Automatic calibration method, device and equipment in line laser three-dimensional measurement system

Abstract

The invention discloses an automatic calibration method, device and equipment in a line laser three-dimensional measurement system, and the method comprises the steps: selecting a calibration target, fixing the calibration target, and building a calibration target composed of the calibration target and an automatic displacement device; controlling the automatic displacement device to move the calibration target to form feature points; establishing a three-dimensional world coordinate system, and obtaining three-dimensional world coordinate information of each feature point; acquiring a calibration image by a camera, and performing digital image processing on the calibration image to obtain pixel coordinates of feature points; establishing a direct mapping model of an image plane and a light plane according to the pixel coordinates of the feature points and the corresponding three-dimensional world coordinate information; adopting a least square method to calculate homography matrix parameters of the direct mapping model; calculating line laser three-dimensional measurement system parameters as related system parameters according to the input equipment parameters; and according to related system parameters, correcting homography matrix parameters. According to the invention, errors caused by manual calibration are solved, and the calibration efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of three-dimensional measurement, in particular to an automatic calibration method, device and equipment in a line laser three-dimensional measurement system. BACKGROUND

[0002] In recent years, with the continuous development and integration of optical, sensor and measurement theory technologies, it has become feasible to realize automatic measurement of objects. Line structured light vision measurement technology has the characteristics of high measurement accuracy, good real-time performance and strong anti-interference ability, and has a wide range of applications in industrial measurement, three-dimensional reconstruction, reverse engineering and other fields. In these applications, it is crucial to quickly and accurately extract the three-dimensional data of the object contour. In the process of calculating the three-dimensional contour information of an object, the mapping relationship between the two-dimensional image plane and the three-dimensional space needs to be obtained, and the actual three-dimensional contour information of the object is solved. The process of solving this mapping relationship is called system calibration. Due to complex measurement environments and product structures and other factors, the requirements for measuring object three-dimensional contour equipment tend to be convenient, high-precision and intelligent.

[0003] However, most existing calibration methods use manual calibration, which has the problems of insufficient precision, low calibration efficiency and other problems caused by manual calibration errors. SUMMARY

[0004] The technical problem to be solved by the present application is the insufficient precision and low calibration efficiency caused by the existing calibration method. The present application aims to provide an automatic calibration method, device and equipment in a line laser three-dimensional measurement system. The calibration device is placed in the line laser three-dimensional measurement system, and the parameters can be set by the host computer to automatically control the operation of the calibration device for calibration. Some parameters in the calibration steps can be adjusted according to the requirements to obtain the homography matrix under different conditions and improve the calibration efficiency. The present application solves the errors caused by manual calibration, can set parameters according to requirements, obtains a suitable homography matrix, and improves the calibration efficiency.

[0005] The present application is realized by the following technical solutions:

[0006] In a first aspect, the present application provides an automatic calibration method in a line laser three-dimensional measurement system, which comprises:

[0007] Selecting a calibration target and fixing the calibration target to establish a calibration target composed of the calibration target and an automatic displacement device;

[0008] Controlling the automatic displacement device to move the calibration target to form feature points;

[0009] Establishing a three-dimensional world coordinate system to obtain three-dimensional world coordinate information of each feature point;

[0010] The camera acquires a calibration image, and a digital image processing is performed on the calibration image to obtain feature point pixel coordinates;

[0011] According to the feature point pixel coordinates and corresponding three-dimensional world coordinate information, a direct mapping model of the image plane and the light plane is established, and a homography matrix parameter of the direct mapping model is calculated by using a least square method;

[0012] According to the input device parameters, a linear laser three-dimensional measurement system parameter is calculated as a related system parameter;

[0013] According to the related system parameter, the homography matrix parameter is corrected to obtain a calibration result and store all parameters.

[0014] Further, the calibration target is selected, including:

[0015] According to the laser reflection characteristics and the requirements of the linear laser three-dimensional measurement system, an optical glass plate with ceramic material is selected as the calibration target;

[0016] The shape of the calibration target is a stripe type, and the width between the stripes is equal to the stripe pitch.

