CN110599548A - Camera calibration method and device, camera and computer readable storage medium - Google Patents
Camera calibration method and device, camera and computer readable storage medium Download PDFInfo
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- CN110599548A CN110599548A CN201910830035.0A CN201910830035A CN110599548A CN 110599548 A CN110599548 A CN 110599548A CN 201910830035 A CN201910830035 A CN 201910830035A CN 110599548 A CN110599548 A CN 110599548A
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T7/00—Image analysis
- G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
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- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06T—IMAGE DATA PROCESSING OR GENERATION, IN GENERAL
- G06T2207/00—Indexing scheme for image analysis or image enhancement
- G06T2207/10—Image acquisition modality
- G06T2207/10004—Still image; Photographic image
Abstract
The invention discloses a camera calibration method and device, a camera and a mobile terminal. The calibration method of the camera comprises the following steps: collecting the calibration plate through a camera to obtain a calibration image; processing the calibration image to obtain image coordinates of feature points in the calibration image, wherein the feature points comprise checkerboard corner points and feature points; calculating according to the image coordinates of the characteristic points and the world coordinates of the characteristic points to obtain a homography matrix from a calibration plate plane to a calibration image plane; obtaining an internal parameter matrix of the camera; mapping the world coordinates of the characteristic points to a coordinate system of a camera according to the intrinsic parameter matrix and the homography matrix to obtain camera coordinates of the characteristic points under the undistorted condition, and mapping image coordinates of the characteristic points to the camera coordinate system according to the intrinsic parameter matrix to obtain camera coordinates of the characteristic points under the distorted condition; and finally, carrying out distortion parameter fitting to obtain distortion correction parameters. The invention can improve the calibration accuracy.
Description
Technical Field
The present invention relates to the field of camera technologies, and in particular, to a method and an apparatus for calibrating a camera, and a computer-readable storage medium.
Background
With the improvement of the living standard of people and the development of science and technology, photographing becomes one of important contents in daily life of people. At present, before the camera is used, the parameters of a camera in the camera need to be calibrated.
Disclosure of Invention
The invention mainly aims to provide a camera calibration method, a camera calibration device, a camera and a computer readable storage medium, and aims to improve the camera calibration accuracy.
In order to achieve the above object, the present invention provides a calibration method for a camera, including:
collecting the calibration plate through the camera to obtain a corresponding calibration image;
processing the calibration image to obtain image coordinates of the feature points in the calibration image;
the characteristic points comprise checkerboard angular points and circle centers of round points;
obtaining world coordinates of the feature points on the calibration plate, and calculating according to image coordinates of the feature points and the world coordinates of the feature points on the calibration plate to obtain a homography matrix from a plane where the calibration plate is located to a plane where the calibration image is located;
obtaining an internal parameter matrix of a camera to which the camera belongs;
mapping the world coordinates of the feature points to a coordinate system of the camera according to the intrinsic parameter matrix and the homography matrix to obtain camera coordinates of the feature points under a distortion-free condition, and mapping image coordinates of the feature points to the camera coordinate system according to the intrinsic parameter matrix to obtain camera coordinates of the feature points under a distortion condition;
and performing distortion parameter fitting on the camera coordinates of the characteristic points under the undistorted condition and the distorted condition to obtain corresponding distortion correction parameters.
The camera acquires the calibration image for one time on the calibration plate; or
And after the camera continuously collects the calibration plate, selecting a frame meeting a preset index threshold value from the calibration plate as a calibration image.
Wherein, the feature points include checkerboard corner points, and the processing the calibration image to obtain the image coordinates of the feature points in the calibration image includes:
carrying out binarization processing on the calibration image;
carrying out feature point detection on the calibration image subjected to binarization processing to obtain feature points to be confirmed; (ii) a
And obtaining the image coordinates of the checkerboard corner point pixels in the feature points to be confirmed through sub-pixel precision.
Wherein, the feature point also includes the centre of a circle of the dot, the processing the calibration image to obtain the image coordinate of the feature point in the calibration image further includes:
and carrying out contour extraction and ellipse fitting on the calibration image subjected to binarization processing to obtain the image coordinate of the circle center in the calibration image.
Wherein, the obtaining of the intrinsic parameter matrix of the camera to which the camera belongs includes:
obtaining preset optical parameters of the camera;
and obtaining an internal parameter matrix of the camera according to the principal point coordinates, the pixel size and the focal length of the camera in the optical parameters.
