CN112396660B - Method and system for determining optical center of camera - Google Patents

Method and system for determining optical center of camera Download PDF

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Publication number
CN112396660B
CN112396660B CN201910741157.2A CN201910741157A CN112396660B CN 112396660 B CN112396660 B CN 112396660B CN 201910741157 A CN201910741157 A CN 201910741157A CN 112396660 B CN112396660 B CN 112396660B
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calibration
camera
point
optical center
coordinates
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CN112396660A (en
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张竞
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Huawei Cloud Computing Technologies Co Ltd
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Huawei Cloud Computing Technologies Co Ltd
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
    • G06T7/00—Image analysis
    • G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration

Abstract

The application discloses a method and a system for determining a camera optical center, which are used for solving the problem that the determined camera optical center is inaccurate in position. A calibration plate and a calibration object with fixed relative positions to the calibration plate are arranged in the view finding range of the camera, the calibration plate is provided with a calibration surface, and the calibration object is provided with a first calibration point; the optical center determining device determines a second calibration point on the calibration surface and ensures that the second calibration point coincides with the first calibration point in an image obtained by shooting a picture in a view range by the camera; that is, the first calibration point, the second calibration point, and the camera optical center are coaxial, so that the optical center determining means determines the coordinates of the optical center of the camera in the world coordinate system based on the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system. The method does not need to rely on an internal reference matrix and an external reference matrix of the camera, so that the accuracy of the determined optical center of the camera can be improved.

Description

Method and system for determining optical center of camera
Technical Field
The embodiment of the application relates to the technical field of computers, in particular to a method and a system for determining an optical center of a camera.
Background
When the camera images, light rays are converged at a point through the camera lens, and the point is the optical center of the camera. In video localization schemes, it is necessary to use the exact position of the camera's optical center in the world coordinate system, which is the reference coordinate system chosen in the environment to describe the position of the camera and the object. If a large error exists in the calibration position of the optical center of the camera, a large calculation error can be caused when the object to be positioned is positioned later, and the positioning precision is influenced. Therefore, accurately solving the camera optical center position is a necessary precondition for accurate positioning.
In the existing scheme, the optical center of the camera is generally calibrated by utilizing the mapping relation satisfied between the image shot by the camera and the object in the physical space. This mapping relationship is represented by an internal reference matrix and an external reference matrix. When the optical center coordinates of the camera are determined, the internal reference matrix and the external reference matrix are solved in an iterative mode, and then the coordinates of the optical center of the camera in a world coordinate system are solved through the internal reference matrix and the external reference matrix. Solving the internal reference matrix and the external reference matrix in an iterative mode may be in local optimum, so that calculation errors occur, and the determined optical center position of the camera is inaccurate.
Disclosure of Invention
The embodiment of the application provides a method and a system for determining a camera optical center, which are used for solving the problem that the determined camera optical center is inaccurate in position.
In a first aspect, an embodiment of the present application provides a method for determining an optical center of a camera, where a calibration plate and a calibration object fixed in relative position to the calibration plate are disposed in a view-finding range of the camera, the calibration plate has a calibration surface, and the calibration object has a first calibration point; the distance between the first calibration point and the camera in the vertical direction is smaller than the distance between the calibration surface and the camera; the optical center determining device determines a second calibration point on the calibration surface, wherein the second calibration point coincides with the first calibration point in an image obtained by shooting a picture of the view finding range by the camera; the optical center determining device determines the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
The second calibration point is overlapped with the first calibration point in an image obtained by shooting a picture in the view-finding range by the camera, namely the first calibration point, the second calibration point and the camera optical center are coaxial. The optical center determining device determines the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the set relation; wherein the set relationship is that the first calibration point, the second calibration point and the camera optical center are coaxial.
According to the scheme provided by the embodiment of the application, through the special structure in the view finding range of the camera, the first calibration point and the second calibration point are ensured to be overlapped in the image shot by the camera, so that the coordinate of the optical center of the camera in the world coordinate system is determined according to the coordinate of the first calibration point in the world coordinate system and the coordinate of the second calibration point in the world coordinate system, the reference matrix and the external reference matrix of the camera are not required to be relied on, and the accuracy of the determined optical center of the camera can be improved.
In one possible design, the optical center determining device further includes, before determining the second calibration point on the calibration surface: the optical center determining device sends a control instruction to the camera, and the control instruction instructs the camera to send an image obtained by shooting a picture in a view finding range to the optical center determining device; the optical center determining device receives an image obtained by shooting a picture in a view finding range by the camera, wherein the image is sent by the camera; the optical center determining device sends the coordinates of the optical center of the camera in the world coordinate system to the camera after determining the coordinates of the optical center of the camera in the world coordinate system.
The optical center determining device in the above design is independent of the camera and can communicate with the camera. The optical center determining device sends an instruction to the camera to shoot an image to determine whether the first calibration point is overlapped with the second calibration point, and then the determined optical center position can be sent to the camera.
In one possible design, a display screen is arranged on the calibration surface, and a luminous point with a fixed luminous mark is displayed on the display screen; when the optical center determining device determines a second calibration point on the calibration surface, the optical center determining device is realized by the following steps: the optical center determining device determines whether the position of the luminous point with the fixed luminous mark displayed on the display screen is overlapped with the first standard point in the image obtained by shooting the picture in the view-finding range by the camera, and when the position of the luminous point with the fixed luminous mark is not overlapped with the first standard point, the position of the luminous point with the fixed luminous mark displayed on the display screen is adjusted until the adjusted luminous point is overlapped with the first standard point in the image obtained by shooting by the camera; the second calibration point is the luminous point with the fixed luminous mark, and the second calibration point coincides with the first calibration point in the image shot by the camera.
The design can accurately acquire the position of the second calibration point through the display screen on the calibration surface, so that the accuracy of determining the optical center of the camera can be improved.
In one possible design, the calibration surface has a pattern of a fixed physical size thereon; the optical center determining device determines a second calibration point on the calibration surface by the following method: the optical center determining means determines, as the second calibration point, a point overlapping with the first calibration point on a pattern having a fixed physical size in an image captured by the camera.
The design can accurately acquire the position of the second calibration point through the group with fixed physical size on the calibration surface, so that the accuracy of determining the concern of the camera can be improved.
In one possible design, the calibration plate is provided with a level, and the optical center determining device further includes, before determining the second calibration point on the calibration surface: the optical center determining device adjusts the calibration plate according to the level so that the calibration surface is parallel to the horizontal plane.
Illustratively, the level may be disposed on the calibration surface of the calibration plate, or may be disposed on the back of the calibration surface. The calibration surface is ensured to be parallel to the horizontal plane by the level gauge, so that the position of the second calibration point is accurately determined.
In one possible design, the calibration plate and the calibration object are mounted on a bracket of the calibration device, a base is mounted on the bracket, and a drivable universal wheel is fixedly mounted below the base; the lower surface of the base is provided with a camera and N laser lamps, wherein N is an integer greater than 1; the calibration device is characterized in that M marking points are arranged on the ground in a preset range, M is an integer larger than 1, and the optical center determining device further comprises: the optical center determining device drives the universal wheel to move according to the positions of the luminous points irradiated by the L laser lamps on the ground and the positions of the L marking points in the M marking points in a picture shot by the camera installed under the base, so that the luminous points irradiated by the L laser lamps on the ground in the picture shot by the camera are overlapped with the L marking points one by one, L is an integer larger than 1, and is smaller than or equal to N, and L is smaller than or equal to M; the optical center determining device determines the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system, and the optical center determining device comprises: determining the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the coordinates of the L marker points in the world coordinate system and the parameter information of the topological structure of the calibration device; determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system; the parameter information of the topological structure of the calibration device characterizes the relative position relation and the relative posture among all the components in the calibration device.
Through the design, the calibration device can accurately move to the position of the world coordinate system coordinate on the ground, so that the coordinates of the first calibration point and the second calibration point in the world coordinate system can be respectively determined according to the parameter information of the topological structure of the calibration device.