[0017] Further, the calibration target is fixed, and a calibration target mark composed of the calibration target and an automatic displacement device is established, including:

[0018] The calibration target is fixed on the automatic displacement device, and the automatic displacement device is fixed on the linear laser three-dimensional measurement device, so that the calibration target mark plane is parallel to the measured plane;

[0019] The scale of the automatic displacement device is set to zero, and the plane where the calibration target is located is taken as a reference surface to establish the calibration target mark composed of the calibration target and the automatic displacement device.

[0020] Further, the automatic displacement device is controlled to move the calibration target to form feature points, including:

[0021] The automatic displacement device drives the calibration target to move a preset number of times and a preset distance in the vertical direction and parallel to the laser line direction, respectively;

[0022] After each movement of the automatic displacement device, the camera in the linear laser three-dimensional measurement system acquires a calibration image, so that feature point information at different positions is obtained to form a plurality of feature points of the entire light plane.

[0023] Further, a three-dimensional world coordinate system is established to obtain three-dimensional world coordinate information of each feature point, including:

[0024] The position of the calibration target mark is adjusted so that the calibration image is completely located within the field of view of the camera;

[0025] The intersection of the left laser stripe in the camera field of view and the first stripe of the calibration target is the first feature point, and the first feature point is defined as the origin of the three-dimensional world coordinate system;

[0026] Based on the origin of the three-dimensional world coordinate system, three coordinate axes X, Y and Z of the three-dimensional world coordinate system are established: the straight line where the feature points on the calibration target are located is the X axis, the Y axis is perpendicular to the X axis and perpendicular to the light plane where the laser is located, and the Z axis is perpendicular to the X axis and parallel to the light plane;

[0027] Based on the three-dimensional world coordinate system, the X-axis coordinate, Y-axis coordinate and Z-axis coordinate of each feature point in the three-dimensional world coordinate system are obtained.

[0028] Further, the camera captures the calibration image, and the calibration image is subjected to digital image processing to obtain the feature point pixel coordinates, including:

[0029] The camera captures the calibration image, and the calibration image is subjected to image sharpness evaluation to eliminate calibration images that do not meet the requirements, thereby obtaining the first calibration image;

[0030] The first calibration image is preprocessed to obtain the preprocessed first calibration image;

[0031] The preprocessed first calibration image is subjected to stripe straight line extraction and light stripe center line extraction, respectively, to obtain the calibration target image stripe straight line and the light stripe center line;

[0032] According to the calibration target image stripe straight line and the light stripe center line, the equations of the two straight lines are calculated, the intersection information of the two straight lines is calculated, that is, the feature point pixel coordinates are calculated, and the coordinates that do not belong to the feature points are removed;

[0033] After the processing of all images is completed, the feature point pixel coordinates are sorted according to the number of the images captured by the camera, and are one-to-one corresponding to the actual three-dimensional world coordinates.

[0034] Further, the preprocessed first calibration image is subjected to stripe straight line extraction to obtain the calibration target image stripe straight line, including:

[0035] According to the preprocessed first calibration image, the target stripe image is subjected to Canny algorithm rough extraction to obtain the image edge;

[0036] After rough extraction, the Devernay algorithm is used for sub-pixel correction of the image;

[0037] The information of the image edge is subjected to stripe straight line extraction, and the LSD algorithm is used for straight line detection;

[0038] The linear detection using the LSD algorithm is specifically as follows: all points with small gradient direction change and adjacent points are taken as a connected domain, whether the connected domain needs to be disconnected to form multiple domains with larger rectangularity is judged according to the rectangularity of each domain, all generated domains are screened, and the domain meeting the condition is reserved, that is, the linear information of the image.

[0039] According to the above process, the required vertical stripe lines are screened, and parallelism detection is performed on the vertical stripe lines, so as to ensure that the lines are parallel to each other as much as possible.

[0040] Further, the light strip center line is extracted from the preprocessed first calibration image to obtain the light strip center line, including:

[0041] According to the preprocessed first calibration image, the image ROI region is extracted;

[0042] According to the image ROI region, the light strip and the image background are segmented, and each column of light strip region is screened through a threshold value;

[0043] According to the screened each column of light strip region, the light strip center line is extracted by using the gray center method;

[0044] The calculation formula of each center point in the light strip center line is:

[0045] ;

[0046] Wherein, is the sub-pixel center point obtained in the i-th column, is the gray value of the image pixel point , and M is the pixel number of the i-th column of the light strip region.

