CN106910221B - Global calibration method and device - Google Patents
Global calibration method and device Download PDFInfo
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- CN106910221B CN106910221B CN201710064220.4A CN201710064220A CN106910221B CN 106910221 B CN106910221 B CN 106910221B CN 201710064220 A CN201710064220 A CN 201710064220A CN 106910221 B CN106910221 B CN 106910221B
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- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/30—Subject of image; Context of image processing
- G06T2207/30244—Camera pose
Abstract
The invention relates to a global calibration method and a device, which are used for calibrating a system comprising a camera array and a rotary table, wherein at least one calibration chessboard is arranged on the rotary table during execution, and the calibration chessboard can rotate along with the rotary table, and the method comprises the following steps: controlling the rotary table to rotate, and respectively obtaining shot pictures of the calibration chessboard from more than two directions; determining the position relation between the camera and the calibration chessboard and the position relation between the cameras according to the shot pictures; determining the rotation center of the turntable through more than two shot pictures and a three-dimensional world coordinate system of a calibration chessboard; and determining the pose relationship between the camera and the rotary table according to the position relationship between the camera and the calibration chessboard, the position relationship between the cameras and the rotation center of the rotary table. The calibration chessboard auxiliary computer is used for calibrating the pose relation between the camera array and the rotary table in the system, the hardware equipment cost is low, the installation is simple and convenient, and the method is simple in implementation process.
Description
Technical Field
The invention relates to the technical field of computer vision, in particular to a global calibration method and a global calibration device.
Background
In the field of computer vision and industrial measurement, a platform with a matched turntable and a camera is often needed to assist in smooth measurement process. In the conventional calibration method, high-precision and high-stability hardware is often required to be designed to ensure the determined spatial pose relationship between the hardware and the pose relationship, and particularly, under the complex working condition, the method for ensuring the overall calibration precision through the hardware precision has high cost and poor adaptability.
Disclosure of Invention
In view of the foregoing, it is desirable to provide a method and an apparatus for global calibration that perform global calibration with simple hardware configuration.
The global calibration method of one embodiment is used for calibrating a system comprising a camera array and a rotary table, at least one calibration chessboard is arranged on the rotary table, and the calibration chessboard can rotate along with the rotary table, and the method comprises the following steps:
controlling the rotary table to rotate, and respectively obtaining the shot pictures of the calibration chessboard from more than two directions;
determining the position relationship between the camera and the calibration chessboard and the position relationship between the cameras according to the shot pictures;
determining the rotation center of the turntable through more than two shot pictures and the three-dimensional world coordinate system of the calibration chessboard;
and determining the pose relationship between the camera and the rotary table according to the position relationship between the camera and the calibration chessboard, the position relationship between the cameras and the rotation center of the rotary table.
In the global calibration method of one embodiment, two calibration checkerboards, a horizontal calibration checkerboard and a vertical calibration checkerboard are arranged on a turntable, an included angle between the horizontal calibration checkerboard and the turntable is smaller than 90 degrees, the horizontal calibration checkerboard can be shot by at least one camera, and the vertical calibration checkerboard can be shot by all cameras in a camera array.
In the global calibration method of one embodiment, the horizontal calibration chessboard is attached to the table top of the rotary table.
In the global calibration method of one embodiment, the included angle between the vertical calibration chessboard and the turntable top surface is in the range of 80-100 degrees.
In the method of global calibration of one embodiment, the shot pictures of the calibration checkerboard are taken from 8 different orientations.
In the method for global calibration according to one embodiment, the determining a rotation center of the turntable through the two or more taken pictures and the three-dimensional world coordinate system of the calibration chessboard includes:
performing least square fitting to determine an initial coordinate value of the rotation center of the turntable according to the position relationship between a camera coordinate system of a camera capable of shooting a horizontal calibration chessboard and a horizontal calibration chessboard coordinate system and the three-dimensional world coordinates of all horizontal calibration chessboard corner points;
and adopting a rotation radius constraint mode to ensure that the cameras are distributed on the circumference around the center of the turntable, and optimally adjusting the initial coordinate value to obtain the optimal coordinate value of the rotation center of the turntable.
