A method for calibrating telecentric camera parameters using a projector

Abstract

This invention discloses a telecentric camera parameter calibration method using a projector-assisted approach. First, the telecentric camera captures images of a planar calibration plate in multiple poses, and the projector projects images of grating fringes onto the planar calibration plate. The initial parameters of the telecentric camera are then calibrated using an orthographic projection imaging model. Next, three-dimensional feature points are constructed using projector extrinsic parameters; these feature points are used only to complete the missing rotation matrix parameters of the telecentric camera. Finally, a reprojection error model for telecentric camera imaging is constructed, and all parameters of the telecentric camera are nonlinearly optimized. This invention eliminates the need for additional equipment such as lifting platforms when completing the missing rotation matrix parameters, improving the flexibility of the calibration process. Furthermore, the use of projector extrinsic parameters to construct three-dimensional feature points to complete the missing parameters of the telecentric camera rotation matrix effectively reduces the transmission error of the projector calibration results, improving the reliability and accuracy of the results.

Description

Technical Field

[0001] This invention belongs to the field of optical three-dimensional measurement, and more specifically, relates to a method for calibrating the parameters of a telecentric camera using a projector-assisted method. Background Technology

[0002] Telecentric lenses possess characteristics such as constant magnification and low distortion, making them widely used in small field-of-view 3D measurement. Planar calibration plates are widely used in camera calibration due to their ease of fabrication and high precision. However, telecentric camera imaging follows an orthographic projection model; using a planar calibration plate cannot determine the complete rotation matrix, resulting in incomplete calibration results and hindering subsequent work such as telecentric camera-based 3D reconstruction.

[0003] To address this issue, common solutions mainly fall into two categories: using an additional lifting platform or using a projector within the 3D measurement system. However, the first method requires an additional lifting platform, making the calibration process inflexible and inefficient. While the second method doesn't require an additional lifting platform, it calculates the 3D coordinates of the calibration feature points on the planar calibration plate in different poses within the same base coordinate system using the already calibrated projector parameters. These 3D feature points are then used to determine all the intrinsic and extrinsic parameters of the telecentric camera. Although this method offers advantages such as a simple calibration process and high automation, the projector's calibration error can be transmitted to the telecentric camera, thus affecting calibration accuracy.

[0004] Therefore, there is an urgent need for a telecentric camera calibration method that can simultaneously balance flexibility and calibration accuracy, so as to solve the problem of incomplete telecentric camera rotation matrix parameters caused by calibration based on a planar calibration plate without adding additional hardware equipment. Summary of the Invention

[0005] To address the aforementioned deficiencies or improvement needs of existing technologies, this invention provides a telecentric camera parameter calibration method using a projector to solve the problem of incomplete telecentric camera rotation matrix parameters caused by calibration based on a planar calibration plate, while balancing flexibility and calibration accuracy.

[0006] To achieve the above objectives, according to a first aspect of the present invention, a method for calibrating telecentric camera parameters using a projector is provided, comprising:

[0007] S1, a projector projects phase-shifted grating fringe images onto the planar calibration plate at each pose, and a telecentric camera acquires the first image of the planar calibration plate at this time; the telecentric camera acquires the second image of the planar calibration plate at each pose when the projector is not projecting.

[0008] S2, Deconstruct the first image to obtain the coordinates of the calibration feature points on the planar calibration plate inside the projector, so as to obtain the extrinsic parameters of the projector relative to the coordinate system of the planar calibration plate in each pose;

[0009] S3, based on the coordinates of the calibration feature points on the second image, the initial intrinsic parameters of the telecentric camera and the initial extrinsic parameters of the planar calibration plate coordinate system relative to each pose are obtained using an orthographic projection imaging model; wherein, the telecentric camera rotation matrix in the initial extrinsic parameters is incomplete;

[0010] S4. Based on the extrinsic parameters of the projector, each pose is taken as the target pose, and the calibration feature points under other poses are transformed to the target pose to obtain three-dimensional feature points with non-zero Z-axis coordinates; based on the coordinates of the three-dimensional feature points, the missing elements in the rotation matrix of the telecentric camera are determined to obtain the complete extrinsic parameters of the telecentric camera relative to the planar calibration plate coordinate system under the target pose.

