be (u1, v1). Based on the pinhole camera model, solve for the actual pixel coordinates of each spot centroid on the target surface of the first CMOS:

[0014] ;

[0015] ;

[0016] in, The effective focal length of a binocular off-axis multi-lens space camera. The diffraction angle in the x-direction corresponding to the m-th row of light spots. Let be the diffraction angle in the y-direction corresponding to the nth column of light spots, ( , () represents the actual pixel coordinates on the target surface of the first CMOS corresponding to the centroid of the spot in the m-th row and n-th column;

[0017] S5: Substitute the calculation results of step S4 into the camera distortion model, and use the Levenberg-Marquardt optimization algorithm to iteratively solve the camera distortion model to obtain the radial distortion parameters, tangential distortion parameters and principal point positions of the camera corresponding to the first CMOS.

[0018] S6: Replace the first Damman grating image with the second Damman grating image, and repeat steps S2-S5 to obtain the radial distortion parameters, tangential distortion parameters and principal point position corresponding to the second CMOS, thus completing the calibration of the binocular off-axis multi-reflector space camera.

[0019] Furthermore, in step S2, the first Damman grating image is preprocessed to obtain the image to be extracted. The centroid coordinates of each spot on the image to be extracted are extracted, and the centroid coordinates of each spot are mapped one by one onto the first CMOS pixel coordinate system in the order of arrangement to obtain the actual pixel coordinates of the centroid of each spot on the first Damman grating image on the target surface of the first CMOS.

[0020] Furthermore, in step S2, the specific process of preprocessing the first Damman grating image is as follows: the first Damman grating image is converted to grayscale to obtain a first grayscale image.

[0021] The first grayscale image is smoothed and denoised using Gaussian filtering to obtain the first denoised image;

[0022] The first denoised image is binarized based on the Otsu thresholding method to obtain a binary image.

[0023] Morphological denoising and region analysis are performed on the binary image to obtain the image to be extracted.

[0024] Furthermore, in step S3, the formula used to calculate the diffraction angle of the first Dammann grating at different diffraction orders is as follows:

[0025] ;

[0026] ;

[0027] in, Let be the period length of the first Dammann grating in the x-diffraction direction. Let be the period length of the first Damman grating in the y-diffraction direction. Let be the diffraction angle in the x-direction corresponding to the m-th row of light spots. The diffraction angle in the y-direction corresponding to the centroid of the nth column of light spots. λ is the wavelength of the diffracted light.

[0028] Furthermore, the diffraction order of the first and second Damman gratings is m in the x-direction and n in the y-direction.

[0029] Furthermore, in step S5, the calculation formula for the camera distortion model is as follows:

[0030] ;

[0031] ;

[0032] ;

[0033] ;;

[0034] ;

[0035] in, For camera index numbering, Choose 1 or 2. Let be the Euclidean distance between the centroid of the (m,n)th light spot and the principal point of the i-th camera. This is the tangential distortion correction amount in the x-direction calculated based on the (m,n)th spot centroid. This is the tangential distortion correction amount in the y-direction calculated based on the centroid of the (m,n)th spot. This is the radial distortion correction amount in the x-direction calculated based on the (m,n)th spot centroid. The radial distortion correction in the y-direction is calculated for the (m,n)th spot centroid. and For the first The camera's tangential distortion parameters, and For the first The radial distortion parameters of the camera.

[0036] Furthermore, in step S5, the loss function used in the iterative solution of the camera distortion model using the Levenberg-Marquardt optimization algorithm is:

[0037] ;

[0038] ;

[0039] ;

[0040] in,( , Let (m,n) be the actual pixel coordinates of the centroid of the (m,n)th spot on the target surface of the i-th CMOS. and This is an intermediate parameter with no physical meaning. Let be the loss function corresponding to the centroid of the (m,n)th spot.