In the global calibration method of one embodiment, the position relationship between each camera and the camera capable of shooting the horizontal calibration chessboard is determined through the vertical calibration chessboard in the shot pictures in different directions;
the determining the position relationship between the camera and the turntable through the position relationship between the camera and the calibration chessboard, the position relationship between the cameras and the rotation center of the turntable comprises:
the position of the rotation center of the rotary table under the horizontal calibration chessboard coordinate system is used for establishing a global world coordinate system which takes the center of the rotary table as an original point and the table top of the rotary table as an XOY plane through translation transformation of the coordinate system;
determining the position and posture relation of the camera capable of shooting the horizontal calibration chessboard in the global world coordinate system according to the position relation between the camera capable of shooting the horizontal calibration chessboard and the horizontal calibration chessboard coordinate system;
and determining the pose relationship of each camera in the camera array in the global world coordinate system according to the position relationship between each camera and the camera capable of shooting the horizontal calibration chessboard.
Based on the same inventive concept, a global calibration device is further provided, which is used for calibrating a system comprising a camera array and a turntable, wherein at least one calibration chessboard is arranged on the turntable and can rotate along with the turntable, and the global calibration device comprises:
the picture shooting control module is used for controlling the camera to respectively obtain the shot pictures of the calibration chessboard from more than two directions;
the position relation determining module is used for determining the position relation between the camera and the calibration chessboard and the position relation between the cameras according to the shot pictures;
the rotation center determining module is used for determining the rotation center of the turntable through more than two shot pictures and the three-dimensional world coordinate system of the calibration chessboard;
and the position calibration module is used for determining the position and posture relation between the camera and the rotary table according to the position relation between the camera and the calibration chessboard, the position relation between the cameras and the rotation center of the rotary table.
In the global calibration device of one embodiment, two calibration chessboard, one horizontal calibration chessboard and one vertical calibration chessboard, are arranged on a turntable, an included angle between the horizontal calibration chessboard and the turntable is less than 90 degrees, the horizontal calibration chessboard can be shot by at least one camera, and the vertical calibration chessboard can be shot by all cameras in a camera array;
the rotation center determining module includes:
the initial value calculation submodule is used for performing least square fitting to determine the initial coordinate value of the rotation center of the turntable according to the position relation between a camera coordinate system of a camera capable of shooting a horizontal calibration chessboard and a horizontal calibration chessboard coordinate system and the three-dimensional world coordinates of all horizontal calibration chessboard angular points;
and the central coordinate optimization submodule is used for distributing the cameras on a circumference around the center of the rotary table in a rotating radius constraint mode, optimizing and adjusting the initial coordinate value and obtaining the optimal coordinate value of the rotating center of the rotary table.
In the global calibration device of one embodiment, the position relationship between each camera and the camera capable of shooting the horizontal calibration chessboard is determined through the vertical calibration chessboard in the shot pictures in different directions;
the position calibration module comprises:
the global world coordinate system establishing submodule is used for establishing a global world coordinate system which takes the center of the rotary table as an origin and takes the table top of the rotary table as an XOY plane through translation transformation of the coordinate system according to the position of the rotation center of the rotary table under the horizontal calibration chessboard coordinate system;
the horizontal shooting camera pose relationship determining submodule is used for determining the pose relationship of the camera capable of shooting the horizontal calibration chessboard in the global world coordinate system according to the position relationship between the camera capable of shooting the horizontal calibration chessboard and the horizontal calibration chessboard coordinate system;
and the global position and pose determining submodule is used for determining the position and pose relationship of each camera in the camera array in the global world coordinate system according to the position relationship between each camera and the camera capable of shooting the horizontal calibration chessboard.
The beneficial effects of the invention include: according to the global calibration method, the calibration chessboard is arranged on the electric turntable, the position between the cameras and the electric turntable and the position between the cameras are determined through the shot pictures containing the calibration chessboard, and finally the calibration of the position and posture relation between each camera in the camera array and the electric turntable is realized. The method has the advantages of simple implementation process, low cost of required hardware equipment and simple and convenient installation. And the calibration of the pose relationship between the high-precision camera and the electric turntable can be realized by multi-azimuth picture shooting and high-precision image processing of an auxiliary computer.
