CN113655466B - Calibration system and calibration method based on structured light triangulation - Google Patents
Calibration system and calibration method based on structured light triangulation Download PDFInfo
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- CN113655466B CN113655466B CN202110808275.8A CN202110808275A CN113655466B CN 113655466 B CN113655466 B CN 113655466B CN 202110808275 A CN202110808275 A CN 202110808275A CN 113655466 B CN113655466 B CN 113655466B
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Abstract
The invention discloses a calibration method based on structured light triangulation, which relates to the technical field of laser ranging and solves the technical problem of high cost of the existing calibration mode, and comprises the following steps: and (3) calibrating the image acquisition equipment by using the checkerboard calibration plate, irradiating a word line laser to the checkerboard calibration plate, acquiring an image of the checkerboard calibration plate, acquiring crossing points of black and white squares in the image, establishing a checkerboard calibration plate coordinate system, calculating actual coordinates of all crossing points, calculating the relative position relation between the image acquisition equipment coordinate system and the checkerboard calibration plate coordinate system, and calculating to obtain a word line laser plane equation of the word line laser in the image acquisition equipment coordinate system. The invention also discloses a calibration system based on structured light triangulation. According to the invention, the relative relation of the laser planes of the cameras is not required to be calibrated by means of an external mechanical moving platform, the parallel installation of the laser planes and the cameras is not required to be limited, and the complexity and the calibration cost of a calibration system are greatly reduced.
Description
Technical Field
The invention relates to the technical field of laser ranging, in particular to a calibration system and a calibration method based on structured light triangulation.
Background
At present, laser ranging is widely applied at home and abroad, and the triangulation method is widely applied to occasions with high precision requirements of various industries due to high precision. The existing calibration method needs to provide the absolute displacement of a reference object by means of an external mechanism, the position relation between the camera and the one-word line laser is calculated through the absolute displacement, the one-word line laser plane needs to be parallel to the single axis of the camera, a complex control system is needed to be built, and the control precision requirement on the mobile platform is high and the cost is high.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art, and provides a calibration method based on structured light triangulation with low cost.
The invention aims at providing a calibration system based on structured light triangulation with low cost.
In order to achieve the above object, the present invention provides a calibration method based on structured light triangulation, including:
step one, calibrating the image acquisition equipment by using a checkerboard calibration plate to obtain a calibration parameter matrix K of the image acquisition equipment,
wherein f x Is focal length in x-axis direction, f y C is focal length in y-axis direction x C is the x-direction coordinate of the optical axis of the image acquisition device in the image coordinate system y The y-direction coordinate of the optical axis of the image acquisition device in an image coordinate system;
step two, irradiating a word line laser to the checkerboard calibration plate and obtaining an image of the checkerboard calibration plate;
step three, obtaining the crossing points of black and white squares in the image to obtain a point set p of the crossing points, wherein the coordinates of a certain point are p (u, v);
step four, a checkerboard calibration plate coordinate system is established according to the checkerboard calibration plate, the actual coordinates of all the crossing points in the step three are obtained according to the checkerboard calibration plate coordinate system, the point set is marked as P, and the coordinates of the ith row and the jth column of points are marked as P ij (X,Y,Z)；
And fifthly, according to the point P (u, v) and the corresponding point P (X, Y, Z), solving a relative position relation (R, t) between the coordinate system of the image acquisition equipment and the coordinate system of the checkerboard calibration plate by using a PnP method, wherein a solving formula of the PnP is as follows:
wherein, by r j The square matrix is a rotation matrix R, t i The composed column vector is a translation vector t;
step six, selecting any two points p from the laser lines in the image 1 ′、p 2 ' calculating the coordinate P under the coordinate system of the checkerboard calibration plate through the calibration parameters of (R, t) and the image acquisition equipment 1 ′、P 2 ' the calculation formula is:
will P 1 ′、P 2 ' converting to an image acquisition equipment coordinate system, and calculating an actual coordinate P corresponding to two points 1 ″、P 2 "the calculation formula is:
step seven, randomly changing the gesture of the checkerboard calibration plate, repeating the steps three to six until N groups of points are acquired, and recording the point P of the coordinate system of the image acquisition equipment in each group of operation 1 ″、P 2 ", and constitutes a point set P";
step eight, calculating an equation by a least square method according to the point set P' obtained in the step seven:
Z＝AX+BY+C，
a word line laser plane equation of a word line laser in an image acquisition device coordinate system is obtained, and coordinates (X, Y, Z) of any point (u, v) on a laser line in the image acquisition device coordinate system are calculated according to the word line laser plane equation, wherein the calculation formula is as follows:
as a further improvement, the establishing a checkerboard calibration plate coordinate system is specifically as follows: taking the upper left corner of the checkerboard calibration plate as the origin of a checkerboard calibration plate coordinate system, taking the long-side direction of the checkerboard calibration plate as the x axis, taking the short-side direction of the checkerboard calibration plate as the y axis, taking the normal direction of the checkerboard calibration plate as the z axis, and calculating the ith row and jth column point P according to the square size squareSize of the checkerboard calibration plate ij Actual coordinates X, Y, Z of (X, Y, Z):
further, in the seventh step, N is not less than 10.