[0041] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0042] (1) The binocular off-axis multi-reflection space camera calibration system and method based on the Damman grating created in this invention does not require a turntable, theodolite or star simulator. It can complete the camera calibration by relying solely on the Damman grating. The calibration plate made by the present invention uses the Damman grating, which can effectively improve the quality of the light spot, thereby improving the accuracy and direction of the light spot centroid extraction, and realizing sub-pixel accuracy calibration.

[0043] (2) The binocular off-axis multi-reflection space camera calibration system and method based on the damman grating created by the present invention has lower cost and avoids high investment: traditional static calibration relies on high-precision turntables, and the equipment procurement and maintenance costs are high. However, the calibration board of the damman grating has a simple structure and controllable manufacturing process, and does not require complex and precise mechanical turntables or simulation equipment, which significantly reduces the hardware cost of the calibration scheme.

[0044] (3) The binocular off-axis multi-reflector spatial camera calibration system and method based on the Damman grating described in this invention has mature calibration algorithms for the point array generated by the Damman grating, and can switch and use other calibration models more freely; it has stronger adaptability and can calibrate some large-volume, small-field-of-view, long-focal-length cameras that are difficult to calibrate using traditional methods; it is easier to implement and has a fast calibration speed, without the need for tedious point-by-point extraction, and only a few shooting results are needed to complete the calibration; the light spot stability is better and the directionality is better, avoiding the occurrence of corner blur and other situations. Attached Figure Description

[0045] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0046] Figure 1 A schematic diagram of the structure of the binocular off-axis multi-reflector space camera calibration system based on the Damman grating as described in the embodiment of the present invention;

[0047] Figure 2The design drawing of the 23×23 Damman grating described in the embodiment of the present invention;

[0048] Figure 3 The image shows the imaging effect of the Damman grating as described in the embodiment of the present invention;

[0049] Figure 4 A schematic diagram of the focal plane of the binocular off-axis multi-reflector space camera described in an embodiment of the present invention;

[0050] Figure 5 A schematic flowchart of the binocular off-axis multi-reflector space camera calibration method based on a Damman grating, as described in an embodiment of the present invention;

[0051] Figure 6 A schematic diagram of the centroid extraction results described in the embodiments of the present invention;

[0052] Figure 7 This is a schematic diagram illustrating the distortion in an embodiment of the present invention.

[0053] Explanation of reference numerals in the attached figures:

[0054] 1. First laser emitting module; 2. Second laser emitting module; 3. First Dammann grating; 4. Second Dammann grating; 5. Binocular off-axis multi-lens space camera; 6. First CMOS; 7. Second CMOS. Detailed Implementation

[0055] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0056] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0057] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0058] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0059] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0060] like Figure 1 As shown, this invention proposes a binocular off-axis multi-reflector spatial camera calibration system based on a Damman grating, comprising a first laser emitting module 1, a second laser emitting module 2, a first Damman grating 3, a second Damman grating 4, and a data processing module. The first laser beam output from the first laser emitting module 1 is diffracted by the first Damman grating 3 to obtain a first shaped laser beam. Simultaneously, the second laser beam output from the second laser emitting module 2 is diffracted by the second Damman grating 4 to obtain a second shaped laser beam. The first and second shaped laser beams are processed by the binocular off-axis multi-reflector spatial camera 5 and imaged on the target surface of the dual CMOS sensors of the binocular off-axis multi-reflector spatial camera 5, obtaining image points of the first Damman grating 3 and the second Damman grating 4. The data processing module calculates the distortion parameters of the binocular off-axis multi-reflector spatial camera 5 based on the first Damman grating 3 and the second Damman grating 4 image points, thereby achieving the calibration of the binocular off-axis multi-reflector spatial camera 5.

