CN114445493A - Calibration board characteristic region extraction method, calibration method and calibration board - Google Patents
Calibration board characteristic region extraction method, calibration method and calibration board Download PDFInfo
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Abstract
The application provides a calibration plate characteristic region extraction method, a calibration method and a calibration plate. This calibration board includes: the color of the dot area and the background are mutually reverse; among the five reference dots, the connecting lines of four peripheral reference dots form a quadrangle with a perspective relation, the quadrangle is used as the reference of all the reference dots, and the peripheral reference dots are arranged in the central area of the calibration board; the fifth datum point is positioned in the middle of the two peripheral datum dots at the lower side, is set as the origin of the coordinate system of the calibration plate, and is used for recording the position and attitude information of the calibration plate and the sequencing information of the reference dots. According to the method and the device, the complex operation of manually selecting four angular points of the image can be avoided, the automation degree of calibration is improved, the robustness is good, the target area is well and adaptively extracted accurately, and the positioning precision of the characteristic points can be improved by adopting an ellipse fitting algorithm based on the outline.
Description
Technical Field
The application relates to the technical field of computer vision-camera calibration, in particular to a calibration plate characteristic region extraction method, a calibration method and a calibration plate.
Background
Computer vision is a study of how to use cameras and computers to obtain the data and information needed by people, and camera calibration is to establish the mapping relationship between the positions of the pixels of the camera image and the corresponding objects in the world coordinate system. Therefore, camera calibration is the basis of computer vision, and the accuracy of the calibration result directly influences the positioning accuracy of the whole vision system.
The current mainstream camera calibration boards can be classified into checkerboard calibration boards and circular calibration boards according to the feature patterns thereon (as shown in fig. 1). Compared with a chessboard calibration plate, the dot calibration plate has the following advantages:
the anti-noise and anti-fuzzy performance is good.
And when the projector is calibrated, the detection precision reduction caused by the sharp change of black and white pixels at the corner points of the checkerboard can be avoided.
The calibration plate types are further classified into two types with and without a reference according to whether the reference is provided or not:
the method for extracting the feature points of the circular array calibration plate (application number CN201710445416.8) like CN107274454B is a calibration plate without a reference, the reference needs to be manually selected during feature extraction, the automation degree is low, and the use is inconvenient. And because there is no reference, so there is no direction information, not suitable for calibration of multiple devices, hand-eye calibration systems (including mobile and fixed) associated with actuators (robots).
For example, the CN109285194B camera calibration board and the camera calibration data acquisition method (application number CN201811147388.2) are calibration boards with references, and the solution failure of the mapping points due to the partial shielding of the calibration boards or the partial area exceeding the imaging range is avoided.
The feature point extraction algorithm of the currently mainstream circular calibration plate comprises the following steps:
[ findCirclesGrid, HoughCrle, BlobDedetector, SimpleBlobDedetector, etc. in OpenCV.
② the speckle detection algorithm Difference of Gaussian, Laplacian of Gaussian, and Determinant of Hessian.
And thirdly, carrying out ellipse fitting algorithm based on the contour track.
Disclosure of Invention
Based on the above-mentioned purpose, this application has proposed a calibration plate, include:
the color of the dot area and the background are mutually reverse; wherein the content of the first and second substances,
among the five reference dots, the connection lines of four peripheral reference dots form a quadrangle with perspective relation and serve as the reference of all the reference dots, and the peripheral reference dots are arranged in the central area of the calibration plate; the fifth datum point is positioned in the middle of the two peripheral datum dots at the lower side, is set as the origin of a coordinate system of the calibration plate, and is used for recording the pose information of the calibration plate and the sequencing information of the reference dots.
Furthermore, the reference dots on the calibration plate are arranged in an array form, each row is parallel, each column is parallel, the rows and the columns are mutually vertical, and the reference dots are spaced at equal intervals.