In a second aspect, based on the same inventive concept as the first aspect, an embodiment of the present application provides a calibration system for a camera optical center, including a calibration device and an optical center determining device; the calibration device comprises a calibration plate, wherein the calibration plate is provided with a calibration surface; the calibration device further comprises a calibration object fixed on the calibration surface, wherein the calibration object is provided with a first calibration point, and the first calibration point is separated from the calibration surface by a set distance; the optical center determining device is used for determining a second calibration point on the calibration surface through an image obtained by shooting a picture of a view range by the camera, wherein the second calibration point is overlapped with the first calibration point in the image obtained by shooting the picture of the view range by the camera; the optical center determining device is further used for determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
It should be noted that the calibration object may not be fixed on the calibration plate, and the calibration object is disposed at a position fixed relative to the calibration plate.
In one possible design, the optical center determining device may be fixedly mounted on the calibration device, or may be independent of the calibration device. The optical center determining device may also be arranged inside the camera.
In one possible design, the calibration device further comprises a level adjuster and a level meter arranged on the calibration plate, wherein the calibration plate is arranged on the level adjuster, so that the calibration surface of the calibration plate is parallel to the horizontal plane under the adjustment action of the level adjuster.
For example, the calibration surface of the adjustment calibration plate may be determined by the optical center determining means of the calibration device. When the optical center determining device is arranged in the camera, a control device can be further arranged, the control device can be arranged on the calibration device and is connected with the level adjuster and the level meter, and the control device adjusts the level adjuster based on the level meter to enable the calibration surface of the calibration plate to be calibrated.
In one possible design, the optical center determining device is independent of the camera, the optical center determining device has a communication module therein in communication with the camera, and the optical center determining device is further configured to: before a second calibration point is determined on the calibration surface, a control instruction is sent to the camera through the communication module, the control instruction instructs the camera to send an image obtained by shooting a picture in a view-finding range to the optical center determining device, and the image obtained by shooting the picture in the view-finding range by the camera and sent by the camera is received.
In one possible embodiment, the calibration surface has a display screen coupled to the optical center determining device, on which a luminous point with a fixed luminous mark is displayed; the optical center determining device is specifically configured to determine whether a position of a light emitting point with a fixed light emitting mark displayed on the display screen coincides with the first calibration point in an image obtained by capturing a frame within a view range by the camera, and when the position of the light emitting point with the fixed light emitting mark does not coincide with the first calibration point, adjust the position of the light emitting point with the fixed light emitting mark displayed on the display screen until the adjusted light emitting point coincides with the first calibration point in the image captured by the camera; the second calibration point is the luminous point with the fixed luminous mark, and the second calibration point coincides with the first calibration point in the image shot by the camera.
The optical center determining device may be independent of the camera and may be provided inside the camera. For example, when the optical center determining device is provided inside the camera, the position of the light emitting point on the display screen may be adjusted by establishing a connection with the display screen by a control device provided independently of the camera. The control device may be mounted on the calibration device or may be provided outside the calibration device.
In one possible design, the calibration surface has a pattern of a fixed physical size thereon; the optical center determining device is specifically configured to determine, in an image captured by the camera, a point, which coincides with the first calibration point, on a pattern having a fixed physical size as the second calibration point.
The optical center determining device may be independent of the camera and may be provided inside the camera. For example, when the optical center determining device is provided inside the camera, a connection may be established with the camera by a control device provided independently of the camera, and a point overlapping with the first calibration point on a pattern having a fixed physical size in an image captured by the camera is the second calibration point. The control device may be mounted on the calibration device or may be provided outside the calibration device.
In one possible design, the calibration plate is provided with a level, and the optical center determining device is further configured to adjust the calibration plate according to the level such that the calibration surface is parallel to a horizontal plane. Illustratively, the level may be disposed on the calibration surface of the calibration plate, or may be disposed on the back of the calibration surface. The calibration surface is ensured to be parallel to the horizontal plane by the level gauge, so that the position of the second calibration point is accurately determined.
In one possible design, the calibration device further comprises a locator coupled to the optical center determining device, the locator being mounted on the calibration plate; the optical center determining device is further used for determining the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the positioning signals received by the positioner.
In one possible design, the calibration plate and the calibration object are mounted on a bracket of the calibration device, a base is mounted on the bracket, universal wheels are fixedly mounted below the base, and a camera and N laser lamps are mounted on the lower surface of the base, wherein N is an integer greater than 1; the optical center determining device is further used for driving the universal wheel to move according to the positions of the luminous points of the L laser lamps irradiated on the ground in the picture shot by the camera and the positions of the L marking points in the M preset fixed marking points on the ground, so that the luminous points of the L laser lamps irradiated on the ground in the picture shot by the camera are overlapped with the L marking points one by one; wherein M is an integer greater than 1, L is an integer greater than 1, and L is less than or equal to N, and L is less than or equal to M; the optical center determining device is specifically configured to determine the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the coordinates of the L marker points in the world coordinate system and the parameter information of the topological structure of the calibration device; determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system; the parameter information of the topological structure of the calibration device characterizes the relative position relation and the relative posture among all the components in the calibration device.
In one possible design, the optical center determining device is specifically configured to determine, according to a set relationship, coordinates of an optical center of the camera in the world coordinate system according to coordinates of the first calibration point in the world coordinate system and coordinates of the second calibration point in the world coordinate system; wherein the set relationship is that the first calibration point, the second calibration point and the camera optical center are coaxial.
In a third aspect, based on the same inventive concept as the first aspect, an embodiment of the present application provides a calibration system for a camera optical center, including a calibration plate, a calibration object separated from the calibration plate and having a fixed relative position, and an optical center determining device; the calibration plate is provided with a calibration surface, the calibration object is provided with a first calibration point, and the first calibration point is separated from the calibration surface by a set distance; the optical center determining device is used for determining a second calibration point on the calibration surface through an image obtained by shooting a picture of a view range by the camera, wherein the second calibration point is overlapped with the first calibration point in the image obtained by shooting the picture of the view range by the camera; the optical center determining device is further used for determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
In a fourth aspect, embodiments of the present application provide an optical center determining device, which may refer to the description of the first aspect and will not be repeated herein. The optical center determining device comprises a processor and a memory in its structure, wherein the processor is configured to support the optical center determining device to perform the corresponding functions in the method of the first aspect. The memory is coupled to the processor that holds the program instructions and data necessary for the communication device. The communication device also comprises a communication module which is used for communicating with other equipment, such as a level meter, a camera, a laser lamp and the like.
Specifically, the processor is configured to execute the computer-executable instructions stored in the memory to determine a second calibration point on the calibration surface; wherein the calibration surface is positioned on a calibration plate which is arranged in the view finding range of the camera with the optical center to be determined, a calibration object with fixed relative position of the calibration plate is also arranged in the view finding range of the camera, the calibration plate is provided with a calibration surface, and the calibration object is provided with a first calibration point; the distance between the first calibration point and the camera in the vertical direction is smaller than the distance between the calibration surface and the camera; the second calibration point is overlapped with the first calibration point in an image obtained by shooting a picture of the view finding range by the camera;
The processor is further configured to determine coordinates of an optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
In one possible design, the optical center determining device further includes a communication module;
the communication module is used for sending a control instruction to the camera, and the control instruction instructs the camera to send an image obtained by shooting a picture in a view finding range to the optical center determining device; receiving an image obtained by shooting a picture in a view finding range by the camera, wherein the image is sent by the camera;
the communication module is further configured to send the coordinates of the optical center of the camera in the world coordinate system to the camera after the processor determines the coordinates of the optical center of the camera in the world coordinate system.
In one possible design, a display screen is arranged on the calibration surface, and a luminous point with a fixed luminous mark is displayed on the display screen; the processor is specifically configured to determine whether a position of a light emitting point with a fixed light emitting mark displayed on the display screen coincides with the first standard point in an image obtained by capturing a frame within a view range of the camera, and when the position of the light emitting point with the fixed light emitting mark does not coincide with the first standard point, adjust the position of the light emitting point with the fixed light emitting mark displayed on the display screen until the adjusted light emitting point coincides with the first standard point in the image captured by the camera;
The second calibration point is the luminous point with the fixed luminous mark, and the second calibration point coincides with the first calibration point in the image shot by the camera.
