CN103136756B - A kind of demarcation target and scaling method thereof that can be used for different accuracy camera calibration - Google Patents
A kind of demarcation target and scaling method thereof that can be used for different accuracy camera calibration Download PDFInfo
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- CN103136756B CN103136756B CN201310066404.6A CN201310066404A CN103136756B CN 103136756 B CN103136756 B CN 103136756B CN 201310066404 A CN201310066404 A CN 201310066404A CN 103136756 B CN103136756 B CN 103136756B
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Abstract
The invention discloses a kind of the demarcation target and the scaling method thereof that can be used for different accuracy camera calibration, this demarcation target is mainly feature object with standard round, using the center of circle of characteristic circle as unique point, main body array way due to characteristic circle is that hexagonal manner is put, so the distance of circle is equal in center circle to each limit of same layer, on each limit, the distance of adjacent two circles is equal and also equal with the distance of circle in center circle to each limit, and this hexagonal structure has two-layer, and final with described double-layer structure for primitive is formed a large hexagonal one-piece construction, so carry out different operative constraints according to the relative position relation of characteristic circle, the precision that adjustable camera inside and outside parameter is demarcated.Therefore, in the camera interior and exterior parameter scaling method of reality, according to different accuracy requirements, can choose and demarcate relative position constraints different between characteristic circle in target, optimize unique point coordinate figure, improve stated accuracy.
Description
Technical field
The present invention applies to the demarcation of video camera in machine vision, refer in particular to a kind of the demarcation target and the scaling method thereof that can be used for different accuracy camera calibration, relate to the multiple characteristic circle with certain position constraint and demarcate targets, can according to the constraint on diverse location between the characteristic circle center of circle and then the object of camera calibration reaching different accuracy.
Technical background
In machine vision metrology field, a lot of work all needs to demarcate the inside and outside parameter of video camera, the inside and outside parameter only obtaining video camera just can better complete actual measurement, and the stated accuracy of camera interior and exterior parameter will directly affect the final measuring accuracy of vision system.
In image measurement process and machine vision applications, for determining two-dimensional geometry position and its mutual relationship in the picture between corresponding point of certain point of space object surface, must set up the geometric model of video camera imaging, these geometric model parameters are exactly camera parameters.These parameters must just can obtain with calculating by experiment in most conditions, and this process solving parameter is just referred to as camera calibration.No matter be in image measurement or machine vision applications, the demarcation of camera parameters is all unusual the key link, and the precision of its calibration result and the stability of algorithm directly affect the accuracy that camera operation bears results.Therefore, carrying out camera calibration is the prerequisite carrying out follow-up work, improves the emphasis place that stated accuracy is research work.The present invention can be retrained by the diverse location of selected characteristic circle and then be obtained different calibration results according to specific needs.
Summary of the invention
The object of the invention is to provide a kind of demarcation target that can be used for different accuracy camera calibration.This demarcation target according to the different needs of stated accuracy and real-time thereof, by choosing relative position constraint certain between different characteristic circle and the scaling method of correspondence, can realize the demarcation of required precision.
The invention provides a kind of camera calibration target, demarcate target and adopt pottery as a setting, described characteristic circle be plated on the strong and ganoid glass of one piece of light transmission, by the face of the described glass with characteristic circle and described ceramic bond, characteristic circle has degree of precision.On described pottery be white comparatively smooth surface after glaze, there is enough roughness, plate one deck inteferometer coating as white background glass outer surface.This structure both can avoid the interference of back side object projection, can reduce again the mirror-reflection of glass surface, thus improved feature point extraction precision.