Drawings
FIG. 1 is a schematic diagram of a system architecture for global calibration;
FIG. 2 is a flowchart of an embodiment of a global calibration method of the present invention;
FIG. 3 is a schematic view of a calibration checkerboard provided to the system turntable;
FIG. 4 is a schematic diagram of the overall structure of the system provided with the calibration chessboard;
FIG. 5 is a schematic diagram of an embodiment of a global calibration apparatus;
FIG. 6 is a block diagram of a rotation center determining module of an embodiment of a global calibration apparatus;
fig. 7 is a schematic structural diagram of a position calibration module according to an embodiment of the global calibration apparatus.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clearly understood, specific embodiments of the global calibration method and system of the present invention are described below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The global calibration method of the following embodiments is suitable for global calibration of a pose relationship between a camera and a turntable in a system including a camera array and the turntable. As shown in fig. 1, the system to be calibrated generally includes a motor-driven turntable 010 and a camera array including a plurality of cameras. The camera array as shown in fig. 1 includes a first camera 2-1, a second camera 2-2, a third camera 2-3, … …, an nth camera 2-n. Wherein n is a positive integer greater than 3. The number of cameras can be set according to needs, for example, 3, 5 or 8 cameras can be set. Of course, if necessary, only two cameras may be provided in a certain system.
Specifically, in the global calibration method, at least one calibration chessboard is arranged on the rotary table, and the calibration chessboard can rotate together with the rotary table. When the pose relationship between the camera and the rotary table in the system is calibrated, as shown in fig. 2, the method comprises the following steps:
s100, controlling the rotary table to rotate, and respectively obtaining shot pictures for calibrating the chessboard from more than two directions. In the method of this embodiment, in order to determine the pose relationship between the camera and the turntable by calibrating the chessboard, a plurality of images taken on the calibration chessboard need to be taken from a plurality of angles. The control of the electric turntable can be synchronous with the control of the camera, and the electric turntable can also be controlled to rotate independently. The rotation angle of the electric turntable can be recorded, and the electric turntable can play an auxiliary role when the position relation between the camera and the chessboard and between the camera and the electric turntable is calibrated according to the calibrated chessboard in the shot picture. However, the positional relationship between the camera and the electric turntable may be calibrated only from the taken pictures taken at a plurality of angles without recording the rotation angle of the electric turntable.
It should be noted that, in order to determine the position relationship between the camera and the electric turntable according to the calibration chessboard in the captured picture, at least one calibration chessboard which is not perpendicular to the table top of the electric turntable is provided in this embodiment. And only one calibration chessboard which can be shot by all cameras can be arranged, and the calibration chessboard is not vertical to the table top of the electric turntable. And in the subsequent pose calibration process, the position relationship among the cameras and the relationship between the cameras and the electric turntable are determined only according to the position of the calibration chessboard in the shot picture. In other embodiments, more than two calibration chessboards may be provided, at least one of which can be captured by all cameras in the camera array for determining the positional relationship between the cameras. And at least one calibration chessboard which is not vertical to the table top of the electric turntable can be shot by one camera in the camera array and is used for determining the position relation between the camera and the electric turntable.
The number of the shot pictures to be shot and the shooting directions can be set according to requirements, and in order to achieve calibration of the turntable and the camera with higher accuracy, pictures can be shot in multiple directions as much as possible, for example, pictures in 8 directions or more directions can be shot. Of course, only two azimuth pictures may be taken.
S200, determining the position relation between the camera and the calibration chessboard and the position relation between the cameras according to the shot pictures.
With reference to the foregoing description, in this step, if there is only one calibration chessboard, the positional relationship between the cameras and the calibration chessboard is determined according to the shot pictures taken from multiple orientations, and the positional relationship between each camera and the calibration chessboard is determined according to the positional relationship between the cameras.
When the calibration chessboard is not one, one of the cameras can be selected as an initial position camera, and the position relation between the camera and one of the calibration chessboard is determined. And further the position relationship between other cameras and the aforementioned camera can be determined in combination with another calibration chessboard. And further analyzing the determined position relations, and finally calibrating the pose relations between the cameras and the electric rotary table.
