CN114998451B - Calibration board based on equiangular spiral line and camera calibration method - Google Patents
Calibration board based on equiangular spiral line and camera calibration method Download PDFInfo
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- CN114998451B CN114998451B CN202210898112.8A CN202210898112A CN114998451B CN 114998451 B CN114998451 B CN 114998451B CN 202210898112 A CN202210898112 A CN 202210898112A CN 114998451 B CN114998451 B CN 114998451B
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- G06T7/00—Image analysis
- G06T7/80—Analysis of captured images to determine intrinsic or extrinsic camera parameters, i.e. camera calibration
- G06T7/85—Stereo camera calibration
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Abstract
The application relates to a calibration plate based on equiangular spiral, which is used for determining calibration coordinates according to calibration characteristics with preset marks added, wherein the calibration plate is provided with a plurality of characteristic layers, and each characteristic layer comprises a plurality of characteristics generated based on equiangular spiral. The center of the calibration plate is the initial point of an equiangular spiral line, and a first characteristic layer is defined to be composed of N characteristics of which the characteristic centers are distributed on a circle which takes the center of the calibration plate as the circle center and takes the radius of the initial position as the radius; the non-first characteristic layer consists of N characteristics, the characteristic centers of which are distributed on preset points of an equiangular spiral line and are spaced at fixed angles; the calibration feature is provided with a preset mark, and the preset mark is used for indicating the layer number of the calibration feature in the calibration plate and the serial number in the feature layer. Through this application, solved current calibration plate and can't satisfy the problem of the big or small camera demarcation demand in different fields of vision simultaneously, can carry out the demarcation of two cameras of the big or small difference in fields of vision simultaneously through a calibration plate, guaranteed to mark the precision.
Description
Technical Field
The application relates to the field of camera calibration, in particular to a calibration plate based on an equiangular spiral line and a camera calibration method.
Background
The camera calibration process is a process of solving the mapping relation between the three-dimensional coordinates and the two-dimensional image coordinates (which is also equivalent to solving the internal and external parameters of the camera) through a series of mathematical transformations. After calibration, the image deformation caused by lens distortion can be corrected, and three-dimensional scene reconstruction can be carried out according to the two-dimensional image.
In the related art, camera calibration is performed through a calibration plate with uniform characteristics, fig. 1 is a schematic diagram of a checkerboard calibration plate and a dot calibration plate in the related art, as shown in fig. 1, the checkerboard calibration plate has black and white squares with the same size, and vertexes of the squares are uniformly distributed on the calibration plate; the dot calibration plate is provided with circles with the same size, and the centers of the circles are uniformly distributed on the calibration plate.
In practical application, in order to ensure the calibration precision, a proper calibration plate needs to be selected according to the visual field of a camera, if the calibration plate is too large, the pose in the visual field is not rich enough, and the calibration convergence requirement is difficult to meet; if the calibration plate is too small, the problems of difficult feature extraction and low calibration precision are faced.
At present, an effective solution is not provided aiming at the problem that the existing calibration plate cannot be compatible with calibration of cameras with different sizes simultaneously in the related technology.
Disclosure of Invention
The embodiment of the application provides a calibration plate based on an equiangular spiral line, a camera calibration method and a camera calibration system, and aims to at least solve the problem that the calibration plate cannot be compatible with cameras with different visual fields in different sizes simultaneously in the related technology.
In a first aspect, an embodiment of the present application provides an equiangular spiral-based calibration plate, configured to determine calibration coordinates according to a calibration feature in which a preset mark is added:
the calibration plate is provided with a plurality of feature layers, and each feature layer comprises a plurality of features generated based on equiangular spirals, wherein,
the characteristic shape and size in the same characteristic layer are the same, the characteristic shape and size of different characteristic layers are the same but different, and the characteristic that the characteristic center is positioned on the equiangular spiral line is a calibration characteristic;
defining a calibration plate center as a starting point of the equiangular spiral line, defining a first characteristic layer to be composed of N characteristics, wherein the characteristic centers are distributed on a circle which takes the calibration plate center as a circle center and takes an initial position radius as a radius, and the N characteristics are spaced at fixed angles, defining a non-first characteristic layer to be composed of N characteristics, wherein the characteristic centers are distributed on preset points of the equiangular spiral line, and the N characteristics are spaced at fixed angles, and the initial position radius value is a preset constant;
the calibration feature is provided with a preset mark, and the preset mark is used for indicating the layer number of the calibration feature in the calibration plate and the serial number in the feature layer.
In some embodiments, for any non-first feature layer, the predetermined point is a perpendicular bisector of a line connecting centers of two adjacent features in the inner layer feature, and a first outer intersection point of the equiangular spiral line.
In some of these embodiments, where the shape of the feature is circular:
in any one feature layer, the radius of the feature is smaller than half of the length of the connecting line of the centers of two adjacent features;
in the non-first characteristic layer, the radius of any characteristic is smaller than the difference between the connecting line length of the characteristic center of the characteristic and the characteristic center of the adjacent inner layer characteristic and the radius of the inner layer characteristic.