Performing distortion parameter fitting on the camera coordinates of the feature points under the undistorted condition and the distorted condition to obtain corresponding distortion correction parameters, wherein the method comprises the following steps:
distortion parameter fitting was performed by the following formula:
ud＝u(1+k1r2+k2r4+k3r6)+[2p1v+p2(r2+2u2)]；
vd＝v(1+k1r2+k2r4+k3r6)+[2p2u+p1(r2+2v2)]；
wherein the coordinates of the next feature point under the distortion condition are [ ud, vd ], the coordinates of the next feature point under the distortion-free condition are [ u, v ], k1, k2 and k3 are radial distortion parameters of the camera, p1 and p2 are tangential distortion parameters of the camera, and the distortion correction parameters comprise a radial distortion parameter and a tangential distortion parameter.
The connecting line of the camera and the center of the calibration plate is parallel to the horizontal line, and the imaging surface of the camera is parallel to the calibration plate.
In order to achieve the above object, the present invention further provides a calibration device for a camera, where the calibration device for a camera includes:
the image acquisition module is used for acquiring the calibration plate through the camera to obtain a corresponding calibration image;
the image coordinate module is used for processing the calibration image to obtain the image coordinates of the characteristic points in the calibration image;
the calculation module is used for obtaining the world coordinates of the feature points on the calibration plate, calculating according to the image coordinates of the feature points and the world coordinates of the feature points on the calibration plate, and obtaining a homography matrix from the plane where the calibration plate is located to the plane where the calibration image is located;
the obtaining module is used for obtaining an internal parameter matrix of a camera to which the camera belongs;
the mapping module is used for mapping the world coordinates of the characteristic points to a coordinate system of the camera according to the internal parameter matrix and the homography matrix to obtain camera coordinates of the characteristic points under a distortion-free condition, and mapping image coordinates of the characteristic points to the camera coordinate system according to the internal parameter matrix to obtain camera coordinates of the characteristic points under a distortion condition;
and the fitting module is used for performing distortion parameter fitting on the camera coordinates of the characteristic points under the undistorted condition and the distorted condition to obtain corresponding distortion correction parameters, wherein the distortion correction parameters comprise a radial distortion parameter and a tangential distortion parameter.
To achieve the above object, the present invention also provides a camera, comprising: the calibration method comprises a camera, a processor and a memory, wherein the memory stores a calibration program of the camera, and the calibration program of the camera realizes the steps of the calibration method of the camera when being executed by the processor.
In order to achieve the above object, the present invention further provides a computer-readable storage medium, on which a computer program is stored, and the computer program, when executed by a processor, implements the steps of the calibration method for a camera as described above.
The calibration method, the calibration device, the camera and the computer-readable storage medium of the camera provided by the embodiment of the invention are characterized in that a calibration image of a calibration plate is collected, feature points in the calibration image are extracted, calculation is carried out according to coordinates of the feature points in the calibration image and world coordinates of the feature points to obtain a homography matrix from a plane of the calibration plate to a plane of the calibration image, then, coordinates of the feature points in a machine coordinate system under a distortion-free condition and a distortion condition are calculated according to an internal parameter matrix and the homography matrix of the camera, finally, distortion parameter fitting is carried out on the coordinates of the feature points in the machine coordinate system under the distortion-free condition and the distortion condition to obtain corresponding distortion correction parameters, and calibration of the camera is realized. The sample application takes world coordinates as reference, obtains a homography matrix according to the coordinates of the characteristic points in the calibration plate image and the world coordinates, and then maps the corresponding characteristic points in the calibration image to the coordinates of the camera by using the homography matrix and the internal parameter matrix of the camera, thereby improving the calibration accuracy.
In addition, the calibration can be completed only through one calibration image, the calibration process is simple and convenient, and the camera calibration efficiency can be improved.
Drawings
Fig. 1 is a schematic structural diagram of a calibration device of a camera according to an embodiment of the present application;
fig. 2 is a schematic flowchart of an embodiment of a calibration method for a camera according to the present application;
FIG. 3 is a schematic diagram of an image of a calibration board in an embodiment of a calibration method for a camera according to the present application;
fig. 4 is a detailed flowchart of step S200 in an embodiment of the calibration method for a camera according to the present application;
FIG. 5 is a functional block diagram of a calibration apparatus of a camera according to a first embodiment of the present invention;
FIG. 6 is a schematic diagram of a detailed functional module of an image coordinate module in an embodiment of a calibration apparatus for a camera according to the present invention;
fig. 7 is a schematic diagram of a detailed functional module of an obtaining module in an embodiment of the calibration apparatus for a camera according to the present invention.
