3D imaging system, calibration method and calibration apparatus therefor, and calibration device

Abstract

A 3D imaging system, a calibration method and calibration apparatus therefor, and a calibration device. The calibration method comprises: acquiring a calibration image, which is obtained by using a telecentric lens (110) to collect a first calibration target; performing calibration on the telecentric lens (110) according to the calibration image, so as to obtain a first initial calibration parameter of the telecentric lens (110); according to the first initial calibration parameter, determining second coordinates of a reference point, which corresponds to first coordinates, with respect to a coordinate system of a target projection optical machine (120); according to the second coordinates, performing calibration on the target projection optical machine (120), so as to obtain a second initial calibration parameter of the target projection optical machine; and according to the first coordinates, the second coordinates, the first initial calibration parameter and the second initial calibration parameter, performing joint calibration on the telecentric lens (110) and the target projection optical machine (120), so as to obtain a target calibration parameter. Thus, the calibration of a 3D imaging system is realized, the imaging accuracy of the calibrated 3D imaging system can be improved, and the missing of 3D information of components caused by occlusion is avoided.

Description

3D imaging system and calibration method, calibration device and calibration equipment thereof

[0001] This application claims priority to Chinese patent application number 2023107897661, filed on June 30, 2023, entitled “3D imaging system and calibration method, device, equipment and storage medium thereof,” the entire text of which is hereby incorporated by reference. Technical Field

[0002] The present application relates to the field of 3D imaging technology, and in particular to a 3D imaging system and a calibration method, a calibration apparatus, a calibration device, a storage medium, and a computer program product thereof. Background Art

[0003] In recent years, with the advancement of precision manufacturing and semiconductor fabrication, 3D (three-dimensional) imaging and measurement of complex and tiny structures has become increasingly important. Micro-fringe projection 3D measurement technology (MFP-3D) has become a mainstream technology for optical 3D surface imaging and measurement due to its non-contact, fast measurement speed, dense point cloud data, low cost, and ease of implementation, while also balancing system flexibility and measurement accuracy. It holds broad application prospects and practical value in complex industrial production and inspection environments.

[0004] Traditionally, microscopic fringe projection 3D measurement systems typically consist of a telecentric lens and a projection engine, with the telecentric lens looking straight ahead and the projection engine looking sideways. However, when measuring samples with densely packed components or objects with significant height differences, occlusion by adjacent objects can prevent the phase-shifted fringes from being projected onto certain areas, resulting in a loss of 3D information in those areas and affecting the final measurement results.

[0005] Summary of the Invention

[0006] According to various embodiments of the present application, a 3D imaging system and a calibration method, a calibration apparatus, a calibration device, a computer-readable storage medium, and a computer program product are provided.

[0007] In a first aspect, the present application provides a calibration method for a 3D imaging system. The system includes a telecentric lens having a common field of view center and at least two projection optical machines, and the method includes:

[0008] Acquire a calibration image obtained by capturing a first calibration target using the telecentric lens, where a plurality of reference points are provided on the first calibration target;

[0009] Determine a first coordinate of the reference point in the calibration image in a pixel coordinate system, calibrate the telecentric lens according to a preset first imaging model, and obtain a first initial calibration parameter of the telecentric lens;

[0010] Determining, based on the first initial calibration parameters, a second coordinate of the reference point corresponding to the first coordinate relative to a target projection optical machine coordinate system;

[0011] Calibrate the target projection light machine using a preset second imaging model according to the second coordinate to obtain second initial calibration parameters of the target projection light machine;

[0012] The telecentric lens and the target projection optical machine are jointly calibrated according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain target calibration parameters.

[0013] In one embodiment, determining the second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system based on the first initial calibration parameters includes: projecting horizontal phase-shift stripes and vertical phase-shift stripes onto the first calibration target respectively through the target projection optical machine; obtaining a horizontal phase-shift calibration image obtained by projecting horizontal symmetrical stripes onto the first calibration target, and obtaining a vertical phase-shift calibration image obtained by projecting vertical symmetrical stripes onto the first calibration target, which are captured by the telecentric lens; performing distortion correction on the horizontal phase-shift calibration image and the vertical phase-shift calibration image according to the first initial calibration parameters; and performing phase deconvolution on the corrected horizontal phase-shift calibration image and the vertical phase-shift calibration image to obtain the second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system.

[0014] In one embodiment, the telecentric lens and the target projection optical machine are jointly calibrated according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain target calibration parameters, including: determining the initial rotation and translation matrix of the target projection optical machine to the telecentric lens according to the first initial calibration parameter and the second initial calibration parameter; determining the third coordinate of the reference point in the world coordinate system, projecting the third coordinate of the reference point to the telecentric lens coordinate system according to the first initial calibration parameter, the second initial calibration parameter, and the initial rotation and translation matrix to obtain the first projection coordinate of the reference point, and projecting the third coordinate of the reference point to the target projection optical machine coordinate system to obtain the second projection coordinate of the reference point; and performing nonlinear optimization on the first initial calibration parameter, the second initial calibration parameter, and the initial rotation and translation matrix according to the first coordinate, the second coordinate, the first projection coordinate, and the second projection coordinate to obtain optimized target calibration parameters.

[0015] In one embodiment, the method further includes: projecting longitudinal phase-shifted stripes onto a second calibration target through at least two of the projection optical machines, respectively, to obtain at least two sets of phase-shifted images of the second calibration target captured by the telecentric lens; performing phase analysis on the at least two sets of the phase-shifted images to obtain corresponding phase values; and determining the phase height model parameters of the system based on the phase values ​​and the target calibration parameters.

[0016] In one embodiment, the phase height model parameters are used by the 3D imaging system to determine height information of three-dimensional coordinates of a measurement target in three-dimensional measurement.

[0017] In one embodiment, the second calibration target is a flat pure color diffuse reflection plate.

[0018] In one embodiment, the obtaining of the calibration image obtained by capturing the first calibration target using the telecentric lens includes: projecting white light onto the first calibration target through the target projection light machine; and obtaining the calibration image obtained by capturing the first calibration target after the white light is projected using the telecentric lens.

[0019] In one embodiment, the preset first imaging model is a pre-set telecentric lens imaging model for calibrating the telecentric lens.

[0020] In one embodiment, the preset second imaging model is a pinhole imaging model preset for calibrating the target projection light engine.

[0021] In a second aspect, the present application further provides a calibration device for a 3D imaging system. The device comprises:

[0022] An image acquisition module, configured to acquire a calibration image obtained by capturing a first calibration target using the telecentric lens, wherein the first calibration target is provided with a plurality of reference points;

[0023] a first calibration module, configured to determine a first coordinate of the reference point in the calibration image in a pixel coordinate system, calibrate the telecentric lens according to a preset first imaging model, and obtain a first initial calibration parameter of the telecentric lens;

[0024] a second calibration module, configured to determine, based on the first initial calibration parameters, a second coordinate of the reference point corresponding to the first coordinate relative to a target projection optical machine coordinate system; and calibrate the target projection optical machine using a preset second imaging model based on the second coordinate to obtain second initial calibration parameters of the target projection optical machine;

[0025] A calibration parameter determination module is used to jointly calibrate the telecentric lens and the target projection optical machine according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain target calibration parameters.