In some of these embodiments, where the shape of the feature is circular:
presetting a plurality of concentric circles marked as the interior of the calibration feature, wherein the radius proportion of each concentric circle in the calibration feature in different feature layers is different;
in the camera calibration process, the layer number of the calibration feature and the serial number of the calibration feature in the feature layer are obtained according to the radius proportion of each concentric circle in the calibration feature or the number of the concentric circles in the feature.
In some of these embodiments, the equiangular helix may be represented by the following polar equation:
wherein the content of the first and second substances,
is a radius of a polar coordinate, and,
in the form of a polar angle of view,
is the radius of the initial position and is,
is a parameter that controls the degree of curvature of the equiangular helix,
is a first
The initial angular parameters of the strip equiangular helix,
of any equiangular helix in the calibration plate
、
And
all being constant, of different equiangular helices
、
In the same way, the first and second,
different.
In some of these embodiments, the fixed angle has the following relationship to the number of features:
wherein the content of the first and second substances,
it is the fixed angle that is the angle of inclination,
is the number of features;
the initial angle parameter of each equiangular spiral line has the following relation with the fixed angle:
wherein the content of the first and second substances,
is the serial number of the equiangular spiral,
is the first
The initial angular parameter of the strip helix is,
is a constant of the initial angle of rotation,
is the fixed angle.
In a second aspect, an embodiment of the present application provides a camera calibration method, where camera calibration is performed through a calibration board based on an equiangular spiral line, and the method includes:
the plurality of camera devices with different visual field sizes are used for respectively shooting a plurality of groups of calibration images in different areas on the calibration plate;
respectively determining calibration characteristics in the calibration images, respectively determining calibration coordinates according to the calibration characteristics added with preset marks, and respectively calibrating the camera based on the calibration coordinates, wherein,
the calibration plate is provided with a plurality of characteristic layers, each characteristic layer comprises a plurality of characteristics generated based on equiangular spiral lines, the characteristic shapes and sizes in the same characteristic layer are the same, the characteristic shapes of different characteristic layers are the same but the sizes are different, and the characteristic that the characteristic center is positioned on the equiangular spiral lines is a calibration characteristic; defining a calibration plate center as a starting point of the equiangular spiral line, defining a first characteristic layer consisting of N characteristics of which the characteristic centers are distributed on a circle which takes the calibration plate center as a circle center and takes the initial position radius as a radius at intervals of fixed angles, defining a non-first characteristic layer consisting of N characteristics of which the characteristic centers are distributed on a preset point of the equiangular spiral line at intervals of fixed angles, wherein the initial position radius value is a preset constant; the calibration feature is provided with a preset mark, and the preset mark is used for indicating the layer number of the calibration feature in the calibration plate and the serial number in the feature layer.
In some embodiments, determining calibration coordinates according to calibration features added with preset marks, and performing camera calibration based on the calibration coordinates, respectively, includes:
the method comprises the following steps that a plurality of camera devices with different visual field sizes respectively identify calibration images and determine calibration characteristics;
respectively acquiring a layer number of the calibration feature in the calibration plate and a serial number in the feature layer according to a preset mark in the calibration feature;
determining a feature center coordinate corresponding to the calibration feature according to the layer number and the serial number, and taking the feature center coordinate as a calibration coordinate;
and respectively determining a homography transformation matrix between the physical characteristics of the calibration plate and the image characteristics shot by the camera based on the calibration coordinates, and calibrating the camera by using the homography transformation matrix.
In some embodiments, the plurality of image capturing devices with different view field sizes are two image capturing devices with different view field sizes in the same binocular system, or are a plurality of image capturing devices in different systems;
shoot the multiunit calibration image of different regions on the calibration plate respectively, include:
the camera device with the small visual field acquires multiple groups of characteristic images in the upper inner layer area of the calibration plate, and the camera device with the large visual field acquires multiple groups of characteristic images in the outer layer area of the calibration plate.
In a third aspect, an embodiment of the present application provides a camera calibration system, where the system includes: camera device and calibration board, wherein, camera device is the camera device of two field of vision size differences under the same binocular system, perhaps, is the camera device of a plurality of field of vision size differences under the different systems:
the camera shooting device is used for respectively shooting a plurality of groups of calibration images in different areas on the calibration plate, respectively determining calibration characteristics in the calibration images, respectively determining calibration coordinates according to the calibration characteristics added with preset marks, and respectively calibrating the camera based on the calibration coordinates;
the calibration board is used for providing calibration characteristics of camera calibration, wherein,
the calibration plate is provided with a plurality of characteristic layers, each characteristic layer comprises a plurality of characteristics generated based on equiangular spiral lines, the characteristic shapes and sizes in the same characteristic layer are the same, the characteristic shapes of different characteristic layers are the same but the sizes are different, and the characteristic that the characteristic center is positioned on the equiangular spiral lines is a calibration characteristic; defining a calibration plate center as a starting point of the equiangular spiral line, defining a first characteristic layer consisting of N characteristics of which the characteristic centers are distributed on a circle which takes the calibration plate center as a circle center and takes the initial position radius as a radius at intervals of fixed angles, defining a non-first characteristic layer consisting of N characteristics of which the characteristic centers are distributed on a preset point of the equiangular spiral line at intervals of fixed angles, wherein the initial position radius value is a preset constant; the calibration features are provided with preset marks which are used for indicating layer numbers of the calibration features in the calibration plate and serial numbers in the feature layer.