In one possible design, the calibration surface has a pattern of a fixed physical size thereon;
the processor is specifically configured to determine, in an image captured by the camera, a point, which coincides with the first calibration point, on a pattern having a fixed physical size as the second calibration point.
In one possible design, the calibration plate is provided with a level, and the processor is further configured to adjust the calibration plate according to the level before determining the second calibration point on the calibration surface such that the calibration surface is parallel to the horizontal plane.
In one possible design, the calibration plate and the calibration object are mounted on a bracket of the calibration device, a base is mounted on the bracket, and a drivable universal wheel is fixedly mounted below the base; the lower surface of the base is provided with a camera and N laser lamps, wherein N is an integer greater than 1; m marking points are arranged on the ground within a preset range where the calibration device is positioned, wherein M is an integer greater than 1;
The processor is further configured to, before determining a second calibration point on the calibration surface, drive the universal wheel to move according to positions of L laser lamps in the N laser lamps irradiating a luminous point on the ground and positions of L marking points in the M marking points in a picture shot by the camera installed below the base, so that the luminous points of the L laser lamps irradiating the ground in the picture shot by the camera coincide with the L marking points one by one, where L is an integer greater than 1, where L is less than or equal to N, and where L is less than or equal to M; the processor is specifically configured to determine, when determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system, the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the coordinates of the L calibration points in the world coordinate system and the parameter information of the topology structure of the calibration device; determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system;
The parameter information of the topological structure of the calibration device characterizes the relative position relation and the relative posture among all the components in the calibration device.
In one possible design, the processor is specifically configured to, when determining the coordinates of the optical center of the camera in the world coordinate system based on the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system: according to the set relation, determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system; wherein the set relationship is that the first calibration point, the second calibration point and the camera optical center are coaxial.
In a fifth aspect, embodiments of the present application provide a computer program product comprising a computer program which, when executed on a computer or processor, causes the computer or processor to carry out the functions involved in any one of the possible designs of the embodiments of the first aspect and the embodiments of the method.
In a sixth aspect, embodiments of the present application provide a computer readable storage medium, configured to store a program, and instructions, where the program, and the instructions, when executed by a computer, cause the computer to perform the functions involved in any one of the possible designs of the method embodiment and the method embodiment described in the first aspect.
In a seventh aspect, embodiments of the present application provide a chip system, where the chip system includes a processor and may further include a memory, to implement the functions involved in the above method. The chip system may be formed of a chip or may include a chip and other discrete devices.
Drawings
FIG. 1 is a diagram of an image physical coordinate system according to an embodiment of the present application;
FIG. 2 is a schematic diagram of a camera coordinate system according to an embodiment of the present application;
FIG. 3 is a schematic view of a level position relative to a calibration plate in one embodiment of the present application;
FIG. 4 is a schematic view of a second part of the marking device according to an embodiment of the present application;
FIG. 5 is a schematic view of a second part of a device according to an embodiment of the present disclosure;
FIG. 6 is a schematic view of a third part of the marking device according to an embodiment of the present application;
FIGS. 7A and 7B are schematic diagrams of a label and calibration plate structure in accordance with one embodiment of the present application;
FIG. 8 is a schematic illustration of a marking surface in an embodiment of the present application;
fig. 9A and 9B are schematic structural views of the positions of the cameras corresponding to the marker in an embodiment of the present application;
FIG. 10A is a flowchart illustrating a method for determining a camera optical center according to an embodiment of the present disclosure;
FIG. 10B is a schematic diagram of a communication structure of a calibration device between cameras according to an embodiment of the present application;
FIG. 11A is a flowchart illustrating another method for determining the optical center of a camera according to an embodiment of the present disclosure;
FIG. 11B is a schematic view of a first calibration point and a second calibration point in a camera image according to an embodiment of the present application;
FIG. 12 is a flowchart illustrating a method for determining an optical center of a camera according to an embodiment of the present disclosure;
fig. 13 is a flowchart illustrating a method for determining an optical center of a camera according to another embodiment of the present application.
Detailed Description
In the following, first a few technical concepts referred to in the present application will be described.
1) And (3) an image physical coordinate system.
A specific example of an image physical coordinate system can be seen in fig. 1, O i The point is the intersection of the camera optical axis and the camera imaging plane, which is the origin of the physical coordinate system of the image. (u, v) represents the number of columns and rows of pixels, where (O) p U, v) form an imageAnd a plain plane coordinate system. Origin O of pixel plane coordinate system p Is positioned at the upper left corner of the imaging plane of the camera, and two coordinate axes (O p u-axis and O p v-axis) are directed to the right and below, respectively. Origin O of image physical coordinate system i Is positioned at the center of the pixel plane coordinate system, and the coordinates are (u) 0 ,v 0 ) Two coordinate axes (O i x-axis and O i y-axis) are directed to the right and below, respectively. Let dx and dy denote the physical dimensions of a pixel along the u-axis and v-axis, respectively, the relationship between the pixel plane coordinate system and the image physical coordinate system is shown in formula (1).
The above formula (1) can be further expressed as formula (2)
2) And (5) a camera coordinate system.
A specific example of a camera coordinate system can be seen in fig. 2, where the camera coordinate system is a spatial coordinate system with an origin O c Is positioned at the optical center of the camera. O (O) i The point is the intersection point of the camera optical axis and the camera imaging plane, i.e. the origin of the physical coordinate system of the image. As shown in fig. 2, O of camera coordinate system c x c Shaft and O c y c O with axes respectively parallel to the physical coordinate system of the image i x-axis and O i y-axis, O c z c Shaft passing point O i Point O i To point O c The distance of (2) is the focal length, denoted by f. The camera coordinate system and the image physical coordinate system can be known to satisfy the relation shown in the following formula (3) according to the imaging projection relation
3) World coordinate system.
A reference coordinate system, which may be referred to as a world coordinate system, is selected in the environment to describe the position of the camera and the object. The relationship between the camera coordinate system and the world coordinate system can be described by a rotation matrix R and a translation vector T. Thus, the homogeneous coordinates of a point P in space in world and camera coordinates are (x) w ,y w ,z w ) And (x) c ,y c ,z c ) Satisfies the relationship shown in the following formula (4)
Where R is a 3×3 rotation matrix and T is a 3×1 translation vector.
Based on the relationship of the pixel plane coordinate system, the image physical coordinate system, the camera coordinate system and the world coordinate system, the relationship shown in the formula (5) is described.
In the formula (5) of the present invention,is an internal reference matrix, right part of the equal sign is +.>Is an extrinsic matrix.
At present, under the condition that the optical center of the camera is solved based on the internal reference matrix and the external reference matrix of the camera, an image is obtained by shooting a picture through the camera, then the internal reference matrix and the external reference matrix in the formula (5) are obtained, and then the coordinates of the optical center of the camera are obtained based on the internal reference matrix, the external reference matrix and pixel coordinates in the image. The image captured by the camera may have distortion, and therefore the image needs to be deformed to eliminate the distortion, but the deformation process may not be capable of completely eliminating the distortion, and thus may cause errors in the determined optical center coordinates of the camera. In addition, when the internal reference matrix and the external reference matrix are solved, an iterative mode is generally adopted, but when the internal reference matrix and the external reference matrix are solved by adopting the iterative mode, local optimization may be trapped, and thus calculation errors occur. Based on the above, the embodiment of the application provides a method and a system for determining the optical center of a camera, which are not dependent on a method for solving internal parameters and external parameters of the camera, and can accurately determine the coordinates of the optical center of the camera in a world coordinate system. According to the embodiment of the application, the coordinates of the camera optical center position in the world coordinate system are determined in an auxiliary mode through the calibration device with the fixed shape. The calibration device at least comprises a calibration plate and a calibration object, wherein the calibration object is provided with a first calibration point which is spaced from the calibration surface by a set distance, that is, the first calibration point and the calibration surface are not on the same horizontal plane. The number of first calibration points may be one or more, which is not limited in this application.
When the coordinates of the optical center of the camera in the world coordinate system are determined by combining the calibration device, the method can be realized in the following two ways:
in a first possible way, the operation of calculating the coordinates of the camera's optical center in the world coordinate system is performed by optical center determining means arranged outside the camera and capable of establishing communication with the camera, in combination with calibration means.