[0061] It should be noted that a high-precision optical platform is selected as the calibration reference carrier. The optical platform must be placed in a laboratory environment free from significant vibration to ensure the stability of each component during the calibration process. The first laser emitting module 1 and the second laser emitting module 2 have the same structure, both using a helium-neon laser collimator with an output wavelength of 632.8nm. The collimation of the emitted beam is calibrated to ≤1μrad to ensure that the emitted beam is ideally parallel and meets the incident requirements of the binocular off-axis multi-reflector space camera 5. At the same time, the stability of the laser power is checked to ensure that the power fluctuation range is ≤±5%. The two-dimensional Damman grating is fixed on the high-precision optical modulation platform. Through the adjustment mechanism of the high-precision optical modulation platform, the normal direction of the Damman grating surface is made to coincide with the horizontal direction, and the center of the Damman grating is on the same straight line at the same height as the center of the collimator's output port. The binocular off-axis multi-reflector space camera 5 to be calibrated (including a first camera and a second camera, the first camera corresponding to the first CMOS 6 and the second camera corresponding to the second CMOS 7) is mounted on a three-dimensional precision support. The three-dimensional precision support is adjusted so that the optical axis of the binocular off-axis multi-reflector space camera 5 is parallel to the optical platform, and the camera focal plane is parallel to the surface of the Dammann grating. The binocular off-axis multi-reflector space camera 5 to be calibrated is connected to the computer, the camera control system is started, and the imaging parameters of the binocular off-axis multi-reflector space camera 5 to be calibrated are set to ensure that the camera is in a stable working state. A Gaussian fitting algorithm is used to calculate the centroid of each spot, and the centroid coordinates of all diffraction spots on the target surface of the dual CMOS are accurately extracted (extraction accuracy ≤ 0.05 pixels).

[0062] Furthermore, such as Figure 2 As shown, the Dammann grating is an important device in the field of binary optics. As a binary phase grating with a special aperture function, its phase value is 0 or... It possesses advantages such as high diffraction efficiency, ease of fabrication, and uniform beam distribution, and can be widely used in laser beam shaping. Its core characteristic lies in the fact that it produces a Fraunhofer diffraction pattern with a certain number of equal-intensity spots for the incident parallel beam. Simultaneously, thanks to its special binarization design, it completely avoids the spectral intensity non-uniformity problem caused by the sinc function intensity envelope in traditional amplitude-type gratings. The normalized periodic structure of the one-dimensional Damman grating with binary amplitude is determined by the coordinate pairs of abrupt change points in the grating structure, because the amplitude transmittance of the Damman grating... It exhibits periodicity; a Fourier transform of it yields the power spectra of each non-zero diffraction order:

[0063] ;

[0064] ;

[0065] Where m is the diffraction number. arrive and arrive The inflection point is the point where the Damman grating changes. The inflection point varies depending on the number of points in the Damman grating design. The structure of the solution can be designed using the annealing algorithm. Amplitude transmittance The coefficients after Fourier transform For the m-th order diffraction efficiency of a Damman grating, a one-dimensional Damman grating is as follows: Figure 3 As shown.

[0066] In some embodiments, both the first laser emitting module 1 and the second laser emitting module 2 emit collimated 632.8nm helium-neon lasers.

[0067] In some embodiments, after the first shaping laser beam is processed by the binocular off-axis multi-reflector space camera 5, it is imaged on the target surface of the first CMOS 6 of the binocular off-axis multi-reflector space camera 5 to obtain a first Damman grating 3 image point image; after the second shaping laser beam is processed by the binocular off-axis multi-reflector space camera 5, it is imaged on the target surface of the second CMOS 7 of the binocular off-axis multi-reflector space camera 5 to obtain a second Damman grating 4 image point image.

[0068] It should be noted that, as Figure 4 As shown, the binocular off-axis multi-reflective space camera 5 has two CMOS sensors, each with its own principal point and pixel coordinate system.