[0047] In the second aspect, the application further provides an automatic calibration device in a linear laser three-dimensional measurement system, which comprises:

[0048] A calibration target establishment unit is configured to select a calibration target object, fix the calibration target object, and establish a calibration target composed of the calibration target object and an automatic displacement device;

[0049] A feature point forming unit is configured to control the automatic displacement device to move the calibration target object to form a feature point;

[0050] A coordinate information acquisition unit is configured to establish a three-dimensional world coordinate system and acquire three-dimensional world coordinate information of each feature point;

[0051] A digital image processing unit is configured to acquire a calibration image by a camera, perform digital image processing on the calibration image, and obtain a feature point pixel coordinate;

[0052] A homographic matrix parameter calculation unit is configured to establish a direct mapping model of an image plane and a light plane according to the pixel coordinates of the feature points and the corresponding three-dimensional world coordinate information, and to calculate the homographic matrix parameters of the direct mapping model by using a least square method.

[0053] A related system parameter calculation unit is configured to calculate the line laser three-dimensional measurement system parameters as the related system parameters according to the input device parameters.

[0054] A correction unit is configured to correct the homographic matrix parameters according to the related system parameters, to obtain the calibration results and to store all the parameters.

[0055] In a third aspect, the present application further provides an automatic calibration device in a line laser three-dimensional measurement system, which comprises a one-dimensional motion platform, an automatic displacement device, a calibration target, a line laser three-dimensional measurement system and an upper computer program.

[0056] In a fourth aspect, the present application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to realize the automatic calibration method in the line laser three-dimensional measurement system.

[0057] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0058] The automatic calibration method, device and equipment in the line laser three-dimensional measurement system of the present application directly establish a mapping model of the pixel coordinates of the feature points and the three-dimensional world coordinates, use the automatic displacement device to control the movement of the calibration target during the calibration process, do not need manual intervention, simplify the calibration process, are suitable for most application scenarios, correct the calibration parameters according to the system indicators, and improve the calibration precision and the calibration efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0059] The accompanying drawings, which are included to provide a further understanding of the embodiments of the present application and constitute a part of the application, illustrate embodiments of the present application and do not constitute a limitation to the present application. In the drawings:

[0060] Figure 1 A flow chart of the automatic calibration method in the line laser three-dimensional measurement system of the present application;

[0061] Figure 2 A schematic diagram of the shape of the calibration target of the present application;

[0062] Figure 3 A calibration schematic diagram of the line laser three-dimensional measurement system of the present application;

[0063] Figure 4A detailed flow chart of the automatic calibration method in the line laser three-dimensional measurement system of the present application is shown in the figure.

[0064] Figure 5 A structure block diagram of the automatic calibration device in the line laser three-dimensional measurement system of the present application is shown in the figure.

[0065] Figure 6 A structure diagram of the automatic calibration equipment in the line laser three-dimensional measurement system of the present application is shown in the figure. DETAILED DESCRIPTION

[0066] In order to make the purpose, technical scheme and advantages of the present application more clear and explicit, the present application is further described in detail below in combination with examples and drawings, and the schematic implementation mode and its description of the present application are only used for explaining the present application, and do not limit the present application.

[0067] The present application adopts a device capable of automatically controlling the calibration target for automatic calibration, and uses a sub-pixel level image processing algorithm, so that the system calibration can be performed with higher precision and more convenience.

[0068] In practical application, the automatic calibration method in the line laser three-dimensional measurement system can be realized by a computer program; or the method can also be realized as a medium having a related computer program stored therein, such as a U disk, a cloud disk and the like; or the method can also be realized by an entity device integrated or installed with a related computer program, such as a chip, a ball-mounted mobile intelligent device and the like.

[0069] Example 1

[0070] As shown in Figure 1 and Figure 4 , the automatic calibration method in the line laser three-dimensional measurement system of the present application comprises the following steps.

[0071] Step 1, selecting a calibration target object and fixing the calibration target object to establish a calibration target composed of the calibration target object and an automatic displacement device.