Demarcating target is mainly feature object with standard round, and the main body array way of characteristic circle is that hexagonal manner is put; Demarcate target surface and have 7 feature primitive, a central feature Primitive Element Distribution is in centre, and other 6 surface primitives lay respectively on a large hexagonal angle; Each feature primitive is made up of totally a center circle, six inner layer features circles and six round 13 characteristic circle of outer layer feature, every six inner layer features circle composition little hexagon, every six outer layer feature circle composition large hexagon; 7 feature primitive are according to the entirety of identical Structure composing (6+1) * (6+6+1)=91 characteristic circle, unique point coordinate is provided by the center of circle of each characteristic circle, between the described characteristic circle center of circle, there is known position relationship, can be used for correction feature point and extract result, to improve stated accuracy.The size relationship of described each characteristic circle is as follows:
Described feature diameter of a circle is 10mm;
In described feature primitive, central circle is 20mm to the spacing of the round heart of inner layer features;
Distance in described feature primitive between central circle to the outer layer feature center of circle is 40mm;
The center of described central feature primitive and the distance at surface primitive center are 100mm.
Inner at arbitrary feature primitive, between each characteristic circle center of circle, at least there is following position relationship:
1) distance between described central circle to the round heart of inner layer features is equal;
2) distance between described central circle to the round heart of inner layer features is equal with the distance between the round heart of each internal layer adjacent feature;
3) center of circle of all inner layer features circles is in circumferentially same, will be on same ellipse after distortion of camera;
4) distance between described central circle to the round heart of outer layer feature is equal with the distance between the round heart of outer adjacent feature;
5) the round heart of all outer layer feature is in circumferentially same, will be on same ellipse after distortion of camera.
Following relation is at least there is between described 1 central feature primitive and 6 outer layer feature primitives:
1) center of described central feature primitive is equal to the distance at each outer layer feature primitive center;
2) center of described central feature primitive is equal with the distance at any two adjacent outer layer feature primitive centers to the distance at each outer layer feature primitive center;
3) described each outer layer feature primitive center is in circumferentially same, will be on same ellipse after distortion of camera.
When there being different accuracy demand, can certain constraint being chosen according to above statement or the relative position relation of not stating and then improve stated accuracy.
Utilize a kind of demarcation target that can be used for different accuracy camera calibration of the present invention to carry out demarcating and detect, comprising the following steps:
1) described demarcation target is placed in the field range of video camera, and gathers demarcation required image;
2) central coordinate of circle of all 91 characteristic circle in every piece image is extracted;
3) correct the central coordinate of circle of described 91 characteristic circle according to the position relationship of characteristic circle, obtain the coordinate figure of unique point;
4) according to the coordinate figure of described unique point, video camera is demarcated, obtain the inside and outside parameter matrix of video camera, and calculate distortion factor, complete the demarcation of video camera.
Technique effect of the present invention
1) the present invention adopt structure both can avoid the interference of back side object projection, the mirror-reflection of glass surface can be reduced again, thus improve feature point extraction precision;
2) position constraint between unique point of the present invention can improve stated accuracy, and can require to select desired location constraint according to different stated accuracies, and algorithm is flexible;
3) the present invention is with the characteristic circle center of circle as unique point, can reduce the impact of pattern distortion.
Accompanying drawing illustrates:
Fig. 1 demarcates the distribution schematic diagram of target characteristic circle
Fig. 2 demarcates the sexangle position relationship schematic diagram of target characteristic circle
Fig. 3 demarcates the structural representation of target feature primitive
Fig. 4 demarcates the circular position relationship schematic diagram of target characteristic circle
Characteristic circle-1, demarcates target edge-2, inner layer features circle-3, outer layer feature circle-4, feature primitive-5
Embodiment:
In order to deepen the understanding of the present invention; below in conjunction with specific embodiments and the drawings; to the present invention propose a kind of can be used for different accuracy camera calibration demarcation target and scaling method be described in further detail; illustrated embodiment only for explaining the present invention, does not form limiting the scope of the present invention.