And S300, determining the rotation center of the turntable by more than two pictures and calibrating the three-dimensional world coordinate system of the chessboard.
In this step, the determined rotation center of the turntable is based on the three-dimensional world coordinate system of the calibration chessboard, wherein when only one calibration chessboard is set on the electric turntable, the rotation center is determined based on the unique calibration chessboard, and when more than two calibration chessboards are set on the electric turntable, the calibration chessboard based in this step is the calibration chessboard in the positional relationship between the camera corresponding to the initial position camera selected in step S200 and the calibration chessboard. And the rotation center of the turntable finally determined in the step is the rotation center based on the world coordinate system.
And S400, determining the pose relationship between the camera and the rotary table according to the position relationship between the camera and the calibration chessboard, the position relationship between the cameras and the rotation center of the rotary table.
The center of the rotary table is finally determined by combining the calibration chessboard, so that the position relationship between the center of the rotary table and the three-dimensional world coordinate system of the calibration chessboard can be determined, and the position relationship between the camera and the rotation center of the rotary table can be finally determined by combining the position relationship between the camera and the calibration chessboard, namely the position and posture relationship between the camera and the rotary table is determined. Still further, since the positional relationship between the cameras in the camera sequence is determined by taking pictures, the positional relationship between the cameras and the turn table can be determined.
In the global calibration method of this embodiment, a calibration chessboard is arranged on the electric turntable, and the position between the cameras and the electric turntable and the position between the cameras are determined by taking a picture including the calibration chessboard, so as to finally realize the calibration of the pose relationship between each camera in the camera array and the electric turntable. The method has the advantages of simple implementation process, low cost of required hardware equipment and simple and convenient installation. And the calibration of the pose relationship between the high-precision camera and the electric turntable can be realized by multi-azimuth picture shooting and high-precision image processing of an auxiliary computer.
In one embodiment, as shown in FIG. 3, two calibration boards, a horizontal calibration board 3-2 and a vertical calibration board 3-1, are provided on the turntable. The included angle between the horizontal calibration chessboard 3-2 and the rotary table is less than 90 degrees, and preferably close to 0 degree. In the actual installation process, the horizontal calibration chessboard 3-2 can be attached to the table top of the electric turntable. The effect of the mounting of the calibration chessboard to the turntable is shown in figure 4. And the horizontal calibration chessboard can be shot by at least one camera and used for determining the position relation between the initial position camera and the horizontal calibration chessboard. The vertical calibration checkerboard 3-1 can be captured by all cameras in the camera array for determining the positional relationship between the cameras, in particular, the positional relationship between the other cameras in the camera array and the initial position camera.
In a specific example, a vertical calibration chessboard 3-1 for calibrating the position relationship between the cameras is arranged to be perpendicular to the table top of the electric turntable, i.e. the vertical calibration chessboard 3-1 forms an angle of 90 degrees with the table top of the turntable. The setting can greatly reduce the difficulty of subsequent image processing, is convenient for determining the position relation between cameras through pictures, and improves the image processing efficiency, namely the relation processing efficiency.
When the calibration chessboard is arranged, the optical center direction of the camera is adjusted to be opposite to the rotating chessboard. The corresponding focal length of the cameras is properly adjusted, so that the rotary table can clearly image under each camera and fully cover the whole image plane as much as possible. The three-dimensional calibration board (calibration chessboard) is placed on the turntable, the plane direction of the chessboard faces the direction of the array camera as much as possible, the corresponding position of the chessboard is manually adjusted, the horizontal calibration chessboard surface and the vertical calibration chessboard surface can be clearly seen by the camera 2-1 at the same time, and the inclination of the camera 2-1 relative to the horizontal calibration chessboard visual angle cannot be too large, so that the accurate identification and extraction of the subsequent chessboard angular points are ensured. Meanwhile, other cameras in the camera array are ensured to clearly see the vertical calibration chess board surface. Then, by utilizing the rotation of the rotary table and the snapshot function of the camera, when the rotary table rotates for a certain angle, the two cameras synchronously snapshot the calibration image.
