A two-dimensional target-based line structured light plane field calibration method

Abstract

The present application relates to the technical field of non-contact three-dimensional measurement, and particularly relates to a line structured light plane field calibration method based on a two-dimensional target. The present application uses all feature points on the extracted line structured light strip center line and a plane normal vector fitted by a camera optical center to cross multiply with a normal vector of a camera plane where the two-dimensional calibration target is located to obtain a direction vector of an intersection line. Then, the feature points on the line structured light strip center line and the normal vector of the plane where the target is located are used to obtain a direction vector of an intersection line again by moving or rotating the calibration target at the same position once. After obtaining the direction vectors of the two intersection lines, the normal vector of the target line structured light plane is obtained by cross multiplication. Thus, the calibration is completed. The present application solves the problems of less calibration points, the need for multiple movements of the two-dimensional target and large calculation amount when using a traditional two-dimensional target to calibrate a light plane.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of non-contact three-dimensional measurement, in particular to a line structured light plane field calibration method based on a two-dimensional target. BACKGROUND

[0002] In the field of non-contact three-dimensional measurement, line structured light sensors have the advantages of simple structure, high precision and fast speed. Therefore, it is also widely used in industrial measurement and three-dimensional reconstruction of point clouds. The light plane calibration method is an important research content of line structured light three-dimensional measurement technology.

[0003] Only accurate calibration of the line structured light plane can make the three-dimensional measurement accuracy meet the requirements. This research has undergone many technical changes since the 1980s, from the traditional wire drawing method to determine the target points of the structured light plane to fit the light plane, to the use of a three-dimensional calibration object to determine the light plane, and to the current two-dimensional and one-dimensional targets. Therefore, accurate calibration of the light plane is the basis for the accuracy requirements of the line structured light sensor.

[0004] The most commonly used line structured light plane calibration method today is the cross-ratio invariant method based on a two-dimensional target. This method generally uses cross-ratio to calculate the camera coordinates of the points on the two-dimensional target. As shown in Figure 2 When using the cross-ratio invariant method, we need to use the pixel coordinates of points A, B, C, and Q on the line structured light strip L2, as well as the camera coordinates of points A, B, and C, to solve the cross-ratio between them, and then use the cross-ratio invariant theorem to obtain the camera coordinate value of point Q.

[0005] From the above analysis, we can see that to obtain the feature points on the light strip L2, we need to perform the following 7 steps:

[0006] 1. Fit the pixel coordinate points of L2 into a straight line l2;

[0007] 2. Then fit the calibration points on the two-dimensional target into n straight lines L3 (the value of n depends on the number of rows or columns of the target);

[0008] 3. Solve the n intersection points Qn (n = 0, 1, 2,...) of the n straight lines L3 and l2;

[0009] 4. Solve the cross-ratio between the four feature points on the target on the L3 straight line, and use the cross-ratio invariant theorem to obtain the coordinate value of Qn;

[0010] 5. Use 4 to solve the camera coordinate values of the n intersection points on the target;

[0011] 6. Since this method requires fitting the light plane, the fitting result is poor when there is little data. Therefore, the target needs to be moved multiple times and the above steps 1-5 need to be repeated.

[0012] 7. Perform plane fitting on the obtained feature points Qn to obtain the equation of the light plane.

[0013] It is evident that using traditional two-dimensional targets for optical plane calibration has several drawbacks, including a limited number of calibration points, the need to move the two-dimensional target multiple times, and a large computational load. Summary of the Invention

[0014] To address the problems of existing technologies, this invention provides a line structured light plane on-site calibration method based on a two-dimensional target. This method simplifies the system calibration process and improves the calibration speed, accuracy, and efficiency of line structured light sensors. Unlike traditional laser plane calibration methods, this method can obtain the line laser plane equation by moving the two-dimensional target at least twice, which can meet the purpose of rapid and high-precision on-site calibration in practical application scenarios.