The application also provides a calibration plate feature region extraction method using the calibration plate, which comprises the following steps:
placing the calibration plate in the visual field range of a CCD camera, collecting images of the calibration plate, and recording a plurality of groups of images by changing the relative positions and postures of the calibration plate and the camera;
carrying out binarization processing and filtering operation on each group of images;
extracting the outline of each group of images by adopting a Canny operator, selecting a memory outline according to the hierarchical relation of the outlines, and carrying out ellipse fitting on the memory outline based on a least square method to obtain an elliptic outline;
filtering the elliptical contours;
according to the size of the ellipse after filtering, the average diameters of the reference dots and the reference dots are counted, and the morphological self-adaptive proportional coefficient is calculated;
performing morphological opening and closing operation on the circular features to obtain an interested area, namely a preliminary exploration area of the calibration plate;
finding out the reference points in the preliminary exploration area, and calculating the gravity center of the calibration board according to the peripheral 4 reference points. And (3) according to the proportional relation from the gravity center of the ideal calibration board to the reference point and four corner points at the outermost periphery of the calibration board, carrying out proportional amplification on the reference point in the image according to the pixel distance, thereby calculating to obtain an accurate calibration board area.
For a mobile camera, namely the camera is carried on an actuator, the pose of a calibration plate is not changed during image acquisition, and the pose of the actuator is controlled to change after the image of the calibration plate is acquired each time, so that the relative pose between the camera and the calibration plate is changed.
For a fixed camera, i.e., the position and attitude of the camera is fixed, the position and attitude of the calibration plate is changed each time image acquisition is performed.
Further, after obtaining the area where the calibration plate is located, the method further includes:
and when the calibration plate exceeds the visual field range, performing boundary processing on the region of interest.
The application also provides a calibration method of the calibration plate, which comprises the following steps:
carrying out ellipse fitting based on contour characteristics on the area where the calibration plate is located by using the method to obtain all fitted ellipse contours on the area of the calibration plate;
calculating the ellipse position corresponding to the reference circular point according to the size information, and judging the pose of the origin coordinate system of the calibration plate and the four reference ellipse positions according to the cosine value of the vector included angle;
sorting the reference dots according to the pose information of the coordinate system of the calibration plate to obtain image coordinates which correspond to world coordinates one by one;
and finishing camera calibration according to the Zhang calibration method.
Further, the reference dot sorting method includes:
carrying out affine transformation on the reference dots, and then sequencing the reference dots in a manner that row and column coordinate values are monotonically increased; alternatively, the first and second electrodes may be,
and (4) sorting according to the circle center of the vector included angle on the basis of the original image.
In general, the advantages of the present application and the experience brought to the user are:
1. improve the degree of automation of the calibration
Compared with the existing calibration algorithm, the method avoids the complex operation of manually selecting four corner points of the image through the self-adaptive region extraction algorithm of the calibration plate.
Secondly, through the introduction of a coordinate system, the problem of directivity of characteristic point sequencing is solved, and the automation degree is improved.
2. Good robustness
The shooting background of the calibration plate is disordered, and the environment background color is close to or consistent with the background color of the calibration plate, so that the target area can be accurately extracted in a self-adaptive manner.
Secondly, the characteristic points of the target area can still be extracted under the condition that the calibration plate is partially shielded or partially exceeds the visual field range of the camera.
And thirdly, under the condition that an included angle exists between the plane where the calibration plate is located and the image plane of the camera, the feature points of the target area can still be extracted.
3. Ellipse fitting algorithm based on contour features
Under the condition that an included angle exists between the plane where the calibration plate is located and the image plane of the camera, the shape of the feature dots on the calibration plate is changed under the influence of perspective transformation, and the positioning accuracy of the feature dots can be improved by adopting an ellipse fitting algorithm based on the outline.
Drawings
In the drawings, like reference numerals refer to the same or similar parts or elements throughout the several views unless otherwise specified. The figures are not necessarily to scale. It is appreciated that these drawings depict only some embodiments in accordance with the disclosure and are therefore not to be considered limiting of its scope.
Fig. 1 is a schematic diagram of a chessboard pattern calibration plate (left) and a circular calibration plate (right) in the prior art.
FIG. 2 is a schematic diagram of a circular calibration plate with a reference according to the present application.
FIG. 3 is a schematic diagram of the change of the included angle between the calibration plate and the camera plane and a schematic diagram of the extraction result.
FIG. 4 is a diagram illustrating the adaptive region extraction result of the calibration plate beyond the visual field.
Fig. 5 is a schematic diagram of an ellipse fitting image based on graphic features (left: graphic outline right: elliptical outline).
FIG. 6 is a schematic diagram of circle center sorting based on vector angle.