[0026] In one embodiment, the device also includes a phase height model determination module, which is used to: project longitudinal phase-shifted stripes onto a second calibration target through at least two of the projection optical machines, respectively, to obtain at least two sets of phase-shifted images of the second calibration target collected by the telecentric lens; perform phase analysis on at least two sets of the phase-shifted images to obtain corresponding phase values; and determine the phase height model parameters of the system based on the phase values ​​and the target calibration parameters.

[0027] In a third aspect, the present application also provides a 3D imaging system, comprising: a telecentric lens, the telecentric lens being arranged upright relative to a reference plane, the telecentric lens having a first field of view center; at least two projection light machines, at least two of the projection light machines surrounding the telecentric lens and being arranged obliquely relative to the reference plane, the projection light machines having a second field of view center, the second field of view center coinciding with the first field of view center; the system is calibrated using the method described in the first aspect above.

[0028] In a fourth aspect, the present application further provides a calibration device, which includes a memory and a processor, wherein the memory stores a computer program, and the processor implements the method steps described in the first aspect when executing the computer program.

[0029] In a fifth aspect, the present application further provides a computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method steps described in the first aspect above.

[0030] In a sixth aspect, the present application further provides a computer program product, comprising a computer program that, when executed by a processor, implements the method steps described in the first aspect above.

[0031] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0033] FIG1A is a schematic perspective view of a 3D imaging system according to an embodiment;

[0034] FIG1B is a bottom view schematic diagram of a 3D imaging system according to one embodiment;

[0035] FIG1C is a schematic projection diagram of a 3D imaging system according to one embodiment;

[0036] FIG2 is a schematic flow chart of a calibration method for a 3D imaging system according to an embodiment;

[0037] FIG3 is a schematic diagram of a flow chart of steps for obtaining a calibration image in one embodiment;

[0038] FIG4 is a schematic diagram of a flow chart of a step of determining a second coordinate in one embodiment;

[0039] FIG5 is a schematic diagram of a flow chart of steps for obtaining target calibration parameters in one embodiment;

[0040] FIG6 is a schematic flow chart of the steps of determining phase height model parameters in one embodiment;

[0041] FIG7 is a schematic flow chart of a calibration method for a 3D imaging system according to another embodiment;

[0042] FIG8A is a schematic diagram of a calibration image under white light projection in one embodiment;

[0043] FIG8B is a schematic diagram of a calibration image under transverse fringe projection in one embodiment;

[0044] FIG8C is a schematic diagram of a calibration image under longitudinal fringe projection in one embodiment;

[0045] FIG8D is a schematic diagram of locating the center of the circle in FIG8A in one embodiment;

[0046] FIG8E is a schematic diagram of a diffuse reflection longitudinal phase shift image in one embodiment;

[0047] FIG9 is a structural block diagram of a calibration device for a 3D imaging system according to an embodiment;

[0048] FIG10 is a diagram showing the internal structure of a calibration device in one embodiment. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0050] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0051] An embodiment of the present application provides a 3D (i.e., three-dimensional stereographic) imaging system, as shown in FIG1A , which may include a telecentric lens 110 and four projection light machines 120 (four projection light machines are used as an example in the figure, and the actual number of projection light machines may be more or less, for example, 2, 6, 8, etc.). As shown in FIG1B and FIG1C , the telecentric lens 110 is arranged face-on relative to a reference plane 130, and the telecentric lens 110 has a first field of view center. In this embodiment, the four projection light machines 120 surround the telecentric lens 110 and are arranged obliquely relative to the reference plane 130, each projection light machine 120 has a second field of view center, and the second field of view center of each projection light machine 120 coincides with the first field of view center of the telecentric lens 110.

[0052] Specifically, the field of view refers to the size of the capture range of the telecentric lens 110 or the size of the projection range of the projector 120, and the field of view center refers to the center point of the corresponding range. For example, the first field of view center refers to the center point of the capture range of the telecentric lens 110, and the second field of view center refers to the center point of the projection range of the projector 120. In this embodiment, a 3D imaging system is formed by the telecentric lens 110 and four projectors 120, and the field of view center of the telecentric lens 110 and the field of view centers of the four projectors 120 are aligned. This avoids the problem of missing 3D information of components due to occlusion, thereby improving imaging accuracy.

[0053] In one embodiment, as shown in FIG2 , the present application further provides a calibration method for a 3D imaging system, which may specifically include the following steps:

[0054] Step 202: Acquire a calibration image obtained by capturing a first calibration target using a telecentric lens.

[0055] The first calibration target is provided with multiple reference points. The first calibration target can be a calibration plate or calibration plate used for system calibration, such as an asymmetric black and white circular calibration plate, a symmetrical circular calibration plate, a ring calibration plate, a checkerboard calibration plate, etc. The reference points can be feature points on the first calibration target, such as the center of a circle on a circular or ring-shaped calibration plate or calibration plate, or the diagonal points of a checkerboard on a checkerboard calibration plate. The calibration image is an image of the first calibration target captured by the system's telecentric lens.

[0056] In this embodiment, when the system shown in FIG1A is to be calibrated, a calibration image of the first calibration target can be captured by the telecentric lens of the system to obtain the calibration image, and the calibration image can be analyzed in subsequent steps to achieve calibration of the system.

[0057] Step 204 : calibrate the telecentric lens according to the calibration image to obtain first initial calibration parameters of the telecentric lens.

[0058] The first initial calibration parameters may be calibration parameters obtained by calibrating the telecentric lens using a preset calibration model, and may include corresponding intrinsic parameters, extrinsic parameters, and distortion coefficients. The intrinsic parameters are related to the characteristics of the telecentric lens itself, such as the focal length and pixel size of the telecentric lens, and are used to convert coordinates from the telecentric lens coordinate system to the pixel coordinate system. The extrinsic parameters are parameters of the telecentric lens in the world coordinate system, such as the position and rotation direction of the telecentric lens, and are used to convert coordinates from the world coordinate system to the telecentric lens coordinate system. The distortion coefficients are parameters related to correcting image distortion caused by deviations in the telecentric lens assembly process.

[0059] Specifically, in this embodiment, a reference point in the calibration image can be located at a first coordinate in a pixel coordinate system, and the telecentric lens can be calibrated based on a preset first imaging model and the first coordinates, thereby obtaining first initial calibration parameters of the telecentric lens. The first coordinates are the pixel coordinates of the reference point in the calibration image in the pixel coordinate system. Since the calibration image is acquired using a telecentric lens, the first coordinates are pixel coordinates based on the pixel coordinate system of the telecentric lens. The preset first imaging model can be a pre-set model for calibrating the telecentric lens, for example, a telecentric lens imaging model.

[0060] Step 206 : Determine, based on the first initial calibration parameters, a second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system.

