Profilometer external parameter calibration method, device and equipment

Abstract

The present application provides a kind of profilometer external parameter calibration method, device and equipment, comprising: in the process of rotary table driving calibration block body rotation, rotary table encoder triggers profilometer to collect brightness map and height map according to fixed angle interval;Based on brightness map and height map, the rotary table angle corresponding to the center of mark point and its corresponding projection three-dimensional coordinates in profilometer coordinate system are determined;Calibration block digital model is generated to determine the real three-dimensional coordinates corresponding to the center of mark point in digital model coordinate system, combined with rotary table angle and projection three-dimensional coordinates, the initial calibration of the rotation axis parameter of profilometer is carried out to obtain the initial solution of rotation axis parameter;The surface topography of calibration block body is reconstructed, and the parameter optimization residual function is constructed based on the reconstruction result and calibration block digital model, and the initial solution of rotation axis parameter is optimized to obtain the target solution of rotation axis parameter.The present application can significantly improve the calibration accuracy of profilometer, and help to reduce the manufacturing cost and difficulty of calibration block.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of calibration, in particular to a contour instrument external parameter calibration method, device and equipment. BACKGROUND

[0002] In industrial production, the size of the workpiece often needs to be measured for product quality control and production process optimization. With the iteration of production process, obtaining the surface topography of the workpiece with high precision is an important condition for further optimizing the production process.

[0003] In order to obtain complete object surface topography information, the commonly used method at present is to use a three-dimensional scanner to scan the surface or to obtain part of the point cloud through a structured light camera and then splice it together. The former can achieve high repeatability and absolute accuracy, but generally needs to paste reference points on the workpiece surface, and the scanning speed is slow, which is unacceptable in most cases. The latter needs to calibrate the camera external parameters of each shooting position in advance, which will introduce additional errors, and the repeatability of the structured light camera is generally in the sub-millimeter level, so the final splicing accuracy often cannot meet the use requirements.

[0004] In recent years, there have also been methods of using high-precision line laser profilers combined with high-precision rotary tables to obtain object surface topography, but their calibration schemes have certain requirements for the installation method of the hardware (such as the need for the profiler light plane to pass through the rotary table shaft), which often limits their application in actual production.

[0005] Existing rotary shaft calibration schemes generally use a standard ball or a standard cylinder as a calibration block to obtain the profile of the calibration block at each angle for system parameter calibration and optimization. There are also schemes that use a stepped shaft as a calibration block for system parameter optimization. However, the intersection line between the curved surface of the calibration block and the light plane changes smoothly with the angle, and the linearity of the profiler itself also has certain deviations, i.e. there is a certain distortion between the object profile obtained by the profiler and the actual intersection line between the light plane and the object surface. Therefore, the direction of the rotary shaft often has a large error in the rotation direction of the axis and the axis, and in schemes that use a single standard ball as a calibration block, there is also a large error in the rotation direction of the axis due to less constraints. There are also other schemes that use a stepped block and an auxiliary camera for calibration, but the method is too complex and the cost is too high due to the machining problem of the block when measuring large objects, which cannot be applied in practice. SUMMARY

[0006] In view of this, the object of the present invention is to provide a method, device and equipment for calibrating the external parameters of a profilometer, which can significantly improve the calibration accuracy of the profilometer and help reduce the production cost and difficulty of the calibration block.

[0007] In a first aspect, the present invention provides a method for calibrating external parameters of a profiler, wherein the calibration block body is fixed on a turntable, and the method comprises:

[0008] When the turntable drives the calibration block to rotate, the turntable encoder triggers the profilometer to collect the calibration block brightness image and calibration block height image corresponding to the calibration block body at fixed angle intervals;

[0009] Based on the calibration block brightness map and the calibration block height map, determine the turntable angle corresponding to the center of each marker point contained in the calibration block body and its corresponding projected three-dimensional coordinates in the profilometer coordinate system;

[0010] Generate a digital model of the calibration block corresponding to the calibration block body to determine the real three-dimensional coordinates of the center of each marker point in the digital model coordinate system. Combined with the turntable angle and projected three-dimensional coordinates corresponding to each marker point center, perform an initial calibration on the profiler's axis parameters to obtain the initial solution of the profiler's axis parameters.

[0011] The surface topography of the calibration block is reconstructed, and a parameter optimization residual function is constructed based on the reconstruction result and the calibration block digital model. The initial solution of the shaft parameters is optimized to obtain the target solution of the shaft parameters corresponding to the profilometer.

[0012] In one embodiment, based on the calibration block brightness map and the calibration block height map, determining the turntable angle corresponding to the center of each marker point included in the calibration block body and its corresponding projected three-dimensional coordinates in the profilometer coordinate system includes:

[0013] Based on the calibration block brightness map, the center coordinates of each elliptical shape contained therein are fitted as the projected pixel coordinates of the center of each marker point contained in the calibration block body on the calibration block brightness map or the calibration block height map;

[0014] Determine the turntable angle corresponding to the center of each marker point based on the projected pixel coordinates and the fixed angle interval;

[0015] In addition, based on the projected pixel coordinates, the neighboring pixel points corresponding to the center of the marker point are extracted from the calibration block height map, and the height values ​​of the neighboring pixel points are used to fit the height value corresponding to the center of the marker point; under the condition that the vertical coordinate value of the projected three-dimensional coordinate is 0, the projected three-dimensional coordinates corresponding to the center of the marker point in the profilometer coordinate system are constructed based on the horizontal spacing, projected pixel coordinates and height values ​​of the pixels corresponding to the calibration block height map.

[0016] In one embodiment, the horizontal coordinate in the projected three-dimensional coordinate is the product of the horizontal spacing of the pixel points and the horizontal coordinate of the projected pixel coordinate; the vertical coordinate in the projected three-dimensional coordinate is 0; and the vertical coordinate in the projected three-dimensional coordinate is the height value corresponding to the center of the marker point.