[0015] The technical solution adopted in this invention is as follows:

[0016] A line structured light planar on-site calibration method based on a two-dimensional target includes the following steps:

[0017] A. Use the camera extrinsic parameter matrix to obtain the equation of the plane containing the two-dimensional target;

[0018] B. Extract the light stripe feature points and fit them to the plane with the camera optical center coordinates;

[0019] C. Move the two-dimensional target once and fit the plane again;

[0020] D. Intersect the planes obtained in steps B and C with the two-dimensional target plane obtained in step A to obtain the direction vectors of the two intersection lines;

[0021] E. The normal vector of the light plane can be obtained by the cross product of the direction vectors of the two intersection lines, which is the equation of the light plane.

[0022] Preferably, the method specifically includes:

[0023] A1. First, calibrate the monocular camera using the Zhang Zhengyou calibration method and obtain the camera's intrinsic and extrinsic parameter matrix; then, take two images of line structured light stripes in different poses of the calibration plate.

[0024] A2. The coordinate systems used in the camera calibration process are the camera coordinate system, image coordinate system, pixel coordinate system, and world coordinate system; the transformation relationship between the pixel coordinate system and the camera coordinate system is obtained through the camera calibration results and the corresponding relationships.

[0025] A3, after obtaining the conversion relationship between the pixel coordinates and the camera coordinates, the sub-pixel precision light stripe center point is extracted by using a line structured light stripe center point extraction algorithm to obtain the light stripe center point coordinates;

[0026] A4, the world coordinate system is established on the two-dimensional calibration target plane, and the equation of the two-dimensional calibration target in the world coordinate system is established; according to the conversion relationship between the world coordinate system and the camera coordinate system, the plane equation of the plane where the calibration board is located in the camera coordinate system is obtained; finally, the equation of the plane where the calibration board is located in the camera coordinate system is determined; the normal vector of the second plane is obtained;

[0027] A5, after obtaining the light stripe center point coordinates, the light stripe center point coordinates in the camera coordinate system can be obtained through the camera intrinsic parameter matrix and the plane equation coefficients of the second plane; after converting the light stripe center point pixel coordinates into camera coordinates, the first plane equation passing through the camera optical center and the laser line center point is fitted together with the camera optical center, and the normal vector of the first plane is obtained;

[0028] A6, the direction vector of the intersection line of the two planes is obtained according to the normal vectors of the first plane and the second plane; the equation of the laser plane in the camera coordinate system is obtained according to the direction vectors of the two intersection lines.

[0029] Preferably, the conversion relationship in step A2 is:

[0030] Suppose the image coordinates of a point p are p(x, y), and the corresponding relationship between the pixel coordinates and the image coordinates of the point p is:

[0031]

[0032] The above formula is converted to obtain:

[0033]

[0034] Where u0, v0 are the image principal point coordinates, generally selected as the pixel coordinate system origin; dx, dy are the scaling factors, representing how many millimeters each pixel corresponds to;

[0035] Through the camera calibration result and the above corresponding relationship, the conversion relationship between the pixel coordinate system and the camera coordinate system is obtained:

[0036]

[0037] Preferably, step A4 specifically comprises:

[0038] The world coordinate system is established on the two-dimensional calibration target plane, denoted as O w -X w Y w Z w , and the two-dimensional calibration target plane is parallel to the Xw O w Y w They are coplanar. Therefore, we set the equation of the two-dimensional calibration target in the world coordinate system as:

[0039] aX w +bY w +cZ w +d=0 (4)

[0040] Where a, b, c, and d are the constant coefficients of the equation, the above equation can be rewritten as:

[0041]

[0042] Furthermore, the transformation relationship between the world coordinate system and the camera coordinate system is as follows:

[0043]

[0044] The plane equation in the camera coordinate system of the plane where the calibration plate is located can be obtained as follows:

[0045]

[0046] Because the world coordinates are set on the plane of the calibration plate, a = b = d = 0. That is:

[0047] Z w =0 (8)

[0048] Therefore, the equation in the camera coordinate system of the plane where the calibration plate is located can be determined as follows:

[0049]

[0050] In the formula, R is the rotation matrix of the camera coordinates in the world coordinate system, which is usually a (3×3) matrix, and T is the translation matrix of the camera coordinates in the world coordinate system, which is usually a (3×1) matrix.

