CN114004741A - Splicing method for laser scanning calibration template of horizontal motion platform - Google Patents
Splicing method for laser scanning calibration template of horizontal motion platform Download PDFInfo
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T3/00—Geometric image transformations in the plane of the image
- G06T3/40—Scaling of whole images or parts thereof, e.g. expanding or contracting
- G06T3/4038—Image mosaicing, e.g. composing plane images from plane sub-images
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
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Abstract
The invention relates to the technical field of image and data processing, and discloses a splicing method of a horizontal motion platform laser scanning calibration template. The invention realizes the calibration of the calibration plate by the double calibration equipment in a camera moving mode, thereby realizing the 3D scanning of a special body.
Description
Technical Field
The invention relates to the technical field of image and data processing, in particular to a splicing method of a horizontal motion platform laser scanning calibration template.
Background
The existing 3D data scanning imaging principle is to scan an object through a laser emitter, and then take a picture through a camera, and combine the picture into a 3D image. In the process, firstly, a calibration block is used for data calibration, then, the object is scanned in a rotating mode, and finally, the scanned images are spliced into 3D image data.
The method requires that the scanned object has small volume and regular shape, and can be completely irradiated by laser when rotating on the turntable, so that the 3D image modeling can be completed.
Disclosure of Invention
The invention aims to solve the problems and provides a splicing method of a horizontal motion platform laser scanning calibration template, which realizes calibration of a calibration plate by using double calibration devices in a camera moving mode so as to realize 3D scanning of a special body.
The technical scheme adopted by the invention is as follows:
a splicing method of a horizontal moving platform laser scanning calibration template is characterized in that,
the calibration template is a dot calibration template, dots on the calibration template are arranged in an m-n array, double lasers and double cameras are arranged on a horizontal motion platform and synchronously move on the horizontal motion platform, the calibration template falls into the visual field of the double cameras, and one camera and one laser form a calibration device, wherein the splicing method comprises the following steps:
(1) the camera moves on the horizontal motion platform, and at a plurality of preset time points, the camera takes pictures of the calibration template to obtain an image point-object point pair matrix of the calibration template;
(2) calculating a first camera attitude and a second camera attitude according to the image point-object point pair matrix;
(3) converting the pixel coordinates of the dots on the calibration template into world coordinates according to the posture of the camera;
(4) establishing a second camera calibration template coordinate system by taking a calibration template plane as an XOY plane, taking a Z axis as vertical to the calibration template, and taking an original point as a central point of an image point-object point pair matrix;
(5) calculating a transformation matrix from the world coordinate system coordinates of the second camera to the coordinate system coordinates of the calibration template of the second camera;
(6) transforming the transformation matrix of the second camera into the constructed second camera calibration template coordinate system to form a second camera calibration template matrix;
(7) transforming the second camera calibration template matrix into a transformed second camera calibration template matrix corresponding to the first camera calibration template matrix;
(8) converting the transformed second camera calibration template matrix into a world coordinate system of a second camera;
(9) splicing a second camera calibration template matrix in the world coordinate system converted to the second camera and a first camera calibration template matrix in the world coordinate system into a spliced matrix, and calculating an inverse matrix of the spliced matrix;
(10) multiplying the left side of the inverse matrix of the splicing matrix by the first camera attitude matrix to obtain a new second camera attitude matrix, wherein the new second camera attitude matrix and the second camera attitude matrix are mirrored about an X-axis and a Y-axis;
(11) calculating a transformation matrix for changing the second camera attitude matrix into a new second camera attitude matrix;
(12) calculating a transformation matrix from the second camera pose matrix to the first camera pose matrix;
(13) and (4) pre-multiplying the transformation matrix obtained in the step (11) by the transformation matrix obtained in the step (12) to obtain an overall splicing matrix.