[0069] Based on the fact that the image spot produced by the Dammann grating is conducive to centroid extraction, and its accuracy can reach sub-pixel accuracy, as well as its precise pointing characteristics, the calibration process is described below:

[0070] like Figure 5 As shown, this invention proposes a calibration method for a binocular off-axis multi-lens spatial camera based on a Damman grating. This method is implemented using a Damman grating-based binocular off-axis multi-lens spatial camera calibration system and specifically includes the following steps:

[0071] S1: Acquire images of the first and second Damman gratings;

[0072] S2: Extract the actual pixel coordinates on the target surface of the first CMOS 6 corresponding to the centroid of each spot on the first Damman grating image point;

[0073] S3: Based on the period length of the first Damman grating 3, calculate the diffraction angle of the first Damman grating 3 at different diffraction orders;

[0074] S4: Let the coordinates of the principal point of the first camera on the target surface of the first CMOS 6 be (u1, v1). Based on the pinhole camera model, solve for the actual pixel coordinates of each spot centroid on the target surface of the first CMOS 6:

[0075] ;

[0076] ;

[0077] in, The effective focal length of the binocular off-axis multi-reflective space camera 5. The diffraction angle in the x-direction corresponding to the m-th row of light spots. Let be the diffraction angle in the y-direction corresponding to the nth column of light spots, ( , () represents the actual pixel coordinates on the target surface of the first CMOS 6 corresponding to the centroid of the spot in the m-th row and n-th column;

[0078] S5: Substitute the calculation results of step S4 into the camera distortion model, and use the Levenberg-Marquardt optimization algorithm to iteratively solve the camera distortion model to obtain the radial distortion parameters, tangential distortion parameters and principal point positions of the camera corresponding to the first CMOS 6.

[0079] S6: Replace the first Damman grating image with the second Damman grating image, repeat steps S2-S5, obtain the radial distortion parameters, tangential distortion parameters and principal point position corresponding to the second CMOS 7, and complete the calibration of the binocular off-axis multi-reflection space camera 5.

[0080] In some embodiments, in step S2, the first Damman grating 3-pixel image is preprocessed to obtain the image to be extracted, the centroid coordinates of each spot on the image to be extracted are extracted, and the centroid coordinates of each spot are mapped one by one to the first CMOS pixel coordinate system in the order of arrangement to obtain the actual pixel coordinates of the centroid of each spot on the target surface of the first CMOS 6 corresponding to the centroid of each spot on the first Damman grating 3-pixel image.

[0081] In some embodiments, the specific process of preprocessing the first Damman grating image in step S2 is as follows: convert the first Damman grating image to grayscale to obtain a first grayscale image.

[0082] The first grayscale image is smoothed and denoised using Gaussian filtering to obtain the first denoised image;

[0083] The first denoised image is binarized based on the Otsu thresholding method to obtain a binary image.

[0084] Morphological denoising and region analysis are performed on the binary image to obtain the image to be extracted.

[0085] It should be noted that the imaging results are sequentially subjected to grayscale conversion and Gaussian filtering for smoothing, followed by Otsu thresholding, morphological denoising, and region analysis to obtain the corresponding processing results, which then enable centroid extraction. Figure 6 As shown. Figure 7 As shown, the camera distortion model reflects the deviation between the ideal image point and the actual image point, where the ideal image point is the ideal image point and the real image point is the actual image point. For tangential distortion, This is radial distortion, which takes the form of a classic distortion model. The point array generated by the Damman grating has a mature calibration algorithm, and other calibration models, distortion models, or algorithms can be used instead. For example, the Zhang Zhengyou algorithm or the Tasi calibration model, which are relatively classic in the field of camera calibration, can be used. In addition, the Levenberg-Marquardt optimization algorithm is an existing algorithm, which will not be elaborated here.

[0086] In some embodiments, in step S3, the formula used to calculate the diffraction angle of the first Damman grating 3 at different diffraction orders is as follows:

[0087] ;

[0088] ;

[0089] in, Let be the period length of the first Dammann grating 3 in the x-diffraction direction. Let be the period length of the first Damman grating 3 in the y-diffraction direction. Let be the diffraction angle in the x-direction corresponding to the m-th row of light spots. The diffraction angle in the y-direction corresponding to the centroid of the nth column of light spots. λ is the wavelength of the diffracted light.