[0061] The second coordinate refers to the coordinate of the reference point in the target projection light machine coordinate system. The target projection light machine can be any projection light machine in the system shown in Figure 1B. Since the projection light machine cannot capture image data, it is impossible to directly extract the coordinates of the reference point in its coordinate system like a telecentric lens. Based on this, in this embodiment, the second coordinate of the reference point corresponding to the first coordinate can be further determined relative to the target projection light machine coordinate system based on the first initial calibration parameters of the telecentric lens determined in the previous step, thereby calibrating the target projection light machine.

[0062] Step 208 : calibrate the target projection light engine according to the second coordinates to obtain second initial calibration parameters of the target projection light engine.

[0063] The second initial calibration parameters may be calibration parameters obtained by calibrating the target projection optical machine using a preset calibration model, and may include corresponding internal parameters, external parameters, and distortion coefficients. The internal parameters are related to the characteristics of the target projection optical machine itself, and their function is to convert coordinates from the target projection optical machine coordinate system to the pixel coordinate system. The external parameters are parameters of the target projection optical machine in the world coordinate system, such as the position and rotation direction of the target projection optical machine, and their function is to convert coordinates from the world coordinate system to the target projection optical machine coordinate system. The distortion coefficients are parameters related to correcting image distortion caused by deviations in the assembly process of the target projection optical machine.

[0064] Specifically, in this embodiment, the target projection light engine can be calibrated using a preset second imaging model based on the second coordinates, thereby obtaining second initial calibration parameters of the target projection light engine. The preset second imaging model can be a pre-set model for calibrating the target projection light engine, for example, a pinhole imaging model.

[0065] Step 210 : Jointly calibrate the telecentric lens and the target projection optical machine according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain target calibration parameters.

[0066] The target calibration parameter may be a final calibration logarithm obtained by optimizing the first initial calibration parameter of the telecentric lens and the second initial calibration parameter of the projection optical engine.

[0067] In this embodiment, the reference point determined according to the above steps is based on the first coordinate of the telecentric lens in the pixel coordinate system, the first initial calibration parameter of the calibrated telecentric lens, the second coordinate of the reference point in the pixel coordinate system of the target projection light machine, and the second initial calibration parameter of the target projection light machine. The first initial calibration parameter and the second initial calibration parameter can be optimized by minimizing the reprojection error of the telecentric lens and the target projection light machine to obtain the optimized target calibration parameter, thereby realizing the joint calibration of the telecentric lens and the target projection light machine.

[0068] In the calibration method of the above-mentioned 3D imaging system, a calibration image obtained by capturing a first calibration target using a telecentric lens is obtained, and the telecentric lens is calibrated based on the calibration image to obtain the first initial calibration parameters of the telecentric lens. Based on the first initial calibration parameters, the second coordinates of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system are determined. Based on the second coordinates, the target projection optical machine is calibrated to obtain the second initial calibration parameters of the target projection optical machine. The telecentric lens and the target projection optical machine are jointly calibrated based on the first coordinates, the second coordinates, the first initial calibration parameters, and the second initial calibration parameters to obtain the target calibration parameters. This achieves the calibration of the 3D imaging system, which not only improves the imaging accuracy of the calibrated 3D imaging system, but also avoids the problem of missing 3D information of components due to occlusion.

[0069] In one embodiment, as shown in FIG3 , in step 202 , obtaining a calibration image obtained by capturing a first calibration target using a telecentric lens may specifically include:

[0070] Step 302: Project white light onto a first calibration target through a target projection optical machine.

[0071] Specifically, the first calibration target may be placed in the field of view of the system, and white light may be projected toward the first calibration target by a target projection optical machine, so as to determine the position of the reference point in the first calibration target.

[0072] Step 304 : Acquire a calibration image obtained by using a telecentric lens to capture the first calibration target after projecting white light.

[0073] Specifically, a calibration image of the first calibration target after white light is projected is collected through a telecentric lens, thereby acquiring the calibration image.

[0074] It can be understood that the first calibration target can be transformed in any direction and angle within the field of view of the system (i.e., posture transformation), so as to obtain calibration images of the first calibration target in various postures, and then analyze the calibration images in each posture, for example, extracting the coordinates of the reference points in the calibration image in each posture for coordinate analysis, thereby realizing system calibration.

[0075] In one embodiment, as shown in FIG4 , in step 206 , determining the second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system according to the first initial calibration parameter may specifically include:

[0076] Step 402 : projecting horizontal phase-shifted fringes and vertical phase-shifted fringes onto a first calibration target through a target projection optical machine.

[0077] Because the projector cannot capture image data, it cannot directly extract the coordinates of the reference point in its coordinate system like a telecentric lens. Based on this, in this embodiment, any projector in the system can be selected as the target projector. The target projector then projects horizontal and vertical stripes onto the first calibration target. The coordinates of the reference point in the target projector's coordinate system are then analyzed in subsequent steps.

[0078] Step 404 : Acquire a transverse phase shift calibration image and a longitudinal phase shift calibration image of the first calibration target captured by a telecentric lens.

[0079] The horizontal phase shift calibration image is an image captured by the telecentric lens after the target projection optical machine projects horizontal phase shift stripes onto the first calibration target, and the vertical phase shift calibration image is an image captured by the telecentric lens after the target projection optical machine projects vertical phase shift stripes onto the first calibration target. In this embodiment, the horizontal phase shift calibration image is captured by the telecentric lens after the horizontal phase shift stripes are projected onto the first calibration target, and the vertical phase shift calibration image is captured by the telecentric lens after the vertical phase shift stripes are projected onto the first calibration target, thereby obtaining the corresponding horizontal phase shift calibration image and vertical phase shift calibration image.

[0080] Step 406 : Perform distortion correction on the horizontal phase shift calibration image and the vertical phase shift calibration image according to the first initial calibration parameters.

[0081] Specifically, the distortion of the transverse phase shift calibration image and the longitudinal phase shift calibration image are respectively corrected by using the first initial calibration parameter, thereby obtaining the corrected transverse phase shift calibration image and the longitudinal phase shift calibration image.

[0082] Step 408 : De-phase the corrected transverse phase shift calibration image and the longitudinal phase shift calibration image to obtain a second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system.

[0083] Specifically, this embodiment can perform phase deconvolution on the corrected transverse phase shift calibration image and the longitudinal phase shift calibration image to obtain the second coordinate of the reference point corresponding to the first coordinate in the telecentric lens coordinate system relative to the target projection optical machine coordinate system.

[0084] In this embodiment, transverse phase-shift stripes and longitudinal phase-shift stripes are projected onto the first calibration target respectively by a target projection optical machine, and a transverse phase-shift calibration image and a longitudinal phase-shift calibration image of the first calibration target captured by a telecentric lens are obtained. The transverse phase-shift calibration image and the longitudinal phase-shift calibration image are subjected to distortion correction according to the first initial calibration parameters, and the corrected transverse phase-shift calibration image and the longitudinal phase-shift calibration image are phase-deconstructed to obtain a second coordinate of a reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system, thereby realizing the determination of the second coordinate of the reference point relative to the target projection optical machine coordinate system.