Further, the process of the step (7) is as follows:
(71) carrying out mirror image transformation on the second camera calibration template matrix relative to the X axis of the second camera calibration template coordinate system;
(72) and carrying out mirror image transformation on the mirrored second camera calibration template matrix relative to the Y axis of the second camera calibration template coordinate system to obtain a transformed second camera calibration template matrix.
Further, the process of the step (7) is as follows:
and carrying out 180-degree rotation transformation on the second camera calibration template relative to the Z axis of the second camera calibration template coordinate system to obtain a transformed second camera calibration template matrix.
Furthermore, the first camera and the first laser form a first calibration device, and the second camera and the second laser form a second calibration device.
Furthermore, the first camera and the second laser form a first calibration device, and the second camera and the first laser form a second calibration device. The invention has the beneficial effects that:
(1) the calibration is carried out through the calibration template, so that the method is simple and convenient;
(2) the calibration object is fixed, so that the calibration object is suitable for various calibration objects, and the deviation caused by the rotation of the calibration object is reduced;
(3) moreover, the method is processed by software, so that the cost is low and the modification is convenient.
Drawings
FIG. 1 is a schematic view of a horizontal motion laser scanning platform;
FIG. 2 is a schematic diagram of a calibration template dot matrix collected by two cameras;
FIG. 3 is a schematic diagram of a three-dimensional coordinate matrix calculated by two cameras;
FIG. 4 is a schematic diagram of a coordinate system of a constructed camera calibration template;
FIG. 5 is a schematic diagram of a mirror transformation of a dot three-dimensional coordinate matrix of a second camera with respect to an X-axis of a calibration template coordinate system;
FIG. 6 is a schematic diagram of the mirror transformation of the dot three-dimensional coordinate matrix of the second camera with respect to the Y-axis of the calibration template coordinate system.
Detailed Description
The following describes in detail a specific embodiment of the method for splicing a horizontal motion platform laser scanning calibration template according to the present invention with reference to the accompanying drawings.
Referring to fig. 1, the horizontal motion platform moves the laser and the camera through a slide rail disposed at a side of the object to be measured. During calibration, a calibration template is arranged on the side edge of the slide rail, the calibration template is 5-by-5 array dots, the dot pitch is determined, and the reading direction can be marked. The array of calibration templates is M N, typically based on an odd array. Taking an array of 5 × 5 as an example, the dot calibration template is placed on a horizontal moving laser scanning platform, the number of the lasers and the number of the cameras are two, and the two cameras are respectively a first camera, a first laser, a second camera and a second laser, the calibration template is placed horizontally, an arrow in an image of the calibration template acquired by the first camera faces upwards, and the first camera and the second camera can both see the complete calibration template. In the image processing process, two combinations can be considered when calibrating the two laser lines, wherein the first combination is that a first camera and a first line laser form first equipment, a second camera and a second line laser form second equipment, the second combination is that the first camera and the second line laser form the first equipment, and the second camera and the first line laser form the second equipment. The technical scheme of the invention can be realized in two modes.
The first combination is used to describe the process of assembling the calibration template data.
1. The equipment is arranged according to the requirements.
2. The dot matrix of the calibration template collected by the first camera and the second camera is shown in fig. 2, and the collected images are artificially attached, wherein the lower left position is the image collected by the first camera, and the upper right position is the image collected by the second camera.
3. Analyzing the acquired data to form an image point-object point pair matrix, wherein the obtained image point-object point pair matrix has the following form:
wherein imnCoordinates of the image point in the m-th row and n-th column, omnRepresenting the object point coordinates of the mth row and nth column.
4. Then, the attitude of the first camera and the attitude matPosture of the second camera are solved according to the image point-object point pair matrix1And matPosture2. The calculation algorithm can be found in the literature [1]]：“Lu,Chien-Ping,Hager,et al.Fast and Globally Convergent Pose Estimation from Video Images.[J].IEEE Transactions on Pattern Analysis &Machine Intelligence,2000”。
5. And calculating and calibrating the three-dimensional coordinates of the dots of the template according to the camera attitude.