[0090] In some embodiments, in step S5, the calculation formula for the camera distortion model is:

[0091] ;

[0092] ;

[0093] ;

[0094] ;;

[0095] ;

[0096] in, For camera index numbering, Choose 1 or 2. Let be the Euclidean distance between the centroid of the (m,n)th light spot and the principal point of the i-th camera. This is the tangential distortion correction amount in the x-direction calculated based on the (m,n)th spot centroid. This is the tangential distortion correction amount in the y-direction calculated based on the centroid of the (m,n)th spot. This is the radial distortion correction amount in the x-direction calculated based on the (m,n)th spot centroid. The radial distortion correction in the y-direction is calculated for the (m,n)th spot centroid. and For the first The camera's tangential distortion parameters, and For the first The radial distortion parameters of the camera.

[0097] In some embodiments, in step S5, the loss function used in iteratively solving the camera distortion model using the Levenberg-Marquardt optimization algorithm is:

[0098] ;

[0099] ;

[0100] ;

[0101] in,( , Let (m,n) be the actual pixel coordinates of the centroid of the (m,n)th spot on the target surface of the i-th CMOS. and This is an intermediate parameter with no physical meaning. Let be the loss function corresponding to the centroid of the (m,n)th spot.

[0102] In all embodiments, the first camera corresponds to the first CMOS 6, and the second camera corresponds to the second CMOS 7. The calculation formula and loss function of the camera distortion model are obtained according to the camera index number to obtain the radial distortion parameters, tangential distortion parameters and principal point position of the corresponding camera, that is, i or 2 are substituted into the formula.

[0103] Radial distortion parameter when the evaluation function is minimized , and tangential distortion parameters , and the location of the main point This refers to the distortion parameters required for the i-th lens.

[0104] This invention can calibrate cameras with other structures, such as by replacing them with a refractive optical system or other off-axis reflective systems.

[0105] 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.

[0106] 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 calibration method for a binocular off-axis multi-lens spatial camera based on a Damman grating, implemented using a calibration system for a binocular off-axis multi-lens spatial camera based on a Damman grating, characterized in that: The binocular off-axis multi-reflector spatial camera calibration system based on Damman gratings includes a first laser emitting module, a second laser emitting module, a first Damman grating, a second Damman grating, and a data processing module. The first laser beam output from the first laser emitting module is diffracted by the first Damman grating to obtain a first shaped laser beam. Simultaneously, the second laser beam output from the second laser emitting module is diffracted by the second Damman grating to obtain a second shaped laser beam. The first and second shaped laser beams are processed by the binocular off-axis multi-reflector spatial camera and imaged on the target surface of the camera's dual CMOS sensors, obtaining first and second Damman grating image point images. The data processing module calculates the distortion parameters of the binocular off-axis multi-reflector spatial camera based on the first and second Damman grating image point images, thereby calibrating the binocular off-axis multi-reflector spatial camera. The method includes the following steps: S1: Acquire images of the first and second Damman gratings; S2: Extract the actual pixel coordinates on the target surface of the first CMOS corresponding to the centroid of each spot on the first Damman grating image point; S3: Based on the period length of the first Damman grating, calculate the diffraction angle of the first Damman grating at different diffraction orders; S4: Let the coordinates of the principal point of the first camera on the target surface of the first CMOS be (u1, v1). Based on the pinhole camera model, solve for the actual pixel coordinates of each spot centroid on the target surface of the first CMOS: ； ； in, The effective focal length of a binocular off-axis multi-lens space camera. Let be the diffraction angle in the x-direction corresponding to the m-th row of light spots. Let be the diffraction angle in the y-direction corresponding to the nth column of light spots, ( , () represents the actual pixel coordinates on the target surface of the first CMOS corresponding to the centroid of the spot in the m-th row and n-th column; S5: Substitute the calculation results of step S4 into the camera distortion model, and use the Levenberg-Marquardt optimization algorithm to iteratively solve the camera distortion model to obtain the radial distortion parameters, tangential distortion parameters and principal point positions of the camera corresponding to the first CMOS. In step S5, the calculation formula for the camera distortion model is: ； ； ； ；； ； in, For camera index numbering, Choose 1 or 2. Let be the Euclidean distance between the centroid of the (m,n)th light spot and the principal point of the i-th camera. This is the tangential distortion correction amount in the x-direction calculated based on the (m,n)th spot centroid. This is the tangential distortion correction amount in the y-direction calculated based on the centroid of the (m,n)th spot. This is the radial distortion correction amount in the x-direction calculated based on the (m,n)th spot centroid. The radial distortion correction in the y-direction is calculated for the (m,n)th spot centroid. and For the first The camera's tangential distortion parameters, and For the first The radial distortion parameters of the camera; S6: Replace the first Damman grating image with the second Damman grating image, and repeat steps S2-S5 to obtain the radial distortion parameters, tangential distortion parameters and principal point position corresponding to the second CMOS, thus completing the calibration of the binocular off-axis multi-reflector space camera.