[0085] In one embodiment, as shown in FIG5 , in step 210, the telecentric lens and the target projection optical machine are jointly calibrated according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain the target calibration parameter, which may specifically include:

[0086] Step 502 : Determine an initial rotation and translation matrix from the target projection optical machine to the telecentric lens according to the first initial calibration parameter and the second initial calibration parameter.

[0087] The initial rotation and translation matrix is ​​used to characterize the conversion relationship between the target projection optical machine coordinate system and the telecentric lens coordinate system. Since the first initial calibration parameters include the parameters of the telecentric lens in the world coordinate system, i.e., the extrinsic parameters of the telecentric lens, and the second initial calibration parameters include the parameters of the target projection optical machine in the world coordinate system, i.e., the extrinsic parameters of the target projection optical machine, the conversion relationship between the target projection optical machine coordinate system and the telecentric lens coordinate system can be determined based on the first initial calibration parameters and the second initial calibration parameters, i.e., the initial rotation and translation matrix from the target projection optical machine to the telecentric lens can be determined.

[0088] Step 504 : Determine that the reference point is located at the third coordinate of the world coordinate system, and project the third coordinate of the reference point into the telecentric lens coordinate system to obtain the first projection coordinate of the reference point.

[0089] The third coordinate is the coordinate of the reference point in the world coordinate system. In this embodiment, based on the calibration image obtained above, the third coordinate of the reference point in the world coordinate system in the calibration image can be determined. Furthermore, based on the first initial calibration parameter, the second initial calibration parameter, and the initial rotation and translation matrix, the third coordinate of the reference point in the world coordinate system can be projected into the telecentric lens coordinate system to obtain the first projected coordinate of the reference point.

[0090] Step 506 : Project the third coordinate of the reference point into the target projection optical coordinate system to obtain the second projection coordinate of the reference point.

[0091] Specifically, the third coordinate of the reference point in the world coordinate system can be projected into the target projection optical coordinate system according to the first initial calibration parameter, the second initial calibration parameter and the initial rotation and translation matrix, thereby obtaining the second projection coordinate of the reference point.

[0092] Step 508 : Perform nonlinear optimization on the first initial calibration parameters, the second initial calibration parameters, and the initial rotation and translation matrix to obtain optimized target calibration parameters.

[0093] Specifically, the first initial calibration parameters, the second initial calibration parameters, and the initial rotation and translation matrix can be nonlinearly optimized according to the first coordinate, the second coordinate, the first projection coordinate, and the second projection coordinate, so as to obtain optimized target calibration parameters.

[0094] In the above embodiment, the initial rotation and translation matrix of the target projection optical machine to the telecentric lens can be determined based on the first initial calibration parameters and the second initial calibration parameters, and the third coordinate of the reference point in the world coordinate system can be determined. The third coordinate of the reference point is projected into the telecentric lens coordinate system to obtain the first projection coordinate of the reference point. The third coordinate of the reference point is projected into the target projection optical machine coordinate system to obtain the second projection coordinate of the reference point. Then, the first initial calibration parameters, the second initial calibration parameters and the initial rotation and translation matrix are nonlinearly optimized to obtain the optimized target calibration parameters, thereby realizing the calibration of the 3D imaging system.

[0095] In one embodiment, as shown in FIG6 , in step 210 , after obtaining the target calibration parameters, the method may further include:

[0096] Step 602 : projecting longitudinal phase-shifted fringes onto a second calibration target through at least two optical projection machines, respectively, to obtain at least two sets of phase-shifted images of the second calibration target captured by a telecentric lens.

[0097] The second calibration target is used to solve the phase value of the projection optical engine. Specifically, the second calibration target can be implemented using a flat pure color diffuse reflection plate, thereby ensuring the accuracy of the subsequent phase value solution.

[0098] In this embodiment, at least two optical projectors are used to project longitudinal phase-shifted stripes onto a second calibration target, and at least two sets of phase-shifted images are acquired through a telecentric lens. For example, one of the optical projectors can project longitudinal phase-shifted stripes onto the second calibration target, where the second calibration target can move up and down within the depth of field, i.e., the second calibration target can be positioned at different locations within the depth of field. A set of phase-shifted images is acquired through a telecentric lens after projecting longitudinal phase-shifted stripes onto the second calibration target at different locations. Similarly, a corresponding set of phase-shifted images can be acquired based on each of the other optical projectors in the system. Because the system of this embodiment utilizes at least two optical projectors, at least two corresponding sets of phase-shifted images can be acquired.

[0099] Step 604: Perform phase analysis on at least two sets of phase-shifted images to obtain corresponding phase values.

[0100] Specifically, by performing phase analysis on at least two sets of phase-shifted images, corresponding phase values ​​can be obtained. Because different sets of phase-shifted images are projected using different projection engines, the phase values ​​obtained by performing phase analysis on each set of phase-shifted images are related to the corresponding projection engine.

[0101] Step 606: Determine the phase height model parameters of the system according to the phase value and the target calibration parameters.

[0102] The phase-height model parameters are the parameters required for converting phase and height based on the phase-height model. Specifically, the system's phase-height model parameters can be calculated based on the preset phase-height model, the phase values ​​corresponding to each projection optical engine, and the target calibration parameters of the system determined in the above steps to establish a phase-height conversion relationship.

[0103] In one scenario, once the system's phase-height model parameters are determined, the system can be used for subsequent 3D imaging or 3D measurement to determine the Z value of the 3D coordinate based on the measured phase value and the system's phase-height model parameters. Furthermore, because the telecentric lens has a constant magnification, the X and Y coordinates can be directly obtained by multiplying the pixel coordinates by the pixel accuracy to achieve 3D reconstruction. Furthermore, when calculating the phase value, only the longitudinal fringe image obtained by projecting longitudinal fringe patterns onto the target to be measured is required to determine the corresponding phase value, without the need to obtain the transverse fringe image of the target to be measured, further improving reconstruction efficiency.

[0104] In one embodiment, as shown in FIG7 , the calibration method of the 3D imaging system is further described below, which may specifically include:

[0105] Step 702: Calibrate image acquisition.

[0106] Specifically, the first calibration target is placed in different spatial directions within the field of view of the system (i.e., the first calibration target is in different postures), and then white light projection, transverse phase-shifted fringe projection, and longitudinal phase-shifted fringe projection are performed respectively by one of the projection optical machines (i.e., the target projection optical machine), and images of the first calibration target in different postures under different projections are collected by a telecentric lens. For example, calibration images of the first calibration target in different postures under white light projection, transverse phase-shifted calibration images of the first calibration target in different postures under transverse phase-shifted fringe projection, and longitudinal phase-shifted calibration images of the first calibration target in different postures under longitudinal phase-shifted fringe projection are collected. The other projection optical machines of the system are not projected for the time being. In this embodiment, the first calibration target is an asymmetric black and white circular calibration plate as an example, and the reference point is the center of the circle in the calibration plate. For example, the calibration image of the first calibration target under white light projection collected can be the image shown in Figure 8A, the transverse phase-shifted calibration image is shown in Figure 8B, and the longitudinal phase-shifted calibration image is shown in Figure 8C.