More specifically, as an implementation manner, when picture shooting is performed, the rotation of the turntable is controlled, shot images are synchronously captured and obtained from 8 different angles of the turntable respectively, and it is ensured that in all 8 obtained images, the camera 2-1 can clearly see the horizontal and vertical calibration chessboard angular points, and other cameras can clearly see the vertical calibration chessboard angular points.
Specifically, when two calibration chessboard are set for calibrating the pose relationship between the camera and the electric turntable as shown in fig. 3, step S300 is performed to determine the rotation center of the turntable by taking more than two pictures and calibrating the three-dimensional world coordinate system of the chessboard, which includes the following steps:
s310, according to the position relation between the camera coordinate system of the camera capable of shooting the horizontal calibration chessboard and the horizontal calibration chessboard coordinate system and the three-dimensional world coordinates of all horizontal calibration chessboard corner points, performing least square fitting to determine the initial coordinate value of the rotating center of the rotating platform.
Specifically, as shown in fig. 3, a camera 2-1 is set as an initial position camera, and an image of an angular point 3-2 of a horizontal calibration chessboard acquired by the camera 2-1 rotates horizontally around the center of a rotating shaft of a turntable along with the turntable during the rotation of the turntable. Therefore, the rotating center position of the turntable can be obtained through fitting according to the three-dimensional world coordinates of the chessboard angular points obtained under different angles.
As shown in fig. 4, when the camera is fixed and the turntable 100 rotates, the camera moves around the center of the turntable in a spatial cone, which is the same as the case where the turntable is fixed. Obtaining an external parameter [ R ] between a camera coordinate system and a checkerboard coordinate system through a camera at 8 different positions (1) - (8)i Ti](i ═ 1, …, 8). Under the three-dimensional world coordinate system of the horizontal calibration chessboard 3-2, the three-dimensional world coordinate of each corner point is Pi＝[xi yi zi](i-1, …, N), where N is the number of corners of the board, ziDefault to 0. When the horizontal calibration chessboard 3-2 rotates 8 different positions, the three-dimensional world coordinates of all the angular points (8 x N) are utilized to obtain the rotation center (x) of the turntable through least square fittingc,yc，0)。
And S320, distributing the cameras on the circumference around the center of the turntable in a rotating radius constraint mode, and optimizing and adjusting the initial coordinate value to obtain the optimal coordinate value of the rotating center of the turntable.
The theoretical distance between the origin of the central coordinate system of the turntable and the origin coordinate system of the camera 2-1 is a constant value d. Therefore, by using a Bundle Adjustment (Bundle Adjustment) algorithm, the constraint of the rotation radius d is increased, the cameras are distributed on the circumference around the center of the turntable, and the optimal rotation center coordinate is obtained by optimizing and adjusting.
In the embodiment, the position relationship between each camera and the camera capable of shooting the horizontal calibration chessboard 3-2 is determined through the vertical calibration chessboard in the shot pictures in different directions. Specifically, step S400, determining the position relationship between the camera and the turntable through the position relationship between the camera and the calibration board, the position relationship between the camera and the rotation center of the turntable includes:
s410, the position of the rotating center of the rotary table under the horizontal calibration chessboard coordinate system is subjected to translation transformation of the coordinate system, and a global world coordinate system of a global world coordinate system with the center of the rotary table as an origin and the tabletop of the rotary table as an XOY plane is established. Finally determining the central coordinates (x) of the turntablec,yc，0)。
And S420, determining the position and posture relation of the camera capable of shooting the horizontal calibration chessboard in the global world coordinate system according to the position relation between the camera capable of shooting the horizontal calibration chessboard and the horizontal calibration chessboard coordinate system.
And S430, determining the pose relationship of each camera in the camera array in the global world coordinate system according to the position relationship between each camera and the camera capable of shooting the horizontal calibration chessboard.