[0072] In this embodiment, the calibration target object is selected, specifically as follows.

[0073] The calibration scheme adopted by the method of the present application is to take the intersection points of the calibration plate profile and the line laser center line as the calibration target, and to calculate the mapping relationship between the target at different heights and the corresponding pixel position; according to the laser reflection characteristics and the requirements of the line laser three-dimensional measurement system, an optical glass plate with ceramic material is selected as the calibration target object; wherein the shape of the calibration target object is stripe type, and the width and the pitch between the stripes are equal, as shown in Figure 2 .

[0074] In this embodiment, the calibration target object is fixed to establish a calibration target composed of the calibration target object and an automatic displacement device, including the following steps.

[0075] Fix the calibration target on the automatic displacement device, and fix the automatic displacement device on the line laser three-dimensional measurement device, so that the calibration target plane is parallel to the measured plane;

[0076] Set the scale of the automatic displacement device to zero, and take the plane where the calibration target is located as the reference surface, to establish the calibration target composed of the calibration target and the automatic displacement device.

[0077] Step 2, control the automatic displacement device to move the calibration target to form feature points;

[0078] In this embodiment, step 2 specifically includes:

[0079] The line laser emits a line of laser light, and the projected light bar forms a laser line on the calibration target. The intersection of the line laser and the stripe image on the calibration target is the feature point located on a straight line. The required number of rows and columns of feature points and the displacement distance each time are set on the host computer program. After starting, the automatic displacement device drives the calibration target to move a certain number of times and a certain distance in the vertical direction and parallel to the laser line direction; after each movement of the automatic displacement device, the camera in the line laser three-dimensional measurement system captures a calibration image, so as to obtain the feature point information at different positions, thereby forming a plurality of feature points of the entire light plane, as shown in Figure 3 .

[0080] Step 3, establish a three-dimensional world coordinate system to obtain three-dimensional world coordinate information of each feature point;

[0081] In this embodiment, step 3 specifically includes:

[0082] Step 31, adjust the position of the calibration target so that the calibration image is completely located in the camera field of view;

[0083] Step 32, the intersection of the left laser stripe and the first stripe of the calibration target in the camera field of view is the first feature point, and the first feature point is defined as the origin of the three-dimensional world coordinate system;

[0084] Step 33, based on the origin of the three-dimensional world coordinate system, establish three coordinate axes X axis, Y axis and Z axis of the three-dimensional world coordinate system: the straight line where the feature points on the calibration target are located is the X axis, the Y axis is perpendicular to the X axis and perpendicular to the light plane where the line laser is located, and the Z axis is perpendicular to the X axis and parallel to the light plane; as shown in Figure 3 .

[0085] Step 34, based on the three-dimensional world coordinate system, obtain the X axis coordinate, Y axis coordinate and Z axis coordinate of each feature point in the three-dimensional world coordinate. Specifically:

[0086] (1) Obtain the X-axis coordinate of each feature point in the three-dimensional world coordinate. Because the width of the stripe on the calibration target and the distance between the stripes are equal, the X-axis coordinate of all feature points in the first image can be calculated according to the distance relationship between the first feature point and the other feature points, i.e., the position relationship between the origin of the three-dimensional world coordinate system and the other feature points. In subsequent calibration images, according to the number of movements in the X-axis direction and the single movement distance parameters set in the automatic displacement device before calibration, the X-axis coordinates of all feature points can be calculated.

[0087] (2) Obtain the Z-axis coordinate of each feature point in the three-dimensional world coordinate. According to the number of vertical upward movements in the Z-axis direction and the single movement distance parameters set in the automatic displacement device before calibration, the Z-axis coordinates of all feature points can be calculated.

[0088] (3) Obtain the Y-axis coordinate of each feature point in the three-dimensional world coordinate. Because the calibration target will not move in the Y direction, according to the established three-dimensional world coordinate system, the Y-axis coordinates of all feature points are equal to 0. In the actual measurement process, the Y-axis of the world coordinate system is calculated by the camera's acquisition rate and the number of frames. Finally, the three-dimensional world coordinates (X, Y, Z) of the feature points are obtained.