The optical center determining means may comprise a processor for performing an operation of calculating coordinates of the camera optical center in the world coordinate system. By way of example, a processor to which embodiments of the present application relate may include one or more processing units, such as: the processors may include application processors (application processor, AP), modem processors, graphics processors (graphics processing unit, GPU), image signal processors (image signal processor, ISP), controllers, memories, video codecs, digital signal processors (digital signal processor, DSP), baseband processors, and/or neural network processors (neural-network processing unit, NPU), etc. Wherein the different processing units may be separate devices or may be integrated in one or more processors.
The camera and the optical center determining device may each be configured with a communication module, so that both sides can establish communication through the communication module. The communication module may use any one of communication technologies such as bluetooth, infrared, wireless fidelity (wireless fidelity, wiFi), zigBee (ZigBee) communication, ultra Wide Band (UWB), or near field communication (near field communication, NFC) to implement communication.
In a second possible way, the operation of calculating the coordinates of the camera's optical centre in the world coordinate system is performed by the camera in combination with calibration means, so that the optical centre determining means may be arranged inside the camera, for example the optical centre determining means arranged inside the camera may be a processor inside the camera.
In the above two possible embodiments, the calibration device may be placed in the view-finding range of the camera, so that the optical center determining device determines a second calibration point on the calibration surface through an image obtained by the camera shooting a picture of the view-finding range, where the second calibration point coincides with the first calibration point in the image obtained by the camera shooting the picture of the view-finding range; and then determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system, specifically determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to a set relation, wherein the set relation is that the first calibration point, the second calibration point and the optical center of the camera are coaxial. That is, by ensuring that the first calibration point and the second calibration point are located on the optical axis of the optical center of the camera, that is, that the optical center, the first calibration point, and the second calibration point are located on the same straight line.
The following describes the structure of the calibration device provided in the embodiment of the present application in detail. The calibration device provided by the embodiment of the application at least comprises a first part, wherein the first part comprises the calibration plate and the calibration object, and the calibration plate is provided with a calibration surface; the calibration object can be fixed on the calibration surface or not, but the relative position of the calibration object and the calibration surface is fixed, and the calibration object is provided with a first calibration point which is spaced from the calibration surface by a set distance. The calibration plate is of a flat plate structure, and the calibration plate can be in a regular pattern such as a rectangle, a triangle, a circle and the like, and can also be in other irregular patterns, and the rectangle is taken as an example when the calibration plate is described below. The calibration object may be a rod-like structure, a plate-like structure or other structures such as a triangular prism structure. When the calibration object is in a rod-shaped structure, for convenience of description, the calibration object in the rod-shaped structure is called as a calibration rod, one end of the calibration rod can be pointed, the pointed top can be used as a first calibration point, one or more calibration rods can be included in the calibration device, the distances between the pointed tops in the plurality of calibration rods and the calibration surface can be the same or different, and the distances are known. The calibration rod can be a round column or a square column. For another example, the calibration object is a calibration plate, one end of the calibration plate may be in a saw tooth shape, and each pointed top on the saw tooth may be used as the first calibration point.
In one possible embodiment, the calibration device may further comprise a second part, in which the bracket is comprised. The calibration plate is arranged on the bracket. The support may be non-adjustable or adjustable, such as a folding lifter or a vertical up-down adjustable lifter. The height of the calibration plate can be adjusted by the adjustable bracket. The second part may also comprise a level adjuster (described in more detail later) and a level gauge, to which the calibration plate is fixed. The level is mounted on a calibration plate, such as on the back of the calibration plate, as shown in fig. 3, and in fig. 3, a calibration object is taken as an example of a calibration rod. The level gauge is used for assisting the level adjuster to adjust the calibration surface to the horizontal plane. The level adjuster is used for adjusting the calibration surface to be a horizontal plane with the aid of the level meter, so that the coordinates of a second calibration point on the calibration surface in the world coordinate system can be determined conveniently. In order to facilitate the movement of the calibration device, a base can be arranged below the bracket, and wheels are fixedly arranged below the base. The wheels may be universal wheels, may be drivable universal wheels, and the drivable universal wheels may be moved by the optical center determining device.
It should be noted that the second portion of the calibration device may not include a level adjuster, and the second portion may include a sensor for measuring the rotation angle of the folding lifting lever. In this case, the attitude information of the calibration surface can be obtained according to the sensor without adjusting the calibration surface to the horizontal plane, that is, the angle of the calibration surface inclined to the horizontal plane is obtained, so that the coordinates of the first calibration point and the second calibration point in the world coordinate system can be determined subsequently.
As an example, reference is made to fig. 4 and 5, which are illustrations of a second part of the calibration device. It should be noted that, in fig. 4 and 5, the calibration object in the calibration device is not illustrated.
Referring to fig. 4, the stand is a vertical type lifter, and since the folder type lifter does not have a rotation function, the level adjuster may be divided into an inner ring and an outer ring. The inner ring is provided with an inner rotating shaft, the outer ring is provided with an outer rotating shaft, and the horizontal regulator can regulate angles of the calibration plate in two directions respectively taking the inner rotating shaft as an axis and taking the outer rotating shaft as an axis, so that the calibration surface of the calibration plate is regulated to be a horizontal plane. And the outer ring is also provided with a lantern ring which is used for connecting the vertical lifting rod and adjusting the height of the calibration plate.
Referring to fig. 5, the bracket is a folding lifting rod, and the height of the calibration plate can be adjusted. The level adjuster may include only an inner ring having an inner rotational axis thereon. The level adjuster has no outer ring, only has an outer rotating shaft, and the outer rotating shaft can be connected with the lifting rod. The horizontal regulator can regulate the calibration surface of the calibration plate to be a horizontal plane by regulating the angles of the calibration plate in two directions respectively taking the inner rotating shaft as an axis and taking the outer rotating shaft as an axis.
In one possible embodiment, the calibration device may further comprise a third part. The third portion may be used to determine the coordinates of the second calibration point on the calibration surface on the world coordinate system.
As a first example of the third part, see fig. 6, the third part may comprise a camera and N laser lamps, N being an integer greater than 1, fig. 6 taking N as 4 as an example. The camera and the N laser lamps are arranged on the back surface of the base, namely, the downward surface of the base.
On a certain place of the ground in front of the camera of the optical center to be calibrated, M marking points can be configured, and M is an integer greater than 1. The positions of the marking points in the world coordinate system are known, and the relative position relationship between the marking points and the relative position relationship between the laser lamps on the base can be kept consistent. The optical center determining device can determine the positions of the L marking points in the luminous points irradiated to the ground by the laser and the M marking points on the ground through the base camera, and the positions of the calibrating device are automatically adjusted by driving the universal wheels, so that the L luminous points irradiated to the ground by the L laser lamps in the N laser lamps are aligned with the L marking points on the ground one by one, the coordinates of each laser lamp in a world coordinate system can be obtained, and the coordinates of any point on the calibrating device in the world coordinate system can be obtained according to the relative position relation among each part in the calibrating device, namely the coordinates of the first calibrating point and the second calibrating point in the world coordinate system can be obtained. L is an integer greater than 1, and L is less than or equal to M, L and less than or equal to N.
A second example of the third part may comprise a locator which is mounted on the calibration device, for example on a calibration plate. The optical center determining device can determine the coordinates of the first calibration point and the second calibration point in a world coordinate system according to the positioning signals received by the positioner. Specifically, the calibration device can be moved to a fixed position in the view-finding range of the camera according to the positioning signal received by the positioner, and the coordinates of the position of the positioner in the world coordinate system can be determined according to the positioning signal of the positioner, so that the coordinates of any point on the calibration device in the world coordinate system can be obtained according to the relative position relation of all the components in the calibration device, and the coordinates of the first calibration point and the second calibration point in the world coordinate system can be obtained, so that the purpose is the same as that achieved by the first example. The locator may be located using Ultra Wideband (UWB) technology, or using real-time kinematic (RTK) carrier phase differential technology, or using global positioning system (global positioning system, GPS) location, etc.