[0017] In one embodiment, the profiler's rotation axis parameters are initially calibrated based on the turntable angle and projected three-dimensional coordinates corresponding to the center of each marker point to obtain an initial solution for the profiler's rotation axis parameters, including:

[0018] For any turntable angle, do the following:

[0019] Determine the rotation matrix corresponding to the turntable angle;

[0020] Based on the first conversion matrix between the axis coordinate system and the profilometer coordinate system, the second conversion matrix between the digital-analog coordinate system and the axis coordinate system, and the rotation matrix, a coordinate conversion model between the real three-dimensional coordinates and the projected three-dimensional coordinates is constructed. The first conversion matrix and the second conversion matrix in the coordinate conversion model are the axis parameters to be solved.

[0021] Generate a rough solution population, and use the fitness function to evaluate each rough solution of the axis parameter contained in the rough solution population based on the real three-dimensional coordinates and projected three-dimensional coordinates corresponding to the center of the landmark point, so as to update the rough solution population until the optimal rough solution of the axis parameter is determined from the updated rough solution population when the preset conditions are met;

[0022] The optimal rough solution of the shaft parameters is subjected to nonlinear optimization to obtain the initial solution of the shaft parameters corresponding to the profiler.

[0023] In one embodiment, the fitness function of the particle swarm optimization algorithm and the residual function of the nonlinear optimization are as follows:

[0024] ;

[0025] in, is the fitness value, is the total number of landmark centers contained in the calibration block body, For the The rotation matrix of the turntable angle corresponding to the center of the landmark point, For the The projected three-dimensional coordinates corresponding to the centers of the landmark points are: For the The real three-dimensional coordinates corresponding to the centers of the landmark points, is the first transformation matrix, is the axis parameter to be solved in the first transformation matrix, is the second transformation matrix, is the axis parameter to be solved in the second transformation matrix.

[0026] In one embodiment, the reconstruction result includes the reconstructed projected three-dimensional coordinates corresponding to the center of each marker point; a parameter optimization residual function is constructed based on the reconstruction result and the calibration block digital model, and the initial solution of the axis parameters is optimized to obtain the target solution of the axis parameters corresponding to the profilometer, including:

[0027] The projection of the calibration block body in the calibration block height map is recorded as a contour point, and multiple target contour points are selected from the contour points;

[0028] Align the reconstructed projected 3D coordinates corresponding to the target contour points to the digital model coordinate system to determine the patch structure with the closest distance between the target contour points and the calibration block digital model;

[0029] The residual function is optimized by parameters. Based on the distance between the target contour point and its nearest patch structure, the registration degree between the reconstruction result and the calibration block digital model is determined. The initial solution of the shaft parameters is optimized with the goal of minimizing the registration degree, and the target solution of the shaft parameters corresponding to the profilometer is obtained.

[0030] In one embodiment, the registration between the reconstruction result and the calibration block model is determined based on the distance between the target contour point and its nearest patch structure using a parameter-optimized residual function, including:

[0031] The parameter optimization residual function is used to determine the registration between the reconstruction result and the calibration block digital model based on the rotation matrix of the turntable angle corresponding to the target contour point, the projected three-dimensional coordinates, and the distance between the target contour point and its nearest patch structure.

[0032] In one embodiment, the expression of the parameter optimization residual function is as follows:

[0033] ;

[0034] in, is the alignment, is the total number of target contour points, is the distance between the target contour point and its nearest patch structure, It is the patch structure with the closest distance between the target contour point and the calibration block model. To calibrate the block digital model, For the The rotation matrix of the turntable angle corresponding to the target contour points, For the The projected three-dimensional coordinates corresponding to the target contour points, is the first transformation matrix, is the axis parameter to be solved in the first transformation matrix, is the second transformation matrix, to-be-solved rotation axis parameters in the second conversion matrix.

[0035] In a second aspect, the present application further provides a contour instrument rotation axis parameter calibration device based on a calibration block number module, the calibration block body is fixed on a rotary table, and the device comprises:

[0036] an image acquisition module, configured to trigger the contour instrument to acquire calibration block brightness images and calibration block height images corresponding to the calibration block body at fixed angle intervals in a process in which the rotary table drives the calibration block body to rotate;

[0037] a rotary table angle and projection coordinate determination module, configured to determine rotary table angles corresponding to each mark point center contained in the calibration block body and projection three-dimensional coordinates corresponding to the mark point center in a contour instrument coordinate system based on the calibration block brightness images and the calibration block height images;

[0038] an initial calibration module, configured to generate calibration block number modules corresponding to the calibration block body to determine real three-dimensional coordinates corresponding to each mark point center in a number module coordinate system, and to combine the rotary table angles corresponding to each mark point center and the projection three-dimensional coordinates to perform initial calibration on rotation axis parameters of the contour instrument to obtain initial solutions of the rotation axis parameters corresponding to the contour instrument;

[0039] an optimization module, configured to reconstruct a surface topography of the calibration block body, to construct a parameter optimization residual function based on a reconstruction result and the calibration block number module, and to optimize the initial solutions of the rotation axis parameters to obtain target solutions of the rotation axis parameters corresponding to the contour instrument.

[0040] In a third aspect, the present application further provides an electronic device comprising a processor and a memory, the memory stores computer executable instructions capable of being executed by the processor, and the processor executes the computer executable instructions to implement any one of the methods provided in the first aspect.

[0041] The application provides a profile instrument external parameter calibration method, device and equipment. First, in the process of rotating the calibration block body driven by the turntable, the turntable encoder triggers the profile instrument to collect the calibration block brightness map and the calibration block height map corresponding to the calibration block body at fixed angle intervals. Then, based on the calibration block brightness map and the calibration block height map, the turntable angle corresponding to each mark point center contained in the calibration block body and the corresponding projection three-dimensional coordinates in the profile instrument coordinate system are determined. Then, the calibration block number model corresponding to the calibration block body is generated to determine the real three-dimensional coordinates of each mark point center in the number model coordinate system. Combined with the turntable angle and the projection three-dimensional coordinates corresponding to each mark point center, the rotation shaft parameter of the profile instrument is initially calibrated to obtain the rotation shaft parameter initial solution of the profile instrument. Finally, the surface topography of the calibration block body is reconstructed, and based on the reconstruction result and the calibration block number model, a parameter optimization residual function is constructed to optimize the rotation shaft parameter initial solution to obtain the rotation shaft parameter target solution of the profile instrument. The above method directly obtains the turntable angle and the projection three-dimensional coordinates of the mark point center in the profile instrument coordinate system based on the calibration block brightness map and the calibration block height map, and then performs initial calibration of the rotation shaft parameter and parameter optimization based on the registration degree of the reconstruction result and the calibration block number model to obtain the rotation shaft parameter target solution of the profile instrument. The calibration precision can be effectively improved, and the shape and hardware installation condition posture of the calibration block are not strictly required, so that the manufacturing cost and difficulty of the calibration block are reduced.

