CN111242901A - Space point-based global calibration system and method for automobile detection camera without common view field - Google Patents
Space point-based global calibration system and method for automobile detection camera without common view field Download PDFInfo
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Abstract
The invention discloses a space point-based global calibration system and method for a common-view-field-free camera in automobile detection, and aims to solve the problem that the space point-based global calibration system and method for the common-view-field-free camera in the automobile detection are not provided. The automobile detection common-view-field-free camera global calibration system based on the space points mainly comprises a main camera (1), a main camera support (2), a branch camera left (3), a branch camera support left (4), a branch camera right (5), a branch camera support right (6) and a cylindrical target (7). The global calibration method of the automobile detection common-view-field-free camera based on the space points comprises the steps of image acquisition, calculation of a homography matrix converted from a cylindrical target (7) to a total camera (1) coordinate system according to an image acquired by the total camera (1) and the like, and provides the global calibration system and method of the automobile detection common-view-field-free camera based on the space points, which are simple in structure and reliable in performance.
Description
Technical Field
The invention relates to a measuring device and a measuring method in the field of automobile detection, in particular to a space point-based automobile detection common-view-field-free camera global calibration system and method.
Background
The research aim in the field of automobile performance detection is to regularly detect important performances such as safety, reliability and trafficability of an automobile, and ensure safe operation of the automobile and life and property safety of road users. The visual detection has the advantages of non-contact, low cost, high precision and the like, and has important research significance and wide application prospect in important research directions of automobile performance detection such as automobile wheel alignment parameter detection, automobile wheelbase difference detection, automobile appearance detection, multi-axis axle deflection angle detection, automobile type identification and the like. Because the field of view of a single video camera is limited, the requirements for measuring the appearance of large-sized measured objects such as vehicles and the requirements for measuring the positions of long-distance measured objects such as positioning parameters among a plurality of wheels cannot be met, and therefore a large-scale camera measuring field or a large-scale detection field formed by a plurality of cameras is required to be used for measuring and calibrating. For a double camera or a plurality of cameras, the situation that a calibration reference object cannot be simultaneously present in the common view field of the two cameras may exist, but the measurement results of the two cameras need to be combined and unified into a coordinate system for measurement and reconstruction, so that the determination of the pose relationship between the two cameras without the common view field is an indispensable important step of the whole measurement system. The two-camera method can be popularized to the research of a plurality of coordinate systems without a common view field camera, so that the method has the same important research value for the research of the related fields of wheel positioning, wheel positioning parameters, wheel base difference, appearance reconstruction and the like of high-speed rail vehicles. The two-phase machine calibration method in the prior art needs large-scale external auxiliary equipment such as a guide rail workbench and the like to participate in work, has complex structure, higher cost and inconvenient operation, and cannot be used in field calibration. According to the method, the independent camera and the cylindrical target are adopted to construct the three-dimensional space point as a bridge of the two cameras, and the unified coordinate system without the common view field camera for the automobile detection based on the space point is realized.
Disclosure of Invention
The invention provides a flexible, simple and convenient calibration system and method with safe and reliable work and simple structure, aiming at solving the problems that in the automobile detection process, a single camera cannot meet the measurement requirement of a large-scale system due to limited field of view, and a calibration reference object possibly exists in two cameras and cannot simultaneously appear in the public field of view of the two cameras. Images in each field of view are acquired by the three cameras respectively, the position and posture relation among the three cameras is determined, and the unification of coordinate systems of cameras without common fields of view in the automobile detection of space points is realized.
The invention is realized by adopting the following technical scheme by combining the attached drawings of the specification:
the overall calibration system of the automobile detection camera without the common view field based on the space points comprises a main camera, a main camera support, a branch camera left side, a branch camera support left side, a branch camera right side, a branch camera support right side and a cylindrical target;
the main camera support, the right branch camera support, the left branch camera support and the cylindrical target are placed on the ground, the left branch camera and the right branch camera do not have a common view field, and the main camera, the left branch camera and the right branch camera are respectively and fixedly connected with the main camera support, the left branch camera support and the right branch camera support through threaded holes in the bottoms in a threaded manner.