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
As shown in fig. 1, fig. 1 is a schematic device structure diagram of a hardware operating environment according to an embodiment of the present invention.
The device of the embodiment of the invention can be a device with a camera, such as a PC, a tablet computer, a portable computer, a smart phone and the like.
As shown in fig. 1, the apparatus may include: the processor 1001 includes, for example, a CPU, a communication bus 1002, a camera 1003, and a memory 1005. Wherein a communication bus 1002 is used to enable connective communication between these components. The camera 1003 is used for performing exposure according to a user instruction or other program instruction to obtain a captured image. The memory 1005 may be a high-speed RAM memory or a non-volatile memory (e.g., a magnetic disk memory). The memory 1005 may alternatively be a storage device separate from the processor 1001.
Those skilled in the art will appreciate that the terminal structure shown in fig. 1 is not intended to be limiting and may include more or fewer components than those shown, or some components may be combined, or a different arrangement of components.
As shown in fig. 1, a memory 1005, which is a kind of computer storage medium, may include therein an operating system and a calibration program of a camera.
In the apparatus shown in fig. 1, the processor 1001 may be configured to call up a calibration program of a camera stored in the memory 1005, and perform the following operations of the embodiments of the calibration method of a camera.
Based on the calibration device of the camera, various embodiments of the calibration method of the camera in the application are provided.
Fig. 2 shows a flowchart of a calibration method for a camera, which includes the following steps:
and S100, acquiring the calibration board through the camera to obtain a corresponding calibration image.
Before the calibration, a calibration board is firstly arranged, as an example, the calibration board comprises a checkerboard with a plurality of black and white squares arranged at intervals, at least one dot is arranged in at least one black or white grid in the checkerboard, the calibration board can be as shown in fig. 3, and the dot can be arranged in the middle of the calibration board or in other positions. In other embodiments, the calibration board may also replace the pattern of the black-and-white chessboard with another shape, for example, a black-and-white rectangle is used to replace the black-and-white square block pattern in fig. 3, and the description of the type, the pattern shape, the pattern size, and the arrangement of the calibration board in the embodiment of the present invention does not limit the present invention. In the embodiment of the invention, the calibration board is subjected to image acquisition through the camera. In order to obtain a better shooting effect, the camera can be a wide-angle camera.
In order to improve the calibration efficiency, before the images of the calibration plate are collected, the camera where the camera is located and the calibration plate can be placed on the same horizontal plane, and the connection line of the lens center of the wide-angle camera and the center of the calibration plate is ensured to be parallel to the horizontal plane. Preferably, the camera imaging surface and the calibration plate plane are arranged in parallel, and then the calibration plate is collected through the camera to obtain a corresponding calibration image.
In the embodiment of the invention, the subsequent calibration process can be completed only by acquiring one calibration image, so that the calibration efficiency can be effectively improved. In other embodiments, in order to improve the calibration accuracy, a plurality of calibration plate images can be continuously collected, and a frame of image with the best collection effect is preferably selected as the calibration image, so that the problem of degradation of the collected calibration image caused by shooting jitter, inaccurate focusing, poor shooting angle or poor shooting range in the shooting process can be effectively avoided. The index for evaluating the acquisition effect may be one or more of parameters such as definition, image distortion, size range of the acquired image, and number of feature points, and the evaluation process of the acquisition effect may be performed by the system automatically according to a preset program to select the image frame, so that the user may manually perform input selection, which is not limited in the embodiment of the present invention.
And step S200, processing the calibration image to obtain the image coordinates of the characteristic points in the calibration image.
