CN103136756A - Demarcated target for demarcating cameras with different accurate degrees and demarcating method thereof - Google Patents
Demarcated target for demarcating cameras with different accurate degrees and demarcating method thereof Download PDFInfo
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- CN103136756A CN103136756A CN2013100664046A CN201310066404A CN103136756A CN 103136756 A CN103136756 A CN 103136756A CN 2013100664046 A CN2013100664046 A CN 2013100664046A CN 201310066404 A CN201310066404 A CN 201310066404A CN 103136756 A CN103136756 A CN 103136756A
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Abstract
The invention discloses a demarcated target for demarcating cameras with different accurate degrees and a demarcating method thereof. The demarcated target mainly serves a standard circle as a characteristic target, and a centre of a characteristic circle serves as a characteristic point. Due to the fact that a main body array manner of the characteristic circle is arranged in a hexagon manner, distances of a center circle to circles at each edge at the same layer are equal. The distance of two adjacent circles at each edge is equal and equal to the distance of the center circle to the circles at each edge. The hexagon structure is provided with two layers, and a big hexagon-shaped whole structure is formed by an element which is the two-layer structure finally. Then different operative constraints are carried out according to relative location relationships of the characteristic circle, and demarcated accurate degrees of inner parameters and outer parameters of the cameras can be adjusted. Thus in the practical the demarcating method of the inner parameters and the outer parameters of the cameras, different relative location constraints among characteristic circles in the demarcated target can be selected according to different accurate degrees, and a coordinate value of the characteristic point can be optimized, and demarcated accurate degrees can be improved.
Description
Technical field
The present invention applies to the demarcation of video camera in machine vision, refer in particular to a kind of demarcation target and scaling method thereof that can be used for the different accuracy camera calibration, relate to a plurality of characteristic circle with certain position constraint and demarcate targets, can and then reach the purpose of the camera calibration of different accuracy according to the constraint on diverse location between the characteristic circle center of circle.
Technical background
A lot of work all need the inside and outside parameter of video camera is demarcated in the machine vision metrology field, only obtained the inside and outside parameter of video camera and 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 between corresponding point in image of surperficial certain point of space object, 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 under most of conditions, and this process of finding the solution parameter just is 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 stability of the precision of its calibration result and algorithm directly affects the accuracy that video camera work bears results.Therefore, carrying out camera calibration is the prerequisite of carrying out follow-up work, and improving stated accuracy is the emphasis place of research work.The diverse location that the present invention can justify by selected characteristic according to specific needs retrains and then obtains different calibration results.
Summary of the invention
The object of the invention is to provide a kind of demarcation target and a kind of scaling method that can be used for the different accuracy scaling method.This demarcates target can according to the different needs of stated accuracy and real-time thereof, by choosing relative position constraint certain between different characteristic circle and corresponding scaling method, 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 is plated on a light transmission by force and ganoid on glass, face and the described pottery of described glass with characteristic circle is bonding, and characteristic circle has degree of precision.On described pottery after glaze be white than smooth surface, have enough roughness, as white background glass outer surface plating one deck inteferometer coating.This structure both can have been avoided the interference of back side object projection, can reduce again the mirror-reflection of glass surface, thereby improved the feature point extraction precision.
Demarcate target mainly take standard round as feature object, the main body array way of characteristic circle is that the hexagon mode is put; There are 7 feature primitives on demarcation target surface, and a central feature Primitive Element Distribution is in the centre, and other 6 surface primitives lay respectively on a large hexagonal angle; Each feature primitive is comprised of a center circle, six internal layer characteristic circle and six round 13 characteristic circle of outer layer feature totally, and every six internal layer characteristic circle form a little hexagon, and every six outer layer feature circle forms a large hexagon; 7 feature primitives consist of the integral body of (6+1) * (6+6+1)=91 characteristic circle according to identical structure, the unique point coordinate is provided by the center of circle of each characteristic circle, described characteristic circle has known position relationship between the center of circle, 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, the center circle center of circle is 20mm to distance between the internal layer characteristic circle center of circle;
In described feature primitive, the center circle center of circle is 40mm to the distance between the outer layer feature center of circle;
The distance at the center of described central feature primitive and surface primitive center is 100mm.
Described arbitrary feature primitive is inner, has at least following position relationship between each characteristic circle center of circle:
1) the described center circle center of circle equates to the distance between the internal layer characteristic circle center of circle;
2) the described center circle center of circle equates with distance between the round heart of each internal layer adjacent feature to the distance between the internal layer characteristic circle center of circle;
3) center of circle of all internal layer characteristic circle is on same circumference, will be in after distortion of camera on same ellipse;
4) the described center circle center of circle equates with distance between the round heart of described outer adjacent feature to the distance between the round heart of outer layer feature;
5) the round heart of described all outer layer feature is on same circumference, will be on same ellipse after distortion of camera.