Embodiment
1-4 by reference to the accompanying drawings, use a kind of demarcation target that can be used for different accuracy camera calibration of the present invention to carry out camera calibration, concrete calibration process is as follows:
1. set up calibration system, video camera is fixed on ad-hoc location, demarcation target of the present invention is placed in camera field of view, regulate video camera and demarcate target, demarcation target is made to occupy the position of about 75 percent of image, and make clear picture, gather multiple images demarcating the different appearance position of target, at least obtain the image of three appearance positions.
2. demarcate the characteristic circle of target and the extraction of unique point thereof shown in Fig. 1-4:
Because shooting image produces distortion, former characteristic circle will become oval, and the feature center of circle will become elliptical center, and utilize least square method to extract eigenellipse and centre coordinate thereof, leaching process is as follows:
1) canny operator extraction image border is utilized;
2) line segment that filtering length is less than certain threshold value and the line segment significantly do not closed;
3) least square method is utilized this line segment to be had a fitted ellipse and obtains eigenellipse and unique point thereof.
3. the position constraint between the unique point coordinate according to Fig. 2-4, optimize gained unique point coordinate:
1) demarcating target is mainly feature object with standard round, and the main body array way of characteristic circle is that hexagonal manner is put; Demarcate target surface and have 7 feature primitive, a central feature Primitive Element Distribution is in centre, and other 6 surface primitives lay respectively on a large hexagonal angle; Each feature primitive is made up of totally a center circle, six inner layer features circles and six round 13 characteristic circle of outer layer feature, every six inner layer features circle composition little hexagon, every six outer layer feature circle composition large hexagon; 7 feature primitive are according to the entirety of identical Structure composing (6+1) * (6+6+1)=91 characteristic circle, unique point coordinate is provided by the center of circle of each characteristic circle, between the described characteristic circle center of circle, there is known position relationship, can be used for correction feature point and extract result, to improve stated accuracy; This demarcation target background adopts whiteware, and as white background, characteristic circle has metallic luster, is plated on surface layer of glass, and surface layer of glass plates one deck inteferometer coating, reduces the mirror-reflection of glass surface, with glass surface and the ceramic bond of characteristic circle.The size relationship of each characteristic circle is as follows:
Described feature diameter of a circle is 10mm;
In described feature primitive, central circle is 20mm to the spacing of the round heart of inner layer features;
Distance in described feature primitive between central circle to the outer layer feature center of circle is 40mm;
The center of described central feature primitive and the distance at surface primitive center are 100mm.
2) inner at arbitrary feature primitive, between each characteristic circle center of circle, at least there is following position relationship:
Distance between described central circle to the round heart of inner layer features is equal;
Distance between described central circle to the round heart of inner layer features is equal with the distance between the round heart of each internal layer adjacent feature;
The center of circle of all inner layer features circles is in circumferentially same, will be on same ellipse after distortion of camera;
Distance between described central circle to the round heart of outer layer feature is equal with the distance between the round heart of outer adjacent feature;
The round heart of all outer layer feature is in circumferentially same, will be on same ellipse after distortion of camera.
3) between described 1 central feature primitive and 6 outer layer feature primitives, at least there is following relation:
The center of described central feature primitive is equal to the distance at each outer layer feature primitive center;
The center of described central feature primitive is equal with distance in the heart in any two adjacent outer layer feature primitives to the distance at each outer layer feature primitive center;
Described each outer layer feature primitive center is in circumferentially same, will be on same ellipse after distortion of camera.
4. set up the position relationship constraint of unique point according to above two kinds of relations, step 2 gained unique point coordinate is optimized, obtains new unique point coordinate.
5. according to step 4 gained unique point coordinate, inside and outside parameter and distortion factor are solved:
1) homography matrix is obtained;
2) inside and outside parameter and distortion factor solve.