And after acquiring a calibration image corresponding to the calibration plate, performing image processing on the calibration image, and extracting feature points in the image. In the embodiment of the present invention, the extracted feature points may include: the checkerboard angular points are points at four angular positions of black squares or white squares. The coordinates of each feature point in the image are determined according to a preset coordinate system of the calibration board, that is, coordinates of a checkerboard corner point and a circle center of a dot are obtained, the coordinates are based on the image coordinate system, so that the coordinates of the feature point in the image are defined as image coordinates, wherein an origin of a world coordinate system of the calibration board is generally the upper left corner of the calibration board, the horizontal right side is the positive x-axis direction, the vertical horizontal downward direction is the positive y-axis direction, the origin of a coordinate system for collecting the image can also be the upper left corner of the image, the horizontal right side is the positive x-axis direction, the vertical horizontal downward direction is the positive y-axis direction, of course, other positions can also be set as the origins in the world coordinate system of the calibration board and the coordinate system of the image, and other directions can be the x-.
And step S300, obtaining world coordinates of the feature points on the calibration plate, calculating according to the image coordinates of the feature points and the world coordinates of the feature points, and further obtaining a homography matrix from the plane where the calibration plate is located to the plane where the calibration image is located.
In the embodiment of the invention, the world coordinates of the characteristic points on the calibration board can be obtained by automatically measuring the world coordinates of the characteristic points (such as the centers of circles) on the calibration board through the system. In other embodiments, the world coordinates of the feature point (e.g., the center of a circle) may be pre-stored in the system or may be input according to an input device. The homography matrix from the plane of the calibration plate to the plane of the calibration image is obtained by calculating world coordinates of characteristic points (such as the centers of circles of the dots) and image coordinates of the characteristic points (such as the centers of the circles of the dots).
And S400, obtaining an internal parameter matrix of a camera to which the camera belongs.
The intrinsic parameter matrix of the camera to which the camera belongs is obtained after the homography matrix is obtained, the intrinsic parameter matrix can be preset in a program, in order to improve the compatibility of the program, optical parameters preset by a camera of the camera can also be read, and then the intrinsic parameter matrix of the camera is obtained according to the coordinates of the principal point of the camera in the optical parameters of the camera, the pixel size and the focal length. In a specific implementation, the intrinsic parameter matrix of the camera to which the camera belongs may also be obtained before the homography matrix is obtained, which is not limited herein.
Step S500, mapping the world coordinates of the feature points to a coordinate system of the camera according to the internal parameter matrix and the homography matrix to obtain camera coordinates of the feature points under a distortion-free condition, and mapping the image coordinates of the feature points to the coordinate system of the camera according to the internal parameter matrix to obtain camera coordinates of the feature points under a distortion condition;
after obtaining the internal parameter matrix of the camera to which the camera belongs, an external parameter matrix is obtained through calculation according to the internal parameter matrix and the homography matrix, then the world coordinates of the feature points are mapped to the coordinate system of the camera according to the external parameter matrix, and the camera coordinates of the feature points under the distortion-free condition are obtained, that is, the coordinates of the feature points in the camera coordinate system under the distortion-free condition are obtained.
And mapping the image coordinates of the characteristic points to a camera coordinate system according to the internal parameter matrix to obtain the camera coordinates of the characteristics under the distortion condition, namely obtaining the coordinates of the characteristic points in the camera coordinate system under the distortion condition, wherein the camera coordinates are the coordinate system where the camera is located and can be set according to the actual condition of a user.
And S600, performing distortion parameter fitting on the camera coordinates of the feature points under the undistorted condition and the distorted condition to obtain corresponding distortion correction parameters.
And finally, carrying out distortion parameter fitting on the obtained camera coordinates of the characteristic points under the distortion-free condition and the obtained camera coordinates of the characteristic points under the distortion condition so as to obtain distortion correction parameters, and specifically carrying out distortion parameter fitting through the following formula:
ud＝u(1+k1r2+k2r4+k3r6)+[2p1v+p2(r2+2u2)]；
vd＝v(1+k1r2+k2r4+k3r6)+[2p2u+p1(r2+2v2)]；
wherein the coordinate of a feature point under the distortion condition is [ u ]d，vd]The coordinates of a feature point under the distortion-free condition are [ u, v ]]，k1、k2And k3Is a radial distortion parameter, p, of the camera1And p2The distortion correction parameters include a sagittal distortion parameter and a tangential distortion parameter for the camera. It should be noted that the method for parameter fitting in the embodiment of the present invention is not limited to the invention, and in other embodiments, other transformation combination methods known to those skilled in the art may be further adopted to perform distortion parameter fitting on the camera coordinates under the distortion condition and under the distortion-free condition to obtain the final distortion correction parameters, which may also improve the calibration accuracy.