The total camera support in the technical scheme is a triangular support with adjustable height.
In the technical scheme, the left side of the sub camera support is a triangular support with adjustable height.
In the technical scheme, the right part of the sub camera support is a triangular support with adjustable height.
The total video camera in the technical scheme is a wide-angle industrial camera.
The left side of the sub-camera in the technical scheme is a wide-angle industrial camera.
In the technical scheme, the right side of the sub-camera is a wide-angle industrial camera.
The cylindrical target in the technical scheme is a hollow cylinder, and checkerboard patterns are adhered to the outer surface of the cylindrical target.
The method for globally calibrating the camera without the common view field for the automobile detection based on the space points comprises the following specific steps:
the first step is as follows: the method comprises the following steps of (1) acquiring an image of a common-view-field-free camera global calibration in the automobile detection based on space points:
the main camera, the branch camera left and the branch camera right are respectively fixed on the main camera support, the branch camera support left and the branch camera support right, the main camera support, the branch camera support left and the branch camera support right are placed on the ground, the branch camera left and the branch camera right have no public view field according to the requirement of automobile detection on a large detection range, the cylindrical target is placed on the ground and is positioned in the view field of the main camera and the branch camera left, the main camera and the branch camera left respectively collect an image, the cylindrical target is moved to be positioned in the view field of the main camera and the branch camera right, and the main camera and the branch camera right respectively collect an image;
the second step is that: when the cylindrical target is in the left public view field of the master camera and the slave cameras, a homography matrix for converting the coordinate system of the cylindrical target to the coordinate system of the master camera is solved according to the image collected by the master camera:
the transformation relation from the cylindrical target coordinate system to the image coordinate system acquired by the total camera is
PT1，I0XT1＝sxI0，T1
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT1，I0＝KT1，I0[RT1，I0tT1，I0]，KT1，I0Is an internal parameter of the overall camera, RT1，I0，tT1，I0Is the external parameter, X, of the total camera obtained from QR decompositionT1Coordinates of the cylindrical target coordinate system, x, which are characteristic points of the cylindrical targetI0，T1For cylindrical target feature point XT1The coordinates of the image under the image acquired by the overall camera, s being a scale factor, are given by a rotation matrix RT1，I0And a translation vector tT1，I0The homography matrix for converting the coordinate system of the cylindrical target under the left view field of the partial camera to the coordinate system of the total camera can be obtained
The third step: when the cylindrical target is in the right common field of view of the main camera and the sub-cameras, a homography matrix for converting the cylindrical target to the coordinate system of the main camera is calculated according to the image collected by the main camera 1:
the conversion relation between the cylindrical target coordinate system and the image coordinate system acquired by the general camera 1 is
PT2，I0XT2＝sxI0，T2
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT2，I0＝KT2，I0[RT2，I0tT2，I0]，KT2，I0Is an internal parameter of the overall camera, RT2，I0，tT2，I0Is the external parameter, X, of the total camera obtained from QR decompositionT2Coordinates of the cylindrical target coordinate system, x, which are characteristic points of the cylindrical targetI0，T2For cylindrical target feature point XT2Image coordinates under the image acquired by the overall camera, by the rotation matrix RT2，I0And a translation vector tT2，I0Conversion of the coordinate system of the cylindrical target in the right field of view of the partial cameras into the coordinate system of the total camera can be determinedHomography matrix
According to the obtained HT1，COAnd HT2，COHomography matrix from left coordinate system of the sub-camera to right coordinate system of the sub-camera can be obtained
HT2，T1＝HT2，C0(HT1，C0)-1
H is to beT2，T1Further spread out to obtain
The fourth step: when the cylindrical target is in the common field of view of the total camera and the branch cameras, a homography matrix for converting the cylindrical target to the left coordinate system of the branch cameras is calculated according to the image collected by the left branch cameras:
the conversion relation between the cylindrical target coordinate system and the image coordinate system acquired by the left branch camera is
PT1，I1XT1＝sxI1，T1