Compared with the prior art, the calibration plate based on the equiangular spiral line is provided by the embodiment of the application. The calibration board utilizes the self-similarity characteristic of the equiangular spiral line, and multilayer features which are wide in generation range and identical in shape based on the equiangular spiral line are distributed in the calibration board. Therefore, the camera calibration device can provide suitable calibration characteristics for cameras with different visual field sizes through one calibration plate. In practical application, the cameras respectively shoot images of the calibration plates, corresponding position coordinates (namely calibration coordinates) are obtained by identifying preset marks in the image calibration characteristics, and then the calibration coordinates can be used for calibrating the cameras. The problem of current calibration plate can't satisfy the big or small camera of different fields of vision simultaneously and mark the demand is solved in this application, can carry out the demarcation of two cameras of field of vision variation simultaneously through a calibration plate, has guaranteed the demarcation precision.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
FIG. 1 is a schematic view of a checkerboard calibration plate and a dot calibration plate according to the related art;
FIG. 2 is a schematic diagram of an application environment of an equiangular spiral-based calibration board according to an embodiment of the present application;
FIG. 3 is a schematic illustration of an equiangular helix based calibration plate according to an embodiment of the present application;
FIG. 4 is a schematic diagram of inner and outer layer feature circles according to an embodiment of the application;
FIG. 5 is a schematic diagram of a preset mark for determining a layer number of a calibration feature according to an embodiment of the present application;
FIG. 6 is a schematic diagram of another preset mark for determining a layer number of a calibration feature according to an embodiment of the present application;
FIG. 7 is a flowchart of a camera calibration method according to an embodiment of the present application;
FIG. 8 is a flowchart illustrating a method for determining calibration coordinates according to a predetermined mark to calibrate a camera according to an embodiment of the present disclosure;
fig. 9 is a block diagram of a camera calibration system according to an embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more clearly understood, the present application is described and illustrated below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of and not restrictive on the broad application. All other embodiments obtained by a person of ordinary skill in the art based on the embodiments provided in the present application without any inventive step are within the scope of protection of the present application.
It is obvious that the drawings in the following description are only examples or embodiments of the application, and that it is also possible for a person skilled in the art to apply the application to other similar contexts on the basis of these drawings without inventive effort. Moreover, it should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another.
Reference in the specification to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the specification. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is to be expressly and implicitly understood by one of ordinary skill in the art that the embodiments described herein may be combined with other embodiments without conflict.
The calibration board based on the equiangular spiral can be applied to the application environment shown in fig. 2, and fig. 2 is a schematic application environment diagram of the calibration board based on the equiangular spiral according to an embodiment of the present application. As shown in fig. 2, cameras with different view sizes capture images of different areas on the calibration plate, further determine calibration features of the images by recognizing the images, determine position coordinates (i.e., calibration coordinates) according to preset marks added to the calibration features, and finally perform mathematical calculation according to the calibration coordinates to calibrate the cameras. In this embodiment, since the features in the calibration plate are generated based on an equiangular spiral, the corresponding coordinates can be determined by the "preset mark" added by the calibration features during the identification process. Therefore, by utilizing the self-similar characteristic of the equiangular spiral line, the calibration plate can provide the characteristics of meeting the requirements and ensuring the precision for cameras with different visual fields (the visual field range of the camera is in the processing precision and the scale range of the calibration plate), and then a plurality of cameras are calibrated simultaneously, so that the calibration precision is improved.
Fig. 3 is a schematic view of an equiangular spiral-based calibration plate according to an embodiment of the present application, as shown in fig. 3,
the calibration plate is provided with a plurality of characteristic layers, each characteristic layer comprises a plurality of characteristics generated based on an equiangular spiral line, the characteristic shapes and the sizes of the same characteristic layer are the same, the characteristic shapes of different characteristic layers are the same but the sizes of the different characteristic layers are different, and the characteristic that the characteristic center is positioned on the equiangular spiral line is a calibration characteristic.
The feature intersected with the equiangular spiral line in each feature layer is a calibration feature, when only one equiangular spiral line exists in the calibration plate, only one calibration feature exists in each feature layer, and when a plurality of equiangular spiral lines exist in the calibration plate, a plurality of calibration features exist in each feature layer.