According to the above description, the image coordinates of the feature points are converted into the coordinate system where the camera is located, and the camera coordinates of the corresponding features under the distortion condition are obtained; and will be the worldAnd converting the coordinates into a coordinate system where the camera is located, and obtaining the camera coordinates of the corresponding features under the distortion-free condition. And then carrying out distortion parameter fitting on the characteristic point coordinates in the machine coordinate system under the distortion-free condition and the distortion condition to realize the calibration process. And according to the calculation formula, the coordinates of the five characteristic points are selected to complete the calculation, and k is obtained1、k2、k3、p1And p2So any five feature points can be selected for conversion to camera coordinates.
The calibration method, the calibration device, the camera and the computer-readable storage medium of the camera provided by the embodiment of the invention are characterized in that a calibration image of a calibration plate is collected, feature points in the calibration image are extracted, calculation is carried out according to coordinates of the feature points in the calibration image and world coordinates of the feature points to obtain a homography matrix from a plane of the calibration plate to a plane of the calibration image, then, coordinates of the feature points in a machine coordinate system under a distortion-free condition and a distortion condition are calculated according to an internal parameter matrix and the homography matrix of the camera, finally, distortion parameter fitting is carried out on the coordinates of the feature points in the machine coordinate system under the distortion-free condition and the distortion condition to obtain corresponding distortion correction parameters, and calibration of the camera is realized. The sample application takes world coordinates as reference, obtains a homography matrix according to the coordinates of the characteristic points in the calibration plate image and the actual world coordinates, and then maps the corresponding characteristic points in the calibration image to the coordinates of the camera by using the homography matrix and the internal parameter matrix of the camera, thereby improving the calibration accuracy.
In addition, the calibration can be completed only through one calibration image, the calibration process is simple and convenient, and the camera calibration efficiency can be improved.
Further, referring to fig. 4, fig. 4 is a schematic detailed flow chart of step S200 in an embodiment of the calibration method for the camera according to the present application, and based on the first embodiment, step S200 includes:
step S210, carrying out binarization processing on the calibration image;
step S220, carrying out feature point detection on the calibration image subjected to binarization processing to obtain feature points to be confirmed;
and step S230, obtaining the image coordinates of the checkerboard corner pixels in the feature points to be confirmed through sub-pixel precision.
And S240, carrying out contour extraction and ellipse fitting on the calibration image subjected to binarization processing to obtain the image coordinates of the circle center in the calibration image.
In order to further improve the accuracy of the result, in the process of extracting the feature points, in this embodiment, binarization processing is performed on the obtained calibration image first, so as to eliminate interference of other factors such as ambient brightness on the feature points. Then, feature points of the binarized image are extracted, so that feature points to be confirmed are obtained, namely, checkerboard corner points to be confirmed in the calibrated image, pixels of the checkerboard corner points in the calibrated image are determined through the sub-pixel progress, and finally, image coordinates of the checkerboard corner points are determined according to an image coordinate system preset by the calibrated image, wherein the calibrated image can be binarized by selecting an OSTU algorithm (Dajin algorithm) and the Harris algorithm is selected for feature point detection. After binarization, contour extraction and ellipse fitting are carried out on the calibration image, the circle center of a dot in the calibration image is determined, and the image coordinate of the circle center is determined according to an image coordinate system preset by the calibration image. If the calibration plate is calibrated by other images, the same method is adopted, namely after binarization is carried out, the image coordinates of pixels at the intersection positions of the black and white images are selected through sub-pixel precision.
Referring to fig. 5, fig. 5 is a functional module schematic diagram of a calibration device of a camera according to a first embodiment of the present invention.
The invention also provides a calibration device of the camera, which comprises:
the image acquisition module 10 is used for acquiring the calibration plate through the camera to obtain a corresponding calibration image;
the image coordinate module 20 is configured to process the calibration image to obtain image coordinates of feature points in the calibration image;
the calculation module 30 is configured to obtain world coordinates of the feature points on the calibration board, and perform calculation according to the image coordinates of the feature points and the world coordinates of the feature points on the calibration board to obtain a homography matrix from a plane where the calibration board is located to a plane where the calibration image is located;
an obtaining module 40, configured to obtain an internal parameter matrix of a camera to which the camera belongs;
a mapping module 50, configured to map the world coordinates of the feature points to a coordinate system of the camera according to the intrinsic parameter matrix and the homography matrix, obtain camera coordinates of the feature points under a distortion-free condition, and map image coordinates of the feature points to a camera coordinate system according to the intrinsic parameter matrix, obtain camera coordinates of the feature points under a distortion condition;
and a fitting module 60, configured to perform distortion parameter fitting on the camera coordinates of the feature points under the undistorted condition and the distorted condition, so as to obtain corresponding distortion correction parameters. The distortion correction parameters may include a radial distortion parameter and a tangential distortion parameter.