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT1，I1＝KT1，I1[RT1，I1tT1，I1]，KT1，I1Is an internal parameter of the left side of the partial camera, RT1，I1，tT1，I1Is an external parameter, x, of the left side of the sub-camera obtained from QR decompositionI1，T1For cylindrical target feature point XT1Image coordinates under the image acquired at the left of the partial camera are determined by the rotation matrix RT1，I1And a translation vector tT1，I1The homography matrix from the coordinate system of the cylindrical target under the left view field of the sub-camera to the left coordinate system of the sub-camera can be obtained
The fifth step: when the cylindrical target is in the common view field of the right of the main camera and the sub-cameras, a homography matrix for converting the cylindrical target to the right coordinate system of the sub-cameras is calculated according to the image collected by the right of the sub-cameras:
the conversion relation between the cylindrical target coordinate system and the image coordinate system acquired by the sub-cameras is
PT2，I2XT2＝sxI2，T2
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT2，I2＝KT2，I2[RT2，I2tT2，I2]，KT2，I2Is an internal parameter, R, to the left of the partial cameraT2，I2，tT2，I2Is an external parameter, x, to the partial camera obtained from QR decompositionI2，T2For cylindrical target feature point XT2Image coordinates under the image acquired by the partial camera on the right, from the rotation matrix RT2，I2And a translation vector tT2，I2The homography matrix from the coordinate system of the cylindrical target under the right view field of the sub-camera to the right coordinate system of the sub-camera can be obtained
And a sixth step: and (3) solving a homography matrix between the left coordinate system of the sub-camera and the right coordinate system of the sub-camera:
according to a series of homography matrixes obtained by the solution from the second step to the fifth step, the homography matrix for converting the left coordinate system of the sub-camera to the right coordinate system of the sub-camera can be obtained
HC1，C2＝(HT2，C2)-1HT2，T1HT1，C1
Homography matrix HC1，C2The relationship between the homography matrix for converting the left coordinate system of the sub-camera into the right coordinate system of the sub-camera and each rotation matrix and translation vector obtained in the second step to the fifth step is
The invention has the beneficial effects that:
(1) aiming at the problem of global calibration of cameras without common view fields, the method introduces a third camera and a cylindrical target to construct three-dimensional space points, establishes a conversion bridge between the cameras without common view fields, and realizes the unification of a coordinate system of the cameras without common view fields in the automobile detection based on the space points. The method can realize high-precision calibration, and homography matrixes among cameras can be determined without knowing the relation among targets at different positions.
(2) The system of the invention is convenient and flexible to use, overcomes the defects of large external auxiliary equipment, limited space, poor convenience and the like in the traditional calibration method, and can further realize the calibration of multiple cameras by expanding the number of the cameras.
(3) The system has the advantages of wide measurement range, reliable performance, simple structure, simple and convenient operation and low cost, and solves the problems that the traditional single-camera reconstruction measurement range is small, a large fixed contact type measurement system is expensive and the measurement efficiency is low in a double-camera reconstruction non-public view field calibration method.
Drawings
FIG. 1 is an isometric view of a common field-of-view camera-free global calibration system for vehicle inspection based on spatial points;
FIG. 2 is an isometric view of a general camera 1 in a global calibration system for automobile inspection without a common view field camera based on spatial points;
FIG. 3 is an isometric view of the total camera mount 2 in the global calibration system for vehicle inspection without a common view field camera based on spatial points;
FIG. 4 is an isometric view of a cylindrical target 8 in a spatial point based automotive inspection common field camera-less global calibration system;
FIG. 5 is a schematic diagram of a global calibration method for automobile inspection without a common view field camera based on spatial points;
FIG. 6 is a flow chart of solving homography matrix converted from a cylindrical target 7 coordinate system to a total camera 1 and to a branch camera left 3 coordinate system in the automobile detection common-view-field-free camera global calibration method based on space points;
FIG. 7 is a flow chart of solving homography matrix converted from a cylindrical target 7 coordinate system to a total video camera 1 and to a partial video camera right 5 coordinate system in the automobile detection common-view-field-free camera global calibration method based on space points;
FIG. 8 is a flow chart of solving a homography matrix converted from a left 3 coordinate system of a sub-camera to a right 5 coordinate system of the sub-camera in the global calibration method of the automobile detection common-view-field-free camera based on the space points;
in the figure: 1. the system comprises a main camera, 2 a main camera support, 3 a branch camera left, 4 a branch camera support left, 5 a branch camera right, 6 a branch camera support right and 7 a cylindrical target.