In the embodiment, a vertical calibration checkerboard image is obtained by two cameras, and internal parameters In _ a and In _ b of the two cameras 2-1 and 2-2 are calibrated simultaneously by using a Zhangyingyou plane checkerboard calibration method. Since the mutual positional relationship between the two cameras is fixed at each image acquisition position. Therefore, the global optimization method can be used to obtain the optimized position relationship between the two cameras for different external parameters obtained from 8 calibration images [ R T ]]. The central coordinate system of the turntable is taken as a world coordinate system WcObtaining a 2-1 coordinate system W of the camerac2-12-2 coordinate system W of camerac2-2With the world coordinate system WcThe pose relationship between the two cameras realizes the pose calibration between the two cameras and the rotary table. Further, due to the arrangement in the camera arraySome cameras can shoot the vertical calibration chessboard, so that the pose relationship between each camera and the camera 2-1 can be determined according to shot pictures, and the global calibration of the array camera system and the rotary table is realized by adopting the same steps as the camera 2-2 calibration.
It should be noted that, In the present embodiment, the intrinsic parameters In _ a and In _ b of the two cameras 2-1 and 2-2 are calibrated simultaneously by using the calibration method of the Zhangyingyou plane chessboard, and In other embodiments, the intrinsic parameters of the cameras may also be calibrated by using other calibration methods.
In addition, it should be further described that in the global calibration method of this embodiment, the shot pictures acquired by the camera may be uploaded to an upper computer (computer) for analysis and processing, and the control of the turntable and the control of the camera snapshot may also be implemented by the same upper computer.
Based on the same inventive concept, a global calibration device is also provided, and as the principle of solving the problems of the device is similar to that of the global calibration method, the implementation of the device can be realized according to the specific steps of the method, and repeated parts are not repeated. The device is used for calibrating a system comprising a camera array and a rotary table, at least one calibration chessboard is also arranged on the rotary table in the implementation process, and the calibration chessboard can rotate along with the rotary table.
As shown in fig. 5, the apparatus for global calibration according to an embodiment includes a picture taking control module 100, a position relation determining module 200, a rotation center determining module 300, and a position calibration module 400. The picture shooting control module 100 is configured to control a camera to respectively obtain shot pictures for calibrating a chessboard from more than two directions; the position relation determining module 200 is configured to determine a position relation between the camera and the calibration chessboard and a position relation between the cameras according to the shot pictures; the rotation center determining module 300 is configured to determine a rotation center of the turntable through more than two taken pictures and a three-dimensional world coordinate system of the calibration chessboard; the position calibration module 400 is configured to determine a pose relationship between the camera and the turntable according to a position relationship between the camera and the calibration chessboard, a position relationship between the cameras, and a rotation center of the turntable.
The device adopts the mode of arranging the calibration chessboard on the electric turntable to calibrate the camera array and the turntable, has simple structure and convenient installation, and has good overall calibration effect by adopting a computer image analysis mode.
In one embodiment, two calibration chessboard, one horizontal calibration chessboard and one vertical calibration chessboard are arranged on the rotary table, the included angle between the horizontal calibration chessboard and the rotary table is less than 90 degrees, and the horizontal calibration chessboard can be shot by at least one camera and is used for determining the center of the rotary table. The vertical calibration chessboard can be shot by all the cameras in the camera array, and is used for determining the position relationship among the cameras, mainly the position relationship between each camera and the camera which can shoot the horizontal calibration chessboard in front.
In this embodiment, as shown in FIG. 6, the rotation center determining module 300 includes an initial value calculating sub-module 310 and a center coordinate optimizing sub-module 320. The initial value calculating submodule 310 is configured to perform least square fitting according to a position relationship between a camera coordinate system of a camera capable of shooting a horizontal calibration chessboard and a horizontal calibration chessboard coordinate system and three-dimensional world coordinates of corner points of all horizontal calibration chessboard to determine an initial value of a coordinate of a rotation center of a turntable; the central coordinate optimization submodule 320 is configured to distribute the cameras on a circumference around the center of the turntable in a rotation radius constraint manner, and optimize and adjust an initial coordinate value to obtain a coordinate optimized value of the rotation center of the turntable.