[0042] Other features and advantages of the present application will be set forth in the descriptions below, and in part will be apparent from the description, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and attained by the structure particularly pointed out in the description, claims and drawings.

[0043] In order to make the above-mentioned objects, features and advantages of the present application more obvious and easy to understand, the following preferred embodiments are specifically described below, and the accompanying drawings are described in detail as follows. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the following will briefly introduce the drawings needed to be used in the specific embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0045] Figure 1 A flowchart of a profile instrument external parameter calibration method provided by an embodiment of the present application;

[0046] Figure 2 A technical framework diagram of a profile instrument external parameter calibration method provided by an embodiment of the present application;

[0047] Figure 3 A schematic diagram of a calibration block brightness map and a calibration block height map is provided for an embodiment of the present application.

[0048] Figure 4 A landmark point schematic diagram is provided for an embodiment of the present application.

[0049] Figure 5 A coordinate system relationship diagram is provided for an embodiment of the present application.

[0050] Figure 6 A rotation shaft parameter optimization flowchart is provided for an embodiment of the present application.

[0051] Figure 7 A structural schematic diagram of a profile instrument rotation shaft parameter calibration device based on a calibration block digital model is provided for an embodiment of the present application.

[0052] Figure 8 A structural schematic diagram of an electronic device is provided for an embodiment of the present application. DETAILED DESCRIPTION

[0053] To make the objectives, technical solutions and advantages of embodiments of the present application clearer, the technical solutions of the present application will be described below in connection with embodiments. Obviously, the described embodiments are only some, but not all, of the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of the present application.

[0054] At present, the existing rotation shaft calibration scheme has problems such as large error, too complex method, and high processing cost. Based on this, the present application provides a profile instrument external parameter calibration method, device and equipment, which can significantly improve the calibration accuracy of the profile instrument, and help to reduce the manufacturing cost and difficulty of the calibration block.

[0055] To facilitate the understanding of the present embodiment, first, a profile instrument external parameter calibration method disclosed by the present embodiment will be described in detail. The present embodiment focuses on the profile instrument external parameter calibration method and the rotation shaft calibration method, which can be used for hub blank size detection and internal appearance restoration. Specifically, the calibration block body is fixed on the rotary table, and a flowchart of a profile instrument external parameter calibration method is shown in Figure 1 The method mainly includes the following steps S102 to S108:

[0056] In step S102, in the process of rotating the calibration block body driven by the rotary table, the rotary table encoder triggers the profile instrument to collect the calibration block brightness map and the calibration block height map corresponding to the calibration block body at fixed angle intervals.

[0057] Wherein, the calibration block body has a mark point, the mark point is used for initial calibration, the calibration block is used for parameter optimization, the calibration points are uniformly distributed around the calibration block body, and are also uniformly distributed in the x-axis direction of the camera, which is reflected in the calibration block brightness map as being uniformly distributed in the row direction and the column direction. The calibration block brightness map is a conventional 8-bit integer or floating point map, and the calibration block height map is a floating point map. The size of the calibration block brightness map and the calibration block height map is consistent, and there is a one-to-one correspondence between the pixels, and the projection of the mark point in the calibration block body in the calibration block brightness map and the calibration block height map is approximately an elliptical shape.

[0058] In step S104, based on the calibration block brightness map and the calibration block height map, the rotation angle of each mark point center contained in the calibration block body and its corresponding projection three-dimensional coordinates in the profilometer coordinate system are determined.

[0059] In an example, the center of the ellipse can be fitted by the calibration block brightness map to obtain the projection pixel coordinates of each mark point center contained in the calibration block body in the calibration block brightness map (or the calibration block height map), and then the corresponding rotation angle and its corresponding projection three-dimensional coordinates in the profilometer coordinate system are determined based on the projection pixel coordinates.

[0060] In step S106, a calibration block number model corresponding to the calibration block body is generated to determine the real three-dimensional coordinates of each mark point center in the number model coordinate system, and the rotation shaft parameters of the profilometer are initially calibrated by combining the corresponding rotation angle and the projection three-dimensional coordinates of each mark point center to obtain the initial solution of the rotation shaft parameters of the profilometer.

[0061] Wherein, the calibration block number model, i.e. the mathematical model corresponding to the calibration block body, is composed of a patch structure for describing the surface of the calibration block body; the real three-dimensional coordinates of the mark point center in the number model coordinate system are known, and the real three-dimensional coordinates and the projection three-dimensional coordinates are one-to-one corresponding. In an example, the rotation coordinates corresponding to each rotation angle are determined, and the coordinate conversion model between the real three-dimensional coordinates and the projection three-dimensional coordinates is constructed by combining the conversion relationship between the rotation shaft coordinate system and the profilometer coordinate system, and the conversion relationship between the number model coordinate system and the rotation shaft coordinate system, wherein the conversion relationship between the rotation shaft coordinate system and the profilometer coordinate system, and the conversion relationship between the number model coordinate system and the rotation shaft coordinate system are to-be-solved rotation shaft parameters. Then, the rotation shaft parameter rough solution is searched by the particle swarm algorithm, and the initial solution of the rotation shaft parameters is obtained by nonlinear optimization of the rotation shaft parameter rough solution.

[0062] In step S108, the surface topography of the calibration block body is reconstructed, and the parameter optimization residual function is constructed based on the reconstruction result and the calibration block number model to optimize the initial solution of the rotation shaft parameters to obtain the target solution of the rotation shaft parameters corresponding to the profilometer.