Claims (5)
1. can be used for a demarcation target for different accuracy camera calibration, it is characterized in that: demarcating target is mainly feature object with standard round, and the main body array way of characteristic circle is that hexagonal manner is put; Demarcate target surface and have 7 feature primitive, a central feature Primitive Element Distribution is in centre, and other 6 surface primitives lay respectively on a large hexagonal angle; Each feature primitive is made up of totally a center circle, six inner layer features circles and six round 13 characteristic circle of outer layer feature, every six inner layer features circle composition little hexagon, every six outer layer feature circle composition large hexagon; 7 feature primitive are according to the entirety of identical Structure composing (6+1) * (6+6+1)=91 characteristic circle, unique point coordinate is provided by the center of circle of each characteristic circle, between the described characteristic circle center of circle, there is known position relationship, can be used for correction feature point and extract result, to improve stated accuracy; This demarcation target background adopts whiteware, and as white background, characteristic circle has metallic luster, is plated on surface layer of glass, and surface layer of glass plates one deck inteferometer coating, reduces the mirror-reflection of glass surface, with glass surface and the ceramic bond of characteristic circle.
2. a kind of demarcation target that can be used for different accuracy camera calibration according to claim 1, it is characterized in that, the size relationship of each characteristic circle is as follows:
Described feature diameter of a circle is 10mm;
In described feature primitive, central circle is 20mm to the spacing of the round heart of inner layer features;
Distance in described feature primitive between central circle to the outer layer feature center of circle is 40mm;
The center of described central feature primitive and the distance at surface primitive center are 100mm.
3. a kind of demarcation target that can be used for different accuracy camera calibration according to claim 1, is characterized in that, inner at arbitrary feature primitive, at least has following position relationship between each characteristic circle center of circle:
1) distance between described central circle to the round heart of inner layer features is equal;
2) distance between described central circle to the round heart of inner layer features is equal with the distance between the round heart of each internal layer adjacent feature;
3) center of circle of all inner layer features circles is in circumferentially same, will be on same ellipse after distortion of camera;
4) distance between described central circle to the round heart of outer layer feature is equal with the distance between the round heart of outer adjacent feature;
5) the round heart of all outer layer feature is in circumferentially same, will be on same ellipse after distortion of camera.
4. a kind of demarcation target that can be used for different accuracy camera calibration according to claim 1, is characterized in that, between described 1 central feature primitive and 6 outer layer feature primitives, at least there is following relation:
1) center of described central feature primitive is equal to the distance at each outer layer feature primitive center;
2) center of described central feature primitive is equal with distance in the heart in any two adjacent outer layer feature primitives to the distance at each outer layer feature primitive center;
3) described each outer layer feature primitive center is in circumferentially same, will be on same ellipse after distortion of camera.
5. utilize the method for demarcating target as claimed in claim 1 and carrying out demarcating, it is characterized in that, utilize described a kind of demarcation target that can be used for different accuracy camera calibration to carry out the demarcation of video camera, comprise the following steps:
Described demarcation target is placed in the field range of video camera by step 1, and gathers demarcation required image;
Step 2 extracts the central coordinate of circle of all 91 characteristic circle in every piece image;
Step 3 optimizes the central coordinate of circle of described 91 characteristic circle according to the position relationship of characteristic circle;
All central coordinate of circle values after optimization as given value, are demarcated video camera by step 4, obtain the inside and outside parameter matrix of video camera, and calculate distortion factor, complete the demarcation of video camera.
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| CN105627914B (en) * | 2015-12-21 | 2018-08-07 | 中国科学院长春光学精密机械与物理研究所 | A kind of interferometer measuration system image deformation caliberating device |
| CN109099883A (en) * | 2018-06-15 | 2018-12-28 | 哈尔滨工业大学 | The big visual field machine vision metrology of high-precision and caliberating device and method |
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| EP1176557A1 (en) * | 2000-07-24 | 2002-01-30 | Setrix AG | Method and arrangement for camera calibration |
| CN101520897A (en) * | 2009-02-27 | 2009-09-02 | 北京机械工业学院 | Video camera calibration method |
| CN101882309A (en) * | 2009-05-07 | 2010-11-10 | 上海世汇电子科技有限公司 | Calibration pattern of camera and calibration and detection method based on same |
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