Note that, in the present embodiment, the characteristic shape shown in fig. 3 is a circular shape, which is a specific example. In this application, features may also be other shapes, including but not limited to: circular, square, snowflake, etc., and further, the feature center is the geometric center of each feature.
It should be understood that the shape of the feature has no influence on the calibration effect, and a user can select a proper feature shape within a certain range according to the self requirement, the convenience and the precision of feature extraction. However, in the actual production link, in order to reduce the engineering complexity and realize mass production, the characteristics should be selected from a simple shape, such as a circular shape.
In addition, the more the number of layers of the features on the calibration plate is, the wider the calibration application range of the calibration plate is. The number of the characteristic layers is increased, and the size difference between the outer-layer characteristic and the inner-layer characteristic is increased, so that the method can be more suitable for calibrating a plurality of groups of cameras with larger differences of visual field ranges.
The method comprises the steps of defining a calibration plate center as an initial point of an equiangular spiral line, defining a first characteristic layer, wherein the characteristic center is distributed on a circle which takes the calibration plate center as a circle center and takes an initial position radius as a radius, and the first characteristic layer is formed by N characteristics at intervals of fixed angles, defining a non-first characteristic layer, and is distributed on a preset point of the equiangular spiral line by the characteristic center and N characteristics at intervals of fixed angles, wherein the initial position radius value is a preset constant. The calibration feature is internally provided with a preset mark, the preset mark is used for indicating the layer number of the calibration feature in the calibration plate and the serial number in the feature layer, and the feature quantity N of each layer is consistent.
For any non-first characteristic layer, the preset point is a perpendicular bisector of a connecting line of centers of two adjacent characteristics in the characteristics of the inner layer and a first outer side intersection point of the equiangular spiral line.
The first featured layer is the innermost layer of the calibration board and the non-first featured layers are featured layers other than the first featured layer. Furthermore, the initial position radius and the fixed angle are both fixed constants, and specific numerical values are set by combining actual requirements of users.
It is emphasized that the calibration plate is provided with predetermined marks on the calibration features of the respective layers. During actual calibration, the camera can identify preset marks in the image, determine the layer number and the serial number of each calibration feature in the calibration plate, and further determine the feature center coordinates of the calibration features according to the layer number and the serial number.
When only one spiral line is arranged on the calibration plate, the serial number is fixed to be 1. When there are multiple spirals on the calibration plate, the above mentioned serial numbers are used to determine the spiral (on which spiral) on which the calibration feature is located. The layer number is used to determine the specific feature layer in which the calibration feature is located in the calibration plate. After the layer number sum is obtained, the camera can determine the calibration coordinate through the corresponding relation.
Furthermore, in the embodiment, the core invention point lies in how to provide calibration features suitable for cameras with different visual field sizes through the calibration board, and how to determine calibration coordinates according to the preset marks. After the calibration coordinates are obtained, how to determine a homography transformation matrix between the physical features of the calibration plate and the image features shot by the camera according to the calibration coordinates, and then utilize the homography transformation matrix to calibrate the camera does not relate to the core invention point of the present application, and can be realized by the conventional technical means of the technicians in the field, so the technical details are not described again in this embodiment.
In some of these embodiments, the equiangular spiral may be represented by the following polar equation:
equation 1:
wherein, the first and the second end of the pipe are connected with each other,
is a radius of a polar coordinate, and,
is an angle of a polar coordinate, and is,
is the radius of the initial position, and the radius of the initial position,
is a parameter that controls the degree of curvature of the equiangular helix,
is as follows
Initial angle parameters of a plurality of equiangular spiral lines, and calibration of any equiangular spiral line in the plate
、
And
all being constant, of different equiangular helices
、
In the same way, the first and second,
different.
The number of features per layer is the same, and the following relationship exists between the number of features and the fixed angle:
equation 2:
wherein the content of the first and second substances,
it is the fixed angle that is the angle of inclination,
is the number of features;
the initial angle parameter of each equiangular spiral is in the following relation with the fixed angle:
equation 3:
wherein, the first and the second end of the pipe are connected with each other,
is the serial number of the equiangular spiral,
is the first
The initial angular parameter of the strip helix is,
is the initial angular constant of the angle of rotation,
is the fixed angle.
In some embodiments, the feature in the calibration plate is illustrated as a circle:
first, a suitable initial position radius is selected
And determining a fixed angle for spacing
Generating radius distributed at initial position by using the center of the target as the center of a circle
And determining a fixed angle for the spacing
Generating radius distributed at initial position by using the center of the target as the center of a circle
At the end point of (1), interval
N circles of, wherein, the angle is fixed
There is a relationship with the number of features N as shown in the above equation 2. It should be noted that, in order to avoid the feature circles in the same layer from overlapping, in any one feature layer, the radius of each feature circle should be less than half of the length of the feature center connecting line of two adjacent feature circles ((the specific value can be flexibly selected)). Of course, when the feature shapes are other shapes, mutual overlapping between the features should also be avoided, and specific implementation manners are not described in this application again.