[0063] The parameter optimization residual function is constructed based on the degree of registration between the reconstruction result and the calibration block digital model. The degree of registration is used to describe the distance from the midpoint of the reconstruction result to the surface of the calibration block digital model. In one example, the surface topography of the calibration block body is reconstructed to obtain a reconstruction result, which includes the reconstructed projected three-dimensional coordinates corresponding to the center of each marker point. After aligning the reconstructed projected three-dimensional coordinates to the digital model coordinate system, the patch structure closest to the marker point center is determined. Combining the real three-dimensional coordinates with the projected three-dimensional coordinates, the degree of registration between the reconstruction result and the calibration block digital model is determined. This is used to evaluate and nonlinearly optimize the initial solution of the axis parameters. The above process is repeated with the goal of minimizing the degree of registration to obtain the target solution of the axis parameters corresponding to the profilometer.

[0064] The method for calibrating the external parameters of a profiler provided in an embodiment of the present invention directly obtains the projected three-dimensional coordinates of the turntable angle and the center of the marker point in the profiler coordinate system based on the brightness map and height map of the calibration block, and performs initial calibration of the rotation axis parameters and parameter optimization based on the alignment between the reconstruction results and the digital model of the calibration block to obtain the target solution of the rotation axis parameters corresponding to the profiler. This method can not only effectively improve the calibration accuracy, but also has no mandatory requirements for the shape of the calibration block and the hardware installation conditions and posture, thereby helping to reduce the production cost and difficulty of the calibration block.

[0065] For ease of understanding, the present invention provides a specific implementation of a method for calibrating external parameters of a profiler. The profiler scans the brightness map and height map of the calibration block to obtain the marker points on the calibration block body. Turntable angle corresponding to the center and its projected three-dimensional coordinates in the corresponding contour coordinate system , perform axis parameters The initial calibration is performed, and the axis parameters are calculated by reconstructing the calibration block point cloud and calculating the registration degree of the calibration block point cloud to the calibration block digital model. Nonlinear optimization.

[0066] For details, see Figure 2 The technical framework diagram of a profilometer extrinsic parameter calibration method shown in FIG. 1 includes:

[0067] (1) Collect the calibration block brightness map and calibration block height map.

[0068] Fix the calibration block on the turntable. When the turntable drives the calibration block to rotate, the calibration block is rotated at a fixed angle. Trigger the laser line profiler to obtain the calibration block brightness map and calibration block height map, such as Figure 3 A schematic diagram of a calibration block brightness map and a calibration block height map is shown, Figure 3 (a) is the calibration block brightness map, (b) is the calibration block height map, and Figure 4 A schematic diagram of a landmark point is shown.

[0069] (2) Obtain the turntable angle corresponding to the center of the marker point and the corresponding projected 3D coordinates in the contour coordinate system. Specifically including:

[0070] (2.1) Based on the calibration block brightness map, fit the center coordinates of each elliptical shape contained in it as the center of each landmark point contained in the calibration block body Projected pixel coordinates on the calibration block brightness map or calibration block height map .

[0071] (2.2) Based on the projected pixel coordinates and the fixed angle interval, determine the turntable angle corresponding to the center of each landmark. In one example, the formula for calculating the turntable angle is as follows: ;

[0072] in, For the The turntable angle corresponding to the center of the landmark point, For the The horizontal coordinate of the projected pixel coordinates of the center of the marker point, Fixed angle interval.

[0073] (2.3) Based on the projected pixel coordinates, extract the neighboring pixels corresponding to the center of the marker from the calibration block height map, and use the height values ​​of the neighboring pixels to fit the height value corresponding to the center of the marker. Under the condition that the vertical coordinate value of the projected three-dimensional coordinate is 0, construct the projected three-dimensional coordinate corresponding to the center of the marker in the profilometer coordinate system based on the horizontal spacing of the pixels corresponding to the calibration block height map, the projected pixel coordinates, and the height value. The horizontal coordinate in the projected three-dimensional coordinate is the product of the horizontal spacing of the pixels and the horizontal coordinate of the projected pixel coordinate; the vertical coordinate in the projected three-dimensional coordinate is 0; and the vertical coordinate in the projected three-dimensional coordinate is the height value corresponding to the center of the marker.

[0074] In the specific implementation, the projected three-dimensional coordinates of the center of the marker point in the calibration block height map are used The height values ​​of nearby pixels (i.e., adjacent pixel points) are used to fit the projected three-dimensional coordinates The height value at ,Due to the nature of profilometer imaging, in the calibration block height map, The distance between each pixel in the direction is equidistant, that is, there is a known horizontal spacing between pixels. The projected three-dimensional coordinates of the center of the marker point in the profiler coordinate system can be calculated ,in This is because each frame profile (each row in the height map) is relative to the profilometer. In-plane.

[0075] (Three) combined with particle swarm optimization and nonlinear optimization to solve the initial solution of the rotation axis parameters.

[0076] First, the calibration block number model corresponding to the calibration block body is generated to determine the corresponding real three-dimensional coordinates of each landmark center in the number model coordinate system.

[0077] Then, combined with the corresponding rotation table angle and the projected three-dimensional coordinates of each landmark center, the rotation axis parameters of the profiler are initially calibrated to obtain the initial solution of the rotation axis parameters corresponding to the profiler. The real three-dimensional coordinates of the landmark center in the calibration block number model It is known that the landmark corresponds one-to-one to the projected three-dimensional coordinates in the calibration block height map , and referring to the coordinate system relationship diagram shown in Figure 5 , it can be seen that the real three-dimensional coordinates and the projected three-dimensional coordinates have the following relationship: ;

[0078] Among them, is the rotation matrix of the rotation table angle corresponding to the th landmark center, and its expression is as follows:

[0079] ;

[0080] is the first conversion matrix between the rotation axis coordinate system and the profiler coordinate system when the rotation axis is at the reference angle (θ0) , , is a three-dimensional rotation matrix, which can be transformed between the three-dimensional rotation matrix and the rotation vector through the Rodrigues transformation, is a displacement vector, which constitutes six unknowns ;

[0081] is the second conversion matrix between the number model coordinate system and the rotation axis coordinate system, which is the same as , and can be converted to constitute six unknowns .

[0082] Based on the above relationship, the following operations can be performed for any rotation table angle:

[0083] (3.1) Determine the rotation matrix corresponding to the rotation table angle.