[0107] Step 704: Telecentric lens calibration.

[0108] Specifically, by locating the center of the circle in the calibration image under white light projection (as shown in FIG8D ), the corresponding pixel coordinates can be obtained. (i.e., the first coordinate), where the subscript i represents the calibration images collected at different postures, and j represents the different center points in the calibration images, such as the jth center point in the calibration image at the i-th posture. In this embodiment, according to the pixel coordinates corresponding to the center points in the calibration images at different postures, a telecentric lens imaging model can be used for calibration to obtain the first initial calibration parameters of the telecentric lens, which can specifically include the internal parameters External Reference and distortion coefficient K c Among them, the intrinsic parameters are related to the characteristics of the telecentric lens itself, such as the focal length and pixel size of the telecentric lens. Their function is to convert the coordinates from the telecentric lens coordinate system to the pixel coordinate system. The extrinsic parameters are the parameters of the telecentric lens in the world coordinate system, such as the position and rotation direction of the telecentric lens. Their function is to convert the coordinates from the world coordinate system to the telecentric lens coordinate system. The distortion coefficient is a parameter related to correcting image distortion caused by deviations in the telecentric lens assembly process.

[0109] Step 706: calibrate the target projection optical machine.

[0110] Specifically, the first coordinate of the reference point located based on the above steps is the pixel coordinate As well as the first initial calibration parameters of the telecentric lens, the captured lateral phase shift calibration image and the longitudinal phase shift calibration image are subjected to distortion correction and phase solution, thereby obtaining the pixel coordinates in the target projection optical machine coordinate system corresponding to the pixel coordinates of the circle center under the telecentric lens, i.e., the first coordinates. (i.e. the second coordinate), where the subscripts i and j have the same meaning as above. Then, the pinhole imaging model is used to calibrate the target projection optical machine, i.e., the second initial calibration parameters of the target projection optical machine are obtained, including the internal reference A p (f x , f y , u0, v0), external reference and distortion coefficient K p . Among them, the superscripts c and p represent the telecentric lens and the tilt-shift projector respectively. The internal parameters are related to the characteristics of the target projection optical machine itself, and their function is to convert the coordinates from the target projection optical machine coordinate system to the pixel coordinate system. The external parameters are the parameters of the target projection optical machine in the world coordinate system, such as the position and rotation direction of the target projection optical machine. Their function is to convert the coordinates from the world coordinate system to the target projection optical machine coordinate system. The distortion coefficient is a parameter related to correcting the image distortion caused by the deviation of the target projection optical machine assembly process.

[0111] Step 708, joint calibration.

[0112] Specifically, after completing the above calibration, the external reference of the telecentric lens and the external parameters of the target projection optical machine The rotation and translation matrix [R|T] from the target projection optical machine to the telecentric lens can be obtained by calculation, where:

[0113] Then, the calibration accuracy of the system can be improved by simultaneously minimizing the reprojection error of the telecentric lens and the target projection optical machine. The joint calibration formula is as follows:

[0114] in, is the first coordinate, i.e. the pixel coordinate of the circle center in the pixel coordinate system based on the telecentric lens, is the second coordinate, i.e. the pixel coordinate of the circle center based on the target projection optical coordinate system, is the first projection coordinate, which is the projection of the world coordinate of the circle center to the coordinate of the telecentric lens coordinate system. A is the second projection coordinate, which is the projection of the world coordinate of the center of the circle to the coordinate of the target projection optical machine coordinate system. c is the internal reference of the telecentric lens, A p is the internal parameter of the target projection optical machine, is the external parameter of the target projection optical machine, Kp is the distortion coefficient of the target projection optical machine, R and T are the rotation and translation matrices from the target projection optical machine to the telecentric lens. The above formula can be used to optimize the internal parameters of the telecentric lens External Reference and distortion coefficient K c , and can also optimize the internal parameter A of the target projection optical machine p (f x , f y , u0, v0), external reference and distortion coefficient K p , and optimize the rotation and translation matrix of the target projection optical machine to the telecentric lens, so as to obtain the target calibration parameters of the system, that is, the optimized parameters mentioned above.

[0115] Then, based on the target calibration parameters of the system, the first calibration target in different poses can be reconstructed in three dimensions using the following formula:

[0116] in,

[0117] The definitions of the parameters in the formula are the same as those described in the above embodiment, and will not be repeated in this embodiment.

[0118] Step 710: Calculate the phase value.

[0119] Specifically, a pure-color flat diffuse reflector (the second calibration target) is placed directly below the imaging system and moved up and down several times within the depth of field. Two projectors project longitudinal phase-shifted fringes, and a telecentric lens collects two sets of diffuse longitudinal phase-shifted images at several positions (as shown in Figure 8E). Each set of diffuse longitudinal phase-shifted images is then dephased to obtain the phase value of the corresponding projector.

[0120] Step 712: Solve the phase height model parameters.

[0121] Specifically, the pure color plane diffuse reflector can be reconstructed in three dimensions based on the target calibration parameters, thereby obtaining the Z values ​​of the pure color plane diffuse reflector at different positions. The phase height model parameters of each projection optical machine can then be solved using the following phase height model. The phase height model can be expressed as:

[0122] Among them, p1, p2, p3, and p4 are used to represent different projection optical machines. Used to characterize the phase values ​​corresponding to different projection optical machines, Z p1 、Z p2 、Zp3 , Z p4 It is the Z value reconstructed when the pure color plane diffuse reflector is at different positions. By substituting each parameter into the above phase height model, the phase height model parameters can be obtained. That is, the phase values ​​of different projection optical machines are converted into corresponding Z value height information, thereby improving imaging accuracy.

[0123] In one scenario, the phase height model is not limited to the third-order polynomial mentioned above. Its order can be changed according to actual needs during application. For example, a fifth-order polynomial can also be used. This embodiment does not limit this.

[0124] It should be understood that, although the various steps in the flowcharts involved in the various embodiments described above are displayed in sequence according to the instructions of the arrows, these steps are not necessarily executed in sequence in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and these steps can be executed in other orders. Moreover, at least a portion of the steps in the flowcharts involved in the various embodiments described above can include multiple steps or multiple stages, and these steps or stages are not necessarily executed and completed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily to be carried out in sequence, but can be executed in turn or alternately with other steps or at least a portion of steps or stages in other steps.

[0125] Based on the same inventive concept, embodiments of the present application also provide a 3D imaging system calibration device for implementing the aforementioned 3D imaging system calibration method. The solution provided by this device is similar to the solution described in the aforementioned method. Therefore, the specific limitations of the one or more 3D imaging system calibration device embodiments provided below can be found in the limitations of the 3D imaging system calibration method described above and will not be further elaborated here.