In order to achieve the second purpose, the invention provides a calibration system based on structured light triangulation, which comprises image acquisition equipment, a word line laser transmitter, a checkerboard calibration plate and a computer processing unit, wherein the computer processing unit is in signal connection with the image acquisition equipment and the word line laser transmitter, and the image acquisition equipment and the word line laser transmitter form a triangulation position relationship and are fixed in position;
the word line laser transmitter is used for irradiating a word line laser to the checkerboard calibration plate;
the computer processing unit acquires the image of the checkerboard calibration plate through the image acquisition equipment, and calculates the coordinates of any point selected on the laser line in the image according to the method.
As a further refinement, the image acquisition device is a video camera or a still camera or a video camera.
Advantageous effects
Compared with the prior art, the invention has the advantages that:
the invention does not need to calibrate the relative relation of the laser planes of the cameras by means of an external mechanical moving platform, does not need to limit the parallel installation of the laser planes and the cameras, greatly reduces the complexity of a calibration system and reduces the calibration cost.
Drawings
FIG. 1 is a calibration flow chart of the present invention;
fig. 2 is a schematic diagram of the system of the present invention.
Wherein: 1-image acquisition equipment, 2-word line laser emitter, 3-checkerboard calibration plate and 4-computer processing unit.
Detailed Description
The invention will be further described with reference to specific embodiments in the drawings.
Referring to fig. 1 and 2, a calibration method based on structured light triangulation includes:
step one, calibrating the image acquisition equipment 1 by using the checkerboard calibration plate 3 to obtain a calibration parameter matrix K of the image acquisition equipment 1,
wherein f x Is focal length in x-axis direction, f y C is focal length in y-axis direction x C is the x-direction coordinate of the optical axis of the image acquisition device in the image coordinate system y The y-direction coordinate of the optical axis of the image acquisition device in an image coordinate system;
step two, placing the checkerboard calibration plate 3 in the field of view of the image acquisition equipment 1, irradiating a word line laser to the checkerboard calibration plate 3, and obtaining an image of the checkerboard calibration plate 3;
acquiring a crossing point of black and white squares in the image in a coordinate system on the image to obtain a point set p of the crossing point, wherein the coordinate of a certain point is p (u, v), and u and v represent pixels;
step four, establishing a checkerboard calibration plate coordinate system according to the checkerboard calibration plate 3, obtaining the actual coordinates of all the crossing points in the step three according to the checkerboard calibration plate coordinate system, marking a point set as P, and marking the coordinates of the ith row and the jth column of points as P ij (X,Y,Z)；
Fifth, the point set P corresponds to the points in the point set P one by one, and according to the point P (u, v) and the corresponding point P (X, Y, Z), the relative position relation (R, t) between the coordinate system of the image acquisition device and the coordinate system of the checkerboard calibration plate is solved by using a PnP method, wherein the calculation formula of PnP is as follows:
wherein the vector of the left column of the equal sign is the coordinate of the intersection point on the image, the first matrix of the right side of the equal sign is the calibration parameter matrix K of the image acquisition equipment, the second matrix of the right side of the equal sign is the matrix to be solved, and r is used for solving the problem j The square matrix is a rotation matrix R, t i The formed column vectors are translation vectors t, (R, t) describe the position relationship between the coordinate system of the image acquisition equipment and the coordinate system of the checkerboard calibration plate, and the rightmost column vector is the coordinate of each characteristic point in the coordinate system of the checkerboard calibration plate;