[0084] (3.2) Based on the first conversion matrix between the rotation axis coordinate system and the profiler coordinate system, the second conversion matrix between the number model coordinate system and the rotation axis coordinate system, and the rotation matrix , construct a coordinate transformation model between real three-dimensional coordinates and projected three-dimensional coordinates. The first transformation matrix and the second transformation matrix in the coordinate transformation model are the axis parameters to be solved, that is, ;

[0085] (3.3) Generate a rough solution population, and use the fitness function to evaluate each rough solution of the axis parameter contained in the rough solution population based on the real three-dimensional coordinates and projected three-dimensional coordinates corresponding to the center of the landmark point, so as to update the rough solution population. When the preset conditions are met, the optimal rough solution of the axis parameter is determined from the updated rough solution population, and the optimal rough solution of the axis parameter is nonlinearly optimized to obtain the initial solution of the axis parameter corresponding to the profilometer.

[0086] In one example, a rough solution of the axis parameters can be obtained by using a particle swarm algorithm, where the following fitness function can be constructed as the fitness function of the particle swarm algorithm and the residual function of the nonlinear optimization:

[0087] ;

[0088] in, is the fitness value, is the total number of landmark centers contained in the calibration block body, For the The rotation matrix of the turntable angle corresponding to the center of the landmark point, For the The projected three-dimensional coordinates corresponding to the centers of the landmark points are: For the The real three-dimensional coordinates corresponding to the centers of the landmark points, is the first transformation matrix, is the axis parameter to be solved in the first transformation matrix, is the second transformation matrix, is the axis parameter to be solved in the second transformation matrix.

[0089] Searching for rough solutions of shaft parameters using particle swarm optimization Then, the initial solution of the shaft parameters is obtained by performing nonlinear optimization on the rough solution of the shaft parameters. .

[0090] (4) Calibration block surface topography reconstruction. The reconstruction process is as follows: Based on the calibration block height map at different angles, the corresponding local point cloud is obtained. The local point cloud is transformed into the same coordinate system. In this coordinate system, all local point clouds are spliced ​​to obtain the complete calibration block surface point cloud, which is then 3D reconstructed to obtain the calibration block surface topography.

[0091] (V) The alignment between the reconstruction result and the calibration block digital model is used as an evaluation index to optimize the axis parameters. In practical applications, due to the rotation angle positioning error of the turntable, the repeatability and linearity errors of the profilometer, and the projection method of the calibration block body to the calibration block brightness map in the system, the circular marker point is only an approximate ellipse in the calibration block brightness map. The center point coordinates obtained by ellipse fitting are not the correct projection of the marker point center. Therefore, the initial solution of the axis parameters is obtained. It is not the optimal solution. It is necessary to reconstruct the surface topography of the calibration block, calculate the distance (alignment) between the midpoint of the reconstruction result and the digital model of the calibration block as an evaluation index, and then perform nonlinear optimization on the initial solution of the axis parameters to obtain the target solution of the axis parameters. Specifically:

[0092] (6.1) The projection of the calibration block body in the calibration block height map is recorded as a contour point, and multiple target contour points are selected from the contour points. In one example, the number of selections and the thinning interval can be pre-set to thin out the contour points to select multiple target contour points, thereby reducing the computational complexity of the axis parameter calibration.

[0093] (6.2) Align the reconstructed projected three-dimensional coordinates corresponding to the target contour point to the digital model coordinate system to determine the patch structure with the closest distance between the target contour point and the calibration block digital model.

[0094] (6.3) Using the parameter optimization residual function, the registration degree between the reconstruction result and the calibration block digital model is determined based on the rotation matrix of the turntable angle corresponding to the target contour point, the projected three-dimensional coordinates, and the distance between the target contour point and its nearest patch structure. The initial solution of the axis parameters is optimized with the goal of minimizing the registration degree, and the target solution of the axis parameters corresponding to the profiler is obtained. The expression of the parameter optimization residual function is as follows:

[0095] ;

[0096] in, is the alignment, is the total number of target contour points, is the distance between the target contour point and its nearest patch structure, It is the patch structure with the closest distance between the target contour point and the calibration block model. To calibrate the block digital model, For the The rotation matrix of the turntable angle corresponding to the target contour points, For the The projected three-dimensional coordinates corresponding to the target contour points, is the first transformation matrix, is the axis parameter to be solved in the first transformation matrix, is the second transformation matrix, To-be-solved rotation axis parameters in the second conversion matrix.

[0097] Referring to Figure 6 An optimization flow chart of rotation axis parameters is shown in the figure, which includes: screening a proper number of target profile points as observation data, and calibrating a block number model as reference data; setting rotation axis parameter initial solution and nonlinear optimization parameters; performing nonlinear optimization on the rotation axis parameter initial solution; after reconstructing the surface topography of the calibration block and aligning to the block model coordinate system, calculating evaluation indexes as residuals; judging whether the optimization exit condition is reached, if not, continuing to perform nonlinear optimization on the rotation axis parameter initial solution, if yes, outputting rotation axis parameter target solution.

[0098] In summary, the profile instrument external parameter calibration method provided by the embodiment of the present application has at least the following characteristics: the same point data of the mark points is obtained in the height map and the brightness map directly according to the method, the system parameter initial value is solved, and then the system parameter is further optimized by using the block model, so that there is no forced requirement for the shape and overall hardware installation posture of the calibration block. When the workpiece is large, the calibration block can be processed in blocks and fixedly installed on the support, and then the accurate block model thereof is obtained through other ways (such as a three-dimensional scanner or a three-coordinate measuring instrument), so that the calibration can be performed, which can greatly reduce the manufacturing cost and difficulty of the calibration block. Since there is no requirement for the shape of the calibration block, the surface shape of the calibration block can be designed to enhance the constraint and reduce the posture deviation of the profile instrument caused by the weak or missing constraint in a specific direction in the method of using the standard ball, the standard cylinder or the stepped shaft.

[0099] On the basis of the foregoing embodiment, the embodiment of the present application provides a profile instrument external parameter calibration device, and the calibration block body is fixed on the rotary table, referring to Figure 7 A structure diagram of a profile instrument external parameter calibration device is shown in the figure, and the device mainly includes the following parts:

[0100] The image acquisition module 702 is configured to trigger the profile instrument to acquire the calibration block brightness map and the calibration block height map corresponding to the calibration block body at fixed angular intervals in a process in which the rotary table encoder triggers the profile instrument to rotate the calibration block body.