FIG. 7 is a diagram showing the results of sorting (left: right before sorting: after sorting).
Fig. 8 is a flowchart of an adaptive extraction process for a region of interest of a calibration plate according to the present application.
Fig. 9 is a flowchart of a calibration method based on an ellipse fitting manner in the present application.
Fig. 10 is a schematic structural diagram of an electronic device according to an embodiment of the present application;
fig. 11 is a schematic diagram of a storage medium provided in an embodiment of the present application.
Detailed Description
The present application will be described in further detail with reference to the following drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the relevant invention and not restrictive of the invention. It should be noted that, for convenience of description, only the portions related to the related invention are shown in the drawings.
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments with reference to the attached drawings.
The purpose of the application comprises the following four points:
1. the full-automatic function of extracting the target area of the calibration board and sequencing the characteristic dots is realized.
2. The problem that the traditional dot calibration algorithm fails to solve the mapping points due to the fact that partial areas are shielded or the partial areas exceed the imaging range is solved.
3. The robustness of feature point and dot extraction is improved:
when an included angle exists between the plane where the calibration board is located and the image plane of the camera, the situation that characteristic dots cannot be identified can occur in the mainstream OpenCV-based circular detection algorithm and the mainstream spot detection algorithm, and the robustness of characteristic dot extraction can be well improved by adopting the outline-track-based ellipse fitting algorithm.
4. Improving the positioning accuracy of the reference dots
Under the condition that an included angle exists between the plane where the calibration plate is located and the image plane of the camera, the positioning accuracy of the feature dots can be improved by adopting an ellipse fitting algorithm based on the outline.
The core of the application is to provide a circular calibration plate with a reference, a calibration plate self-adaptive area extraction algorithm based on the circular calibration plate, and an ellipse fitting algorithm based on a characteristic outline on the calibration plate. The technical solutions in the examples of the present application will be described below with reference to the drawings in the examples of the present application (it should be noted that the protection content of the present application is not limited to the following description):
example 1, a circular calibration plate with fiducials.
Fig. 2 shows a diagram of a calibration plate used in the present application. The calibration plate is composed of the following aspects: the color-changing printing ink is composed of 5 reference dots and a plurality of reference dots (the number and the arrangement shape of the reference dots are not limited), and the dot areas and the background color are opposite. Among the 5 reference dots, the connection line of 4 peripheral reference dots can form a quadrangle with perspective relation, is the reference of all reference points, and is arranged in the central area of the calibration plate. And the fifth reference point is set as the origin of the coordinate system of the calibration plate and used for recording the pose information of the calibration plate and the sequencing information of the reference points. The reference points on the calibration plate are arranged in an array mode, each row (column) is parallel, the rows and the columns are mutually vertical, and the reference points are spaced at equal intervals.
Example 2, extraction of panel adaptation regions was calibrated.
Step 1: the calibration plate is placed in the visual field range of a Charge Coupled Device (CCD) camera, images of the calibration plate are collected, and a plurality of groups of images are recorded by changing the relative position and posture of the calibration plate and the camera. Due to different arrangement modes of the cameras, the cameras can be divided into a movable type and a fixed type:
the mobile camera is carried on an actuator (mechanical arm), and the pose of the calibration plate needs to be ensured not to change when image acquisition is carried out. After each acquired calibration plate image, the pose change of an actuator (mechanical arm) needs to be controlled, so that the relative pose change between the camera and the calibration plate is realized.
The fixed position and the fixed gesture for the camera are fixed, and the position and the gesture of the calibration plate need to be changed when image acquisition is carried out at every time.
Step 2: the image is binarized using OTSU (ohio-maximum inter-class variance method). If a threshold value T exists in the image, the size relation between each pixel in the image and the T is judged, then the pixels can be divided into a background B and a foreground F, and when the optimal threshold value T is selected, the difference between the background and the foreground is the largest. The method comprises the following implementation steps:
1. selecting a segmentation threshold value T, and counting the proportion p of points with foreground pixel values smaller than T in all pixel points0And average gray a0. Counting p of background pixel greater than T in the same way1And a1；
2. Calculating the average gray scale of all pixels;
Ag＝p0a0+p1a1
3. calculating the between-class variance
g＝p0(p0-Ag)2+p1(a1-Ag)2
4. And traversing all the segmentation threshold values T, and repeating 1-3 to obtain the threshold value T with the maximum inter-class variance g.