[0126] In one embodiment, as shown in FIG9 , a calibration apparatus for a 3D imaging system is provided, comprising: an image acquisition module 902 , a first calibration module 904 , a second calibration module 906 , and a calibration parameter determination module 908 , wherein:

[0127] An image acquisition module 902 is configured to acquire a calibration image obtained by capturing a first calibration target using the telecentric lens, where a plurality of reference points are provided on the first calibration target;

[0128] The first calibration module 904 is used to determine the first coordinate of the reference point in the calibration image in the pixel coordinate system, and to calibrate the distance according to the preset first imaging model.

[0129] Calibrate the telecentric lens to obtain the first initial calibration parameters of the telecentric lens;

[0130] A second calibration module 906 is configured to determine, based on the first initial calibration parameters, a second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system; and calibrate the target projection optical machine using a preset second imaging model based on the second coordinate to obtain second initial calibration parameters of the target projection optical machine;

[0131] The calibration parameter determination module 908 is configured to jointly calibrate the telecentric lens and the target projection optical machine according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain target calibration parameters.

[0132] In one embodiment, the second calibration module is further used to: project horizontal phase-shift stripes and vertical phase-shift stripes onto the first calibration target respectively through the target projection optical machine; obtain a horizontal phase-shift calibration image obtained by projecting horizontal symmetrical stripes onto the first calibration target using the telecentric lens, and obtain a vertical phase-shift calibration image obtained by projecting vertical symmetrical stripes onto the first calibration target; perform distortion correction on the horizontal phase-shift calibration image and the vertical phase-shift calibration image according to the first initial calibration parameters; perform phase deconvolution on the corrected horizontal phase-shift calibration image and the vertical phase-shift calibration image to obtain a second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system.

[0133] In one embodiment, the calibration parameter determination module is also used to: determine the initial rotation and translation matrix of the target projection optical machine to the telecentric lens based on the first initial calibration parameter and the second initial calibration parameter; determine the third coordinate of the reference point in the world coordinate system, and project the third coordinate of the reference point to the telecentric lens coordinate system based on the first initial calibration parameter, the second initial calibration parameter and the initial rotation and translation matrix to obtain the first projection coordinate of the reference point, and project the third coordinate of the reference point to the target projection optical machine coordinate system to obtain the second projection coordinate of the reference point; perform nonlinear optimization on the first initial calibration parameter, the second initial calibration parameter and the initial rotation and translation matrix based on the first coordinate, the second coordinate, the first projection coordinate and the second projection coordinate to obtain the optimized target calibration parameter.

[0134] In one embodiment, the device also includes a phase height model determination module, which is used to project longitudinal phase-shifted stripes onto a second calibration target through at least two of the projection optical machines, respectively, to obtain at least two sets of phase-shifted images of the second calibration target collected by the telecentric lens; perform phase analysis on the at least two sets of the phase-shifted images to obtain corresponding phase values; and determine the phase height model parameters of the system based on the phase values ​​and the target calibration parameters.

[0135] In one embodiment, the second calibration target is a flat pure color diffuse reflection plate.

[0136] In one embodiment, the image acquisition module is further configured to: project white light onto the first calibration target through the target projection light machine; and acquire a calibration image of the first calibration target after the projected white light is captured by the telecentric lens.

[0137] Each module in the calibration device for a 3D imaging system described above can be implemented in whole or in part through software, hardware, or a combination thereof. Each module can be embedded in or independent of a processor in a computer device in hardware form, or can be stored in a computer device memory in software form, so that the processor can call and execute the corresponding operations of each module.

[0138] As used in this application, the terms "component," "module," and "system" are intended to refer to a computer-related entity, which can be hardware, a combination of hardware and software, software, or software in execution. For example, a component can be, but is not limited to, a process running on a processor, a processor, an object, an executable code, a thread of execution, a program, and / or a computer. As an illustration, an application running on a server and a server can both be components. One or more components can reside in a process and / or thread of execution, and a component can be located within a computer and / or distributed between two or more computers.

[0139] In one embodiment, a calibration device is provided. The calibration device may be a terminal, and its internal structure may be shown in Figure 10. The calibration device includes a processor, memory, an input / output interface, a communication interface, a display unit, and an input device. The processor, memory, and input / output interface are connected via a system bus, and the communication interface, display unit, and input device are connected to the system bus via the input / output interface. The processor of the calibration device is used to provide computing and control capabilities. The memory of the calibration device includes a non-volatile storage medium and internal memory. The non-volatile storage medium stores an operating system and computer programs. The internal memory provides an environment for the operation of the operating system and computer programs in the non-volatile storage medium. The input / output interface of the calibration device is used to exchange information between the processor and external devices. The communication interface of the calibration device is used to communicate with external terminals via wired or wireless communication, and the wireless communication may be achieved via Wi-Fi, a mobile cellular network, NFC (near-field communication), or other technologies. When executed by the processor, the computer program implements a calibration method for a 3D imaging system. The display unit of the calibration device is used to form a visually visible image and may be a display screen, a projection device, or a virtual reality imaging device. The display screen can be a liquid crystal display screen or an electronic ink display screen, and the input device of the calibration device can be a touch layer covering the display screen, or a button, trackball or touchpad set on the calibration device casing, or an external keyboard, touchpad or mouse, etc.

[0140] Those skilled in the art will understand that the structure shown in Figure 10 is merely a block diagram of a portion of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific calibration device may include more or fewer components than shown in the figure, or combine certain components, or have a different component arrangement.

[0141] In one embodiment, a calibration device is provided, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor executes the computer program, the following steps are implemented:

[0142] Acquire a calibration image obtained by capturing a first calibration target using the telecentric lens, where a plurality of reference points are provided on the first calibration target;

[0143] Determine a first coordinate of the reference point in the calibration image in a pixel coordinate system, calibrate the telecentric lens according to a preset first imaging model, and obtain a first initial calibration parameter of the telecentric lens;

[0144] Determining, based on the first initial calibration parameters, a second coordinate of the reference point corresponding to the first coordinate relative to a target projection optical machine coordinate system;

[0145] Calibrate the target projection light machine using a preset second imaging model according to the second coordinate to obtain second initial calibration parameters of the target projection light machine;

[0146] The telecentric lens and the target projection optical machine are jointly calibrated according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain target calibration parameters.

[0147] In one embodiment, when the processor executes the computer program, the following steps are further implemented: projecting horizontal phase-shift stripes and vertical phase-shift stripes onto the first calibration target respectively through the target projection optical machine; acquiring a horizontal phase-shift calibration image obtained by projecting horizontal symmetrical stripes onto the first calibration target, and acquiring a vertical phase-shift calibration image obtained by projecting vertical symmetrical stripes onto the first calibration target, which are captured using the telecentric lens; performing distortion correction on the horizontal phase-shift calibration image and the vertical phase-shift calibration image according to the first initial calibration parameters; performing phase deconvolution on the corrected horizontal phase-shift calibration image and the vertical phase-shift calibration image to obtain a second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system.