[0101] The rotary table angle and projection coordinate determination module 704 is configured to determine the rotary table angle corresponding to each mark point center contained in the calibration block body and the projection three-dimensional coordinate corresponding to each mark point center in the profile instrument coordinate system based on the calibration block brightness map and the calibration block height map.

[0102] The initial calibration module 706 is configured to generate the calibration block model corresponding to the calibration block body, to determine the real three-dimensional coordinate corresponding to each mark point center in the block model coordinate system, and to combine the rotary table angle corresponding to each mark point center and the projection three-dimensional coordinate to perform initial calibration on the rotation axis parameters of the profile instrument, to obtain the rotation axis parameter initial solution corresponding to the profile instrument.

[0103] The optimization module 708 is used to reconstruct the surface morphology of the calibration block body, construct a parameter optimization residual function based on the reconstruction result and the calibration block digital model, and optimize the initial solution of the axis parameters to obtain the target solution of the axis parameters corresponding to the profilometer.

[0104] The contour meter axis parameter calibration device based on the calibration block digital model provided by the embodiment of the present invention directly obtains the projected three-dimensional coordinates of the turntable angle and the center of the mark point in the contour meter coordinate system based on the calibration block brightness map and the calibration block height map, and performs initial calibration of the axis parameters and parameter optimization based on the alignment between the reconstruction results and the calibration block digital model on this basis to obtain the target solution of the axis parameters corresponding to the contour meter. This can not only effectively improve the calibration accuracy, but also has no mandatory requirements on the shape of the calibration block and the hardware installation conditions and posture, thereby helping to reduce the production cost and difficulty of the calibration block.

[0105] In one embodiment, the turntable angle and projection coordinate determination module 704 is specifically configured to:

[0106] Based on the calibration block brightness map, the center coordinates of each elliptical shape contained therein are fitted as the projected pixel coordinates of the center of each marker point contained in the calibration block body on the calibration block brightness map or the calibration block height map;

[0107] Determine the turntable angle corresponding to the center of each marker point based on the projected pixel coordinates and the fixed angle interval;

[0108] In addition, based on the projected pixel coordinates, the neighboring pixel points corresponding to the center of the marker point are extracted from the calibration block height map, and the height values ​​of the neighboring pixel points are used to fit the height value corresponding to the center of the marker point; under the condition that the vertical coordinate value of the projected three-dimensional coordinate is 0, the projected three-dimensional coordinates corresponding to the center of the marker point in the profilometer coordinate system are constructed based on the horizontal spacing, projected pixel coordinates and height values ​​of the pixels corresponding to the calibration block height map.

[0109] In one embodiment, the horizontal coordinate in the projected three-dimensional coordinate is the product of the horizontal spacing of the pixel points and the horizontal coordinate of the projected pixel coordinate; the vertical coordinate in the projected three-dimensional coordinate is 0; and the vertical coordinate in the projected three-dimensional coordinate is the height value corresponding to the center of the marker point.

[0110] In one embodiment, the initial calibration module 706 is specifically configured to:

[0111] For any turntable angle, do the following:

[0112] Determine the rotation matrix corresponding to the turntable angle;

[0113] The first conversion matrix between the rotation axis coordinate system and the coordinate system of the profiler, the second conversion matrix between the digital model coordinate system and the rotation axis coordinate system, and the rotation matrix are used to construct a coordinate conversion model between the real three-dimensional coordinates and the projected three-dimensional coordinates, and the first conversion matrix and the second conversion matrix in the coordinate conversion model are the rotation axis parameters to be solved;

[0114] A rough solution population is generated, and each rotation axis parameter rough solution in the rough solution population is evaluated based on the real three-dimensional coordinates and the projected three-dimensional coordinates corresponding to the center of the marker point by using a fitness function, so as to update the rough solution population until the optimal rotation axis parameter rough solution is determined from the updated rough solution population when a preset condition is met;

[0115] The optimal rotation axis parameter rough solution is subjected to nonlinear optimization to obtain the initial solution of the rotation axis parameters corresponding to the profiler.

[0116] In an embodiment, the fitness function of the particle swarm algorithm and the residual function of the nonlinear optimization are as follows:

[0117] ;

[0118] Wherein, is a fitness value, is the total number of marker point centers included in the calibration block body, is the rotation matrix of the rotation angle corresponding to the i-th marker point center, is the projected three-dimensional coordinate corresponding to the i-th marker point center, is the real three-dimensional coordinate corresponding to the i-th marker point center, is the first conversion matrix, is the rotation axis parameter to be solved in the first conversion matrix, is the second conversion matrix, is the rotation axis parameter to be solved in the second conversion matrix. In an embodiment, the reconstruction result includes the reconstructed projected three-dimensional coordinates corresponding to each marker point center; and the optimization module 708 is specifically configured to: The projection of the calibration block body in the calibration block height map is recorded as a contour point, and a plurality of target contour points are selected from the contour point;

[0119] The reconstructed projected three-dimensional coordinates corresponding to the target contour points are aligned to the digital model coordinate system to determine the closest sheet structure of the target contour points and the digital model of the calibration block;

[0120]

[0121]

[0122] ​​​The parameter optimization residual function is used to determine the registration degree between the reconstruction result and the calibration block model based on the distance between the target contour point and the nearest patch structure, and the initial solution of the rotation axis parameter is optimized with the minimum registration degree as the target to obtain the target solution of the rotation axis parameter corresponding to the profilometer.

[0123] In an embodiment, the optimization module 708 is specifically configured to:

[0124] The parameter optimization residual function is used to determine the registration degree between the reconstruction result and the calibration block model based on the rotation matrix of the target contour point corresponding to the rotation table angle, the projected three-dimensional coordinates, and the distance between the target contour point and the nearest patch structure.

[0125] In an embodiment, the expression of the parameter optimization residual function is as follows:

[0126] ;

[0127] wherein, is the registration degree, is the total number of target contour points, is the distance between the target contour point and the nearest patch structure, is the target contour point and the nearest patch structure in the calibration block model, is the calibration block model, is the rotation matrix of the target contour point corresponding to the rotation table angle, is the projected three-dimensional coordinates corresponding to the target contour point, is the first conversion matrix, is the rotation axis parameter to be solved in the first conversion matrix, is the second conversion matrix, is the rotation axis parameter to be solved in the second conversion matrix. The device provided by the embodiment of the present application has the same implementation principle and technical effects as the foregoing method embodiment, and for brevity of description, the part not mentioned in the device embodiment can be referred to the corresponding content in the foregoing method embodiment.