[0051] Since the first two terms of the linear equation are known constants, it can be further simplified to:

[0052] a 01 X c +a 11 Y c +a 21 =Z c (10)

[0053] In the formula a 01 a 11 a 21 It is by The results can be obtained from the camera calibration results. Therefore, we can obtain the normal vector of the planar target as:

[0054] n1= [a 01 a 11 -1] (11)

[0055] After obtaining the coordinates of the center points of the light stripes, the camera intrinsic matrix in equation (3) is M, and the coordinates of the center points p(u, v) of the light stripes in the camera coordinate system satisfy the following formula:

[0056]

[0057] where P c (X c Y c Z c ) is the coordinates of the point p in the camera coordinate system, and here Z c = 1, so the line connecting all feature points on the light stripe and the camera optical center is collinear with the intersection P c (X c1 , Y c1 , Z c1 ) of the perspective projection plane expressed in the camera coordinate system with Z c = 1 and the camera optical center, that is, the straight line equation can be expressed as:

[0058]

[0059] where X c1 = (u-u0) / f x ; Y c1 = (v-v0) / f y ; Z c = 1;

[0060] By combining equations (4), (5), and (12), the camera coordinate values of all light stripe center points can be obtained.

[0061] After converting the pixel coordinates of the light stripe center points into camera coordinates, the camera optical center O c (x c , y c , z c ) = (0, 0, 0) is fitted together to obtain the plane equation passing through the camera optical center and the center point of the laser line. In order to facilitate calculation, we let the equation of the plane π1 be as follows:

[0062] a0X c +a1Y c +a2=Z c (14)

[0063] where a0, a1, and a2 are the constant coefficients of the plane, so the normal vector of the plane is:

[0064] n0 = [a0 a1 -1] (15)

[0065] From which we can get the normal vector n0, n1 of two planes. Thus the direction vector of the intersection line of two planes can be expressed as:

[0066] s = [m n q] = n1 x n0 (16)

[0067] After obtaining the direction vector of an intersection line, the direction vector s of at least one intersection line is obtained n The equation of the laser plane π0 in the camera coordinate system can be obtained as:

[0068] AX c +BY c +CZ c +D = 0 (17)

[0069] Where [A B C] is the normal vector of the laser plane, which can be obtained as follows:

[0070] N = [A B C] = s x s n (18)

[0071] The technical solution provided by the application has the beneficial effects that:

[0072] The application only needs the following five steps:

[0073] 1. Using the camera extrinsic matrix to obtain the plane equation of the two-dimensional target;

[0074] 2. After converting the light strip feature points into camera coordinate values, fitting the plane with the camera optical center coordinates;

[0075] 3. Moving the two-dimensional target once and fitting the plane again;

[0076] 4. Obtaining the direction vectors of the two intersection lines by intersecting the results obtained by the plane equation of the two fitted planes;

[0077] 5. The normal vector of the light plane, that is, the light plane equation, can be obtained by cross-multiplying the direction vectors of the two intersection lines.

[0078] Therefore, the intersection ratio method is limited by the number of straight lines connected by the plane target calibration points, so it is necessary to move the calibration board multiple times to obtain sufficient data points. Thus, the fitted plane has high reliability, but the calculation amount is multiplied.

[0079] The method provided by the application effectively reduces the calculation amount and involves all feature points on the light strip in the calculation, further reducing the situation of fewer target points caused by fewer two-dimensional target calibration points. BRIEF DESCRIPTION OF DRAWINGS

[0080] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort based on these drawings.