Step 3: the conventional filter needs to sort the pixels according to the range of the filter at each pixel position, which is time-consuming, when the window moves one column (row) along the row (column), the content of the window changes only by replacing one column (row) at the left with a new column (row) at the right, and for the m n filter, the (m n-2 m) pixels do not change.
1. Counting median positions, wherein ceil is an upward rounding function, and t is the median position:
2. sorting the window content and establishing a pixel histogram H, counting the number n of brightness smaller than the median (i.e. the pixel value corresponding to the t position)m。
3. Moving filters, p for each luminance on the left side of the shiftgIs operated by one, HpgHistogram for pixel p:
Hpg＝Hpg-1
nm＝nm-1
4. for each shifted-in luminance pgThe pixel p of (a) is subjected to an increase operation
Hpg＝Hpg+1
nm＝nm+1
5. According to nmAnd (4) the relation with t is discussed according to the situation and the boundary judgment is carried out, and finally the high-efficiency median filtering operation is completed.
Step 4: and (3) extracting the outline of the image by adopting a Canny operator of the OPENCV, and selecting the memory outline according to the hierarchical relation of the outline. On the basis, the ellipse fitting based on the least square method is adopted for the profile to obtain the elliptical profile:
1. known ellipse equation
ax2+bxy+cy2+dx+ey＝1
2. Let a be [ a, b, c, d, e]T，x＝[x2,xy,y2,x,y]TThen the equation can be expressed as
ax＝1
3. The ellipse fitting optimization problem can be expressed as
min||Sa||2
Is limited by aTCa＝1
Wherein S is a sample set, a is an ellipse equation parameter, and a constant matrix C is
4. According to a Lagrange multiplier method, a Lagrange factor lambda is introduced to obtain the following equation:
2STSa-2λCa＝0
5. solving for STSa is a sum vector of characteristic values of λ Ca (λ Ca)i，ui) Finally, solve to obtain
6. Let ai＝μiuiTaking λi>0 corresponding to the feature vector uiI.e. can be used as a fitting equation solution for the curve.
Step 5: filtering the circular features on the calibration plate to obtain a relatively pure profile (it should be noted that although circular features are used in this application, the scope of protection should not be limited to the geometric shape of the graph); the filtering method in the step can adopt common filtering algorithms, such as elliptic filtering operation based on area, length-width ratio and outlier, so as to eliminate the interference of the elliptic contour in the background environment to the elliptic contour on the calibration board. And filtering out unsuitable elliptical tracks in the fitted image by adopting an effective filtering means according to the parameters of the calibration plate.
Step 6: according to the size of the ellipse after filtering, the average diameter of the reference circle and the reference circle is counted, and therefore the morphological self-adaptive proportional coefficient is calculated; in this step, the adaptive size of the calibration plate is calculated from the reference ellipsoid points in the calibration plate.
Step7：
Performing morphological opening and closing operation on the circular feature by using an elementsizeconzengeCLOSE () function and an elementsizecongestopen () function in the OPENCV to obtain an interested region, namely a preliminary exploration region of the calibration board; finding out the reference points in the preliminary exploration area, and calculating the gravity center of the calibration board according to the peripheral 4 reference points. And (3) according to the proportional relation from the gravity center of the ideal calibration board to the reference point and four corner points at the outermost periphery of the calibration board, carrying out proportional amplification on the reference point in the image according to the pixel distance, thereby calculating to obtain an accurate calibration board area. In this step, the area of the calibration plate in the image is obtained by performing the opening and closing or closing operation on the filtered elliptical image model morphology according to the adaptive adjustment size information. By the end of this step, the extraction of the calibration plate has been completed. Further, the method can also comprise the following steps:
step 8: and (3) performing boundary processing on the region of interest, and handling the condition that the calibration plate exceeds the visual field range:
1. calculating and calibrating gravity center xc、ycWherein x isi、yiIs a reference dot P1,P2,P3,P4The coordinates of (a):
2. calculating the reference dot P1,P2,P3,P4Distance to center of gravity
3. According to the arrangement mode of the reference points of the calibration plate, the reference points are arranged according to d in step2iAppropriate magnification is performed so that the new point obtained serves as the contour reference for the calibration plate.