[0148] In one embodiment, when the processor executes the computer program, it also implements the following steps: determining the initial rotation and translation matrix of the target projection optical machine to the telecentric lens based on the first initial calibration parameters and the second initial calibration parameters; determining the third coordinate of the reference point in the world coordinate system, and projecting the third coordinate of the reference point to the telecentric lens coordinate system based on the first initial calibration parameters, the second initial calibration parameters and the initial rotation and translation matrix to obtain the first projection coordinate of the reference point, and projecting the third coordinate of the reference point to the target projection optical machine coordinate system to obtain the second projection coordinate of the reference point; and performing nonlinear optimization on the first initial calibration parameters, the second initial calibration parameters and the initial rotation and translation matrix based on the first coordinates, the second coordinates, the first projection coordinates and the second projection coordinates to obtain the optimized target calibration parameters.

[0149] In one embodiment, when the processor executes the computer program, it further implements the following steps: projecting longitudinal phase-shifted stripes onto a second calibration target through at least two of the projection optical machines, respectively, to obtain at least two sets of phase-shifted images of the second calibration target captured by the telecentric lens; performing phase analysis on the at least two sets of the phase-shifted images to obtain corresponding phase values; and determining the phase height model parameters of the system based on the phase values ​​and the target calibration parameters.

[0150] In one embodiment, when the processor executes the computer program, the processor further implements the following steps: projecting white light onto the first calibration target through the target projection light machine; and acquiring a calibration image of the first calibration target after the projected white light is captured by the telecentric lens.

[0151] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the following steps are implemented:

[0152] Acquire a calibration image obtained by capturing a first calibration target using the telecentric lens, where a plurality of reference points are provided on the first calibration target;

[0153] Determine a first coordinate of the reference point in the calibration image in a pixel coordinate system, calibrate the telecentric lens according to a preset first imaging model, and obtain a first initial calibration parameter of the telecentric lens;

[0154] Determining, based on the first initial calibration parameters, a second coordinate of the reference point corresponding to the first coordinate relative to a target projection optical machine coordinate system;

[0155] Calibrate the target projection light machine using a preset second imaging model according to the second coordinate to obtain second initial calibration parameters of the target projection light machine;

[0156] The telecentric lens and the target projection optical machine are jointly calibrated according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain target calibration parameters.

[0157] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: projecting horizontal phase-shift stripes and vertical phase-shift stripes onto the first calibration target respectively through the target projection optical machine; acquiring a horizontal phase-shift calibration image obtained by projecting horizontal symmetrical stripes onto the first calibration target, and acquiring a vertical phase-shift calibration image obtained by projecting vertical symmetrical stripes onto the first calibration target, which are captured by the telecentric lens; performing distortion correction on the horizontal phase-shift calibration image and the vertical phase-shift calibration image according to the first initial calibration parameters; performing phase deconvolution on the corrected horizontal phase-shift calibration image and the vertical phase-shift calibration image to obtain a second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system.

[0158] In one embodiment, when the computer program is executed by the processor, the following steps are also implemented: determining the initial rotation and translation matrix of the target projection optical machine to the telecentric lens based on the first initial calibration parameters and the second initial calibration parameters; determining the third coordinate of the reference point in the world coordinate system, projecting the third coordinate of the reference point to the telecentric lens coordinate system based on the first initial calibration parameters, the second initial calibration parameters and the initial rotation and translation matrix to obtain the first projection coordinate of the reference point, and projecting the third coordinate of the reference point to the target projection optical machine coordinate system to obtain the second projection coordinate of the reference point; performing nonlinear optimization on the first initial calibration parameters, the second initial calibration parameters and the initial rotation and translation matrix based on the first coordinates, the second coordinates, the first projection coordinates and the second projection coordinates to obtain the optimized target calibration parameters.

[0159] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: projecting longitudinal phase-shifted stripes onto a second calibration target through at least two of the projection optical machines, respectively, to obtain at least two sets of phase-shifted images of the second calibration target captured by the telecentric lens; performing phase analysis on the at least two sets of the phase-shifted images to obtain corresponding phase values; and determining the phase height model parameters of the system based on the phase values ​​and the target calibration parameters.

[0160] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: projecting white light onto the first calibration target through the target projection light machine; and acquiring a calibration image of the first calibration target after the projected white light is captured by the telecentric lens.

[0161] In one embodiment, a computer program product is provided, comprising a computer program, which, when executed by a processor, implements the following steps:

[0162] Acquire a calibration image obtained by capturing a first calibration target using the telecentric lens, where a plurality of reference points are provided on the first calibration target;

[0163] Determine a first coordinate of the reference point in the calibration image in a pixel coordinate system, calibrate the telecentric lens according to a preset first imaging model, and obtain a first initial calibration parameter of the telecentric lens;

[0164] Determining, based on the first initial calibration parameters, a second coordinate of the reference point corresponding to the first coordinate relative to a target projection optical machine coordinate system;

[0165] Calibrate the target projection light machine using a preset second imaging model according to the second coordinate to obtain second initial calibration parameters of the target projection light machine;

[0166] The telecentric lens and the target projection optical machine are jointly calibrated according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain target calibration parameters.

[0167] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: projecting horizontal phase-shift stripes and vertical phase-shift stripes onto the first calibration target respectively through the target projection optical machine; acquiring a horizontal phase-shift calibration image obtained by projecting horizontal symmetrical stripes onto the first calibration target, and acquiring a vertical phase-shift calibration image obtained by projecting vertical symmetrical stripes onto the first calibration target, which are captured by the telecentric lens; performing distortion correction on the horizontal phase-shift calibration image and the vertical phase-shift calibration image according to the first initial calibration parameters; performing phase deconvolution on the corrected horizontal phase-shift calibration image and the vertical phase-shift calibration image to obtain a second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system.

[0168] In one embodiment, when the computer program is executed by the processor, the following steps are also implemented: determining the initial rotation and translation matrix of the target projection optical machine to the telecentric lens based on the first initial calibration parameters and the second initial calibration parameters; determining the third coordinate of the reference point in the world coordinate system, projecting the third coordinate of the reference point to the telecentric lens coordinate system based on the first initial calibration parameters, the second initial calibration parameters and the initial rotation and translation matrix to obtain the first projection coordinate of the reference point, and projecting the third coordinate of the reference point to the target projection optical machine coordinate system to obtain the second projection coordinate of the reference point; performing nonlinear optimization on the first initial calibration parameters, the second initial calibration parameters and the initial rotation and translation matrix based on the first coordinates, the second coordinates, the first projection coordinates and the second projection coordinates to obtain the optimized target calibration parameters.

[0169] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: projecting longitudinal phase-shifted stripes onto a second calibration target through at least two of the projection optical machines, respectively, to obtain at least two sets of phase-shifted images of the second calibration target captured by the telecentric lens; performing phase analysis on the at least two sets of the phase-shifted images to obtain corresponding phase values; and determining the phase height model parameters of the system based on the phase values ​​and the target calibration parameters.

[0170] In one embodiment, when the computer program is executed by the processor, the following steps are further implemented: projecting white light onto the first calibration target through the target projection light machine; and acquiring a calibration image of the first calibration target after the projected white light is captured by the telecentric lens.