[0089] Step 4, the camera acquires the calibration image, and the calibration image is subjected to digital image processing to obtain the pixel coordinates of the feature points;

[0090] In this embodiment, step 4 specifically includes:

[0091] Step 41, the camera acquires the calibration image, and the calibration image is subjected to image sharpness evaluation, and the calibration image that does not meet the requirements is removed to obtain the first calibration image;

[0092] Specifically, the camera acquires an image of the calibration target once the automatic displacement device changes its position each time, and the acquired image is numbered according to the set parameter information, so as to correspond to its three-dimensional world coordinates. The acquired calibration image is subjected to sharpness evaluation, and the variance function is selected as the evaluation function. The formula is as follows:

[0093]

[0094] wherein, is the average value of the image gray scale.

[0095] According to the image quality, the calibration image that does not meet the requirements is removed to obtain the first calibration image.

[0096] Step 42, the first calibration image is preprocessed to obtain the preprocessed first calibration image;

[0097] Specifically, the preprocessing includes image filtering to reduce the influence of noise on subsequent image processing.

[0098] Step 43, respectively performing stripe straight line extraction and light strip center line extraction on the pre-processed first calibration image to obtain the calibration target image stripe straight line and the light strip center line;

[0099] Specifically, the stripe straight line extraction is performed on the pre-processed first calibration image to obtain the calibration target image stripe straight line, including:

[0100] Step A1, performing Canny algorithm coarse extraction on the collected target stripe image according to the pre-processed first calibration image to obtain the image edge; the extraction steps are as follows:

[0101] First step: Gaussian filtering is performed to smooth the image and suppress noise.

[0102] Second step: the gradient amplitude and direction of the pixel point are calculated by using the first-order partial derivative finite difference method:

[0103]

[0104] The gradient amplitude is:

[0105]

[0106] The gradient direction is represented as:

[0107]

[0108] Third step: non-maximum suppression is performed on the smoothed image to retain the local maximum value and suppress the non-edge pixels.

[0109] Fourth step: a double-threshold method is used to detect and connect the edges.

[0110] Fifth step: all weak edges are suppressed by using the lagging edge tracking.

[0111] Step A2, after coarse extraction, the Devernay algorithm is used to perform sub-pixel correction on the image;

[0112] Let A, B, C be three pixel points perpendicular to the edge direction, and η be a sub-pixel point with a gradient modulus greater than A, B, and C. The calculation formula is:

[0113]

[0114] Wherein, , , are the gradient moduli of A, B, and C.

[0115] Step A3, the information of the image edge is subjected to stripe straight line extraction, and specifically, the LSD algorithm is adopted for straight line detection; the straight line detection by using the LSD algorithm is specifically as follows: all point gradient direction changes of an image are connected domains with adjacent points, whether the connected domains need to be disconnected to form multiple domains with greater rectangularity is judged according to the rectangularity of each domain, all generated domains are screened, and the domains meeting the conditions are reserved, that is, the straight line information of the image.

[0116] Step A5, according to the above process, the required vertical stripe straight line is screened, and parallelism detection is performed on the vertical stripe straight line, so as to ensure that the straight lines are mutually parallel as much as possible.

[0117] Specifically, the light strip center line is extracted from the preprocessed first calibration image to obtain the light strip center line, including:

[0118] Step B1, according to the preprocessed first calibration image, the image ROI region is extracted;

[0119] Specifically, in step B1, for the line laser stripe center line, the image ROI region is extracted according to the preprocessed first calibration image.

[0120] Step B2, according to the image ROI region, the light strip and the image background are segmented, and each column of light strip region is screened by threshold value;

[0121] Step B3, according to the screened each column of light strip region, the light strip center line is extracted by using the gray center method; the calculation formula of each center point in the light strip center line is as follows:

[0122]

[0123] Wherein, is the sub-pixel center point of the i-th column, is the gray value of the image pixel point , and M is the pixel number of the i-th column of the light strip region.

[0124] Step 44, according to the calibration target image stripe straight line and the light strip center line, the equations of the two straight lines are calculated, the intersection information of the two straight lines is calculated, that is, the feature point pixel coordinates are calculated, and the coordinates not belonging to the feature points are removed.