At least there is following relation between described 1 central feature primitive and 6 outer layer feature primitives:
1) center of described central feature primitive equates to the distance at each outer layer feature primitive center;
2) center of described central feature primitive equates to the distance at each outer layer feature primitive center distance with any two adjacent outer layer feature primitive centers;
3) described each outer layer feature primitive center is on same circumference, will be on same ellipse after distortion of camera.
When the different accuracy demand is arranged, can choose certain constraint and then improve stated accuracy according to the relative position relation of above statement or not statement.
The invention provides a kind of scaling method, it is characterized in that, described demarcation target with 91 characteristic circle is demarcated and is detected, and comprises the following steps:
1) will demarcate target and be placed in required calibration system visual field, and gather and demarcate required image;
2) extract characteristic circle and obtain central coordinate of circle;
3) optimize the unique point coordinate figure according to the position relationship of characteristic circle;
4) calibration system is demarcated and is calculated distortion factor;
5) by the described distortion factor that obtains, the described image that collects is carried out distortion correction.
Technique effect of the present invention
1) structure that the present invention adopts both can have been avoided the interference of back side object projection, can reduce again the mirror-reflection of glass surface, thereby improved the feature point extraction precision;
2) position constraint between unique point of the present invention can improve stated accuracy, and can require to select the desired location constraint according to different stated accuracies, and algorithm is flexible;
3) the present invention's use characteristic circle center of circle as unique point, can reduce the impact of pattern distortion.
Description of drawings:
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
Target edge-2, internal layer characteristic circle-3, outer layer feature circle-4, feature primitive-5 are demarcated in characteristic circle-1
Embodiment:
In order to deepen the understanding of the present invention; below in conjunction with specific embodiments and the drawings; a kind of demarcation target and scaling method thereof that can be used for the different accuracy camera calibration that the present invention is proposed is described in further detail; illustrated embodiment only is used for explaining the present invention, does not consist of the restriction to protection domain of the present invention.
Embodiment
1-4, use a kind of demarcation target and scaling method thereof that can be used for the different accuracy camera calibration of the present invention by reference to the accompanying drawings, and concrete calibration process is as follows:
1. set up calibration system, video camera is fixed in ad-hoc location, demarcation target of the present invention is placed in camera field of view, regulate video camera and demarcate target, make and demarcate the position that target occupies 75 percent left and right of image, and make clear picture, gather to demarcate many images of the different appearances of target position, obtain at least 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 photographic images produces distortion, former characteristic circle will become ellipse, and the feature center of circle will become elliptical center, utilize least square method to extract eigenellipse and centre coordinate thereof, and leaching process is as follows:
1) utilize canny operator extraction image border;
2) filtering length is less than the line segment of certain threshold value and the line segment that does not significantly seal;
3) utilize least square method with a fitted ellipse that this line segment has and obtain eigenellipse and unique point.
3. according to the position constraint between the unique point coordinate shown in Fig. 2-4, optimize gained unique point coordinate:
1) demarcate target mainly take standard round as feature object, the main body array way of characteristic circle is that the hexagon mode is put; There are 7 feature primitives on demarcation target surface, and a central feature Primitive Element Distribution is in the centre, and other 6 surface primitives lay respectively on a large hexagonal angle; Each feature primitive is comprised of a center circle, six internal layer characteristic circle and six round 13 characteristic circle of outer layer feature totally, and every six internal layer characteristic circle form a little hexagon, and every six outer layer feature circle forms a large hexagon; 7 feature primitives consist of the integral body of (6+1) * (6+6+1)=91 characteristic circle according to identical structure, the unique point coordinate is provided by the center of circle of each characteristic circle, described characteristic circle has known position relationship between the center of circle, can be used for correction feature point and extract result, to improve stated accuracy; This is demarcated the target background and adopts whiteware, and as white background, characteristic circle has metallic luster, is plated on surface layer of glass, surface layer of glass plating one deck inteferometer coating, and the mirror-reflection of minimizing glass surface, bonding with pottery with the glass surface 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, the center circle center of circle is 20mm to distance between the internal layer characteristic circle center of circle;
In described feature primitive, the center circle center of circle is 40mm to the distance between the outer layer feature center of circle;
The distance at the center of described central feature primitive and surface primitive center is 100mm.
2) inner at described arbitrary feature primitive, have at least following position relationship between each characteristic circle center of circle:
The described center circle center of circle equates to the distance between the internal layer characteristic circle center of circle;
The described center circle center of circle equates with distance between the round heart of each internal layer adjacent feature to the distance between the internal layer characteristic circle center of circle;
The center of circle of all internal layer characteristic circle is on same circumference, will be in after distortion of camera on same ellipse;
The distance of the described center circle center of circle between the round heart of outer layer feature equates with distance between the round heart of described outer adjacent feature;
The round heart of described all outer layer feature is on same circumference, will be on same ellipse after distortion of camera.