Detailed Description
The invention is described in further detail below with reference to the attached drawing figures:
referring to fig. 1 to 4, the space point-based global calibration system for the automobile detection camera without the common view field comprises a main camera 1, a main camera support 2, a branch camera left 3, a branch camera support left 4, a branch camera right 5, a branch camera support right 6 and a cylindrical target 7;
the general camera support 2, divide camera support left 4 and divide camera support right 6 to be the same adjustable height's A-frame, general camera support 2, divide camera support left 4, divide camera support right 6 and cylinder target 7 to place subaerial, general camera 1, divide camera left 3 and divide camera right 5 to be wide angle industrial camera, general camera 1, divide camera left 3 and divide camera right 5 respectively with general camera support 2, divide camera support left 4 and divide the bolt screw thread fixed connection at camera support right 6 top through the screw hole of bottom, according to the needs of automobile inspection to big detection range, divide camera left 3 and divide camera right 5 not have the field of vision altogether, cylinder target 7 is a hollow cylinder, the surface pastes there is the checkerboard pattern.
Referring to fig. 5 to 8, the global calibration method for the automobile detection camera without the common view field based on the space points can be divided into the following six steps:
the first step is as follows: the method comprises the following steps of (1) acquiring an image of a common-view-field-free camera global calibration in the automobile detection based on space points:
the main camera 1, the branch camera left 3 and the branch camera right 5 are respectively fixed on the main camera support 2, the branch camera support left 4 and the branch camera support right 6, the main camera support 2, the branch camera support left 4 and the branch camera support right 6 are placed on the ground, the branch camera left 3 and the branch camera right 5 have no public view field according to the requirement of large detection range of automobile detection, the cylindrical target 7 is placed on the ground and is positioned in the view field of the main camera 1 and the branch camera left 3, the main camera 1 and the branch camera left 3 respectively acquire an image, the cylindrical target 7 is moved to be positioned in the view field of the main camera 1 and the branch camera right 5, and the main camera 1 and the branch camera right 5 respectively acquire an image;
the second step is that: when the cylindrical target 7 is in the common field of view of the master camera 1 and the branch cameras 3, a homography matrix for converting the coordinate system of the cylindrical target 7 to the master camera 1 is calculated according to the image acquired by the master camera 1:
the transformation from the cylindrical target 7 coordinate system to the image coordinate system acquired by the overall camera 1 is
PT1，I0XT1＝sxI0，T1
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT1，I0＝KT1，I0[RT1，I0tT1，I0]，KT1，I0Is an internal parameter of the overall camera 1, RT1，I0，tT1，I0Is an external parameter, X, of the overall camera 1 obtained from QR decompositionT1Coordinates, x, of the cylindrical target 7 coordinate system which are characteristic points of the cylindrical target 7I0，T1For cylindrical target 7 characteristic points XT1The coordinates of the image under the image acquired by the overall camera 1, s being a scale factor, are given by a rotation matrix RT1，I0And a translation vector tT1，I0The homography matrix for converting the coordinate system of the cylindrical target 7 under the field of view of the branch camera left 3 to the coordinate system of the total camera 1 can be obtained
The third step: when the cylindrical target 7 is in the common field of view of the master camera 1 and the slave cameras 5, a homography matrix for converting the coordinate system of the cylindrical target 7 to the master camera 1 is calculated according to the image acquired by the master camera 1:
the conversion relation between the coordinate system of the cylindrical target 7 and the coordinate system of the image acquired by the general camera 1 is
PT2，I0XT2＝sxI0，T2