[0128] The embodiment of the present application provides an electronic device, specifically, the electronic device comprises a processor and a storage device; the storage device stores a computer program, and the computer program performs the method of any one of the above embodiments when being run by the processor.

[0129] The embodiment of the present application provides an electronic device, specifically, the electronic device comprises a processor and a storage device; the storage device stores a computer program, and the computer program performs the method of any one of the above embodiments when being run by the processor.

[0130] Figure 8 ​A structural schematic diagram of an electronic device provided by the embodiment of the present application is shown in the figure, which comprises a processor 80, a memory 81, a bus 82 and a communication interface 83, and the processor 80, the communication interface 83 and the memory 81 are connected through the bus 82; the processor 80 is used for executing the executable modules stored in the memory 81, such as computer programs.

[0131] The memory 81 can contain a high-speed random access memory (RAM), and can also contain a non-volatile memory, such as at least one disk memory. The communication connection between the system network element and at least one other network element is realized through at least one communication interface 83 (which can be wired or wireless), and the Internet, a wide area network, a body network, a metropolitan area network, etc. can be used.

[0132] The bus 82 can be an ISA bus, a PCI bus or an EISA bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For the convenience of representation, Figure 8 Only one bidirectional arrow is used to represent the bus in the figure, but it does not mean that there is only one bus or one type of bus.

[0133] The memory 81 is used for storing programs, and the processor 80 executes the programs after receiving execution instructions. The method executed by the device defined by the flow process disclosed in any of the foregoing embodiments of the present application can be applied to the processor 80 or realized by the processor 80.

[0134] The processor 80 can be an integrated circuit chip with signal processing capability. In implementation, each step of the above method can be completed by integrated logic circuit of hardware in the processor 80 or by instructions in the form of software. The processor 80 described above can be a general processor, including a central processing unit (CPU), a network processor (NP), etc.; can also be a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component. Each method, step and logic block diagram disclosed in the embodiments of the present application can be implemented or executed. The general processor can be a microprocessor or the processor can also be any conventional processor. The steps of the method disclosed in combination with the embodiments of the present application can be directly embodied as a hardware code processor for execution, or a combination of hardware and software modules in the code processor for execution. The software module can be located in a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium in the art. The storage medium is located in the memory 81, and the processor 80 reads the information in the memory 81, and combines the hardware to complete the steps of the above method.

[0135] The computer program product of the readable storage medium provided by the embodiments of the present application comprises a computer readable storage medium storing program codes, and the program codes comprise instructions for executing the method described in the foregoing method embodiments. For specific implementation, reference can be made to the foregoing method embodiments, which will not be described here.

[0136] If the functions are realized in the form of software function units and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, the technical solutions of the present application or the parts of the present application that essentially contribute to the prior art or the parts of the technical solutions can be embodied in the form of software products. The computer software product is stored in a storage medium and includes instructions for making a computer device (which can be a personal computer, a server, or a network device, etc.) execute all or part of the steps of the method described in the embodiments of the present application. The aforementioned storage medium includes: a U disk, a mobile hard disk, a read-only memory (ROM, Read-Only Memory), a random access memory (RAM, Random Access Memory), a magnetic disk or an optical disk, and various media that can store program codes.

[0137] Finally, it should be noted that: the above-described embodiments are only specific embodiments of the present application, which are used to illustrate the technical solutions of the present application, but not to limit them. The protection scope of the present application is not limited to this. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can modify or easily think of changes to the technical solutions recorded in the foregoing embodiments within the technical range disclosed by the present application, or make equivalent replacements to some technical features. The modifications, changes or replacements do not make the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for calibrating external parameters of a profiler, characterized in that: The calibration block body is fixed on a turntable, and the method includes: In the process of the turntable driving the calibration block body to rotate, the turntable encoder triggers the profilometer to collect the calibration block brightness image and the calibration block height image corresponding to the calibration block body at fixed angle intervals; Based on the calibration block brightness map and the calibration block height map, determining the turntable angle corresponding to the center of each marker point contained in the calibration block body and its corresponding projected three-dimensional coordinates in the profiler coordinate system, including: fitting the center coordinates of each elliptical shape contained therein based on the calibration block brightness map as the projected pixel coordinates of the center of each marker point contained in the calibration block body on the calibration block brightness map or the calibration block height map; determining the turntable angle corresponding to the center of each marker point based on the projected pixel coordinates and the fixed angle interval; and extracting the neighboring pixel points corresponding to the center of the marker point from the calibration block height map based on the projected pixel coordinates; fitting the height value corresponding to the center of the marker point using the height values ​​of the neighboring pixel points; and constructing the projected three-dimensional coordinates corresponding to the center of the marker point in the profiler coordinate system based on the horizontal spacing of the pixels corresponding to the calibration block height map, the projected pixel coordinates and the height value, under the condition that the vertical coordinate value of the projected three-dimensional coordinate is 0; Generate a digital model of the calibration block corresponding to the calibration block body to determine the real three-dimensional coordinates corresponding to the center of each marker point in the digital model coordinate system, combine the turntable angle and the projected three-dimensional coordinates corresponding to each marker point center, and perform an initial calibration on the axis parameters of the profiler to obtain an initial solution for the axis parameters corresponding to the profiler; The surface topography of the calibration block body is reconstructed, and a parameter optimization residual function is constructed based on the reconstruction result and the calibration block digital model. The initial solution of the shaft parameters is optimized to obtain the target solution of the shaft parameters corresponding to the profilometer.

2. The method for calibrating external parameters of a profiler according to claim 1, characterized in that: The horizontal coordinate in the projected three-dimensional coordinate is the product of the horizontal spacing of the pixel points and the horizontal coordinate of the projected pixel coordinate; the vertical coordinate in the projected three-dimensional coordinate is 0; and the vertical coordinate in the projected three-dimensional coordinate is the height value corresponding to the center of the marker point.