2. The calibration method for a binocular off-axis multi-lens space camera based on a Damman grating according to claim 1, characterized in that: Both the first laser emitting module and the second laser emitting module emit collimated 632.8nm helium-neon lasers.

3. The calibration method for a binocular off-axis multi-lens space camera based on a Dammann grating according to claim 1, characterized in that: After being processed by a binocular off-axis multi-reflector space camera, the first shaped laser beam is imaged on the target surface of the first CMOS of the binocular off-axis multi-reflector space camera to obtain the first Damman grating image point image. After being processed by a binocular off-axis multi-reflector space camera, the second shaped laser beam is imaged on the target surface of the second CMOS of the binocular off-axis multi-reflector space camera to obtain a second Damman grating image point.

4. The calibration method for a binocular off-axis multi-lens space camera based on a Damman grating according to claim 1, characterized in that: In step S2, the first Damman grating image is preprocessed to obtain the image to be extracted. The centroid coordinates of each spot on the image to be extracted are extracted, and the centroid coordinates of each spot are mapped one by one onto the first CMOS pixel coordinate system in the order of arrangement to obtain the actual pixel coordinates of the centroid of each spot on the first Damman grating image on the target surface of the first CMOS.

5. The calibration method for a binocular off-axis multi-lens space camera based on a Damman grating according to claim 1, characterized in that: In step S2, the specific process of preprocessing the first Damman grating image is as follows: the first Damman grating image is converted to grayscale to obtain a first grayscale image. Gaussian filtering is applied to the first grayscale image to smooth and denoise it, resulting in the first denoised image. The first denoised image is binarized based on the Otsu thresholding method to obtain a binary image. Morphological denoising and region analysis are performed on the binary image to obtain the image to be extracted.

6. The calibration method for a binocular off-axis multi-lens space camera based on a Damman grating according to claim 1, characterized in that: In step S3, the formula used to calculate the diffraction angle of the first Dammann grating at different diffraction orders is as follows: ； ； in, Let be the period length of the first Dammann grating in the x-diffraction direction. Let be the period length of the first Damman grating in the y-diffraction direction. Let be the diffraction angle in the x-direction corresponding to the m-th row of light spots. Let be the diffraction angle in the y-direction corresponding to the centroid of the nth column of light spots. λ is the wavelength of the diffracted light.

7. The calibration method for a binocular off-axis multi-lens space camera based on a Damman grating according to claim 6, characterized in that: The first and second Damman gratings have a diffraction order of m in the x-direction and n in the y-direction.

8. The calibration method for a binocular off-axis multi-lens space camera based on a Damman grating according to claim 1, characterized in that: In step S5, the loss function used in the iterative solution of the camera distortion model using the Levenberg-Marquardt optimization algorithm is: ； ； ； in,( , Let (m,n) be the actual pixel coordinates of the centroid of the (m,n)th spot on the target surface of the i-th CMOS. and This is an intermediate parameter with no physical meaning. Let be the loss function corresponding to the centroid of the (m,n)th spot.

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