[0125] Step 45, after the processing of all images is completed, the feature point pixel coordinates are sorted according to the number of the camera collected images, and the three-dimensional world coordinates are one-to-one corresponding.

[0126] Step 5, according to the feature point pixel coordinates and the corresponding three-dimensional world coordinate information, a direct mapping model of the image plane and the light plane is established; the homography matrix parameters of the direct mapping model are calculated by using the least square method;

[0127] In this embodiment, the homography matrix parameters are:

[0128]

[0129] Step 6, according to the input device parameters, the line laser three-dimensional measurement system parameters are calculated as the related system parameters;

[0130] In this embodiment, in the line laser three-dimensional measurement system, the whole system and the system parameters also need to be analyzed to meet the index requirements. The input device parameters are, for example, the camera chip size, the pixel size, the resolution, the focal length, the angle with the laser, and the height to the focusing plane. According to the related formula, the three-dimensional measurement system parameters, such as the height and width measurement range, the repeat accuracy, the data profile interval, and the height linearity, are automatically calculated in the host computer program.

[0131] Step 7, according to the related system parameters, the homography matrix parameters are corrected, the calibration results are obtained, and all parameters are stored.

[0132] In this embodiment, in the host computer program, the homography matrix is corrected according to the related system parameters, the cumulative error of hardware installation is reduced, and the reprojection error is used to evaluate the system calibration index.

[0133] After determining that the calibration results meet the index, all parameter data are packaged and stored for use in the actual measurement process of the system.

[0134] Embodiment 2

[0135] As shown in Figure 5 The difference between this embodiment and embodiment 1 is that this embodiment further provides an automatic calibration device in a line laser three-dimensional measurement system. The system corresponds to the automatic calibration method of the line laser three-dimensional measurement system in embodiment 1. The device comprises:

[0136] A calibration target establishment unit is used to select a calibration target object, fix the calibration target object, and establish a calibration target composed of the calibration target object and the automatic displacement device.

[0137] A feature point forming unit is used to control the automatic displacement device to move the calibration target object to form feature points.

[0138] A coordinate information acquisition unit is used to establish a three-dimensional world coordinate system and acquire three-dimensional world coordinate information of each feature point.

[0139] A digital image processing unit is used for the camera to collect calibration images, perform digital image processing on the calibration images, and obtain feature point pixel coordinates.

[0140] The homographic matrix parameter calculation unit is configured to establish a direct mapping model of the image plane and the light plane according to the pixel coordinates of the feature points and the corresponding three-dimensional world coordinate information, and calculate the homographic matrix parameter of the direct mapping model by using a least square method.

[0141] The related system parameter calculation unit is configured to calculate the line laser three-dimensional measurement system parameter as the related system parameter according to the input device parameter.

[0142] The correction unit is configured to correct the homographic matrix parameter according to the related system parameter, obtain the calibration result, and store all the parameters.

[0143] The execution process of each unit can be performed according to the automatic calibration method flow steps of the line laser three-dimensional measurement system described in Embodiment 1, and will not be repeated here.

[0144] Meanwhile, as shown in Figure 6 The present application further provides an automatic calibration device for a line laser three-dimensional measurement system, which comprises a one-dimensional motion platform, an automatic displacement device, a calibration target, a line laser three-dimensional measurement system, and an upper computer program; wherein the upper computer program is stored in a computer and controls the automatic displacement device, the one-dimensional motion platform, and the line laser three-dimensional measurement system to perform the automatic calibration method for the line laser three-dimensional measurement system.

[0145] Meanwhile, the present application further provides a computer readable storage medium, which stores a computer program, and the computer program is executed by a processor to realize the automatic calibration method for the line laser three-dimensional measurement system.

[0146] Those skilled in the art should understand that the embodiments of the present application can be provided as a method, a system, or a computer program product. Therefore, the present application can be in the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application can be in the form of a computer program product implemented on one or more computer readable storage media containing computer usable program code (including but not limited to disk memory, CD-ROM, optical memory, etc.).