[0011] S5, optimize the initial intrinsic parameters and complete extrinsic parameters to reduce the reprojection error of the telecentric camera imaging, and finally obtain the intrinsic and extrinsic parameters of the telecentric camera.

[0012] According to a second aspect of the present invention, a telecentric camera parameter calibration device using a projector is provided, comprising:

[0013] The first processing module is used to project phase-shift grating fringe images onto the planar calibration plate at each pose using a projector, and to obtain the first image of the planar calibration plate at this time using a telecentric camera; and to obtain the second image of the planar calibration plate at each pose using a telecentric camera when the projector is not projecting.

[0014] The second processing module is used to decode the first image to obtain the coordinates of the calibration feature points on the planar calibration plate inside the projector, so as to obtain the extrinsic parameters of the projector relative to the coordinate system of the planar calibration plate in each pose.

[0015] The third processing module is used to obtain the initial intrinsic parameters of the telecentric camera and the initial extrinsic parameters of the planar calibration plate coordinate system relative to each pose, based on the coordinates of the calibration feature points on the second image and using an orthographic projection imaging model; wherein the telecentric camera rotation matrix in the initial extrinsic parameters is incomplete.

[0016] The fourth processing module is used to transform the calibration feature points in each pose to the target pose to obtain three-dimensional feature points with non-zero Z-axis coordinates based on the extrinsic parameters of the projector; and to determine the missing elements in the rotation matrix of the telecentric camera based on the coordinates of the three-dimensional feature points, so as to obtain the complete extrinsic parameters of the telecentric camera relative to the coordinate system of the planar calibration plate in the target pose; wherein, the target pose is any pose of the planar calibration plate;

[0017] The fifth processing module is used to optimize the initial intrinsic parameters and complete extrinsic parameters to reduce the reprojection error of the telecentric camera imaging, and finally obtain the intrinsic and extrinsic parameters of the telecentric camera.

[0018] According to a third aspect of the present invention, a telecentric camera parameter calibration system using a projector is provided, comprising: a computer-readable storage medium and a processor;

[0019] The computer-readable storage medium is used to store executable instructions;

[0020] The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in the first aspect.

[0021] According to a fourth aspect of the invention, a computer-readable storage medium is provided, the computer-readable storage medium storing computer instructions for causing a processor to perform the method as described in the first aspect.

[0022] According to a fifth aspect of the present invention, a telecentric camera parameter calibration system is provided, comprising: a telecentric camera, a projector, a planar calibration plate, and a controller;

[0023] The controller is used to perform the method as described in the first aspect.

[0024] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0025] 1. The telecentric camera parameter calibration method using a projector assisted by the present invention solves the problem of incomplete telecentric camera rotation matrix parameters without adding other auxiliary equipment (such as a lifting platform). Compared with other methods, it has lower cost, greater flexibility, and is better suited for practical application scenarios.

[0026] 2. The three-dimensional feature points constructed by the extrinsic parameters of the projector used in this invention are only used to complete the missing parameters of the telecentric camera rotation matrix, which effectively reduces the transmission error of the projector calibration results and improves the reliability and accuracy of the results. Attached Figure Description

[0027] Figure 1This is a flowchart illustrating a telecentric camera parameter calibration method using a projector assisted by an embodiment of the present invention.

[0028] Figure 2 This is a schematic diagram of the structure of the telecentric camera parameter calibration system provided in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of a telecentric camera imaging model;

[0030] Figure 4 A schematic diagram of a projector-assisted construction of three-dimensional calibration points provided in an embodiment of the present invention. Detailed Implementation

[0031] 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 embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0032] This invention provides a method for calibrating telecentric camera parameters using a projector-assisted method, such as... Figure 1 As shown, it includes:

[0033] S1, a projector projects phase-shifted grating fringe images onto the planar calibration plate at each pose, and a telecentric camera acquires the first image of the planar calibration plate at this time; the telecentric camera acquires the second image of the planar calibration plate at each pose when the projector is not projecting.