The method for calculating the three-dimensional coordinates of the calibration template dots comprises the following steps: and transforming the pixel coordinates of the dot calibration template to world coordinates according to the calibrated camera parameters. Assuming an intrinsic parameter matrix of a camera
Pose matrix of camera
Then the transformation from pixel coordinates to world coordinates is as follows:
wherein
Indicating the coordinates of the pixel that has been distortion corrected,
is the world coordinate obtained.
In the internal parameter matrix of the camera, reference may also be made to document [1] for calibrated and standard parameters of the camera, where f is the focal length of the camera, and u and v are the translation of the optical axis of the camera. R refers to a camera rotation attitude matrix, and T refers to a camera translation attitude matrix.
Referring to fig. 3, it can be seen that the position of the matrix collected and solved by the second camera and the position of the matrix collected and solved by the first camera show a mirror image and an opposite state when the dot matrix of the calibration template is converted into world coordinates.
6. And constructing a second camera dot calibration template coordinate system according to the dot three-dimensional coordinate matrix.
Referring to FIG. 4, a coordinate system is constructed in which the origin of the coordinate system is W22, the XOY plane is the plane of the calibration template, the Z-axis is perpendicular to the plane of the calibration template, the X-axis is from the center point W22 to W20, and the Y-axis is perpendicular to the X-axis and the Z-axis, and the left-hand coordinate system rule is satisfied.
7. Computing a transformation matrix CvtCoord from a second camera world coordinate system to a second camera dot calibration template coordinate system2。
8. And transforming the second camera dot three-dimensional coordinate matrix into the constructed calibration template coordinate system. Hypothetical coordinate system transformation matrix
The second camera dot three-dimensional coordinate matrix is
Then the dot three-dimensional coordinate matrix after being transformed to the calibration template coordinate systemHas the following forms:
matPtBd3D2＝CvtCoord2*matPt3D2equation (3).
9. Referring to FIG. 5, for the second camera dot three-dimensional coordinate matrix matPtBd3D obtained in step 82The mirror transformation is performed with respect to the X-axis.
10. Referring to fig. 6, the second camera dot three-dimensional coordinate matrix obtained in step 9 is subjected to mirror image transformation with respect to the Y-axis.
11. And inversely transforming the dot three-dimensional coordinate matrix subjected to XY-axis mirror image transformation to the original coordinate system.
Assuming a mirror transformation matrix with respect to the X-axis and the Y-axis of
The inverse transformation matrix from the camera 2 calibration template coordinate system to the world coordinate system is
Then the transformation process is as follows:
formula (5) ═ CvtCoordInv2·Imagingxy·matPtBd3D2Equation (6).
12. Calculating a splicing matrix matStitching from the dot three-dimensional coordinate matrix of the second camera inverse transformation to the dot three-dimensional coordinate matrix of the first camera2To1And inverse matrix thereof
13. And (4) multiplying the inverse matrix obtained in the step (12) by the first camera attitude matrix obtained in the step (4) to obtain a new second camera attitude matrix. The new second camera pose matrix can be regarded as the second camera pose matPostpost obtained in the step 42About the X-axis and Y-axis:
14. and calculating a transformation matrix from the second camera attitude used in the laser of the second calibration equipment to the second camera attitude obtained in the step 13. The second camera attitude matrix used when the laser of the second calibration device is assumed to be matPosturceClaib2Then the calculation formula of the transformation matrix is as follows:
matCvtPosture2To2＝matPostureI2 -1·matPostureCalib2equation (8).
15. And calculating a transformation matrix from the second camera pose obtained in the step 4 to the first camera pose obtained in the step 4. The transformation matrix from the second camera pose obtained in step 4 to the first camera pose obtained in step 4 is as follows:
matCrtPosture2To1＝matPosture1 -1·matPosture2...
16. The overall splicing matrix is the transformation matrix obtained in the step 15 multiplied by the transformation matrix obtained in the step 14. The overall splicing matrix is calculated as follows:
matStitchingTotal2To1＝matCvtPosture2To1·matCvtPosture2To2...