[0147] The present application is described with reference to flowcharts and / or block diagrams according to the method, device (system), and computer program product of the embodiments of the present application. It should be understood that each flow and / or block in the flowcharts and / or block diagrams, and the combination of the flows and / or blocks in the flowcharts and / or block diagrams can be implemented by computer program instructions. These computer program instructions can be provided to a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to produce a machine, so that the instructions executed by the computer or other programmable data processing devices produce a device for implementing the functions described in the flowcharts and / or block diagrams.Figure 1 apparatuses that implement the functions specified in the flowchart Figure 1 block or blocks.

[0148] These computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instructions which implement the flowchart Figure 1 apparatuses that implement the functions specified in the flowchart Figure 1 block or blocks.

[0149] These computer program instructions can also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the flowchart Figure 1 apparatuses that implement the functions specified in the flowchart Figure 1 block or blocks.

[0150] The above detailed description merely describes a specific implementation of the application, and the only purpose of the above detailed description is to explain the purpose, technical solutions and beneficial effects of the application. It should be understood that the above detailed description is only a specific implementation of the application, and is not intended to limit the protection scope of the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. An automatic calibration method in a line laser three-dimensional measurement system, characterized in that, The method includes: Select a calibration target and fix the calibration target to establish a calibration target consisting of the calibration target and an automatic displacement device; The automatic displacement device is controlled to move the calibration target to form feature points; Establish a three-dimensional world coordinate system and obtain the three-dimensional world coordinate information of each feature point; The camera acquires a calibration image, and the calibration image undergoes digital image processing to obtain the pixel coordinates of the feature points; Based on the pixel coordinates of the feature points and the corresponding three-dimensional world coordinates, a direct mapping model between the image plane and the light plane is established; the homography matrix parameters of the direct mapping model are calculated using the least squares method. Based on the input device parameters, calculate the parameters of the line laser 3D measurement system as relevant system parameters; Based on the relevant system parameters, the homography matrix parameters are corrected to obtain calibration results and store all parameters.

2. The automatic calibration method in a line laser three-dimensional measurement system according to claim 1, characterized in that, Select calibration targets, including: Based on the laser reflection characteristics and the requirements of the line laser three-dimensional measurement system, an optical glass plate made of ceramic material was selected as the calibration target. The calibration target is striped, and the width between the stripes is equal to the stripe spacing.

3. The automatic calibration method in a line laser three-dimensional measurement system according to claim 1, characterized in that, Fixing the calibration target and establishing a calibration target consisting of the calibration target and an automatic displacement device includes: The calibration target is fixed on the automatic displacement device, and the automatic displacement device is fixed on the online laser three-dimensional measurement equipment so that the plane of the calibration target is parallel to the plane being measured. The scale of the automatic displacement device is set to zero, and the plane where the calibration target is located is used as the reference plane to establish a calibration target composed of the calibration target and the automatic displacement device.

4. The automatic calibration method in a line laser three-dimensional measurement system according to claim 1, characterized in that, Controlling the automatic displacement device to move the calibration target and form feature points includes: The automatic displacement device drives the calibration target to move, displacing it a preset number of times and a preset distance in the vertical direction and parallel to the laser line direction, respectively; After each movement of the automatic displacement device, the camera in the line laser 3D measurement system acquires a calibration image to obtain feature point information at different positions, thereby forming multiple feature points on the entire optical plane.

5. The automatic calibration method in a line laser three-dimensional measurement system according to claim 1, characterized in that, Establish a three-dimensional world coordinate system and obtain the three-dimensional world coordinate information of each feature point, including: Adjust the position of the calibration target so that the calibration image is completely within the camera's field of view; The intersection of the laser stripe on the left side of the camera's field of view and the first stripe of the calibration target is the first feature point, and the first feature point is defined as the origin of the three-dimensional world coordinate system. Based on the origin of the three-dimensional world coordinate system, three coordinate axes of the three-dimensional world coordinate system are established: the X-axis, the Y-axis and the Z-axis. The straight line where the feature point on the target is located is the X-axis, the Y-axis is perpendicular to the X-axis and perpendicular to the plane where the line laser is located, i.e., the light plane, and the Z-axis is perpendicular to the X-axis and parallel to the light plane. Based on the three-dimensional world coordinate system, obtain the X-axis coordinate, Y-axis coordinate, and Z-axis coordinate of each feature point in the three-dimensional world coordinate system.