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT2，I0＝KT2，I0[RT2，I0tT2，I0]，KT2，I0Is an internal parameter of the overall camera 1, RT2，I0，tT2，I0Is an external parameter, X, of the overall camera 1 obtained from QR decompositionT2Coordinates, x, of the cylindrical target 7 coordinate system which are characteristic points of the cylindrical target 7I0，T2For cylindrical target 7 characteristic points XT2Image coordinates under the image acquired by the overall camera 1, by the rotation matrix RT2，I0And a translation vector tT2，I0The homography matrix for converting the coordinate system of the cylindrical target 7 under the view field of the partial camera at the right 5 to the coordinate system of the total camera 1 can be obtained
According to the obtained HT1，COAnd HT2，COHomography matrix from the left 3 coordinate system of the partial camera to the right 5 coordinate system of the partial camera can be obtained
HT2，T1＝HT2，C0(HT1，C0)-1
H is to beT2，T1Further spread out to obtain
The fourth step: when the cylindrical target 7 is in the common field of view of the total camera 1 and the partial cameras, a homography matrix for converting the coordinate system of the cylindrical target 7 to the partial cameras from the left 3 is calculated according to the images collected by the partial cameras from the left 3:
the conversion relation between the coordinate system of the cylindrical target 7 and the image coordinate system obtained by the left 3 of the partial camera is
PT1，I1XT1＝sxI1，T1
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT1，I1＝KT1，I1[RT1，I1tT1，I1]，KT1，I1Is an internal parameter of the left 3 of the partial camera, RT1，I1，tT1，I1Is the external parameter, x, of the left 3 of the partial camera obtained from QR decompositionI1，T1For cylindrical target 7 characteristic points XT1Image coordinates under the image acquired by the partial camera left 3, from the rotation matrix RT1，I1And a translation vector tT1，I1The homography matrix from the coordinate system of the cylindrical target 7 under the left 3 view field of the partial camera to the left 3 coordinate system of the partial camera can be obtained
The fifth step: when the cylindrical target 7 is in the common field of view of the total camera 1 and the partial cameras right 5, a homography matrix for converting the coordinate system of the cylindrical target 7 to the coordinate system of the partial cameras right 5 is calculated according to the images collected by the partial cameras right 5:
the conversion relation between the coordinate system of the cylindrical target 7 and the image coordinate system obtained by the sub-camera right 5 is
PT2，I2XT2＝sxI2，T2
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT2，I2＝KT2，I2[RT2，I2tT2，I2]，KT2，I2Is an internal parameter of the partial camera right 5, RT2，I2，tT2，I2Is the external parameter, x, of the right sub-camera 5 obtained from QR decompositionI2，T2For cylindrical target 7 characteristic points XT2Image coordinates under the image acquired by the partial camera right 5, from the rotation matrix RT2，I2And a translation vector tT2，I2The homography matrix from the coordinate system of the cylindrical target 7 under the right 5 view fields of the sub-cameras to the right 5 coordinate system of the sub-cameras can be obtained
And a sixth step: and (3) solving a homography matrix between the left 3 coordinate system of the sub-camera and the right 5 coordinate system of the sub-camera:
according to a series of homography matrixes obtained by the solution from the second step to the fifth step, the homography matrix for converting the left 3 coordinate system of the sub-camera to the right 5 coordinate system of the sub-camera can be obtained
HC1，C2＝(HT2，C2)-1HT2，T1HT1，C1
Homography matrix HC1，C2The relationship between the homography matrix which can be developed to convert the left 3 coordinate system of the sub-camera into the right 5 coordinate system of the sub-camera and each rotation matrix and translation vector obtained in the second step to the fifth step is
Claims (9)
1. A space point-based global calibration system for a camera without a common view field for automobile detection is characterized by comprising a total camera (1), a total camera support (2), a branch camera left (3), a branch camera support left (4), a branch camera right (5), a branch camera support right (6) and a cylindrical target (7);
the main camera support (2), the branch camera support left (4), the branch camera support right (6) and the cylindrical target (7) are placed on the ground, the branch camera left (3) and the branch camera right (5) have no public view field, and the main camera (1), the branch camera left (3) and the branch camera right (5) are respectively fixedly connected with the main camera support (2), the branch camera support left (4) and the bolt thread at the top of the branch camera support right (6) through the threaded holes at the bottom.