And secondly, determining the feature center of the second layer of features by the intersection point of the perpendicular bisector of the connecting line between the two feature centers of the first layer of features and the equiangular spiral line. Fig. 4 is a schematic diagram of inner and outer layer feature circles according to an embodiment of the present application, and as shown in fig. 4, the smaller circles are two adjacent feature circles in the first layer, the thin dotted line indicates a line connecting feature centers thereof, the thick dotted line indicates a perpendicular bisector of the line connecting feature centers, and the closest outer intersection point of the thick dotted line and the spiral line indicates a first outer intersection point. It should be noted that, in order to separate the inner layer feature from the outer layer feature, the radius of the outer layer feature circle should be smaller than the value obtained by subtracting the radius of the inner layer feature circle from the distance between feature centers of the adjacent inner layer feature circles.
Furthermore, on the basis of the second layer of feature circle, the 3 rd layer and the 4 th layer of 8230are generated by analogy in sequence according to the logic, wherein the 8230is formed, and the N layer of feature circle is formed.
In some embodiments, when determining the calibration coordinates according to the layer number and the sequence number, the method specifically includes:
first, since the equiangular spiral can be expressed by a set of equations with variables (ρ, θ), the equation can be expressed by the above equation 1. In the formula 1, because
And
is a user-defined setting, and thus, can be based on
And
and determining the feature center coordinates of all feature circles in the first feature layer.
Further, a perpendicular bisector equation of a connecting line between two adjacent feature centers in the first feature layer can be determined; and further, the center coordinates of the calibration features in the second feature layer can be determined through a perpendicular bisector equation and an equation of an equiangular spiral line, and by analogy, the coordinates of the centers of all the calibration features in all the feature layers can be determined.
In some embodiments, the preset mark added to the calibration feature may have various forms, which is not specifically limited in this embodiment. Specifically, in the case that the feature is a circle, the following manner may be selected to add the preset mark, fig. 5 is a schematic diagram of one preset mark for determining the layer number of the feature according to the embodiment of the present application, and fig. 6 is a schematic diagram of another preset mark for determining the layer number of the feature according to the embodiment of the present application:
1: with the circle center of the calibration feature as the circle center, adding a fixed number of concentric circles with the radius smaller than that of the feature circle in each calibration feature, wherein the radius proportion of the concentric circles in each feature circle is in accordance with a certain proportion, for example, 1. The radius ratios of the concentric circles in the characteristic circles are arranged in different characteristic layers, for example, as shown in fig. 5, the ratio of the concentric circles in the characteristic circle of the layer 3 is 1; in the layer 4 feature, the ratio of concentric circles in each feature circle is 1.
Correspondingly, when the camera calibration link identifies the image, the layer number of each characteristic circle can be determined according to the radius proportion of each concentric circle in the characteristic circle.
2: with the circle center of the calibration feature as the center of the circle, different numbers of concentric circles are added to the feature circles of different layers according to the layer number where the feature circle is located, for example, as shown in fig. 6, 3 concentric circles are added to the feature circle of the 3 rd layer, and 4 concentric circles are added to the feature circle of the 4 th layer.
Correspondingly, when the camera calibration link identifies the image, the layer number of each characteristic circle can be determined according to the number of concentric circles in each characteristic circle.
On the other hand, for the division of the serial numbers, any one calibration feature can be selected as an initial quantity, the serial number of the calibration feature is set to be 1, and the serial numbers of the calibration features are 2 and 3 \8230insequence in the counterclockwise direction.
Of course, the above implementation manners are only some specific examples, and the preset marks can be added in other manners by specifically selecting features of different shapes. It should be understood that all ways that can be used to distinguish the layer number and serial number of the calibration feature based on the design concept of the calibration plate in the present application should be considered as part of the protection of the present application.
In addition, the present application also provides a camera calibration method, which performs camera calibration based on a calibration board of an equiangular spiral, and fig. 7 is a flowchart of the camera calibration method according to the embodiment of the present application, and as shown in fig. 7, the flowchart includes the following steps:
s701, a plurality of camera devices with different view sizes shoot a plurality of groups of calibration images in different areas on a calibration plate respectively;
s702, respectively determining calibration characteristics in the calibration images, respectively determining calibration coordinates according to the calibration characteristics added with the preset marks, and respectively calibrating the camera based on the calibration coordinates;
in this embodiment, the calibration board is provided with a plurality of feature layers, each feature layer includes a plurality of features generated based on an equiangular spiral, the feature shapes and sizes in the same feature layer are the same, the feature shapes and sizes of different feature layers are the same but different, and the feature that the feature center is located on the equiangular spiral is a calibration feature; defining a calibration plate center as a starting point of an equiangular spiral line, defining a first characteristic layer to be composed of N characteristics, wherein the characteristic centers are distributed on a circle which takes the calibration plate center as a circle center and takes an initial position radius as a radius, and the N characteristics are spaced at fixed angles, defining a non-first characteristic layer to be composed of N characteristics, wherein the characteristic centers are distributed on preset points of the equiangular spiral line and are spaced at fixed angles, and the initial position radius value is a preset constant; the calibration feature is provided with a preset mark, and the preset mark is used for indicating the layer number of the calibration feature in the calibration plate and the serial number in the feature layer.