Further, the camera acquires the calibration image for one time on the calibration plate; or
And after the camera continuously collects the calibration plate, selecting a frame meeting a preset index threshold value from the calibration plate as a calibration image.
The connecting line of the camera and the center of the calibration plate is parallel to the horizontal line, and the imaging surface of the camera is parallel to the calibration plate.
Further, referring to fig. 6, fig. 6 is a schematic diagram of a detailed functional module of an image coordinate module in an embodiment of the calibration apparatus for a camera according to the present invention. Based on the above embodiment, the feature points include the corner points of the checkerboard and the circle centers of the dots, and the image coordinate module 20 may include:
a binarization unit 21, configured to perform binarization processing on the calibration image;
a feature point detection unit 22, configured to perform feature point detection on the calibration image after the binarization processing;
a corner image coordinate unit 23, configured to obtain image coordinates of checkerboard corner pixels in the calibration image with sub-pixel precision.
And a circle center image coordinate unit 24, configured to perform contour extraction and ellipse fitting on the binarized calibration image, and obtain an image coordinate of a circle center in the calibration image.
Further, referring to fig. 7, fig. 7 is a schematic diagram of detailed functional modules of an obtaining module in an embodiment of the calibration apparatus for a camera according to the present invention. Based on the above embodiment, the obtaining module 40 includes:
an obtaining unit 41, configured to obtain an optical parameter preset by the camera;
and the internal parameter unit 42 is used for obtaining an internal parameter matrix of the camera according to the principal point coordinates, the pixel size and the focal length of the camera in the optical parameters.
Further, referring to fig. 6, fig. 6 is a functional module schematic diagram of a calibration apparatus of a camera according to a second embodiment of the present invention, and the fitting module 60 is further configured to:
distortion parameter fitting was performed by the following formula:
ud＝u(1+k1r2+k2r4+k3r6)+[2p1v+p2(r2+2u2)]；
vd＝v(1+k1r2+k2r4+k3r6)+[2p2u+p1(r2+2v2)]；
wherein the coordinate of a feature point under the distortion condition is [ u ]d，vd]The coordinates of a feature point under the distortion-free condition are [ u, v ]]，k1、k2And k3Is a radial distortion parameter, p, of the camera1And p2Is a tangential distortion parameter of the camera.
The present invention further provides a computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, implements the steps of the calibration method for a camera according to any one of the above embodiments.
The specific embodiment of the readable storage medium of the present invention is substantially the same as the embodiments of the calibration method of the camera described above, and details are not described herein.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or system. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other like elements in a process, method, article, or system that comprises the element.
The above-mentioned serial numbers of the embodiments of the present invention are merely for description and do not represent the merits of the embodiments.
Through the above description of the embodiments, those skilled in the art will clearly understand that the method of the above embodiments can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware, but in many cases, the former is a better implementation manner. Based on such understanding, the technical solution of the present invention may be embodied in the form of a software product, which is stored in a readable storage medium (such as ROM/RAM, magnetic disk, optical disk) as described above and includes several instructions for causing a terminal to execute the method according to the embodiments of the present invention.
The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications of equivalent structures and equivalent processes, which are made by using the contents of the present specification and the accompanying drawings, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A calibration method of a camera is characterized by comprising the following steps:
collecting the calibration plate through the camera to obtain a corresponding calibration image;
processing the calibration image to obtain image coordinates of the feature points in the calibration image;
obtaining world coordinates of the feature points on the calibration plate, and calculating according to image coordinates of the feature points and the world coordinates of the feature points on the calibration plate to obtain a homography matrix from a plane where the calibration plate is located to a plane where the calibration image is located;
obtaining an internal parameter matrix of a camera to which the camera belongs;
mapping the world coordinates of the feature points to a coordinate system of the camera according to the intrinsic parameter matrix and the homography matrix to obtain camera coordinates of the feature points under a distortion-free condition, and mapping image coordinates of the feature points to the camera coordinate system according to the intrinsic parameter matrix to obtain camera coordinates of the feature points under a distortion condition;
and performing distortion parameter fitting on the camera coordinates of the characteristic points under the undistorted condition and the distorted condition to obtain corresponding distortion correction parameters.