6. The automatic calibration method in a line laser three-dimensional measurement system according to claim 1, characterized in that, The camera acquires a calibration image, and digital image processing is performed on the calibration image to obtain the pixel coordinates of feature points, including: The camera acquires calibration images, the image sharpness of the calibration images is evaluated, and calibration images that do not meet the requirements are discarded to obtain the first calibration image; The first calibration image is preprocessed to obtain the preprocessed first calibration image; The first calibration image after preprocessing is subjected to stripe line extraction and light bar center line extraction respectively to obtain stripe lines and light bar center lines of the calibration target image respectively; Based on the calibrated target image stripe lines and light stripe center lines, calculate the equations of the two lines, obtain the intersection information of the two lines, that is, find the feature point pixel coordinates, and remove the coordinates that do not belong to the feature points; After all images have been processed, the pixel coordinates of the feature points are sorted according to the image numbers acquired by the camera, and then matched one-to-one with the actual 3D world coordinates.

7. The automatic calibration method in a line laser three-dimensional measurement system according to claim 6, characterized in that, Stripe line extraction is performed on the preprocessed first calibration image to obtain stripe lines in the calibration target image, including: Based on the preprocessed first calibration image, the acquired target stripe image is coarsely extracted using the Canny algorithm to obtain the image edges; After coarse extraction, the Devernay algorithm is used to perform subpixel correction on the image; The information of the image edge is used to extract stripe lines, specifically using the LSD algorithm for line detection; The LSD algorithm for line detection is specifically as follows: all points in the image with small gradient direction changes and adjacent points are taken as a connected region. Based on the rectangularity of each region, it is determined whether the connected region needs to be broken to form multiple regions with larger rectangularity. All generated regions are filtered, and the regions that meet the conditions are retained, which are the line information of the image. Based on the above process, the required vertical stripe lines are selected, and the parallelism of the vertical stripe lines is tested.

8. The automatic calibration method in a line laser three-dimensional measurement system according to claim 6, characterized in that, The light stripe centerline is extracted from the preprocessed first calibration image to obtain the light stripe centerline, including: Based on the preprocessed first calibration image, extract the ROI region of the image; Based on the image ROI region, the light bars and image background are segmented, and each column of light bar regions is filtered by a threshold. Based on the selected light stripe regions, the center line of the light stripe is extracted using the gray-scale centroid method; The formula for calculating each center point in the center line of the light stripe is as follows: ； in, The sub-pixel center point is found for the i-th column. For image pixels The grayscale value is M, where M is the number of pixels in the i-th column of the light stripe region.

9. An automatic calibration device in a line laser three-dimensional measurement system, characterized in that, The device includes: The calibration target establishment unit is used to select a calibration target, fix the calibration target, and establish a calibration target consisting of the calibration target and an automatic displacement device. The feature point forming unit is used to control the automatic displacement device to move the calibration target and form feature points; The coordinate information acquisition unit is used to establish a three-dimensional world coordinate system and acquire the three-dimensional world coordinate information of each feature point. A digital image processing unit is used to acquire calibration images by the camera, perform digital image processing on the calibration images, and obtain the pixel coordinates of feature points; The homography matrix parameter calculation unit is used to establish a direct mapping model between the image plane and the light plane based on the pixel coordinates of the feature points and the corresponding three-dimensional world coordinate information; and to calculate the homography matrix parameters of the direct mapping model using the least squares method. The relevant system parameter calculation unit is used to calculate the line laser three-dimensional measurement system parameters as relevant system parameters based on the input equipment parameters; The correction unit is used to correct the homography matrix parameters according to the relevant system parameters, obtain the calibration results, and store all parameters.

10. An automatic calibration device in a line laser three-dimensional measurement system, characterized in that, The device includes a one-dimensional motion platform, an automatic displacement device, a calibration target, a line laser three-dimensional measurement system, and a host computer program; wherein, the host computer program is stored in a computer and controls the automatic displacement device, the one-dimensional motion platform, and the line laser three-dimensional measurement system to execute the automatic calibration method in the line laser three-dimensional measurement system as described in any one of claims 1 to 8.

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