In a third example of the third part, the third part may comprise an auxiliary element which is placed on the ground at a fixed position (which may be located within the view of the camera), the coordinates of which in the world coordinate system are known. The auxiliary element is coupled with the optical center determining device. The auxiliary element may be, for example, a photosensitive element, a pressure-sensitive element, a communication element, or the like. The auxiliary element assists the calibration device to move to the fixed position of the ground through communication with the optical center determining device, so that the coordinates of any point on the calibration device in the world coordinate system can be obtained according to the coordinates of the fixed position of the ground in the world coordinate system and the relative position relation of all components in the calibration device, and the coordinates of the first calibration point and the second calibration point in the world coordinate system can be obtained, which is the same as the purpose achieved by the first example.
It will be appreciated that the third part may not be included in the calibration device, but that the calibration device may be moved to a fixed position manually. The coordinates of the fixed position in the world coordinate system are known. When the calibration device is manually moved, the calibration device may or may not include the second portion. When included, the second portion may include only a bracket therein, which may or may not be adjustable; of course, in order to facilitate the movement of the calibration device, the second part may also comprise a base and wheels, in which case the calibration device may also be provided with a clamping groove for fixing the calibration device by means of the clamping groove against movement when the calibration device is moved to the specified position.
In a possible implementation manner, in the case that the calibration device includes the second portion and/or the third portion, if the optical center determining device is located in the camera, a control device may be further disposed outside the camera, and the control device may be in communication with the optical center determining device in the camera, and the control device may be connected with the second portion and/or the third portion, so that the control device may control the second portion and/or the third portion in the calibration device, for example, the control device may determine, through a base camera of the calibration device, a position of a light emitting point where laser irradiates the ground and L marking points in M marking points on the ground, and then drive the universal wheel to automatically adjust the position of the calibration device, for example, the control device adjusts the level adjuster based on the level meter, so that the calibration surface is located on the horizontal plane. The control device may be mounted on the calibration device or may be independent of the calibration device.
The control device may include a processor and a communication module. In the case of the control device being provided, the second part and/or the third part can no longer be controlled by the optical center determining device inside the camera, but by the control device. Of course, when the optical center determining device is located outside the camera, the second portion and/or the third portion is controlled by the optical center determining device, and no control device is required.
The calibration device can be placed in the view-finding range of the camera, and the distance between the first calibration point and the camera in the vertical direction is smaller than the distance between the calibration surface and the camera, namely, the angle from the camera is ensured, and the projection of the first calibration point is positioned on the calibration surface. In a way the camera lens may be tilted upwards so that the view range of the camera includes the sky or the ceiling, in which way the plane of the first calibration point is lower than the plane of the calibration plane. Alternatively, the camera lens may be tilted downward so that the field of view of the camera includes the ground, in which case the first calibration point lies in a plane that is higher than the plane in which the calibration plane lies. See fig. 7A and 7B. In fig. 7A and 7B, a calibration object is illustrated as an example of a calibration rod. Fig. 7A is a front view and a top view of the calibration plate and the calibration rod in a downward tilting mode of the camera lens. Fig. 7B shows front and bottom views of the calibration plate + calibration rod with the camera lens tilted upward.
In the calibration device, the calibration surface can be realized in the following two ways. In one example, the calibration surface includes a display screen thereon capable of displaying the light emitting points of the fixed light emitting indicia, as shown in fig. 8 (a). The coordinates of the second calibration point on the display screen may be determined by the fixed size of the display screen. The manner in which the second calibration point is specifically determined will be described in detail later, and will not be described in detail here. Illustratively, the fixed luminescent markers may be different colors. Or a part of the pixels of the display screen emits light, which are used to determine the second calibration point. In addition, a pattern of a fixed physical size may be displayed on the display screen, in which case the second calibration point is determined in a manner similar to the manner in which a pattern of a fixed physical size is determined on the calibration surface, which can be seen in the following manner in which a pattern of a fixed physical size is determined on the calibration surface.
In another example, the calibration surface has a pattern of a fixed physical size, such as a low-rank texture pattern, such as a pattern with a horizontal-vertical (e.g., square texture, see fig. 8 (b)), a symmetrical characteristic, or a dot pattern. The method for determining the coordinates of the second calibration point on the calibration surface by fixing the pattern of the physical dimension will be described in detail later, and will not be described in detail here. Fig. 8 exemplifies a manner in which the camera lens is inclined downward.
It should be noted that, when the optical center determining device is independent of the camera, the optical center determining device may be mounted on the calibration device, and the optical center determining device may be mounted on any part of the calibration device, and of course, the optical center determining device may also be independent of the calibration device.
The following describes in detail the calibration scheme of the optical center of the camera provided in the embodiment of the present application in combination with the above calibration device. The first part of the calibration means is located in the view range of the camera. See, for example, fig. 9A and 9B. Fig. 9A and 9B exemplarily depict a schematic structural view of a calibration device including a first portion, a second portion, and a third portion. Fig. 9A is a schematic structural view of the calibration device in a manner that the camera lens is inclined downward, and fig. 9B is a schematic structural view of the calibration device in a manner that the camera lens is inclined upward.
The following is first a detailed description of the first possible way. I.e. the operation of calculating the coordinates of the camera's optical center in the world coordinate system is performed by the optical center determining means in combination with the calibration means. In this implementation, the optical center determining device is mounted on the calibration device.
Example 1, a display screen on a calibration board is taken as an example for illustration. Referring to fig. 10A, the method for determining the optical center of the camera includes:
S901, the optical center determining device controls the calibration device to move to a fixed position in front of the camera lens.
It should be noted that, when the calibration device does not include the third portion, the calibration device may be manually moved to the fixed position. The optical center determining device may also be connected to a remote control, by way of example, the optical center determining device being instructed by the remote control, so that the optical center determining device controls the calibration device to move to a specified position.
When the third part of the calibration device is in the first example, i.e. the third part comprises a camera and N laser lamps, M marker points may be arranged in a fixed position in front of the camera, the positions of the M marker points in the world coordinate system being known. The wheels on the calibration device are driven universal wheels. Referring to fig. 10B, the camera to be calibrated is in communication with the calibration device (including the optical center determining device, the camera, the drivable universal wheel, and the laser light). The optical center determining device drives the universal wheel to move according to the position of the luminous point on the ground, which is irradiated by L laser lamps in the picture shot by the camera on the calibrating device, and the position of the luminous point on the ground, which is irradiated by L laser lamps in the picture shot by the camera, so that the luminous point on the ground, which is irradiated by the L laser lamps, coincides with the L marking points one by one, the luminous point on the ground, which is irradiated by at least two laser lamps, coincides with at least two marking points on the ground one by one, and the first calibrating point and the calibrating surface are both located on the same side of the optical axis of the camera, and in addition, from the camera angle, the projection of the first calibrating point is located on the calibrating surface, so that the coordinate of the laser lamp, which coincides with the marking point, in the world coordinate system can be determined according to the coordinate of the marking point in the world coordinate system.
As an example, a special pattern may be provided on the ground, and when the light emitting points of at least two laser lamps irradiating the ground are overlapped with at least two marking points on the ground one by one in the image captured by the camera, and the position of the special pattern is located at a fixed position in the image, the calibration device is determined to be moved to the fixed position. As another example, different laser lamps may be configured to emit light of different colors, and when light emitting points of at least two light of specific colors, which are irradiated onto the ground, are in one-to-one correspondence with at least two specific mark points on the ground in an image captured by the camera, it is determined that the calibration device is moved to a fixed position. The above exemplary description of two ways, of course, there are other possible ways, and embodiments of the present application are not exemplified.
The third portion may, for example, not include a camera, may include only a laser light. The optical center determining device can be connected with the remote controller, and the optical center determining device is indicated by the remote controller, so that the optical center determining device drives the universal wheel to move, and the luminous points of the L laser lamps on the calibration device, which irradiate on the ground, are controlled to coincide with the L marking points one by one.
When the third part of the calibration device is in the second exemplary manner, i.e. the third part comprises the locator, the calibration device may be placed in the viewing range of the camera, and the distance between the first calibration point and the camera in the vertical direction is smaller than the distance between the calibration surface and the camera, i.e. it is sufficient to ensure that the first calibration point is located above the calibration surface in the picture taken by the camera, in other words from the angle of the camera, the projection of the first calibration point is located on the calibration surface. Based on this, the coordinates of the first calibration point and the second calibration point in the world coordinate system can be determined from the locator.