Wherein the transformation of step (9) and step (10) may be replaced by an equivalent 180 degree rotation around the Z-axis of the second camera calibration template coordinate system.
The calculation of the splicing matrix can calculate the three-dimensional data of the calibration template, and the data acquisition of the three-dimensional object can be carried out on the basis of the calibration template. The double cameras combine the acquired data into 3D data through the method, and provide data bases for subsequent modeling analysis.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (5)
1. A splicing method for a horizontal motion platform laser scanning calibration template is characterized by comprising the following steps:
the calibration template is a dot calibration template, dots on the calibration template are arranged in an m-n array, double lasers and double cameras are arranged on a horizontal motion platform and synchronously move on the horizontal motion platform, the calibration template falls into the visual field of the double cameras, and one camera and one laser form a calibration device, wherein the splicing method comprises the following steps:
(1) the camera moves on the horizontal motion platform, and at a plurality of preset time points, the camera takes pictures of the calibration template to obtain an image point-object point pair matrix of the calibration template;
(2) calculating a first camera attitude and a second camera attitude according to the image point-object point pair matrix;
(3) converting the pixel coordinates of the dots on the calibration template into world coordinates according to the posture of the camera;
(4) establishing a second camera calibration template coordinate system by taking a calibration template plane as an XOY plane, taking a Z axis as vertical to the calibration template, and taking an original point as a central point of an image point-object point pair matrix;
(5) calculating a transformation matrix from the world coordinate system coordinates of the second camera to the coordinate system coordinates of the calibration template of the second camera;
(6) transforming the transformation matrix of the second camera into the constructed second camera calibration template coordinate system to form a second camera calibration template matrix;
(7) transforming the second camera calibration template matrix into a transformed second camera calibration template matrix corresponding to the first camera calibration template matrix;
(8) converting the transformed second camera calibration template matrix into a world coordinate system of a second camera;
(9) splicing a second camera calibration template matrix in the world coordinate system converted to the second camera and a first camera calibration template matrix in the world coordinate system into a spliced matrix, and calculating an inverse matrix of the spliced matrix;
(10) multiplying the left side of the inverse matrix of the splicing matrix by the first camera attitude matrix to obtain a new second camera attitude matrix, wherein the new second camera attitude matrix and the second camera attitude matrix are mirrored about an X-axis and a Y-axis;
(11) calculating a transformation matrix for changing the second camera attitude matrix into a new second camera attitude matrix;
(12) calculating a transformation matrix from the second camera pose matrix to the first camera pose matrix;
(13) and (4) pre-multiplying the transformation matrix obtained in the step (11) by the transformation matrix obtained in the step (12) to obtain an overall splicing matrix.
2. The splicing method of the horizontal moving platform laser scanning calibration template according to claim 1, characterized in that: the process of the step (7) is as follows:
(71) carrying out mirror image transformation on the second camera calibration template matrix relative to the X axis of the second camera calibration template coordinate system;
(72) and carrying out mirror image transformation on the mirrored second camera calibration template matrix relative to the Y axis of the second camera calibration template coordinate system to obtain a transformed second camera calibration template matrix.
3. The splicing method of the horizontal moving platform laser scanning calibration template according to claim 1, characterized in that: the process of the step (7) is as follows:
and carrying out 180-degree rotation transformation on the second camera calibration template relative to the Z axis of the second camera calibration template coordinate system to obtain a transformed second camera calibration template matrix.
4. The splicing method of the horizontal moving platform laser scanning calibration template according to any one of claims 1 to 3, wherein: the first camera and the first laser form first calibration equipment, and the second camera and the second laser form second calibration equipment.
5. The splicing method of the horizontal moving platform laser scanning calibration template according to any one of claims 1 to 3, wherein: the first camera and the second laser form first calibration equipment, and the second camera and the first laser form second calibration equipment.
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