step six, selecting any two points p from the laser lines in the image 1 ′、p 2 ' calculating the coordinate P under the coordinate system of the checkerboard calibration plate through the calibration parameters of (R, t) and the image acquisition equipment 1 ′、P 2 ' the calculation formula is:
wherein, the left column vector of the equal sign is the point coordinate selected under the checkerboard calibration plate coordinate system, R is the rotation matrix calculated in the fifth step, t is the translation vector, K is the calibration parameter matrix of the image acquisition equipment calibrated in the first step, s is the coefficient, and the rightmost column vector is the image pixel coordinate, because of P 1 ′、P 2 'on the same plane, Z' is a constant 0;
will P 1 ′、P 2 ' converting to an image acquisition equipment coordinate system, and calculating an actual coordinate P corresponding to two points 1 ″、P 2 "the calculation formula is:
seventhly, changing the posture of the checkerboard calibration plate 3 as much as possibleRepeating the steps three to six without being parallel to the last time until N groups of points are acquired, wherein N is more than or equal to 10, and recording the point P of the coordinate system of the image acquisition equipment in each group of operation 1 ″、P 2 ", and constitutes a point set P";
step eight, calculating an equation by a least square method according to the point set P' obtained in the step seven:
Z＝AX+BY+C，
a word line laser plane equation of the word line laser in the image acquisition device coordinate system is obtained, and coordinates (X, Y, Z) of any point (u, v) on the laser line in the image acquisition device coordinate system are calculated according to the word line laser plane equation, wherein the calculation formula is as follows:
the calibration parameter matrix K of the camera is obtained through calibration in the step one.
The establishment of the checkerboard calibration plate coordinate system is specifically as follows: the upper left corner of the checkerboard calibration plate 3 is taken as the origin of a checkerboard calibration plate coordinate system, the long side direction of the checkerboard calibration plate 3 is taken as the x axis, the short side direction of the checkerboard calibration plate 3 is taken as the y axis, the normal direction of the checkerboard calibration plate 3 is taken as the z axis, and the j-th row and column point P of the i-th row is calculated according to the square size squareSize of the checkerboard calibration plate 3 ij Actual coordinates X, Y, Z of (X, Y, Z):
the calibration system based on structured light triangulation comprises an image acquisition device 1, a word line laser emitter 2, a checkerboard calibration plate 3 and a computer processing unit 4, wherein the computer processing unit 4 is in signal connection with the image acquisition device 1 and the word line laser emitter 2, for example, the computer processing unit 4 is in signal connection with the image acquisition device 1 and the word line laser emitter 2 through cables, or the computer processing unit 4 is in signal connection with the image acquisition device 1 and the word line laser emitter 2 through wireless signals, and the image acquisition device 1 and the word line laser emitter 2 are in triangulation position relation and fixed in position;
a word line laser emitter 2 for irradiating a word line laser to the checkerboard calibration plate 3;
the computer processing unit 4 acquires the image of the checkered calibration plate 3 through the image acquisition device 1, and calculates coordinates of any point selected on the laser line in the image according to the above method.
The image acquisition device 1 is a video camera or a still camera or a video camera.
The invention does not need to calibrate the relative relation of the laser planes of the cameras by means of an external mechanical moving platform, does not limit the parallel installation of the laser planes and the cameras, reduces the complexity and the calibration cost of a calibration system, and overcomes the defects of the prior calibration scheme that a complex control system is needed and the cost is high.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that modifications and improvements can be made by those skilled in the art without departing from the structure of the present invention, and these do not affect the effect of the implementation of the present invention and the utility of the patent.