Furthermore, the position relation between each camera and the camera capable of shooting the horizontal calibration chessboard is determined through the vertical calibration chessboard in the shot pictures under different directions. The position calibration module 400 for final pose relationship calibration includes a global world coordinate system establishing sub-module 410, a horizontal shooting camera pose relationship determining sub-module 420, and a global pose determining sub-module 430. The global world coordinate system establishing submodule 410 is configured to establish a global world coordinate system with the turntable center as an origin and the turntable top as an XOY plane through coordinate system translation transformation according to the position of the rotation center of the turntable under the horizontal calibration chessboard coordinate system. The horizontal shooting camera pose relationship determining sub-module 420 is configured to determine, according to a position relationship between a camera capable of shooting the horizontal calibration chessboard and a coordinate system of the horizontal calibration chessboard, a pose relationship of the camera capable of shooting the horizontal calibration chessboard in the global world coordinate system. The global pose determining sub-module 430 is configured to determine a pose relationship of each camera in the camera array in the global world coordinate system according to a position relationship between each camera and a camera capable of shooting the horizontal calibration chessboard.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by a computer program, which can be stored in a computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (9)
1. A global calibration method for calibrating a system including a camera array and a turntable, wherein the camera array includes more than three cameras, two calibration boards are disposed on the turntable, a horizontal calibration board and a vertical calibration board, an included angle between the horizontal calibration board and the turntable is less than 90 degrees, the horizontal calibration board can be captured by at least one camera, the vertical calibration board can be captured by all the cameras in the camera array, and the calibration boards can rotate together with the turntable, the method comprising the steps of:
controlling the rotary table to rotate, and controlling the cameras in the camera array to respectively acquire the shot pictures of the calibration chessboard from more than two directions;
determining the position relation between a camera and the horizontal calibration chessboard according to the shot pictures of the horizontal calibration chessboard;
determining the position relation between the cameras according to the shot pictures of the vertical calibration chessboard shot by different cameras;
performing least square fitting to determine a rotation center of the turntable according to the position relation between a camera coordinate system capable of shooting a horizontal calibration chessboard and a horizontal calibration chessboard coordinate system and the three-dimensional world coordinates of all horizontal calibration chessboard angular points;
and determining the pose relationship between the camera and the rotary table according to the position relationship between the camera and the horizontal calibration chessboard, the position relationship between the cameras and the rotation center of the rotary table.
2. The method of global calibration according to claim 1, wherein said horizontal calibration chessboard is attached to said turntable table top.
3. The method for global calibration according to claim 1, wherein the included angle between the vertical calibration chessboard and the turntable top is in the range of 80-100 degrees.
4. Method of global calibration according to claim 1, wherein the taken pictures of the calibration checkerboard are taken from 8 different orientations.
5. The global calibration method as claimed in claim 1, wherein said determining the rotation center of the turntable by performing least square fitting according to the position relationship between the camera coordinate system capable of photographing the horizontal calibration chessboard and the coordinate system of the horizontal calibration chessboard and the three-dimensional world coordinates of all the horizontal calibration chessboard corner points comprises:
performing least square fitting to determine an initial coordinate value of the rotation center of the turntable according to the position relation between a camera coordinate system capable of shooting a horizontal calibration chessboard and a coordinate system of the horizontal calibration chessboard and the three-dimensional world coordinates of all corner points of the horizontal calibration chessboard;
and adopting a rotation radius constraint mode to ensure that the cameras are distributed on the circumference around the center of the turntable, and optimally adjusting the initial coordinate value to obtain the optimal coordinate value of the rotation center of the turntable.
6. The global calibration method according to claim 5, wherein the position relationship between each camera and the camera capable of shooting the horizontal calibration chessboard is determined by the vertical calibration chessboard in the shot pictures under different orientations;
the determining the position relationship between the camera and the rotary table through the position relationship between the camera and the horizontal calibration chessboard, the position relationship between the cameras and the rotation center of the rotary table comprises:
the position of the rotation center of the rotary table under the horizontal calibration chessboard coordinate system is used for establishing a global world coordinate system which takes the center of the rotary table as an original point and the table top of the rotary table as an XOY plane through translation transformation of the coordinate system;
determining the position and posture relation of the camera capable of shooting the horizontal calibration chessboard in the global world coordinate system according to the position relation between the camera capable of shooting the horizontal calibration chessboard and the horizontal calibration chessboard coordinate system;
and determining the pose relationship of each camera in the camera array in the global world coordinate system according to the position relationship between each camera and the camera capable of shooting the horizontal calibration chessboard.