[0034] Specifically, a small field-of-view 3D measurement system with a projector and a telecentric camera is constructed. For planar calibration boards in different poses, the projector projects phase-shifted grating fringe images onto the calibration board, and the telecentric camera acquires the images to obtain the first image, which is used for projector calibration. Simultaneously, a calibration board image without grating projection is acquired for each pose of the calibration board to obtain the second image, which is used for telecentric camera calibration.

[0035] To improve phase resolution accuracy, preferably, the phase-shifting grating fringe image is a three-frequency four-step fringe image.

[0036] Preferably, the three-frequency four-step stripe image includes three-frequency four-step stripe images in the horizontal and vertical directions.

[0037] Accordingly, during phase deconvolution, a four-step phase shift method is used based on the multi-frequency heterodyne principle.

[0038] like Figure 2 As shown, when the projector projects a phase-shifted grating stripe image, it triggers the camera to capture the image, and the captured image is transmitted to the computer for processing.

[0039] Preferably, the entire calibration process requires at least 12 different calibration plate poses. For each calibration plate pose, the telecentric camera needs to acquire 25 images, including 24 calibration plate images under the phase-shift grating fringe images projected by the projector and 1 calibration plate image without a projected image.

[0040] Furthermore, the projector projects 24 phase-shifted grating fringe images, including 12 three-frequency four-step fringe images in the horizontal direction and 12 three-frequency four-step fringe images in the vertical direction. The three frequencies in the horizontal direction can be set to 160, 154, and 149, respectively, and the three frequencies in the vertical direction can be set to 90, 84, and 79, respectively. The phase shift of the four-step grating images in the horizontal and vertical directions is 0, respectively. π,

[0041] S2, the first image is deconstructed to obtain the coordinates of the calibration feature points on the planar calibration plate inside the projector, so as to obtain the intrinsic parameters of the projector and the extrinsic parameters of the planar calibration plate coordinate system relative to each pose.

[0042] Preferably, in step S2, based on the coordinates of the calibration feature points on the planar calibration plate inside the projector, the Zhang Zhengyou calibration method is used to calibrate the projector as a reverse pinhole camera, thereby obtaining the extrinsic parameters of the projector relative to the coordinate system of the planar calibration plate at each pose.

[0043] Specifically, the phase-shifted grating fringe image (i.e., the first image) obtained by S1 is dephased to obtain the corresponding phase of the calibration feature point P of the calibration plate inside the projector. The coordinates p(u,v) of the feature point inside the projector are determined according to the phase. Based on the coordinates, the projector is calibrated as a reverse pinhole camera using the Zhang Zhengyou calibration method to obtain the extrinsic parameters of the projector relative to the calibration plate coordinate system at each pose.

[0044] The method used for calibration when treating a projector as a reverse pinhole camera is the Zhang Zhengyou calibration method. The steps are: establishing a pinhole camera imaging model, obtaining initial intrinsic, extrinsic, and distortion parameters, and performing nonlinear optimization. The pinhole camera imaging model is a pinhole imaging model, defined by the following formula:

[0045]

[0046] Where s is a constant scaling factor, These are homogeneous coordinates in the pixel coordinate system. Let R be the projector's intrinsic parameter, R be the projector's rotation matrix, and t be the projector's translation matrix. R and t together constitute the projector's extrinsic parameter T. The homogeneous coordinates of the feature points on the calibration plate in the world coordinate system are determined. The rotation matrix is ​​a 3×3 orthogonal matrix, and the R obtained above can be recovered to its complete 3×3 form through the orthogonality of the rotation matrix.

[0047] It is understandable that the external parameters of the projector relative to the coordinate system of the planar calibration plate in each pose can also be obtained by using Tsai's "two-step" method.