2. The calibration method of a camera according to claim 1, wherein the camera acquires the calibration image once for a calibration plate; or
And after the camera continuously collects the calibration plate, selecting a frame meeting a preset index threshold value from the calibration plate as a calibration image.
3. The method for calibrating a camera according to claim 1, wherein the feature points comprise checkerboard corner points, and the processing the calibration image to obtain the image coordinates of the feature points in the calibration image comprises:
carrying out binarization processing on the calibration image;
carrying out feature point detection on the calibration image subjected to binarization processing to obtain feature points to be confirmed;
and obtaining the image coordinates of the checkerboard corner point pixels in the feature points to be confirmed through sub-pixel precision.
4. The method for calibrating a camera according to claim 3, wherein the feature point further includes a center of a circular dot, and the processing of the calibration image to obtain the image coordinates of the feature point in the calibration image further includes:
and carrying out contour extraction and ellipse fitting on the calibration image subjected to binarization processing to obtain the image coordinate of the circle center in the calibration image.
5. The method for calibrating a camera according to claim 1, wherein the obtaining an internal parameter matrix of a camera to which the camera belongs comprises:
obtaining preset optical parameters of the camera;
and obtaining an internal parameter matrix of the camera according to the principal point coordinates, the pixel size and the focal length of the camera in the optical parameters.
6. The method for calibrating a camera according to claim 1, wherein the performing distortion parameter fitting on the camera coordinates of the feature points under the undistorted condition and the distorted condition to obtain corresponding distortion correction parameters specifically comprises:
distortion parameter fitting was performed by the following formula:
ud＝u(1+k1r2+k2r4+k3r6)+[2p1v+p2(r2+2u2)]；
vd＝v(1+k1r2+k2r4+k3r6)+[2p2u+p1(r2+2v2)]；
wherein the coordinate of a feature point under the distortion condition is [ u ]d，vd]The coordinates of a feature point under the distortion-free condition are [ u, v ]]，k1、k2And k3Is a radial distortion parameter, p, of the camera1And p2Is a tangential distortion parameter of the camera,the distortion correction parameters include a radial distortion parameter and a tangential distortion parameter.
7. A calibration method for a camera according to any one of claims 1 to 6, characterized in that a line connecting the camera and the center of the calibration plate is parallel to the horizontal line, and an imaging plane of the camera is parallel to the calibration plate.
8. A calibration device of a camera is characterized in that the calibration device of the camera comprises:
the image acquisition module is used for acquiring the calibration plate through the camera to obtain a corresponding calibration image;
the image coordinate module is used for processing the calibration image to obtain the image coordinates of the characteristic points in the calibration image;
the calculation module is used for obtaining the world coordinates of the feature points on the calibration plate, calculating according to the image coordinates of the feature points and the world coordinates of the feature points on the calibration plate, and obtaining a homography matrix from the plane where the calibration plate is located to the plane where the calibration image is located;
the obtaining module is used for obtaining an internal parameter matrix of a camera to which the camera belongs;
the mapping module is used for mapping the world coordinates of the characteristic points to a coordinate system of the camera according to the internal parameter matrix and the homography matrix to obtain camera coordinates of the characteristic points under a distortion-free condition, and mapping image coordinates of the characteristic points to the camera coordinate system according to the internal parameter matrix to obtain camera coordinates of the characteristic points under a distortion condition;
and the fitting module is used for performing distortion parameter fitting on the camera coordinates of the characteristic points under the undistorted condition and the distorted condition to obtain corresponding distortion correction parameters.
9. A camera, characterized in that the camera comprises: camera, a processor and a memory, in which a calibration program of the camera is stored, which when executed by the processor performs the steps of the calibration method of the camera according to any one of claims 1 to 7.
10. A computer-readable storage medium, characterized in that a computer program is stored on the computer-readable storage medium, which computer program, when being executed by a processor, carries out the steps of the calibration method for a camera head according to any one of claims 1 to 7.
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