When the third part of the calibration device is in a third exemplary way, i.e. the third part comprises an auxiliary element, the optical centre determining means receives a signal of the auxiliary element to drive the universal wheel of the calibration device such that the calibration device is moved to a fixed position on the ground.
S902, the optical center determining device sends a control instruction to the camera, where the control instruction is used to instruct the camera to send an image obtained by shooting a picture in a view-finding range to the optical center determining device.
S903, after receiving the control instruction, the camera shoots a picture in a view finding range, obtains an image and sends the image to the optical center determining device.
S904, the optical center determining device receives the image from the camera, determines whether the luminous point with the fixed luminous mark on the display screen is overlapped with the first standard point in the image shot by the camera, if not, executing S905, and if so, executing S906.
S905, the optical center determining device adjusts the position of the light emitting point with the fixed light emitting mark displayed on the display screen, and S902 is performed.
And the luminous point which is displayed on the display screen and provided with a fixed luminous mark and is overlapped with the first standard point in the image shot by the camera is a second standard point. See, for example, the first and second calibration points shown in fig. 9A.
S906, the optical center determining device determines the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
When the calibration device is placed at the fixed position, the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system can be determined according to the coordinates of the fixed position in the world coordinate system and the parameter information of the topological structure of the calibration device. The parameter information of the topological structure of the calibration device characterizes the relative position relation and the relative posture among all the components in the calibration device.
In this embodiment, the parameter information of the topology structure of the calibration device may include information such as a size of the calibration plate, a size of the display screen, a resolution, a size of the bracket, a size of the base, a position of the laser lamp on the base, a height of the base to the ground, and the like.
When the positioning mode of the positioner is adopted, the coordinates of the first calibration point and the second calibration point in the world coordinate system can be determined according to the coordinates of the placed position in the world coordinate system obtained by the positioner and the parameter information of the topological structure of the calibration device.
S907, the optical center determining means determines the coordinates of the camera optical center in the world coordinate system based on the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
Specifically, it is assumed that, in the world coordinate system, the first coordinate point coordinates (x i ,y i ,z i ) And second coordinates (x' i ,y i ′,z i '), i=1, 2, …, n, n is not less than 2; the number of first index points is n. n may take on a positive integer greater than 0.
Camera optical center coordinates (x) 0 ,y 0 ,z 0 ) Because the camera optical center, the first calibration point and the second calibration point meet the three-point and one-line, the relationship shown in the formula (6) is:
further, the relation shown in (7) is satisfied after the conversion of the formula (6):
Wherein A and B are 3n x 3 and 3n x 1 matrices respectively,
from the above formula (6) and formula (7), it can be determined that the position of the camera optical center in the world coordinate system can be obtained based on the coordinates of the n first calibration points and the coordinates of the n second calibration points.
S908, the optical center determining device sends the coordinates of the camera optical center in the world coordinate system to the camera.
In one possible implementation, the camera may take images in real time and send them to the optical center determining device, so that the optical center determining device adjusts the position of the light emitting point with the fixed light emitting mark in real time. Specifically, a control instruction sent by the optical center determining device to the camera instructs the camera to send a video stream composed of images obtained by shooting pictures in a view range in real time to the optical center determining device, and the optical center determining device adjusts the position of a luminous point with a fixed luminous mark displayed by the display screen according to the video stream received in real time, so that the adjusted luminous point coincides with the first standard point in the images shot by the camera; the second calibration point is a luminous point with a fixed luminous mark displayed on the display screen, and the second calibration point is overlapped with the first calibration point in an image shot by the camera. And then determining the coordinates of the first calibration point and the second calibration point in the world coordinate system, determining the coordinates of the camera optical center in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system, and transmitting the coordinates of the camera optical center in the world coordinate system to the camera. Thus, when the camera receives the coordinates of the camera optical center in the world coordinate system, the real-time shooting of the image is stopped. Alternatively, the optical center determining means may send control instruction feedback to the camera for instructing the camera to stop capturing the image in real time when determining the second calibration point overlapping with the first calibration point.
Example 2 illustrates an example where the calibration plate includes a pattern having a fixed physical size. Referring to fig. 11A, the method for determining the optical center of the camera includes:
S1001-S1003, see S901-S903, which are not described here again.
S1004, the optical center determining device determines, as the second calibration point, a point overlapping with the first calibration point on the pattern having the fixed physical size in the image captured by the camera, for example, as shown in fig. 11B.
S1005, the optical center determining device determines the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the parameter information of the topological structure of the calibration device and the fixed physical size of the pattern on the calibration surface.
Specifically, when the calibration device is placed at a fixed position, the coordinates of the first calibration point and the second calibration point in the world coordinate system can be determined according to the coordinates of the fixed position in the world coordinate system, the parameter information of the topological structure of the calibration device, and the fixed physical dimensions of the pattern on the calibration surface.
When the positioning mode of the positioner is adopted, the coordinates of the first calibration point and the second calibration point in the world coordinate system can be determined according to the acquired coordinates of the placed position in the world coordinate system by the positioner, the parameter information of the topological structure of the calibration device and the fixed physical size of the pattern on the calibration surface.
S1006-S1007, see S907-S908, which are not described here again.
A second possible way is described in detail below. I.e. the operation of calculating the coordinates of the camera's optical center in the world coordinate system is performed by the camera in combination with the calibration means. In this embodiment, the optical center determining device is mounted on the camera, and the control device can be arranged outside the camera, wherein the control device is located on the calibration device.
Example 3, a display screen on a calibration board is taken as an example. Referring to fig. 12, the method for determining the optical center of the camera includes:
s1101, the calibration device moves to a fixed position in front of the camera lens. Specifically, the calibration device can be controlled by a control device in the calibration device to move to a fixed position in front of the camera lens.
The manner in which the control device controls the calibration device to move to the fixed position in front of the camera lens is similar to the manner in which the optical center determining device is controlled in step S901, and the description of the manner in which the optical center determining device is controlled in step S901 will be omitted here.
S1102, a control device in the calibration device sends a control instruction to the camera, wherein the control instruction is used for instructing the camera to send an image obtained by shooting a picture in a view finding range to the calibration device.
S1103, after the camera receives the control instruction, shooting a picture in a view finding range, obtaining an image and sending the image to the calibration device.
S1104, the control device in the calibration device receives the image from the camera, determines whether the luminous point with the fixed luminous mark on the display screen is overlapped with the first calibration point in the image shot by the camera, if not, executes S1105, if so, executes S1106.
S1105, the control device in the calibration device adjusts the position of the luminous point with the fixed luminous mark displayed by the display screen, and S1102 is executed.
S1106, the control device in the calibration device sends the parameter information of the topological structure of the calibration device to the camera.
S1107, the camera determines the coordinates of a first calibration point in the world coordinate system according to the parameter information of the topological structure of the calibration device, and the coordinates of a second calibration point which is overlapped with the first calibration point on the calibration surface in the world coordinate system.
When the calibration means is placed at the fixed position, the control means also transmits the coordinates of the fixed position in the world coordinate system to the camera in S1106, so that the camera can determine the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the coordinates of the fixed position in the world coordinate system and the parameter information of the topology of the calibration means in S1107.
When the positioning mode of the positioner is adopted, in S1106, the control device also sends the coordinates of the position of the positioner in the world coordinate system to the camera, so that when S1107 is executed, the camera can determine the coordinates of the first calibration point and the second calibration point in the world coordinate system according to the coordinates of the position of the positioner and the parameter information of the topological structure of the calibration device.
S1108, the camera determines the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
In one possible implementation, the camera may capture images in real time and send the images to the calibration device, so that the control device in the calibration device adjusts the position of the light emitting point with the fixed light emitting mark in real time after receiving the images. Specifically, a control instruction sent by a control device to a camera instructs the camera to send a video stream composed of images obtained by shooting pictures in a view range in real time to the control device, and the control device adjusts the position of a luminous point with a fixed luminous mark displayed by the display screen according to the video stream received in real time, so that the adjusted luminous point coincides with the first standard point in the images shot by the camera; the second calibration point is a luminous point which is displayed on the display screen, provided with a fixed luminous mark and overlapped with the first calibration point in the image shot by the camera. And then the parameter information of the topological structure of the calibration device is sent to the camera, and the camera stops shooting images after receiving the parameter information of the topological structure. Alternatively, the control means may send control instruction feedback to the camera for instructing the camera to stop capturing images in real time when determining a second calibration point coinciding with the first calibration point.