Claims (6)
1. A structured light triangulation-based calibration method, comprising:
step one, calibrating the image acquisition equipment (1) by using a checkerboard calibration plate (3) to obtain a calibration parameter matrix K of the image acquisition equipment (1),
wherein f x Is focal length in x-axis direction, f y C is focal length in y-axis direction x C is the x-direction coordinate of the optical axis of the image acquisition device in the image coordinate system y The y-direction coordinate of the optical axis of the image acquisition device in an image coordinate system;
step two, irradiating a word line laser to the checkerboard calibration plate (3) and obtaining an image of the checkerboard calibration plate (3);
step three, obtaining the crossing points of black and white squares in the image to obtain a point set p of the crossing points, wherein the coordinates of a certain point are p (u, v);
step four, establishing a checkerboard calibration plate coordinate system according to the checkerboard calibration plate (3), obtaining the actual coordinates of all the crossing points in the step three according to the checkerboard calibration plate coordinate system, marking a point set as P, and marking the point coordinates of the ith row and the jth column as P ij (X,Y,Z)；
And fifthly, according to the point P (u, v) and the corresponding point P (X, Y, Z), solving a relative position relation (R, t) between the coordinate system of the image acquisition equipment and the coordinate system of the checkerboard calibration plate by using a PnP method, wherein a solving formula of the PnP is as follows:
wherein, by r j The square matrix is a rotation matrix R, t i The composed column vector is a translation vector t;
step six, selecting any two points p from the laser lines in the image 1 ′、p 2 ' calculating the coordinate P under the coordinate system of the checkerboard calibration plate through the calibration parameters of (R, t) and the image acquisition equipment 1 ′、P 2 ' the calculation formula is:
will P 1 ′、P 2 ' converting to an image acquisition equipment coordinate system, and calculating an actual coordinate P corresponding to two points 1 ″、P 2 "the calculation formula is:
step seven, randomly changing the gesture of the checkerboard calibration plate (3), repeating the steps three to six until N groups of points are acquired, and recording images in each group of operationsAcquisition of a point P of a device coordinate system 1 ″、P 2 ", and constitutes a point set P";
step eight, calculating an equation by a least square method according to the point set P' obtained in the step seven:
Z＝AX+BY+C，
a word line laser plane equation of a word line laser in an image acquisition device coordinate system is obtained, and coordinates (X, Y, Z) of any point (u, v) on a laser line in the image acquisition device coordinate system are calculated according to the word line laser plane equation, wherein the calculation formula is as follows:
2. the calibration method based on structured light triangulation according to claim 1, wherein the establishing a checkerboard calibration plate coordinate system is specifically: calculating the ith row and jth column point P according to square size squareSize of the checkerboard calibration plate (3) by taking the upper left corner of the checkerboard calibration plate (3) as the origin of the checkerboard calibration plate coordinate system, taking the long side direction of the checkerboard calibration plate (3) as the x axis, taking the short side direction of the checkerboard calibration plate (3) as the y axis and taking the normal direction of the checkerboard calibration plate (3) as the z axis ij Actual coordinates X, Y, Z of (X, Y, Z):
3. the method according to claim 1, wherein in the step seven, N is equal to or greater than 10.
4. A calibration method based on structured light triangulation according to claim 1, characterized in that the image acquisition device (1) is a video camera or a still camera or a video camera.
5. The calibration system based on structured light triangulation is characterized by comprising image acquisition equipment (1), a word line laser emitter (2), a checkerboard calibration plate (3) and a computer processing unit (4), wherein the computer processing unit (4) is in signal connection with the image acquisition equipment (1) and the word line laser emitter (2), and the image acquisition equipment (1) and the word line laser emitter (2) form a triangulation position relationship and are fixed in position;
the word line laser transmitter (2) is used for irradiating a word line laser to the checkerboard calibration plate (3);
the computer processing unit (4) acquires the image of the checkerboard calibration plate (3) through the image acquisition device (1), and calculates coordinates of any point selected on a laser line in the image according to the method of any one of claims 1 to 4.
6. A structured light triangulation based calibration system according to claim 5, characterized in that the image acquisition device (1) is a video camera or a camera head.
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