3. The method for calibrating external parameters of a profiler according to claim 1, characterized in that: Combining the turntable angle and the projected three-dimensional coordinates corresponding to the center of each marker point, the rotation axis parameters of the profiler are initially calibrated to obtain an initial solution of the rotation axis parameters corresponding to the profiler, including: For any of the mentioned turntable angles, do the following: Determine the rotation matrix corresponding to the turntable angle; Based on a first conversion matrix between the rotation axis coordinate system and the profilometer coordinate system, a second conversion matrix between the digital-analog coordinate system and the rotation axis coordinate system, and the rotation matrix, a coordinate conversion model between the real three-dimensional coordinates and the projected three-dimensional coordinates is constructed, where the first conversion matrix and the second conversion matrix in the coordinate conversion model are the rotation axis parameters to be solved; generating a rough solution population, and evaluating each rough solution of the rotation axis parameter contained in the rough solution population based on the real three-dimensional coordinates and the projected three-dimensional coordinates corresponding to the center of the landmark point using a fitness function, so as to update the rough solution population until a preset condition is satisfied and an optimal rough solution of the rotation axis parameter is determined from the updated rough solution population; The optimal rough solution of the rotation axis parameters is subjected to nonlinear optimization to obtain an initial solution of the rotation axis parameters corresponding to the profilometer.

4. The method for calibrating external parameters of a profiler according to claim 3, characterized in that: The fitness function of the particle swarm algorithm and the residual function of nonlinear optimization are as follows: ； in, is the fitness value, is the total number of landmark centers contained in the calibration block body, For the The rotation matrix of the turntable angle corresponding to the center of each of the marker points, For the The projected three-dimensional coordinates corresponding to the centers of the marker points, For the The real three-dimensional coordinates corresponding to the centers of the marker points, is the first transformation matrix, is the axis parameter to be solved in the first transformation matrix, is the second transformation matrix, is the axis parameter to be solved in the second transformation matrix.

5. The method for calibrating external parameters of a profiler according to claim 1, characterized in that: The reconstruction result includes the reconstructed projected three-dimensional coordinates corresponding to the center of each of the marker points; a parameter optimization residual function is constructed based on the reconstruction result and the calibration block digital model, and the initial solution of the axis parameters is optimized to obtain the target solution of the axis parameters corresponding to the profilometer, including: Recording the projection of the calibration block body in the calibration block height map as contour points, and screening a plurality of target contour points from the contour points; Aligning the reconstructed projected three-dimensional coordinates corresponding to the target contour point to the digital model coordinate system to determine the patch structure with the closest distance between the target contour point and the calibration block digital model; By using the parameter optimization residual function, the alignment between the reconstruction result and the calibration block digital model is determined based on the distance between the target contour point and its nearest patch structure. The initial solution of the axis parameters is optimized with the goal of minimizing the alignment, and the target solution of the axis parameters corresponding to the contour meter is obtained.

6. The method for calibrating external parameters of a profiler according to claim 5, characterized in that: Determining the degree of registration between the reconstruction result and the calibration block digital model based on the distance between the target contour point and the nearest patch structure using a parameter-optimized residual function includes: By using parameter-optimized residual functions, the degree of registration between the reconstruction result and the calibration block digital model is determined based on the rotation matrix of the turntable angle corresponding to the target contour point, the projected three-dimensional coordinates, and the distance between the target contour point and its nearest patch structure.

7. The method for calibrating external parameters of a profilometer according to claim 5 or 6, characterized in that: The expression of the parameter optimization residual function is as follows: ； in, is the alignment, is the total number of target contour points, is the distance between the target contour point and its nearest patch structure, is the patch structure with the closest distance between the target contour point and the calibration block model, To calibrate the block digital model, For the The rotation matrix of the turntable angle corresponding to each of the target contour points, For the The projected three-dimensional coordinates corresponding to the target contour points, is the first transformation matrix, is the axis parameter to be solved in the first transformation matrix, is the second transformation matrix, is the axis parameter to be solved in the second transformation matrix.

8. A device for calibrating external parameters of a profiler, characterized in that: The calibration block body is fixed on the turntable, and the device includes: An image acquisition module is configured to, when the turntable drives the calibration block body to rotate, trigger the profilometer to acquire a calibration block brightness image and a calibration block height image corresponding to the calibration block body at fixed angle intervals; A turntable angle and projection coordinate determination module, for determining the turntable angle corresponding to the center of each marker point included in the calibration block body and its corresponding projected three-dimensional coordinates in the profiler coordinate system based on the calibration block brightness map and the calibration block height map, including: fitting the center coordinates of each elliptical shape included therein based on the calibration block brightness map as the projected pixel coordinates of the center of each marker point included in the calibration block body on the calibration block brightness map or the calibration block height map; determining the turntable angle corresponding to the center of each marker point based on the projected pixel coordinates and the fixed angle interval; and extracting the neighboring pixels corresponding to the center of the marker point from the calibration block height map based on the projected pixel coordinates; fitting the height value corresponding to the center of the marker point using the height values ​​of the neighboring pixels; and constructing the projected three-dimensional coordinates corresponding to the center of the marker point in the profiler coordinate system based on the horizontal spacing of the pixels corresponding to the calibration block height map, the projected pixel coordinates and the height value, under the condition that the vertical coordinate value of the projected three-dimensional coordinate is 0; An initial calibration module is used to generate a calibration block digital model corresponding to the calibration block body to determine the real three-dimensional coordinates corresponding to the center of each marker point in the digital model coordinate system, and to perform an initial calibration on the axis parameters of the profiler by combining the turntable angle and the projected three-dimensional coordinates corresponding to each marker point center to obtain an initial solution for the axis parameters corresponding to the profiler; The optimization module is used to reconstruct the surface morphology of the calibration block body, construct a parameter optimization residual function based on the reconstruction result and the calibration block digital model, and optimize the initial solution of the shaft parameters to obtain the target solution of the shaft parameters corresponding to the profilometer.

9. An electronic device, characterized in that: The method comprises a processor and a memory, wherein the memory stores computer-executable instructions that can be executed by the processor, and the processor executes the computer-executable instructions to implement the method according to any one of claims 1 to 7.

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