[0048] During phase deconstruction, the absolute phase values ​​of the horizontal and vertical grating fringe images are calculated using the four-step phase shift method and the multi-frequency heterodyne principle, respectively. Then, the horizontal coordinate u and vertical coordinate v in the internal image coordinate system of the projector are calculated using the absolute phase values, thereby obtaining the internal image coordinates (u, v) of the projector corresponding to each two-dimensional calibration feature point.

[0049] S3, based on the coordinates of the calibration feature points on the second image, the initial intrinsic parameters of the telecentric camera and the initial extrinsic parameters of the planar calibration plate coordinate system relative to each pose are obtained using an orthographic projection imaging model; wherein, the telecentric camera rotation matrix in the initial extrinsic parameters is incomplete;

[0050] Specifically, based on the calibration board image (i.e., the second image) acquired by the telecentric camera, the coordinates p'(u',v') of the calibration feature point P on the calibration board image are determined. The initial intrinsic and extrinsic parameters of the telecentric camera are then calibrated using an orthographic projection imaging model. However, the telecentric camera rotation matrix in the initial extrinsic parameters is incomplete (the initial extrinsic parameters include both the telecentric camera translation and rotation matrices, while the obtained telecentric camera rotation matrix only includes element r). 11 r 12 r 21 r 22 (This is incomplete; therefore, the initial extrinsic parameters are incomplete).

[0051] Furthermore, such as Figure 3 As shown, the imaging model of the telecentric camera is an orthographic projection imaging model. The three-dimensional feature point P is projected onto point p' on the sensor image plane through the second lens, the aperture, and the first lens. The orthographic projection imaging model is defined by the following formula:

[0052]

[0053] in, For telecentric camera internal reference, m x m y Let u0 and v0 be the normalized magnifications in the X and Y directions of the telecentric camera, and u0 and v0 be the optical center coordinates of the telecentric camera. For an incomplete telecentric camera rotation matrix, Let R' and t' be the translation matrix of the telecentric camera, together forming the extrinsic parameter T' of the telecentric camera. Telecentric camera calibration requires calculating the complete 3×3 rotation matrix, but the incomplete telecentric camera rotation matrix obtained from the above steps cannot be used to recover the complete telecentric camera rotation matrix. This is because:

[0054]

[0055] It can be seen that r 13 r 23 It has symbolic ambiguity and requires additional steps to calculate.

[0056] Furthermore, telecentric cameras exhibit lower distortion, so this calibration only considers first-order and second-order radial distortion, defined by the following formula:

[0057]

[0058] Here, distortion is corrected in the camera normalized coordinate system, where (x,y) are the camera normalized coordinates of the distorted point, (x,y) corrected ,y corrected ) represents the normalized coordinates of the camera coordinate system for the distortion-removed points, k1 is the first-order radial distortion parameter, and k2 is the second-order radial distortion parameter.

[0059] S4. Based on the extrinsic parameters of the projector, the calibration feature points under each pose are transformed to the target pose to obtain three-dimensional feature points with non-zero Z-axis coordinates; based on the coordinates of the three-dimensional feature points, the missing elements in the telecentric camera rotation matrix are determined to obtain the complete extrinsic parameters of the telecentric camera relative to the planar calibration plate coordinate system under the target pose.

[0060] Specifically, based on the projector extrinsic parameters obtained in S2, each pose is sequentially taken as the target pose, and the calibration feature points under other poses are transformed to the target pose to obtain the three-dimensional feature points with a non-zero Z coordinate under the target pose. These three-dimensional feature points are then used to complete the missing rotation matrix parameters in S2.