[0081] Figure 1 A method flow chart of a line structured light plane field calibration method based on a two-dimensional target according to the present application;

[0082] Figure 2 A schematic diagram of a common line structured light plane calibration method according to the prior art;

[0083] Figure 3 A diagram of the relative position relationship between a camera and a line structured light plane;

[0084] Figure 4 A schematic diagram of line structured light strip images of different poses of a calibration board according to the present application;

[0085] Figure 5 A schematic diagram of a coordinate system according to the present application;

[0086] Figure 6 A schematic diagram of light strip center extraction according to the present application;

[0087] Figure 7 A schematic diagram of a plane passing through the optical center and the laser center point;

[0088] Figure 8 A schematic diagram of the result of fitting two pi1s from two light strips;

[0089] Figure 9 A schematic diagram of two intersection lines of two pi1s and a two-dimensional target plane;

[0090] Figure 10 A schematic diagram of a light plane according to the present application;

[0091] Figure 11 A schematic diagram of an experimental structure according to the present application;

[0092] Figure 12 A schematic diagram of the distribution of measurement results according to the present application. DETAILED DESCRIPTION

[0093] In order to make the objects, technical solutions and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0094] Embodiment One

[0095] As shown in the accompanying drawings Figure 1The basic concept of the present application is to use the extracted feature points on the line structured light stripe center line and the camera optical center to fit a plane normal vector, and then to cross multiply the normal vector of the camera plane where the two-dimensional calibration target is located to obtain the intersection line direction vector. Then, the calibration target is moved or rotated by a certain angle at the same position, and the feature points on the line structured light stripe center line and the normal vector of the target plane are used to obtain the intersection line direction vector again. After obtaining the direction vectors of the two intersection lines, the normal vector of the target line structured light plane is obtained by cross multiplication. Thus, the calibration is completed.

[0096] A specific embodiment is provided below to illustrate the specific technical solutions of the present application:

[0097] First, the monocular camera is calibrated using the Zhang Zhengyou calibration method, so that the internal and external parameter matrices of the camera can be obtained. Then, two line structured light stripe images of the calibration board in different poses are captured, as shown in the following figure. Figure 4

[0098] In the camera calibration process, the coordinate systems that need to be used include the camera coordinate system, the image coordinate system, the pixel coordinate system, and the world coordinate system. Figure 3 In the present application, the image coordinates of point p are assumed to be p(x, y). Therefore, the corresponding relationship between the pixel coordinates and the image coordinates of point p is as follows:

[0099]

[0100] The above formula is converted to obtain:

[0101]

[0102] where u0 and v0 are the image principal point coordinates, which are generally selected as the origin of the pixel coordinate system; dx and dy are the scaling factors, which represent the number of millimeters corresponding to each pixel. Therefore, through the camera calibration results and the above corresponding relationship, the conversion relationship between the pixel coordinate system and the camera coordinate system can be obtained as follows:

[0103]

[0104] After obtaining the conversion relationship between the pixel coordinates and the camera coordinates, the line structured light stripe center point extraction algorithm is used to extract the sub-pixel accuracy stripe center points. The extraction results are shown in the following figure. Figure 6

[0105] The world coordinate system is established on the two-dimensional calibration target plane, which is represented as O w -X w Y w Z w , and the two-dimensional calibration target plane is perpendicular to the X w O w Y w ​​coplanar. So the equation of the two-dimensional calibration target in the world coordinate system is:

[0106] aX w +bY w +cZ w +d=0 (4)

[0107] where a, b, c, d are constant coefficients of the equation, so the above equation can be rewritten as:

[0108]

[0109] Since the conversion relationship between the world coordinate system and the camera coordinate system is:

[0110]

[0111] The plane equation of the calibration board in the camera coordinate system can be obtained as:

[0112]

[0113] Since the world coordinate is set on the plane of the calibration board, a = b = d = 0. That is:

[0114] Z w =0 (8)

[0115] So the equation of the plane of the calibration board in the camera coordinate system can be determined as:

[0116]

[0117] where R is the rotation matrix of the camera coordinate in the world coordinate system, usually a (3 × 3) matrix, and T is the translation matrix of the camera coordinate in the world coordinate system, usually a (3 × 1) matrix.