Through the steps S701 to S702, compared with the conventional camera calibration method, in the present application, calibration is performed through the calibration board based on the equiangular spiral line, and by using the "self-similarity" characteristic of the equiangular spiral line in the calibration board, calibration features with wide distribution and proper size and number can be provided for cameras with different view field sizes. Therefore, the problem that the calibration of cameras with different visual fields cannot be realized through one calibration plate in the existing calibration mode or the problem that the calibration precision of cameras with different visual fields cannot be met through one calibration plate in the prior art is solved, the calibration precision is improved, and the resource cost is reduced.
In some embodiments, fig. 8 is a flowchart of determining calibration coordinates according to preset marks for camera calibration according to an embodiment of the present application, and as shown in fig. 8, the flowchart includes the following steps:
s801, identifying calibration images respectively by a plurality of camera devices with different view field sizes to determine calibration characteristics;
s802, respectively obtaining the layer number of the calibration feature in the calibration plate and the serial number in the feature layer according to the preset mark in the calibration feature;
s803, respectively determining feature center coordinates corresponding to the calibration features according to the layer numbers and the serial numbers, and taking the feature center coordinates as calibration coordinates;
and S804, respectively determining a homography transformation matrix between the physical characteristics of the calibration plate and the image characteristics shot by the camera based on the calibration coordinates, and calibrating the camera by using the homography transformation matrix.
The homography transformation matrix is data necessary for the camera calibration process, and how to perform mathematical operation on the basis of the data in combination with other data to achieve camera calibration is a conventional technical means in the field, and therefore is not described in detail in this embodiment.
In this embodiment, the plurality of imaging devices with different view sizes may be two imaging devices with different view sizes in the same binocular system, or may be a plurality of imaging devices with different systems.
When the feature shape is a circle, the preset mark may be a concentric circle combination added to the calibration feature to distinguish the layer numbers. After the camera takes an image, the calibration feature is usually mapped to an ellipse due to lens distortion, and first, it can be corrected to a perfect circle according to the ratio of the major axis to the minor axis. Further, according to the number or radius ratio of the concentric circles inside the camera, the coordinates of the calibration features are determined, and then the camera calibration is performed according to the coordinates.
In some embodiments, an embodiment of the present application further provides a camera calibration system, and fig. 9 is a block diagram of a structure of a camera calibration system according to an embodiment of the present application, and as shown in fig. 9, the system includes: camera device and calibration board, wherein, camera device 10 is the camera device of two field of vision size differences under the same binocular system, perhaps, is the camera device of a plurality of field of vision size differences under the different systems:
the camera device 10 is configured to respectively shoot multiple sets of calibration images in different areas on the calibration plate 20, respectively determine calibration features in the calibration images, respectively determine calibration coordinates according to the calibration features added with preset marks, and respectively perform camera calibration based on the calibration coordinates;
the calibration board 20 is used to provide calibration features for camera calibration, wherein,
the calibration board 20 is provided with a plurality of feature layers, each feature layer comprises a plurality of features generated based on equiangular spiral lines, the feature shapes and sizes in the same feature layer are the same, the feature shapes and sizes of different feature layers are the same but different, and the feature that the feature center is positioned on the equiangular spiral line is a calibration feature; defining a calibration plate center as an initial point of an equiangular spiral line, defining a first characteristic layer consisting of N characteristics of which the characteristic centers are distributed on a circle which takes the calibration plate center as a circle center and takes the initial position radius as a radius at intervals of fixed angles, defining a non-first characteristic layer consisting of N characteristics of which the characteristic centers are distributed on a preset point of the equiangular spiral line at intervals of fixed angles, wherein the initial position radius value is a preset constant; the calibration feature is provided with a preset mark, and the preset mark is used for indicating the layer number of the calibration feature in the calibration plate and the serial number in the feature layer.
Through the system, in some calibration scenes with large camera visual field difference (such as a group of binocular systems with large visual field difference), the calibration plate based on the equiangular spiral line is utilized to provide proper characteristics for a plurality of camera devices, so that rich poses can be presented in the camera visual field, the calibration convergence is met, and the calibration precision can be ensured.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above examples only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, and these are all within the scope of protection of the present application. Therefore, the protection scope of the present patent application shall be subject to the appended claims.