[0061] Specifically, such as Figure 4 As shown, the feature points of calibration plate pose 2 are transformed to those of calibration plate pose 1, and the transformation relationship between them is a three-dimensional transformation matrix. Therefore, the formula for converting feature points from other poses to a specific pose is:

[0062]

[0063] Where P' represents the coordinates of the 3D feature point transformed to the target coordinate system. Let be the transformation matrix from the coordinate system to be transformed to the target coordinate system. Let be the transformation matrix from the target coordinate system to the projector coordinate system. Let P be the transformation matrix from the coordinate system to be transformed to the projector coordinate system, and let P be the coordinates of the calibration feature points in the coordinate system to be transformed. All coordinates are obtained from the projector calibration process. The Z coordinate of the 3D feature point P' calculated in this step is not 0. The coordinate system to be transformed is the planar calibration plate coordinate system under the pose to be transformed, and the target coordinate system is the planar calibration plate coordinate system under the target pose.

[0064] Furthermore, the missing parameters of the telecentric camera rotation matrix are calculated using the three-dimensional feature points obtained above. The calculation formula is as follows:

[0065]

[0066] Where, r 13 r 23 r 31 r 32 r 33 The missing elements in the incomplete telecentric camera rotation matrix are A' and T', which are the intrinsic parameters of the telecentric camera and the initial extrinsic parameters of the planar calibration plate coordinate system relative to the target pose. (u', v') are the corresponding pixel coordinates of the three-dimensional feature points in the second image, and (X) are the missing elements in the incomplete telecentric camera rotation matrix. w ,Y w Z w Let be the coordinates of the three-dimensional feature points. This yields the first two rows of the telecentric camera rotation matrix. Due to the orthogonality of the rotation matrix, the third row can be obtained by the cross product of the first two rows, as shown in the following formula:

[0067] [r 31 r 32 r 33 ] T =[r 11 r 12 r 13 ] T ×[r 21 r 22 r 23 ] T (7)

[0068] This yields the complete initial parameters of the telecentric camera rotation matrix, i.e.

[0069] S5, optimize the initial intrinsic parameters and complete extrinsic parameters to reduce the reprojection error of the telecentric camera imaging, and finally obtain the intrinsic and extrinsic parameters of the telecentric camera.

[0070] Specifically, a reprojection error model for telecentric camera imaging is constructed, and all parameters are nonlinearly optimized to obtain complete and accurate intrinsic and extrinsic parameters of the telecentric camera.

[0071] Preferably, the reprojection error model of the telecentric camera is defined as:

[0072]

[0073] Where E is the reprojection error and p ij Let J be the pixel coordinates of the j-th calibration feature point in the second image at the i-th pose. For P j The reprojection coordinates are calculated using the telecentric camera imaging model, where A' is the intrinsic parameter of the telecentric camera, δ' is the distortion parameter of the telecentric camera, and R... i ' is the complete rotation matrix in the i-th pose, t i 'Translation matrix at the i-th pose, P j Let be the coordinates of the j-th feature point of the plane calibration plate in the calibration plate coordinate system. The calculation process of formula (8) is the same as that of formula (2) and formula (4).

[0074] Furthermore, the Levenberg-Marquardt iterative algorithm is used for nonlinear optimization of all parameters of the telecentric camera. The initial parameters for the iteration are obtained from the steps described above, the upper limit of the number of iterations is 50, and the convergence condition for the iteration is as follows:

[0075]

[0076] Here, Δcost represents the change in the objective function before and after the iteration, and cost is the objective function value.

[0077] The telecentric camera parameter calibration device assisted by a projector provided by the present invention will be described below. The telecentric camera parameter calibration device assisted by a projector described below can be referred to in correspondence with the telecentric camera parameter calibration method assisted by a projector described above.

[0078] This invention provides a telecentric camera parameter calibration device using a projector, comprising:

[0079] The first processing module is used to project phase-shift grating fringe images onto the planar calibration plate at each pose using a projector, and to obtain the first image of the planar calibration plate at this time using a telecentric camera; and to obtain the second image of the planar calibration plate at each pose using a telecentric camera when the projector is not projecting.