3) there is at least following relation between described 1 central feature primitive and 6 outer layer feature primitives:
The center of described central feature primitive equates to the distance at each outer layer feature primitive center;
The center of described central feature primitive in the heart distance in the distance at each outer layer feature primitive center and any two adjacent outer layer feature primitives equates;
Described each outer layer feature primitive center is on same circumference, 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, obtain the New Characteristics point coordinate.
5. according to step 4 gained unique point coordinate, inside and outside parameter and distortion factor are found the solution:
1) obtain homography matrix;
2) inside and outside parameter and distortion factor are found the solution.
Claims (5)
1. demarcation target and scaling method thereof that can be used for the different accuracy camera calibration is characterized in that: demarcate target mainly take standard round as feature object, the main body array way of characteristic circle is that the hexagon mode is put; There are 7 feature primitives on demarcation target surface, and a central feature Primitive Element Distribution is in the centre, and other 6 surface primitives lay respectively on a large hexagonal angle; Each feature primitive is comprised of a center circle, six internal layer characteristic circle and six round 13 characteristic circle of outer layer feature totally, and every six internal layer characteristic circle form a little hexagon, and every six outer layer feature circle forms a large hexagon; 7 feature primitives consist of the integral body of (6+1) * (6+6+1)=91 characteristic circle according to identical structure, the unique point coordinate is provided by the center of circle of each characteristic circle, described characteristic circle has known position relationship between the center of circle, can be used for correction feature point and extract result, to improve stated accuracy; This is demarcated the target background and adopts whiteware, and as white background, characteristic circle has metallic luster, is plated on surface layer of glass, surface layer of glass plating one deck inteferometer coating, and the mirror-reflection of minimizing glass surface, bonding with pottery with the glass surface of characteristic circle.
2. a kind of demarcation target and scaling method thereof that can be used for the different accuracy camera calibration according to claim 1, 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, the center circle center of circle is 20mm to distance between the internal layer characteristic circle center of circle;
In described feature primitive, the center circle center of circle is 40mm to the distance between the outer layer feature center of circle;
The distance at the center of described central feature primitive and surface primitive center is 100mm.
3. a kind of demarcation target and scaling method thereof that can be used for the different accuracy camera calibration according to claim 1, is characterized in that, and be inner at described arbitrary feature primitive, has at least following position relationship between each characteristic circle center of circle:
1) the described center circle center of circle equates to the distance between the internal layer characteristic circle center of circle;
2) the described center circle center of circle equates with distance between the round heart of each internal layer adjacent feature to the distance between the internal layer characteristic circle center of circle;
3) center of circle of all internal layer characteristic circle is on same circumference, will be in after distortion of camera on same ellipse;
4) the described center circle center of circle equates with distance between the round heart of described outer adjacent feature to the distance between the round heart of outer layer feature;
5) the round heart of described all outer layer feature is on same circumference, will be on same ellipse after distortion of camera.
4. a kind of demarcation target and scaling method thereof that can be used for the different accuracy camera calibration according to claim 1, is characterized in that, has at least following relation between described 1 central feature primitive and 6 outer layer feature primitives:
1) center of described central feature primitive equates to the distance at each outer layer feature primitive center;
2) center of described central feature primitive in the heart distance in the distance at each outer layer feature primitive center and any two adjacent outer layer feature primitives equates;
3) described each outer layer feature primitive center is on same circumference, will be on same ellipse after distortion of camera.
5. demarcation target and a scaling method thereof that can be used for the different accuracy camera calibration, is characterized in that, described demarcation target with 91 characteristic circle carries out the demarcation of video camera, and the method comprises the following steps:
Step 1 will be demarcated target and will be placed in required calibration system visual field, and gather and demarcate required image;
Step 2 is extracted characteristic circle and is obtained central coordinate of circle;
Step 3 is optimized the unique point coordinate figure according to the position relationship of characteristic circle;
Step 4 pair video camera is demarcated, and obtains the inside and outside parameter matrix of video camera, and calculates distortion factor;
Step 5 is carried out distortion correction by the described distortion factor that obtains to the described image that collects.
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| CN106247972A (en) * | 2015-12-21 | 2016-12-21 | 中国科学院长春光学精密机械与物理研究所 | The calibration system of image deformation and scaling method in a kind of interferometry |
| 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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Cited By (5)
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|---|---|---|---|---|
| CN105627914A (en) * | 2015-12-21 | 2016-06-01 | 中国科学院长春光学精密机械与物理研究所 | Interferometric measurement system imaging distortion calibration device |
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| 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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