Example 4 illustrates an example where the calibration plate includes a pattern having a fixed physical size. In this embodiment, the optical center determining device is mounted on the camera, and the control device can be arranged outside the camera, wherein the control device is located on the calibration device. Referring to fig. 13, the method for determining the optical center of the camera includes:
s1201, see S1101, is not described here again.
S1202, the control device in the calibration device sends parameter information of the topological structure of the calibration device and the fixed physical size of the pattern on the calibration surface to the camera.
S1203, the camera determines the coordinates of a first calibration point in a world coordinate system and the coordinates of a second calibration point overlapped with the first calibration point on the calibration surface in the world coordinate system according to the parameter information of the topological structure of the calibration device and the fixed physical size of the pattern on the calibration surface.
When the calibration means is placed at the fixed position, the control means also transmits the coordinates of the fixed position in the world coordinate system to the camera in S1202, so that the camera can determine the coordinates of the first calibration point and the second calibration point in the world coordinate system according to the coordinates of the fixed position in the world coordinate system and the parameter information of the topology of the calibration means in S1203.
When the positioning manner of the positioner is adopted, in S1202, the control device further sends the coordinates of the position of the positioner in the world coordinate system to the camera, so that when S1203 is executed, the camera can determine the coordinates of the first calibration point and the second calibration point in the world coordinate system according to the coordinates of the position of the positioner and the parameter information of the topological structure of the calibration device.
And S1204, the camera determines the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
In a possible embodiment, the calibration device may comprise only the first part or, on the basis of the first part, also a bracket, on which the calibration surface in the first part is mounted. In this case the calibration device can be placed manually in a fixed position and the parameter information of the topology of the calibration device, the coordinates of the fixed position in the world coordinate system, and the fixed physical dimensions of the pattern on the calibration surface can be stored in the camera in advance, in which case no control device needs to be arranged outside the camera. The control device can be configured in the camera, so that the control device in the camera determines the coordinates of a first calibration point and a second calibration point which coincides with the first calibration point on the calibration surface in the image shot by the camera in the world coordinate system according to the parameter information of the topological structure of the calibration device, the fixed physical size of the pattern on the calibration surface and the coordinates of the fixed position in the world coordinate system.
It should be appreciated that reference throughout this specification to "one embodiment," "one implementation," or "an example" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Thus, the appearances of the phrases "in one embodiment," "one implementation," "one embodiment," or "in an example" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be understood that, in various embodiments of the present application, the sequence numbers of the foregoing processes do not mean the order of execution, and the order of execution of the processes should be determined by the functions and internal logic thereof, and should not constitute any limitation on the implementation process of the embodiments of the present application.
In addition, the term "and/or" herein is merely an association relationship describing an association object, and means that three relationships may exist, for example, a and/or B may mean: a exists alone, A and B exist together, and B exists alone. In addition, the character "/" herein generally indicates that the front and rear associated objects are an "or" relationship. The term "plurality" as used herein refers to two, or more than two, i.e., including two, three and more than two. "at least one of" or the like means any combination of these items, including any combination of single item(s) or plural items(s). For example, at least one (one) of a, b, or c may represent: a, b, c, a-b, a-c, b-c, or a-b-c, wherein a, b, c may be single or plural. It should be appreciated that determining B from a does not mean determining B from a alone, but may also determine B from a and/or other information. And, unless specified to the contrary, the embodiments of the present application refer to the ordinal terms "first," "second," etc., as used to distinguish between multiple objects, and are not to be construed as limiting the order, timing, priority, or importance of the multiple objects. Furthermore, the terms "comprising" and "having" in the embodiments and claims of the present application and in the drawings are not exclusive. For example, a process, method, system, article, or apparatus that comprises a list of steps or modules is not limited to only those steps or modules but may include other steps or modules not listed.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It will be apparent to those skilled in the art that various modifications and variations can be made to the embodiments of the present application without departing from the scope of the embodiments of the present application. Thus, if such modifications and variations of the embodiments of the present application fall within the scope of the claims and the equivalents thereof, the present application is intended to encompass such modifications and variations.

Claims (24)

1. The method for determining the optical center of the camera is characterized in that a calibration plate and a calibration object with fixed relative positions to the calibration plate are arranged in the view finding range of the camera, the calibration plate is provided with a calibration surface, and the calibration object is provided with a first calibration point; the distance between the first calibration point and the camera in the vertical direction is smaller than the distance between the calibration surface and the camera;
the optical center determining device determines a second calibration point on the calibration surface, wherein the second calibration point coincides with the first calibration point in an image obtained by shooting a picture of the view finding range by the camera;
the optical center determining device determines the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
2. The method of claim 1, wherein the optical center determining means further comprises, prior to determining a second calibration point on the calibration surface:
the optical center determining device sends a control instruction to the camera, and the control instruction instructs the camera to send an image obtained by shooting a picture in a view finding range to the optical center determining device;
The optical center determining device receives an image obtained by shooting a picture in a view finding range by the camera, wherein the image is sent by the camera;
the optical center determining device sends the coordinates of the optical center of the camera in the world coordinate system to the camera after determining the coordinates of the optical center of the camera in the world coordinate system.
3. A method according to claim 1 or 2, wherein the calibration surface is provided with a display screen on which a light emitting point with a fixed light emitting mark is displayed;
the optical center determining device determines a second calibration point on the calibration surface, including:
the optical center determining device determines whether the position of the luminous point with the fixed luminous mark displayed on the display screen is overlapped with the first standard point in the image obtained by shooting the picture in the view-finding range by the camera, and when the position of the luminous point with the fixed luminous mark is not overlapped with the first standard point, the position of the luminous point with the fixed luminous mark displayed on the display screen is adjusted until the adjusted luminous point is overlapped with the first standard point in the image obtained by shooting by the camera;
the second calibration point is the luminous point with the fixed luminous mark, and the second calibration point coincides with the first calibration point in the image shot by the camera.
4. A method according to claim 1 or 2, wherein the calibration surface has a pattern of fixed physical dimensions thereon;
the optical center determining device determines a second calibration point on the calibration surface, including:
the optical center determining means determines, as the second calibration point, a point overlapping with the first calibration point on a pattern having a fixed physical size in an image captured by the camera.
5. The method of any one of claims 1-4, wherein the calibration plate is provided with a level, and the optical center determining device further comprises, prior to determining the second calibration point on the calibration surface:
the optical center determining device adjusts the calibration plate according to the level so that the calibration surface is parallel to the horizontal plane.
6. The method according to any one of claims 1 to 5, wherein the calibration plate and the calibration object are mounted on a support of a calibration device, a base is mounted on the support, and a drivable universal wheel is fixedly mounted below the base; the lower surface of the base is provided with a camera and N laser lamps, wherein N is an integer greater than 1;
the calibration device is characterized in that M marking points are arranged on the ground in a preset range, M is an integer larger than 1, and the optical center determining device further comprises:
The optical center determining device drives the universal wheel to move according to the positions of the luminous points irradiated by the L laser lamps on the ground and the positions of the L marking points in the M marking points in a picture shot by the camera installed under the base, so that the luminous points irradiated by the L laser lamps on the ground in the picture shot by the camera are overlapped with the L marking points one by one, L is an integer larger than 1, and is smaller than or equal to N, and L is smaller than or equal to M;
the optical center determining device determines the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system, and the optical center determining device comprises:
determining the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the coordinates of the L marker points in the world coordinate system and the parameter information of the topological structure of the calibration device; determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system;
The parameter information of the topological structure of the calibration device characterizes the relative position relation and the relative posture among all the components in the calibration device.
7. The method of any of claims 1-6, wherein the optical center determining means determines the coordinates of the optical center of the camera in the world coordinate system based on the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system, comprising:
the optical center determining device determines the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the set relation;
wherein the set relationship is that the first calibration point, the second calibration point and the camera optical center are coaxial.