[0080] The second processing module is used to decode the first image to obtain the coordinates of the calibration feature points on the planar calibration plate inside the projector, so as to obtain the extrinsic parameters of the projector relative to the coordinate system of the planar calibration plate in each pose.

[0081] The third processing module is used to obtain the initial intrinsic and extrinsic parameters of the telecentric camera based on the coordinates of the calibrated feature points on the second image using an orthographic projection imaging model; wherein the telecentric camera rotation matrix in the initial extrinsic parameters is incomplete.

[0082] The fourth processing module is used to transform the calibration feature points in each pose to the target pose to obtain three-dimensional feature points with non-zero Z-axis coordinates based on the extrinsic parameters of the projector; and to determine the missing elements in the incomplete telecentric camera rotation matrix based on the coordinates of the three-dimensional feature points, so as to obtain the complete extrinsic parameters of the telecentric camera relative to the coordinate system of the planar calibration plate in the target pose; wherein, the target pose is any pose of the planar calibration plate;

[0083] The fifth processing module is used to optimize the initial intrinsic parameters and complete extrinsic parameters to reduce the reprojection error of the telecentric camera imaging, and finally obtain the intrinsic and extrinsic parameters of the telecentric camera.

[0084] This invention provides a telecentric camera parameter calibration system using a projector, comprising: a computer-readable storage medium and a processor;

[0085] The computer-readable storage medium is used to store executable instructions;

[0086] The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in any of the above embodiments.

[0087] This invention provides a computer-readable storage medium storing computer instructions that cause a processor to perform the method described in any of the above embodiments.

[0088] This invention provides a telecentric camera parameter calibration system, such as... Figure 3 As shown, it includes: a telecentric camera, a projector, a planar calibration plate, and a controller;

[0089] The controller is used to perform the method as described in any of the above embodiments.

[0090] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calibrating telecentric camera parameters using a projector-assisted method, characterized in that, include: S1, a projector projects phase-shifted grating fringe images onto the planar calibration plate at each pose, and a telecentric camera acquires the first image of the planar calibration plate at this time; The telecentric camera acquires a second image of the planar calibration plate in each pose when the projector is not projecting; S2, Deconstruct the first image to obtain the coordinates of the calibration feature points on the planar calibration plate inside the projector, so as to obtain the extrinsic parameters of the projector relative to the coordinate system of the planar calibration plate in each pose; S3, based on the coordinates of the calibration feature points on the second image, the initial intrinsic parameters of the telecentric camera and the initial extrinsic parameters of the planar calibration plate coordinate system relative to each pose are obtained using an orthographic projection imaging model; wherein, the telecentric camera rotation matrix in the initial extrinsic parameters is incomplete; S4. Based on the extrinsic parameters of the projector, each pose is taken as the target pose, and the calibration feature points under other poses are transformed to obtain three-dimensional feature points with non-zero Z-axis coordinates under the target pose. Based on the coordinates of the three-dimensional feature points, the missing elements in the rotation matrix of the telecentric camera are determined to obtain the complete extrinsic parameters of the telecentric camera relative to the planar calibration plate coordinate system under the target pose. S5, optimize the initial intrinsic parameters and complete extrinsic parameters to reduce the reprojection error of the telecentric camera imaging, and finally obtain the intrinsic and extrinsic parameters of the telecentric camera.

2. The method as described in claim 1, characterized in that, In step S4, the formula for calculating the missing elements in the telecentric camera rotation matrix based on the coordinates of the three-dimensional feature points is as follows: [r 31 r 32 r 33 ] T ＝[r 11 r 12 r 13 ] T ×[r 21 r 22 r 23 ] T ； Where, r 13 r 23 r 31 r 32 r 33 r represents the missing element in the telecentric camera rotation matrix. 11 r 12 r 21 r 22 Let A' and T' be the existing elements in the telecentric camera rotation matrix, respectively, and let (u', v') be the initial intrinsic parameters of the telecentric camera and the initial extrinsic parameters of the planar calibration plate coordinate system relative to the target pose. Let (u', v') be the corresponding pixel coordinates of the three-dimensional feature points in the second image, and (X... w ,Y w Z w ) represents the coordinates of the three-dimensional feature point.