[0118] Since the first two terms of the linear equation are known constants, it can be further simplified as:

[0119] a 01 X c +a 11 Y c +a 21 =Z c (10)

[0120] where a 01 , a 11 , a 21 are obtained from and can be obtained in the camera calibration result. So we can get the normal vector of the plane target as:

[0121] n1=[a 01 a11 -1] (11)

[0122] After obtaining the coordinates of the center point of the light stripe, let the camera intrinsic parameter matrix in equation (3) be M, and we can obtain the coordinates of the center point p(u, v) of the light stripe in the camera coordinate system, which satisfy the following formula:

[0123]

[0124] Where P c (X c Y c Z c Let Z be the coordinates of point p in the camera coordinate system. c =1, so the line connecting all feature points on the light stripe to the camera's optical center, and the line connecting the two points in the Z-axis... c =1, the intersection point P of the perspective projection plane in the camera coordinate system. c (X c1 Y c1 Z c1 The line connecting the optical center of the camera and the optical center is collinear, meaning the equation of this line can be expressed as:

[0125]

[0126] Where X c1 =(u-u0) / f x ;Y c1 =(v-v0) / f y Z c =1;

[0127] By combining equations (4), (5), and (12), the camera coordinates of the center points of all light stripes can be obtained.

[0128] After converting the pixel coordinates of the light stripe center point to camera coordinates, and then comparing them with the camera's optical center O... c (x c y c , z c We fit the equation of the plane passing through the optical center of the camera and the center point of the laser line together with (0, 0, 0). For ease of calculation, we let the equation of this plane π1 be as follows:

[0129] a0X c +a1Y c +a2=Z c (14)

[0130] Where a0, a1, and a2 are the constant coefficients of the plane, the normal vector of the plane is:

[0131] n0 = [a0 a1 -1] (15)

[0132] From which we can get the normal vector n0, n1 of the two planes. Then the direction vector of the intersection line of the two planes can be expressed as:

[0133] s = [m n q] = n1 x n0 (16)

[0134] After obtaining the direction vector of one intersection line, the direction vector s of at least one intersection line is obtained n The equation of the laser plane π0 in the camera coordinate system can be obtained as:

[0135] AX c +BY c +CZ c +D = 0 (17)

[0136] Where [A B C] is the normal vector of the laser plane, which can be obtained as follows:

[0137] N = [A B C] = s x s n (18)

[0138] Experimental verification

[0139] After the theoretical analysis, we will perform experimental verification. The experimental equipment used is the Daheng Water Star MER2-503-36U3M black and white industrial camera, 500 million pixels. The laser is a semiconductor linear laser with a wavelength of 405 nm.

[0140] First, use the industrial camera to take 10 photos of the circular calibration board for monocular camera calibration. The camera calibration results are shown in Table 1.

[0141]

[0142] Table 1 Monocular camera calibration results

[0143] In Table 1, Where f = 8 mm is the lens focal length. dx, dy represent the scaling size of x, y in the image coordinate system. u0, v0 represent the position of the image pixel coordinate principal point. The camera extrinsic parameters represent the translation and rotation of the camera coordinate system in the conversion to the world coordinate system.

[0144] Next we perform light plane calibration. When calibrating the light plane, we only need to move the calibration board twice to obtain two different pose light strip images. After center extraction, the camera optical center is fitted to obtain the plane π1 results as shown in Table 2 and Figure 8

[0145]

[0146]

[0147] ​Table 2: The results of π1 for any two positions

[0148] The equation coefficients of the camera coordinate system of the two-dimensional target plane are solved by using formula (12) as follows:

[0149] Z c = 0.0023X c - 0.2562Y c + 13.9319

[0150] The direction vectors of the two intersection lines of the two π1 and the two-dimensional target plane are obtained by using formula (15) as shown in Table 3 and Figure 9 .

[0151]

[0152] Table 3: The direction vectors of the intersection lines

[0153] The normal vectors of the two intersection line direction vectors are finally obtained as follows:

[0154] O = [-0.001201510570000, 0.013383782958000, 0.052239590000001]

[0155] The equation of the light plane π0 is obtained as follows:

[0156] Z c = 0.023X c - 0.2567Y c + 13.9301

[0157] After obtaining the light plane equation, the calibration of the light plane is completed. A 40mm standard gauge block is used to test the calibration accuracy. The specific test method is to place the gauge block at 10 different positions of the laser line to test the width of the gauge block. The experimental structure diagram is as shown in Figure 11 .

[0158] In the aspect of human operation: since the traditional calibration method needs to move the calibration target multiple times to obtain enough reliable feature points to fit the light plane, the method of the present application only needs to move the target twice to complete the calibration, so it is more efficient.