2. The system for global calibration of cameras without common visual field for automobile inspection based on space points as claimed in claim 1 is characterized in that the total camera (1) is a wide-angle industrial camera.
3. The system for global calibration of cameras without common field of view for vehicle inspection based on space points as claimed in claim 1, wherein said total camera support (2) is a tripod with adjustable height.
4. The system for global calibration of cameras without common visual field for automobile inspection based on space points as claimed in claim 1, wherein the left side (3) of the sub-camera is a wide-angle industrial camera.
5. The system for global calibration of cameras without common field of view for automobile inspection based on space points as claimed in claim 1, wherein the left part (4) of the sub-camera support is a tripod with adjustable height.
6. The system for global calibration of common-view-field-free camera for automobile inspection based on spatial points as claimed in claim 1, wherein the right sub-camera (5) is a wide-angle industrial camera.
7. The system for global calibration of cameras without common field of view for vehicle inspection based on space points as claimed in claim 1, wherein said right branch camera support (6) is a tripod with adjustable height.
8. The global calibration system for the non-common-view-field camera for the automobile inspection based on the space points as claimed in claim 1, wherein the cylindrical target (7) is a hollow cylinder, and a checkerboard pattern is pasted on the outer surface.
9. The calibration method of the spatial point-based global calibration system for the automobile inspection camera without the common view field according to the claims 1 to 8 is characterized by comprising the following specific steps:
the first step is as follows: the method comprises the following steps of (1) acquiring an image of a common-view-field-free camera global calibration in the automobile detection based on space points:
the main camera (1), the branch camera left (3) and the branch camera right (5) are respectively fixed on the main camera support (2), the branch camera support left (4) and the branch camera support right (6), the main camera support (2), the branch camera support left (4) and the branch camera support right (6) are placed on the ground, according to the requirement of the automobile detection on a large detection range, the left (3) of the sub-camera and the right (5) of the sub-camera have no common view field, the cylindrical target (7) is placed on the ground, the cylindrical target (7) is moved to be positioned in the fields of view of the main camera (1) and the branch camera right (5), and the main camera (1) and the branch camera right (5) respectively acquire an image;
the second step is that: when the cylindrical target (7) is in the common field of view of the main camera (1) and the branch cameras (3), a homography matrix for converting the coordinate system of the cylindrical target (7) to the main camera (1) is calculated according to the image acquired by the main camera (1):
the conversion relation from the coordinate system of the cylindrical target (7) to the coordinate system of the image acquired by the total camera (1) is
PT1，I0XT1＝sxI0，T1
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT1，I0＝KT1，I0[RT1，I0tT1，I0]，KT1，I0Is an internal parameter of the overall camera (1), RT1，I0，tT1，I0Is an external parameter, X, of the total camera (1) obtained from QR decompositionT1Coordinates of the coordinate system of the cylindrical target (7) which are the characteristic points of the cylindrical target (7), xI0，T1Is a cylinder target (7) characteristic point XT1The coordinates of the image under the image acquired by the overall camera (1), s being a scaling factor, are given by a rotation matrix RT1，I0And a translation vector tT1，I0The homography matrix for the transformation from the coordinate system of the cylindrical target (7) under the view field of the branch camera left (3) to the coordinate system of the total camera (1) can be obtained
The third step: when the cylindrical target (7) is in the common field of view of the main camera (1) and the branch cameras (5), a homography matrix for converting the coordinate system of the cylindrical target (7) to the main camera (1) is solved according to the image acquired by the main camera (1):
the conversion relation between the coordinate system of the cylindrical target (7) and the coordinate system of the image acquired by the general camera (1) is