[0171] Those skilled in the art will appreciate that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, database or other media used in the embodiments provided in this application may include at least one of non-volatile and volatile memory. Non-volatile memory may include read-only memory (ROM), magnetic tape, floppy disk, flash memory, optical memory, high-density embedded non-volatile memory, resistive random access memory (ReRAM), magnetic random access memory (MRAM), ferroelectric random access memory (FRAM), phase change memory (PCM), graphene memory, etc. Volatile memory may include random access memory (RAM) or external cache memory, etc. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM). The database involved in the various embodiments provided herein may include at least one of a relational database and a non-relational database. Non-relational databases may include, but are not limited to, distributed databases based on blockchains. The processor involved in the various embodiments provided herein may be, but are not limited to, a general-purpose processor, a central processing unit, a graphics processing unit, a digital signal processor, a programmable logic unit, a data processing logic unit based on quantum computing, and the like.

[0172] The technical features of the above embodiments can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0173] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. A calibration method for a 3D imaging system, characterized in that: The system includes a telecentric lens having a same field of view center and at least two projection optical machines, and the method includes: Acquire a calibration image obtained by capturing a first calibration target using the telecentric lens, where a plurality of reference points are set on the first calibration target; Determine a first coordinate of the reference point in the calibration image in a pixel coordinate system, calibrate the telecentric lens according to a preset first imaging model, and obtain a first initial calibration parameter of the telecentric lens; Determine, according to the first initial calibration parameter, a second coordinate of the reference point corresponding to the first coordinate relative to a target projection optical machine coordinate system; the target projection optical machine is any one of the at least two projection optical machines; According to the second coordinates, the target projection light machine is calibrated using a preset second imaging model to obtain a second initial calibration parameter of the target projection light machine; The telecentric lens and the target projection optical machine are jointly calibrated according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain target calibration parameters.

2. The method according to claim 1, characterized in that The step of determining, according to the first initial calibration parameter, a second coordinate of the reference point corresponding to the first coordinate relative to a target projection optical machine coordinate system comprises: Projecting horizontal phase-shifted fringes and vertical phase-shifted fringes onto the first calibration target respectively by the target projection optical machine; Acquire a transverse phase-shift calibration image acquired by projecting transverse symmetrical stripes onto the first calibration target using the telecentric lens, and acquire a longitudinal phase-shift calibration image acquired by projecting longitudinal symmetrical stripes onto the first calibration target; Performing distortion correction on the transverse phase shift calibration image and the longitudinal phase shift calibration image according to the first initial calibration parameter; The corrected transverse phase shift calibration image and the longitudinal phase shift calibration image are phase resolved to obtain a second coordinate of the reference point corresponding to the first coordinate relative to the target projection optical machine coordinate system.

3. The method according to claim 1, characterized in that The method of jointly calibrating the telecentric lens and the target projection optical machine according to the first coordinate, the second coordinate, the first initial calibration parameter, and the second initial calibration parameter to obtain the target calibration parameter includes: Determine an initial rotation and translation matrix from the target projection optical machine to the telecentric lens according to the first initial calibration parameter and the second initial calibration parameter; Determine the third coordinate of the reference point in the world coordinate system, and project the third coordinate of the reference point into the telecentric lens coordinate system according to the first initial calibration parameter, the second initial calibration parameter, and the initial rotation and translation matrix to obtain a first projection coordinate of the reference point; Projecting the third coordinate of the reference point into the target projection optical coordinate system to obtain the second projection coordinate of the reference point; According to the first coordinate, the second coordinate, the first projection coordinate and the second projection coordinate, nonlinear optimization is performed on the first initial calibration parameter, the second initial calibration parameter and the initial rotation and translation matrix to obtain optimized target calibration parameters.

4. The method according to any one of claims 1 to 3, characterized in that: The method further comprises: Projecting longitudinal phase-shifted fringes onto a second calibration target respectively by at least two of the projection optical machines, and acquiring at least two groups of phase-shifted images of the second calibration target collected by the telecentric lens; Performing phase analysis on at least two groups of the phase-shifted images to obtain corresponding phase values; The phase height model parameters of the system are determined according to the phase value and the target calibration parameters.

5. The method according to claim 4, characterized in that The phase height model parameters are used by the 3D imaging system to determine height information of the three-dimensional coordinates of a measurement target in three-dimensional measurement.

6. The method according to claim 4, characterized in that The second calibration target is a flat pure color diffuse reflection plate.

7. The method according to any one of claims 1 to 3, characterized in that: The step of acquiring a calibration image obtained by capturing a first calibration target using the telecentric lens includes: Projecting white light toward the first calibration target by the target projection optical machine; A calibration image is obtained by using the telecentric lens to collect the first calibration target after projecting white light.

8. The method according to any one of claims 1 to 3, characterized in that: The preset first imaging model is a pre-set telecentric lens imaging model for calibrating the telecentric lens.

9. The method according to any one of claims 1 to 3, characterized in that: The preset second imaging model is a pinhole imaging model preset for calibrating the target projection optical machine.

10. A calibration device for a 3D imaging system, characterized in that: The device comprises: An image acquisition module, used to acquire a calibration image obtained by capturing a first calibration target using a telecentric lens, wherein a plurality of reference points are provided on the first calibration target; A first calibration module, used to determine a first coordinate of the reference point in the calibration image in a pixel coordinate system, calibrate the telecentric lens according to a preset first imaging model, and obtain a first initial calibration parameter of the telecentric lens; A second calibration module is used to determine, according to the first initial calibration parameters, a second coordinate of the reference point corresponding to the first coordinate relative to a target projection optical machine coordinate system; according to the second coordinate, calibrate the target projection optical machine using a preset second imaging model to obtain a second initial calibration parameter of the target projection optical machine; the target projection optical machine is any one of the at least two projection optical machines; A calibration parameter determination module is used to jointly calibrate the telecentric lens and the target projection optical machine according to the first coordinate, the second coordinate, the first initial calibration parameter and the second initial calibration parameter to obtain a target calibration parameter.

11. The device according to claim 10, characterized in that The device also includes a phase height model determination module, which is used to: Projecting longitudinal phase-shifted fringes onto a second calibration target respectively by at least two of the projection optical machines, and acquiring at least two groups of phase-shifted images of the second calibration target collected by the telecentric lens; Performing phase analysis on at least two groups of the phase-shifted images to obtain corresponding phase values; The phase height model parameters of the system are determined according to the phase value and the target calibration parameters.

12. A 3D imaging system, characterized in that: The system comprises: A telecentric lens, wherein the telecentric lens is arranged in a front view relative to the reference plane, and the telecentric lens has a first field of view center; At least two projection light machines, at least two of the projection light machines are arranged around the telecentric lens and obliquely relative to the reference plane, the projection light machines have a second field of view center, and the second field of view center coincides with the first field of view center; the system is calibrated using the method described in any one of claims 1 to 9.

13. A calibration device, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 9 are implemented.

14. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 9 are implemented.

15. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 9 are implemented.

Images