3. The method as described in claim 1 or 2, characterized in that, The formula for calculating the coordinates of the three-dimensional feature point P' is: in, Let be the transformation matrix from the coordinate system to be transformed to the target coordinate system. Let be the transformation matrix from the target coordinate system to the projector coordinate system. The transformation matrix is ​​denoted as P, which represents the coordinates of the calibration feature points in the coordinate system to be transformed. The coordinate system to be transformed is the planar calibration plate coordinate system in the pose to be transformed, and the target coordinate system is the planar calibration plate coordinate system in the target pose.

4. The method as described in claim 1 or 2, characterized in that, The phase-shifting grating fringe image is a three-frequency four-step fringe image, including different three-frequency four-step fringe images in the horizontal and vertical directions.

5. The method as described in claim 1, characterized in that, In step S2, based on the coordinates of the calibration feature points on the planar calibration plate inside the projector, the Zhang Zhengyou calibration method is used to calibrate the projector as a reverse pinhole camera, thereby obtaining the extrinsic parameters of the projector relative to the coordinate system of the planar calibration plate at each pose.

6. The method as described in claim 1, characterized in that, In step S4, the reprojection error model of telecentric camera imaging is used to perform nonlinear optimization on the initial intrinsic parameters and complete extrinsic parameters of the telecentric camera. The reprojection error model is as follows: Where E is the reprojection error and p ij Let J be the pixel coordinates of the j-th calibration feature point in the second image at the i-th pose. For P j The reprojection coordinates are calculated using the telecentric camera imaging model, where A' is the initial intrinsic parameter of the telecentric camera, δ' is the distortion parameter of the telecentric camera, and R... i ' is the complete rotation matrix in the i-th pose, t i Let P be the translation matrix at the i-th pose. j Let be the coordinates of the j-th feature point on the plane calibration plate in the calibration plate coordinate system.

7. A telecentric camera parameter calibration device using a projector-assisted calibration method, characterized in that, include: The first processing module is used to project phase-shifting grating fringe images onto the planar calibration plate at each pose using a projector, and the telecentric camera acquires the first image of the planar calibration plate at this time. The telecentric camera acquires a second image of the planar calibration plate in each pose when the projector is not projecting; The second processing module is used to decode the first image to obtain the coordinates of the calibration feature points on the planar calibration plate inside the projector, so as to obtain the extrinsic parameters of the planar calibration plate coordinate system relative to the various poses of the projector. The third processing module is used to obtain the initial intrinsic parameters of the telecentric camera and the initial extrinsic parameters of the planar calibration plate coordinate system relative to each pose, based on the coordinates of the calibration feature points on the second image and using an orthographic projection imaging model; wherein the telecentric camera rotation matrix in the initial extrinsic parameters is incomplete. The fourth processing module is used to transform the calibration feature points in each pose to the target pose to obtain three-dimensional feature points with non-zero Z-axis coordinates based on the extrinsic parameters of the projector; and to determine the missing elements in the rotation matrix of the telecentric camera based on the coordinates of the three-dimensional feature points, so as to obtain the complete extrinsic parameters of the telecentric camera relative to the coordinate system of the planar calibration plate in the target pose; wherein, the target pose is any pose of the planar calibration plate; The fifth processing module is used to optimize the initial intrinsic parameters and complete extrinsic parameters to reduce the reprojection error of the telecentric camera imaging, and finally obtain the intrinsic and extrinsic parameters of the telecentric camera.

8. A telecentric camera parameter calibration system using a projector-assisted calibration method, characterized in that, include: Computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in any one of claims 1-6.

9. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing a processor to perform the method as described in any one of claims 1-6.

10. A telecentric camera parameter calibration system, characterized in that, include: Telecentric camera, projector, planar calibration plate and controller; The controller is used to perform the method as described in any one of claims 1-6.

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