7. An apparatus for global calibration for calibrating a system including a camera array and a turntable, wherein the camera array includes more than three cameras, two calibration boards are disposed on the turntable, a horizontal calibration board and a vertical calibration board, an included angle between the horizontal calibration board and the turntable is less than 90 degrees, the horizontal calibration board can be captured by at least one camera, the vertical calibration board can be captured by all the cameras in the camera array, and the calibration boards can rotate with the turntable, the apparatus comprising:
the picture shooting control module is used for controlling the cameras in the camera array to respectively obtain the shot pictures of the calibration chessboard from more than two directions;
the position relation determining module is used for determining the position relation between the camera and the horizontal calibration chessboard according to the shot pictures shot on the horizontal calibration chessboard; determining the position relation between the cameras according to the shot pictures of the vertical calibration chessboard shot by different cameras;
the rotating center determining module is used for performing least square fitting according to the position relation between a camera coordinate system of a camera capable of shooting the horizontal calibration chessboard and a horizontal calibration chessboard coordinate system and the three-dimensional world coordinates of all horizontal calibration chessboard angular points to determine the rotating center of the rotating platform;
and the position calibration module is used for determining the position and posture relation between the camera and the rotary table according to the position relation between the camera and the horizontal calibration chessboard, the position relation between the cameras and the rotation center of the rotary table.
8. Apparatus for global calibration according to claim 7,
the rotation center determining module includes:
the initial value calculation submodule is used for performing least square fitting to determine the initial coordinate value of the rotation center of the turntable according to the position relation between a camera coordinate system of a camera capable of shooting a horizontal calibration chessboard and a horizontal calibration chessboard coordinate system and the three-dimensional world coordinates of all horizontal calibration chessboard angular points;
and the central coordinate optimization submodule is used for distributing the cameras on a circumference around the center of the rotary table in a rotating radius constraint mode, optimizing and adjusting the initial coordinate value and obtaining the optimal coordinate value of the rotating center of the rotary table.
9. The global calibration device according to claim 8, wherein the position relationship between each camera and the camera capable of shooting the horizontal calibration chessboard is determined by the vertical calibration chessboard in the shot pictures under different orientations;
the position calibration module comprises:
the global world coordinate system establishing submodule is used for establishing a global world coordinate system which takes the center of the rotary table as an origin and takes the table top of the rotary table as an XOY plane through translation transformation of the coordinate system according to the position of the rotation center of the rotary table under the horizontal calibration chessboard coordinate system;
the horizontal shooting camera pose relationship determining submodule is used for determining the pose relationship of the camera capable of shooting the horizontal calibration chessboard in the global world coordinate system according to the position relationship between the camera capable of shooting the horizontal calibration chessboard and the horizontal calibration chessboard coordinate system;
and the global position and pose determining submodule is used for determining the position and pose relationship of each camera in the camera array in the global world coordinate system according to the position relationship between each camera and the camera capable of shooting the horizontal calibration chessboard.
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| CN108038886B (en) * | 2017-12-06 | 2020-09-01 | 智车优行科技（北京）有限公司 | Binocular camera system calibration method and device and automobile |
| CN109407613B (en) * | 2018-08-30 | 2020-12-15 | 先临三维科技股份有限公司 | Adjusting method and device of three-dimensional scanning turntable, computer equipment and storage medium |
| CN110246191B (en) * | 2019-06-13 | 2021-03-16 | 易思维（杭州）科技有限公司 | Camera nonparametric model calibration method and calibration precision evaluation method |
| CN110611770B (en) * | 2019-10-08 | 2021-07-30 | 凌云光技术股份有限公司 | Method and system for judging whether line frequency of linear array camera is matched with object motion speed |
| CN110987021B (en) * | 2019-12-25 | 2021-08-24 | 湖北航天技术研究院总体设计所 | Inertial vision relative attitude calibration method based on rotary table reference |
| CN111260721B (en) * | 2020-01-13 | 2023-08-15 | 深圳市美鼎恒自动化科技有限公司 | Remote multi-camera alignment method and device and related equipment |
| CN116188602A (en) * | 2023-04-26 | 2023-05-30 | 西北工业大学青岛研究院 | High-precision calibration method for underwater multi-vision three-dimensional imaging system |
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