[0159] At the computer calculation level: since the traditional calibration method is to extract the laser line on each calibration target, then perform linear fitting, and then calculate the straight line connected by the calibration points on the calibration target, then intersect to obtain n feature points on the calibration target, then move the calibration board m times (m is greater than or equal to 5) and repeat the above operation m times. Finally, the n*m feature points are fitted to obtain the plane equation; and the method of the present application only needs to perform fitting once, that is, the plane fitted in steps A and B, and the subsequent calculation is all vector cross product, so the calculation amount is obviously greatly reduced.

[0160] The measurement data of ten readings are summarized in Table 4.

[0161]

[0162]

[0163] Table 4 Measurement Results

[0164] The measurement results of the same gauge block by the traditional two-dimensional plane target based on the cross ratio invariant method are shown in Table 5:

[0165]

[0166] Table 5 Comparison Data Measurement Results

[0167] From the above data, we can analyze that the present application improves the calculation speed while also considering accuracy and ease of use, and can meet the needs of on-site rapid calibration in production.

[0168] The application of the present embodiment can be applied in the case where the external environmental light interference is small, and the profile scanning measurement of a small object (the length, width and height of the object are recommended to be within 13 cm) is performed, and the effect and accuracy are better; and different specific small range areas on the laser line can perform effective high-precision measurement, if the volume of the object exceeds the recommended length, width and height, or is not in the specific measurement area with high accuracy, the measurement result may be slightly different from the actual result.

[0169] The above only describes the preferred embodiments of the present application, and is not intended to limit the present application, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for on-site calibration of a line structured light plane based on a two-dimensional target, comprising the following steps: A. Use the camera extrinsic parameter matrix to obtain the equation of the plane containing the two-dimensional target; B. Extract the light stripe feature points, convert them into camera coordinates, and then fit them to the plane with the camera optical center coordinates; C. Move the two-dimensional target once and fit the plane again; D. Intersect the planes obtained in steps B and C with the two-dimensional target plane obtained in step A to obtain the direction vectors of the two intersection lines; E. The normal vector of the light plane can be obtained by the cross product of the direction vectors of the two intersection lines, which is the equation of the light plane.

2. The method for on-site calibration of a line structured light plane based on a two-dimensional target according to claim 1, characterized in that, The method specifically includes: A1. First, calibrate the monocular camera using the Zhang Zhengyou calibration method and obtain the camera's intrinsic and extrinsic parameter matrix; then, take two images of line structured light stripes in different poses of the calibration plate. A2. The coordinate systems used in the camera calibration process are the camera coordinate system, image coordinate system, pixel coordinate system, and world coordinate system; the transformation relationship between the pixel coordinate system and the camera coordinate system is obtained through the camera calibration results and the corresponding relationships. A3. After obtaining the conversion relationship between pixel coordinates and camera coordinates, use the line structured light stripe center point extraction algorithm to extract the light stripe center point with sub-pixel precision, and obtain the coordinates of the light stripe center point. A4. The world coordinate system is established on the two-dimensional calibration target plane, and the equation of the two-dimensional calibration target is established in the world coordinate system; according to the transformation relationship between the world coordinate system and the camera coordinate system, the plane equation of the calibration plate in the camera coordinate system is obtained; finally, the equation of the calibration plate in the camera coordinate system is determined; and the normal vector of the target plane is obtained. A5. After obtaining the coordinates of the center point of the light stripe, the coordinates of the center point of the light stripe in the camera coordinate system can be obtained through the plane equation coefficients of the camera intrinsic parameter matrix and the target plane. After converting the pixel coordinates of the center point of the light stripe into camera coordinates, the first plane equation passing through the camera optical center and the center point of the laser line is fitted together with the camera optical center to obtain the normal vector of the first plane. A6. Obtain the direction vector of the intersection line of the two planes based on the normal vectors of the first plane and the target plane; obtain the equation of the laser plane in the camera coordinate system based on the direction vectors of the two intersection lines.