8. The calibration system of the camera optical center is characterized by comprising a calibration device and an optical center determining device; wherein,
the calibration device comprises a calibration plate, wherein the calibration plate is provided with a calibration surface; the calibration device further comprises a calibration object fixed on the calibration surface, a first calibration point is arranged on the calibration object, and the distance between the first calibration point and the camera in the vertical direction is smaller than the distance between the calibration surface and the camera;
The optical center determining device is used for determining a second calibration point on the calibration surface through an image obtained by shooting a picture of a view range by the camera, wherein the second calibration point is overlapped with the first calibration point in the image obtained by shooting the picture of the view range by the camera;
the optical center determining device is further used for determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
9. The system of claim 8, wherein the optical center determining device is fixedly mounted to the calibration device.
10. The system of claim 8 or 9, wherein the calibration device further comprises a level adjuster and a level gauge disposed on the calibration plate, the calibration plate being mounted on the level adjuster such that a calibration surface of the calibration plate is parallel to a horizontal plane under adjustment of the level adjuster.
11. The system of any of claims 8-10, wherein the optical center determining device has a communication module therein in communication with the camera, the optical center determining device further configured to:
Before a second calibration point is determined on the calibration surface, a control instruction is sent to the camera through the communication module, the control instruction instructs the camera to send an image obtained by shooting a picture in a view-finding range to the optical center determining device, and the image obtained by shooting the picture in the view-finding range by the camera and sent by the camera is received.
12. The system of any of claims 8-11, wherein the calibration surface has a display screen coupled to the optical center determining device, the display screen displaying thereon a light emitting point with a fixed light emitting indicia;
the optical center determining device is specifically configured to determine whether a position of a light emitting point with a fixed light emitting mark displayed on the display screen coincides with the first calibration point in an image obtained by capturing a frame within a view range by the camera, and when the position of the light emitting point with the fixed light emitting mark does not coincide with the first calibration point, adjust the position of the light emitting point with the fixed light emitting mark displayed on the display screen until the adjusted light emitting point coincides with the first calibration point in the image captured by the camera;
the second calibration point is the luminous point with the fixed luminous mark, and the second calibration point coincides with the first calibration point in the image shot by the camera.
13. The system of any of claims 8-11, wherein the calibration surface has a pattern of a fixed physical size thereon; the optical center determining device is specifically configured to determine, in an image captured by the camera, a point, which coincides with the first calibration point, on a pattern having a fixed physical size as the second calibration point.
14. The system of any one of claims 8-13, wherein the calibration device further comprises a locator coupled to the optical center determining device, the locator mounted on the calibration plate; the optical center determining device is further used for determining the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the positioning signals received by the positioner.
15. The system of any one of claims 8-13, wherein the calibration plate and the calibration object are mounted on a support of the calibration device, a base is mounted on the support, universal wheels are fixedly mounted below the base, and a camera and N laser lamps are mounted on the lower surface of the base, wherein N is an integer greater than 1;
the optical center determining device is further used for driving the universal wheel to move according to the positions of the luminous points of the L laser lamps irradiated on the ground in the picture shot by the camera and the positions of the L marking points in the M preset fixed marking points on the ground, so that the luminous points of the L laser lamps irradiated on the ground in the picture shot by the camera are overlapped with the L marking points one by one;
Wherein M is an integer greater than 1, L is an integer greater than 1, and L is less than or equal to N, and L is less than or equal to M;
the optical center determining device is specifically configured to determine the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the coordinates of the L marker points in the world coordinate system and the parameter information of the topological structure of the calibration device; determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system;
the parameter information of the topological structure of the calibration device characterizes the relative position relation and the relative posture among all the components in the calibration device.
16. The system according to any one of claims 8-15, wherein the optical centre determining means is in particular adapted to:
according to the set relation, determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system;
Wherein the set relationship is that the first calibration point, the second calibration point and the camera optical center are coaxial.
17. An optical center determining device, comprising a processor and a memory;
the memory is used for storing computer execution instructions;
the processor is used for executing computer-executed instructions stored in the memory to determine a second calibration point on the calibration surface;
wherein the calibration surface is positioned on a calibration plate which is arranged in the view finding range of the camera with the optical center to be determined, a calibration object with fixed relative position of the calibration plate is also arranged in the view finding range of the camera, the calibration plate is provided with a calibration surface, and the calibration object is provided with a first calibration point; the distance between the first calibration point and the camera in the vertical direction is smaller than the distance between the calibration surface and the camera; the second calibration point is overlapped with the first calibration point in an image obtained by shooting a picture of the view finding range by the camera;
the processor is further configured to determine coordinates of an optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system.
18. The optical center determining apparatus according to claim 17, wherein the optical center determining apparatus further comprises a communication module;
the communication module is used for sending a control instruction to the camera, and the control instruction instructs the camera to send an image obtained by shooting a picture in a view finding range to the optical center determining device; receiving an image obtained by shooting a picture in a view finding range by the camera, wherein the image is sent by the camera;
the communication module is further configured to send the coordinates of the optical center of the camera in the world coordinate system to the camera after the processor determines the coordinates of the optical center of the camera in the world coordinate system.
19. The optical center determining device according to claim 17 or 18, wherein a display screen is provided on the calibration surface, and a light emitting point with a fixed light emitting mark is displayed on the display screen;
the processor is specifically configured to determine whether a position of a light emitting point with a fixed light emitting mark displayed on the display screen coincides with the first standard point in an image obtained by capturing a frame within a view range of the camera, and when the position of the light emitting point with the fixed light emitting mark does not coincide with the first standard point, adjust the position of the light emitting point with the fixed light emitting mark displayed on the display screen until the adjusted light emitting point coincides with the first standard point in the image captured by the camera;
The second calibration point is the luminous point with the fixed luminous mark, and the second calibration point coincides with the first calibration point in the image shot by the camera.
20. The optical center determining device according to claim 17 or 18, wherein the calibration surface has a pattern of a fixed physical size;
the processor is specifically configured to determine, in an image captured by the camera, a point, which coincides with the first calibration point, on a pattern having a fixed physical size as the second calibration point.
21. The optical center determining device according to any of claims 17-20, wherein a level is provided on the calibration plate, the processor being further configured to adjust the calibration plate according to the level such that the calibration surface is parallel to a horizontal plane before determining a second calibration point on the calibration surface.
22. The optical center determining device according to any one of claims 17 to 21, wherein the calibration plate and the calibration object are mounted on a bracket of the calibration device, a base is mounted on the bracket, and a drivable universal wheel is fixedly mounted below the base; the lower surface of the base is provided with a camera and N laser lamps, wherein N is an integer greater than 1; m marking points are arranged on the ground within a preset range where the calibration device is positioned, wherein M is an integer greater than 1;
The processor is further configured to, before determining a second calibration point on the calibration surface, drive the universal wheel to move according to positions of L laser lamps in the N laser lamps irradiating a luminous point on the ground and positions of L marking points in the M marking points in a picture shot by the camera installed below the base, so that the luminous points of the L laser lamps irradiating the ground in the picture shot by the camera coincide with the L marking points one by one, where L is an integer greater than 1, where L is less than or equal to N, and where L is less than or equal to M;
the processor is specifically configured to determine, when determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system, the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system according to the coordinates of the L calibration points in the world coordinate system and the parameter information of the topology structure of the calibration device; determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system;
The parameter information of the topological structure of the calibration device characterizes the relative position relation and the relative posture among all the components in the calibration device.
23. The optical center determining device according to any one of claims 17-22, wherein the processor, when determining the coordinates of the optical center of the camera in the world coordinate system based on the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system, is specifically configured to:
according to the set relation, determining the coordinates of the optical center of the camera in the world coordinate system according to the coordinates of the first calibration point in the world coordinate system and the coordinates of the second calibration point in the world coordinate system;
wherein the set relationship is that the first calibration point, the second calibration point and the camera optical center are coaxial.
24. A computer readable storage medium, characterized in that the storage medium stores computer instructions, which, when executed by optical center determining means, cause the optical center determining means to perform the method according to any one of claims 1 to 7.
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