The automatic extraction of the region of interest of the calibration plate is completed, and the flow is shown in fig. 8.
The self-adaptive region extraction algorithm of the calibration plate based on the graphic features has high robustness:
the method can be used for solving the problems that the shooting background is disordered, and the background color of the environment is close to or consistent with that of the calibration plate, and can still extract the feature points of the target area.
Secondly, under the condition that an included angle exists between the plane where the calibration plate is located and the image plane of the camera, the feature points of the target area can still be extracted (as shown in figure 3).
And thirdly, under the condition that the calibration plate is partially blocked or partially exceeds the visual field range of the camera, the characteristic points of the target area can still be extracted (as shown in figure 4).
Example 3, a calibration process based on an ellipse fitting method of a graph contour, as shown in fig. 9, includes the following steps:
step 1: carrying out ellipse fitting based on contour features on the area where the calibration plate is located to obtain all fitted ellipse contours on the area of the calibration plate (step 4 of the implementation process reference example 2); fig. 5 is a schematic diagram of an ellipse fitting image based on graphic features (left: graphic outline right: elliptical outline). The ellipse fitting algorithm based on the contour features can improve the positioning accuracy of the feature points. Secondly, under the condition that an included angle exists between the plane where the calibration plate is located and the image plane of the camera, the robustness of feature dot identification is improved (as shown in figure 5).
Step 2: calculating the ellipse position corresponding to the reference circular point according to the size information, and judging the pose of the origin coordinate system of the calibration plate and the four reference ellipse positions according to the cosine value of the vector included angle;
1. cosine value of vector angle
Where dot () is a vector dot product and cross () is a vector cross product.
2. The intermediate point P is calculated from two vectors of θ being 0 or 180, and is the origin of the calibration plate.
Step 3: the reference point sorting method can be divided into two types, one is to perform affine transformation on the reference dots and then sort the reference dots in a mode of monotone increasing of row (column) coordinate values, and the other is to sort the reference dots according to the circle center of a vector included angle on the basis of an original image. Finally, image coordinates corresponding to world coordinates one by one can be obtained;
circle-center ordering method (as shown in fig. 6):
1. searching characteristic points on the boundary AB and the AC, and sorting according to the length of the distance between the two points, wherein the point on the AC is marked as Vi(i ═ 1,2,. n), points on AB are denoted as Hi(i＝1，2，..，n)；
2. Based on AB (AC), Vi(Hi) Taking any point P in the center dot matrix except the boundary AB and AC as the starting pointiSeparately calculate ViPi(HiPi) Angle theta between vector and AB (AC)vi(θHi)；
3. Selecting thetavi(θHi) Group of smallest value, according to PiVi(PiHi) The reference dots are arranged in monotonically increasing order. FIG. 7 is a diagram showing the results of sorting (left: right before sorting: after sorting).
Affine transformation method:
1. solving an affine transformation matrix according to a reference dot coordinate system and a calibration plate workpiece coordinate system
aiAnd { i ═ 1,2,3,4} is the rotation parameter, tx，tyFor the translation parameters, x, y are the original image positions, x',and y' is the position after affine transformation.
2. The reference dots are affine transformed and arranged according to a monotonically increasing order of x and y.
Step 4: and finishing camera calibration according to the Zhang calibration method.
scIs a proportionality coefficient;
u and v are respectively the horizontal and vertical coordinates of a pixel coordinate system;
dx，dyis the physical size of the pixel on the x-axis and the y-axis, and has the unit: mm/pixel;
f is the focal length of the camera;
rij{ i ═ 0, 1, 2; j is 0, 1,2, which is a rotation matrix;
Tx,Ty,Tzis a translation vector;
xw，yw，zwis the point coordinate in the world coordinate system.
The embodiment of the present application further provides an electronic device corresponding to the calibration board feature region extraction method and the calibration method provided in the foregoing embodiments, so as to execute the calibration board feature region extraction method and the calibration method. The embodiments of the present application are not limited.