Claims (9)
1. A calibration plate based on equiangular spiral for determining calibration coordinates based on calibration features to which preset marks are added, characterized in that:
the calibration plate is provided with a plurality of feature layers, and each feature layer comprises a plurality of features generated based on an equiangular spiral, wherein,
the feature shape and the size in the same feature layer are the same, the feature shapes and the sizes of different feature layers are the same, and the feature that the feature center is positioned on the equiangular spiral line is the calibration feature;
defining a calibration plate center as a starting point of the equiangular spiral line, defining a first characteristic layer to be composed of N characteristics, wherein the characteristic centers are distributed on a circle which takes the calibration plate center as a circle center and takes an initial position radius as a radius, and the N characteristics are spaced at fixed angles, defining a non-first characteristic layer to be composed of N characteristics, wherein the characteristic centers are distributed on preset points of the equiangular spiral line, and the N characteristics are spaced at fixed angles, the initial position radius value is a preset constant, and for any non-first characteristic layer, the preset point is a perpendicular bisector of a connecting line of two adjacent characteristic centers in the inner layer characteristics and is a first outer intersection point of the equiangular spiral line;
the calibration feature is provided with the preset mark, and the preset mark is used for indicating the layer number of the calibration feature in the calibration plate and the serial number in the feature layer.
2. Calibration plate according to claim 1, characterized in that, in the case where the shape of the features is circular:
in any one feature layer, the radius of each feature is smaller than half of the length of a connecting line between the centers of two adjacent features;
in the non-first characteristic layer, the radius of any characteristic is smaller than the difference between the connecting line length of the characteristic center of the characteristic and the characteristic center of the adjacent inner layer characteristic and the radius of the inner layer characteristic.
3. Calibration plate according to claim 2, characterized in that, in the case where the shape of the features is circular:
the preset marks are a plurality of concentric circles in the calibration feature, wherein the radius proportion of each concentric circle in the calibration feature in different feature layers is different;
in the camera calibration process, according to the radius proportion of each concentric circle in the calibration characteristics, the layer number of the calibration characteristics and the serial number of the calibration characteristics in the characteristic layer are determined.
4. Calibration plate according to claim 1, characterized in that the equiangular spiral can be expressed by the following polar equation:
wherein, the first and the second end of the pipe are connected with each other,
is a radius of a polar coordinate, and,
in the form of a polar angle of view,
is the radius of the initial position and is,
is a parameter that controls the degree of curvature of the equiangular helix,
is as follows
The initial angular parameters of the strip equiangular helix,
of said calibration plates, any one of equiangular spiral lines
、
And
all being constant, of different equiangular spirals
、
In the same way, the first and second,
different.
5. Calibration plate according to claim 1, characterized in that the fixed angle is related to the number of features as follows:
wherein the content of the first and second substances,
it is the fixed angle that is the angle of inclination,
is the number of features;
the initial angle parameter of each equiangular spiral line has the following relation with the fixed angle:
wherein the content of the first and second substances,
is the serial number of the equiangular spiral,
is the first
The initial angular parameter of the strip helix is,
is a constant of the initial angle of rotation,
is the fixed angle.
6. A camera calibration method, wherein camera calibration is performed by an equiangular spiral-based calibration board, the method comprising:
the plurality of camera devices with different visual field sizes are used for respectively shooting a plurality of groups of calibration images in different areas on the calibration plate;
respectively determining calibration characteristics in the calibration images, respectively determining calibration coordinates according to the calibration characteristics added with preset marks, and respectively calibrating the camera based on the calibration coordinates, wherein,
the calibration plate is provided with a plurality of characteristic layers, each characteristic layer comprises a plurality of characteristics generated based on equiangular spiral lines, the characteristic shapes and sizes in the same characteristic layer are the same, the characteristic shapes of different characteristic layers are the same but the sizes are different, and the characteristic that the characteristic center is positioned on the equiangular spiral lines is a calibration characteristic; defining a calibration plate center as a starting point of the equiangular spiral line, defining a first characteristic layer consisting of N characteristics of which characteristic centers are distributed on a circle which takes the calibration plate center as a circle center and takes an initial position radius as a radius at intervals of fixed angles, defining a non-first characteristic layer consisting of N characteristics of which characteristic centers are distributed on preset points of the equiangular spiral line at intervals of fixed angles, wherein the initial position radius is a preset constant, and for any non-first characteristic layer, the preset points are midperpendicular lines connecting two adjacent characteristic centers in the inner layer characteristics and a first outer intersection point of the equiangular spiral line; the calibration feature is provided with the preset mark, and the preset mark is used for indicating the layer number of the calibration feature in the calibration plate and the serial number in the feature layer.
7. The method according to claim 6, wherein the determining calibration coordinates according to the calibration feature added with the preset mark, respectively, and performing camera calibration based on the calibration coordinates, respectively, comprises:
the plurality of camera devices with different visual field sizes respectively identify the calibration images and determine the calibration characteristics;
respectively determining the layer number of the calibration feature in the calibration plate and the serial number of the calibration feature in the feature layer according to preset marks in the calibration feature;
respectively determining a feature center coordinate corresponding to the calibration feature according to the layer number and the sequence number, and taking the feature center coordinate as a calibration coordinate;
and respectively determining a homography transformation matrix between the physical characteristics of the calibration plate and the image characteristics shot by the camera based on the calibration coordinates, and calibrating the camera by using the homography transformation matrix.