PT2，I0XT2＝sxI0，T2
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT2，I0＝KT2，I0[RT2，I0tT2，I0]，KT2，I0Is an internal parameter of the overall camera (1), RT2，I0，tT2，I0Is an external parameter, X, of the total camera (1) obtained from QR decompositionT2Coordinates of the coordinate system of the cylindrical target (7) which are the characteristic points of the cylindrical target (7), xI0，T2Is a cylinder target (7) characteristic point XT2The coordinates of the image under the image acquired by the overall camera (1) are determined by a rotation matrix RT2，I0And a translation vector tT2，I0The homography matrix for the transformation from the coordinate system of the cylindrical target (7) under the view field of the partial camera right (5) to the coordinate system of the total camera (1) can be obtained
According to the obtained HT1，COAnd HT2，COHomography matrix from left (3) coordinate system of the partial camera to right (5) coordinate system of the partial camera can be obtained
HT2，T1＝HT2，C0(HT1，C0)-1
H is to beT2，T1Further spread out to obtain
The fourth step: when the cylindrical target (7) is in the common field of view of the total camera (1) and the branch cameras (3), calculating a homography matrix converted from the cylindrical target (7) to the left coordinate system of the branch cameras (3) according to the images acquired by the branch cameras (3):
the conversion relation between the coordinate system of the cylindrical target (7) and the image coordinate system obtained by the left camera (3) is
PT1，I1XT1＝sxI1，T1
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT1，I1＝KT1，I1[RT1，I1tT1，I1]，KT1，I1Is an internal parameter of the left (3) of the partial camera, RT1，I1，tT1，I1Is an external parameter, x, of the left (3) of the partial camera obtained from QR decompositionI1，T1Is a cylinder target (7) characteristic point XT1Image coordinates in the image acquired by the left (3) of the partial camera are determined by the rotation matrix RT1，I1And a translation vector tT1，I1The homography matrix from the coordinate system of the cylindrical target (7) under the view field of the left camera (3) to the coordinate system of the left camera (3) can be obtained
The fifth step: when the cylindrical target (7) is in the common visual field of the total camera (1) and the branch cameras (5), calculating a homography matrix converted from the coordinate system of the cylindrical target (7) to the right (5) of the branch cameras according to the image acquired by the right (5) of the branch cameras:
the conversion relation between the coordinate system of the cylindrical target (7) and the image coordinate system obtained by the right side (5) of the sub-camera is
PT2，I2XT2＝sxI2，T2
Projection matrix P can be obtained by using RANSAC point extraction method and DLT calibration methodT2，I2＝KT2，I2[RT2，I2tT2，I2]，KT2，I2Is an internal parameter of the right (5) of the partial camera, RT2，I2，tT2，I2Is an external parameter, x, of the right (5) of the partial camera obtained from QR decompositionI2，T2Is a cylinder target (7) characteristic point XT2The coordinates of the image obtained from the right (5) of the partial camera are determined by the rotation matrix RT2，I2And a translation vector tT2，I2The homography matrix from the coordinate system of the cylindrical target (7) under the view field of the right (5) of the sub-camera to the coordinate system of the right (5) of the sub-camera can be obtained
And a sixth step: and (3) solving a homography matrix between the left (3) coordinate system of the sub-camera and the right (5) coordinate system of the sub-camera:
according to a series of homography matrixes obtained by the solution of the second step to the fifth step, the homography matrix for converting the left (3) coordinate system of the sub-cameras into the right (5) coordinate system of the sub-cameras can be obtained
HC1，C2＝(HT2，C2)-1HT2，T1HT1，C1
Homography matrix HC1，C2The relationship between the homography matrix for expanding the conversion from the left (3) coordinate system of the scorable camera to the right (5) coordinate system of the scorable camera and each rotation matrix and translation vector obtained in the second step to the fifth step is
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| CN112747673A (en) * | 2020-12-25 | 2021-05-04 | 中国人民解放军陆军工程大学 | Calibration method of monocular multiline structured light sensor based on calibration cylinder |
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