3. The method for on-site calibration of a line structured light plane based on a two-dimensional target according to claim 2, characterized in that, The transformation relationship in step A2 is as follows: Suppose the image coordinates of a point p are p(x, y), the correspondence between the pixel coordinates of point p and its image coordinates is as follows: Transforming the above formula yields: Where u0 and v0 are the coordinates of the principal point of the image, which are generally chosen as the origin of the pixel coordinate system; dx and dy are scaling factors, representing how many mm each pixel corresponds to; By comparing the camera calibration results with the above correspondence, the transformation relationship between the pixel coordinate system and the camera coordinate system is obtained as follows:

4. The method for on-site calibration of a line structured light plane based on a two-dimensional target according to claim 3, characterized in that, Step A4 specifically includes: The world coordinate system is established on the two-dimensional calibration target plane, denoted as O. w -X w Y w Z w Furthermore, the two-dimensional calibration target plane and the X-ray... w O w Y w Coplanar, let the equation of the two-dimensional calibration target in the world coordinate system be: aX w +bY w +cZ w +d=0 (4) Where a, b, c, and d are the constant coefficients of the equation, the above equation can be rewritten as: Furthermore, the transformation relationship between the world coordinate system and the camera coordinate system is as follows: The plane equation in the camera coordinate system of the plane where the calibration plate is located can be obtained as follows: Because the world coordinates are set on the plane where the calibration plate is located, a = b = d = 0, that is: Z w ＝0 (8) Therefore, the equation in the camera coordinate system of the plane where the calibration plate is located can be determined as follows: In the formula, R is the rotation matrix of the camera coordinates in the world coordinate system, which is usually a (3×3) matrix, and T is the translation matrix of the camera coordinates in the world coordinate system, which is usually a (3×1) matrix. Since the first two terms of the linear equation are known constants, it can be further simplified to: a 01 X c +a 11 Y c +a 21 =Z c (10) In the formula a 01 a 11 a 21 It is by The results can be obtained from the camera calibration results; therefore, the normal vector of the planar target is: n1=[a 01 the 11 -1] (11).

5. The method for on-site calibration of a line structured light plane based on a two-dimensional target according to claim 4, characterized in that, Step A5 specifically includes: After obtaining the coordinates of the center point of the light stripe, let the camera intrinsic parameter matrix in equation (3) be M, and we can obtain the coordinates of the center point p(u, v) of the light stripe in the camera coordinate system, which satisfy the following formula: Where P c (X c Y c Z c Let Z be the coordinates of point p in the camera coordinate system. c =1, so the line connecting all feature points on the light stripe to the camera's optical center, and the line connecting the two points in the Z-axis... c =1, the intersection point P of the perspective projection plane in the camera coordinate system. c (X c1 Y c1 Z c1 The line connecting the optical center of the camera and the optical center is collinear, meaning the equation of this line can be expressed as: Where X c1 =(u-u0) / f x ;Y c1 =(v-v0) / f y Z c =1; By solving the plane equations in the camera coordinate system of the target plane, the camera coordinate values ​​of all light fringe center points can be obtained; after converting the pixel coordinates of the light fringe center points to camera coordinates, and then comparing them with the camera optical center O... c (x c y c , z c Together with (0, 0, 0), we fit the plane equation passing through the optical center of the camera and the center point of the laser line. Let the equation of this plane π1 be as follows: a0X c +a1Y c +a2=Z c (14) Where a0, a1, and a2 are the constant coefficients of the plane, the normal vector of plane π1 is: n0 = [a0 a1-1] (15).

6. The method for on-site calibration of a line structured light plane based on a two-dimensional target according to claim 5, characterized in that, Step A6 specifically includes: Based on the normal vectors of the two planes, n0 and n1, the direction vector of the intersection line of the two planes can be expressed as: s=[mnq]=n1×n0 (16) After finding the direction vector of one intersection line, find the direction vector s of at least one intersection line. n The equation of the laser plane π0 in the camera coordinate system can then be obtained as follows: A X c +BY c +CZ c +D=0 (17) Where [ABC] is the normal vector of the laser plane, which can be obtained as follows: N=[A B C]=s×s n (18)。

Images