8. The method of claim 6, wherein:
the plurality of camera devices with different visual field sizes are two camera devices with different visual field sizes under the same binocular system, or a plurality of camera devices under different systems;
respectively shooting a plurality of groups of calibration images of different areas on the calibration plate, including:
the camera device with the small visual field acquires a plurality of groups of characteristic images in the inner layer area on the calibration plate, and the camera device with the large visual field acquires a plurality of groups of characteristic images in the outer layer area of the calibration plate.
9. A camera calibration system, the system comprising: camera device and calibration board, wherein, camera device is the camera device of two field of vision size differences under the same binocular system, perhaps, is the camera device of a plurality of field of vision size differences under the different systems:
the camera shooting device is used for respectively shooting a plurality of groups of calibration images in different areas on the calibration plate, respectively determining calibration characteristics in the calibration images, respectively determining calibration coordinates according to the calibration characteristics added with preset marks, and respectively calibrating the camera based on the calibration coordinates;
the calibration plate is used for providing calibration characteristics required by camera calibration, wherein,
the calibration plate is provided with a plurality of characteristic layers, each characteristic layer comprises a plurality of characteristics generated based on equiangular spiral lines, the characteristic shapes and the sizes of the same characteristic layer are the same, the characteristic shapes of different characteristic layers are the same but the sizes of the different characteristic layers are different, and the characteristic that the characteristic center is positioned on the equiangular spiral lines is a calibration characteristic; defining a calibration plate center as a starting point of the equiangular spiral line, defining a first characteristic layer to be composed of N characteristics which are distributed on a circle which takes the calibration plate center as a circle center and takes an initial position radius as a radius at intervals of a fixed angle, defining a non-first characteristic layer to be composed of N characteristics which are distributed on a preset point of the equiangular spiral line at intervals of a fixed angle, wherein the initial position radius is a preset constant, and for any non-first characteristic layer, the preset point is a perpendicular bisector of a connecting line of two adjacent characteristic centers in the inner layer characteristics thereof and a first outer side intersection point of the equiangular spiral line; the calibration feature is provided with the preset mark, and the preset mark is used for indicating the layer number of the calibration feature in the calibration plate and the serial number in the feature layer.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018057517A1 (en) * | 2016-09-20 | 2018-03-29 | Massachusetts Institute Of Technology | Circular scanning technique for large area imaging |
| CN110160442A (en) * | 2019-04-22 | 2019-08-23 | 南京航空航天大学 | A kind of flexible measuring tooling and its scaling method for conduit end face of flange vision-based detection |
| WO2019196192A1 (en) * | 2018-04-11 | 2019-10-17 | 深圳市瑞立视多媒体科技有限公司 | Capture ball-based sphere distribution method, motion attitude identification method and system, and device |
| CN112171666A (en) * | 2020-09-15 | 2021-01-05 | 深圳市商汤科技有限公司 | Pose calibration method and device for visual robot, visual robot and medium |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110660107A (en) * | 2019-08-23 | 2020-01-07 | 贝壳技术有限公司 | Plane calibration plate, calibration data acquisition method and system |
| CN114463438A (en) * | 2022-01-18 | 2022-05-10 | 湖南视比特机器人有限公司 | Calibration plate, calibration plate identification method, calibration plate identification device and computer readable medium |
-
2022
- 2022-07-28 CN CN202210898112.8A patent/CN114998451B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018057517A1 (en) * | 2016-09-20 | 2018-03-29 | Massachusetts Institute Of Technology | Circular scanning technique for large area imaging |
| WO2019196192A1 (en) * | 2018-04-11 | 2019-10-17 | 深圳市瑞立视多媒体科技有限公司 | Capture ball-based sphere distribution method, motion attitude identification method and system, and device |
| CN110160442A (en) * | 2019-04-22 | 2019-08-23 | 南京航空航天大学 | A kind of flexible measuring tooling and its scaling method for conduit end face of flange vision-based detection |
| CN112171666A (en) * | 2020-09-15 | 2021-01-05 | 深圳市商汤科技有限公司 | Pose calibration method and device for visual robot, visual robot and medium |
Non-Patent Citations (3)
| Title |
|---|
| "A novel camera calibration method combined with calibration toolbox and genetic algorithm";Yuanyuan Dong 等;《IEEE》;20161024;1416-1420 * |
| 基于圆形特征点的非线性相机标定方法;油世明等;《青岛大学学报(自然科学版)》;20091215(第04期);70-74 * |
| 基于圆点阵列的多相机外部参数标定;何国辉等;《五邑大学学报(自然科学版)》;20151115(第04期);36-40 * |
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