Referring to fig. 10, a schematic diagram of an electronic device provided in some embodiments of the present application is shown. As shown in fig. 10, the electronic apparatus 2 includes: the system comprises a processor 200, a memory 201, a bus 202 and a communication interface 203, wherein the processor 200, the communication interface 203 and the memory 201 are connected through the bus 202; the memory 201 stores a computer program that can be executed on the processor 200, and the processor 200 executes the calibration board feature region extraction method and the calibration method provided by any one of the foregoing embodiments when executing the computer program.
The Memory 201 may include a high-speed Random Access Memory (RAM) and may further include a non-volatile Memory (non-volatile Memory), such as at least one disk Memory. The communication connection between the network element of the system and at least one other network element is realized through at least one communication interface 203 (which may be wired or wireless), and the internet, a wide area network, a local network, a metropolitan area network, and the like can be used.
The processor 200 may be an integrated circuit chip having signal processing capabilities. In implementation, the steps of the above method may be performed by integrated logic circuits of hardware or instructions in the form of software in the processor 200. The Processor 200 may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; but may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components. The various methods, steps, and logic blocks disclosed in the embodiments of the present application may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present application may be directly implemented by a hardware decoding processor, or implemented by a combination of hardware and software modules in the decoding processor. The software module may be located in ram, flash memory, rom, prom, or eprom, registers, etc. storage media as is well known in the art. The storage medium is located in the memory 201, and the processor 200 reads the information in the memory 201 and completes the steps of the method in combination with the hardware thereof.
The electronic device provided by the embodiment of the application and the method for extracting the characteristic region of the calibration board provided by the embodiment of the application have the same inventive concept and have the same beneficial effects as the method adopted, operated or realized by the electronic device.
Referring to fig. 11, the computer-readable storage medium is an optical disc 30, and a computer program (i.e., a program product) is stored thereon, and when being executed by a processor, the computer program may execute the calibration board feature region extraction method and the calibration method provided by any of the foregoing embodiments.
It should be noted that examples of the computer-readable storage medium may also include, but are not limited to, phase change memory (PRAM), Static Random Access Memory (SRAM), Dynamic Random Access Memory (DRAM), other types of Random Access Memory (RAM), Read Only Memory (ROM), Electrically Erasable Programmable Read Only Memory (EEPROM), flash memory, or other optical and magnetic storage media, which are not described in detail herein.
The computer-readable storage medium provided by the above-mentioned embodiment of the present application, and the calibration board feature region extraction method and the calibration method provided by the embodiment of the present application have the same inventive concept and have the same beneficial effects as the method adopted, operated or implemented by the application program stored in the computer-readable storage medium.
It should be noted that:
the algorithms and displays presented herein are not inherently related to any particular computer, virtual machine, or other apparatus. Various general purpose systems may also be used with the teachings herein. The required structure for constructing such a system will be apparent from the description above. In addition, this application is not directed to any particular programming language. It will be appreciated that a variety of programming languages may be used to implement the teachings of the present application as described herein, and any descriptions of specific languages are provided above to disclose the best modes of the present application.
In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the application may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Similarly, it should be appreciated that in the foregoing description of exemplary embodiments of the application, various features of the application are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the application and aiding in the understanding of one or more of the various inventive aspects. However, the disclosed method should not be interpreted as reflecting an intention that: this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this application.
Those skilled in the art will appreciate that the modules in the device in an embodiment may be adaptively changed and disposed in one or more devices different from the embodiment. The modules or units or components of the embodiments may be combined into one module or unit or component, and furthermore they may be divided into a plurality of sub-modules or sub-units or sub-components. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and all of the processes or elements of any method or apparatus so disclosed, may be combined in any combination, except combinations where at least some of such features and/or processes or elements are mutually exclusive. Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.
Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the application and form different embodiments. For example, in the following claims, any of the claimed embodiments may be used in any combination.
Various component embodiments of the present application may be implemented in hardware, or in software modules running on one or more processors, or in a combination thereof. Those skilled in the art will appreciate that a microprocessor or Digital Signal Processor (DSP) may be used in practice to implement some or all of the functions of some or all of the components in a virtual machine creation system according to embodiments of the present application. The present application may also be embodied as apparatus or system programs (e.g., computer programs and computer program products) for performing a portion or all of the methods described herein. Such programs implementing the present application may be stored on a computer readable medium or may be in the form of one or more signals. Such a signal may be downloaded from an internet website or provided on a carrier signal or in any other form.
It should be noted that the above-mentioned embodiments illustrate rather than limit the application, and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The application may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the unit claims enumerating several systems, several of these systems may be embodied by one and the same item of hardware. The usage of the words first, second and third, etcetera do not indicate any ordering. These words may be interpreted as names.
The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily conceive various changes or substitutions within the technical scope of the present application, and these should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.
Claims (10)
1. A calibration plate, comprising:
the color of the dot area and the background are mutually reverse; wherein the content of the first and second substances,
among the five reference dots, the connecting lines of four peripheral reference dots form a quadrangle with a perspective relation and serve as the reference of all the reference dots, and the peripheral reference dots are arranged in the central area of the calibration board; the fifth datum point is positioned in the middle of the two peripheral datum dots at the lower side, is set as the origin of a coordinate system of the calibration plate, and is used for recording the pose information of the calibration plate and the sequencing information of the reference dots.
2. Calibration plate according to claim 1,
the reference dots on the calibration plate are arranged in an array mode, each row is parallel, each column is parallel, the rows and the columns are mutually vertical, and the reference dots are spaced at equal intervals.
3. A calibration plate feature region extraction method using the calibration plate of claim 1 or 2, characterized by comprising:
placing the calibration plate in the visual field range of a CCD camera, collecting images of the calibration plate, and recording a plurality of groups of images by changing the relative positions and postures of the calibration plate and the camera;
carrying out binarization processing and filtering operation on each group of images;
extracting the outline of each group of images by adopting a Canny operator, selecting a memory outline according to the hierarchical relation of the outlines, and carrying out ellipse fitting on the memory outline based on a least square method to obtain an elliptic outline;
filtering the elliptical contours;
according to the size of the ellipse after filtering, the average diameters of the reference dots and the reference dots are counted, and the morphological self-adaptive proportional coefficient is calculated;
performing morphological opening and closing operation on the circular features to obtain an interested area, namely a preliminary exploration area of the calibration plate;
finding a reference point in the preliminary exploration area, and calculating the gravity center of the calibration plate according to 4 peripheral reference circle points; and amplifying the reference dots in the image in proportion according to the pixel distance according to the proportional relation from the gravity center of the ideal calibration board to the four corner points of the reference dots and the outermost periphery of the calibration board, thereby calculating to obtain an accurate calibration board area.
4. The method of claim 3,
the camera is carried on the actuator, the pose of the calibration plate is not changed when the image is collected, and the pose of the actuator is controlled to change after the image of the calibration plate is collected every time, so that the change of the relative pose between the camera and the calibration plate is realized.
5. The method of claim 3,
the position and the posture of the camera are fixed, and the position and the posture of the calibration plate are changed each time when image acquisition is carried out.
6. The method of claim 3, after obtaining the area of the calibration plate, further comprising:
and when the calibration plate exceeds the visual field range, performing boundary processing on the region of interest.
7. A calibration method of a calibration plate is characterized by comprising the following steps:
performing an ellipse fitting based on profile features on the area of the calibration plate using the method of any one of claims 3-6 to obtain all fitted elliptical profiles on the area of the calibration plate;
calculating the ellipse position corresponding to the reference circular point according to the size information, and judging the pose of the origin coordinate system of the calibration plate and the four reference ellipse positions according to the cosine value of the vector included angle;
sorting the reference dots according to the pose information of the coordinate system of the calibration plate to obtain image coordinates which correspond to world coordinates one by one;
and finishing camera calibration according to the Zhang calibration method.
8. The method of claim 7,
the reference dot sorting method comprises the following steps:
carrying out affine transformation on the reference dots, and then sequencing the reference dots in a manner that row and column coordinate values are monotonically increased; alternatively, the first and second electrodes may be,
and (4) sorting according to the circle center of the vector included angle on the basis of the original image.
9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor executes the computer program to implement the method of any one of claims 1-8.
10. A computer-readable storage medium, on which a computer program is stored, characterized in that the program is executed by a processor to implement the method according to any of claims 1-8.
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| CN202111602968.8A CN114445493A (en) | 2021-12-24 | 2021-12-24 | Calibration board characteristic region extraction method, calibration method and calibration board |
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| CN202111602968.8A CN114445493A (en) | 2021-12-24 | 2021-12-24 | Calibration board characteristic region extraction method, calibration method and calibration board |
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