CN114087988A - Precision evaluation method of monocular single-line structure optical sensor - Google Patents
Precision evaluation method of monocular single-line structure optical sensor Download PDFInfo
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/002—Measuring arrangements characterised by the use of optical techniques for measuring two or more coordinates
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
Abstract
The invention discloses a precision evaluation method of a monocular single-line structure optical sensor, which is carried out by using a three-dimensional ball target, wherein the three-dimensional ball target is a standard ball with at least three non-collinear ball centers fixed on a bottom plate; the method comprises the following steps: 1) projecting laser at an initial pose, resolving three-dimensional coordinates of each point on a laser bar under a sensor coordinate system, fitting a circle, and solving a circle center coordinate and a radius; the coordinates of the center of a standard sphere under a sensor coordinate system are deduced; 2) constructing a reference coordinate system by using the sphere center of the standard sphere; 3) changing the position and pose for many times, and repeating the step 1) to obtain the three-dimensional coordinates of the center of the standard sphere in each sensor coordinate system; 4) calculating a conversion matrix of each pose and the initial pose, converting the conversion matrix into a reference coordinate system, and splicing the laser stripes in each pose under the reference coordinate system; 5) and fitting the ball, and evaluating the obtained ball diameter, the obtained sphericity and the difference value between the distance between the ball centers and the standard value. The method can reduce the test difficulty; the accuracy of the sensor is comprehensively evaluated in multiple dimensions, so that the evaluation result is more objective.
Description
Technical Field
The invention relates to the field of visual sensor precision detection, in particular to a precision evaluation method of a monocular single-line structure optical sensor.
Background
At present, in a traditional precision evaluation method of a monocular single-line sensor, whether the relative placement positions of the sensor and a step block tend to be perfect or not directly influences the evaluation precision, however, in practice, the position cannot be perfectly placed, and therefore the error always exists in the precision evaluation result of the method.
In view of this problem, in other improved accuracy evaluation methods, since the distance deviation is used as an index for accuracy evaluation, there is a problem that the evaluation dimension is relatively single. In precision measurement, precision evaluation of a sensor in a single dimension often causes the deficiency of precision evaluation of other dimensions. The distance deviation is used as a one-dimensional evaluation index, and the real precision of the three-dimensional shape cannot be completely reflected. For example, in the blue light precision measurement, in addition to the deviation value of the center distance of the sphere, the sphericity (the distance from each point to the sphere is calculated by fitting a sphere and is denoted by d, the number of points is denoted by n, and the sphericity is the root mean square error of the fitted sphere, that is:
) And the deviation value of the ball diameter are used as evaluation criteria, so that the accuracy of the sensor is evaluated more comprehensively.
CN110953988 discloses a method for evaluating accuracy of a line structured light sensor by using a three-dimensional block, which uses a three-dimensional block with holes, requires that centers of the holes are located on the same plane, and requires that a laser plane coincide with a plane where the center of the hole on the three-dimensional block is located when evaluating by using the three-dimensional block; in addition, the evaluation method calculates the three-dimensional coordinates of the hole centers, calculates the center-to-center distance of each hole, compares the center-to-center distance with a reference value to obtain a deviation value, and evaluates the single-line structured light precision according to the deviation value, wherein only one evaluation dimension is considered.
Disclosure of Invention
In order to solve the technical problems, the invention provides a precision evaluation method of a monocular single-line structure optical sensor, which has no strict requirement on the position of a laser surface on a ball, does not introduce errors and can reduce the test difficulty. The accuracy of the single-line structure optical sensor is comprehensively evaluated through the sphericity, the sphere diameter and the sphere center distance, and the evaluation result is more objective.
Therefore, the technical scheme of the invention is as follows:
a precision evaluation method of a monocular single line structure optical sensor is carried out by using a three-dimensional ball target, wherein the three-dimensional ball target is N standard balls fixed on a bottom plate, and the centers of the N standard balls are not collinear; n is more than or equal to 3; laser energy projected by the monocular single-line structure light sensor under different positions can form laser stripes on at least 3 standard balls;
the sphere centers, the sphere diameters and the sphere center distances of all standard spheres on the three-dimensional sphere target are measured by a high-precision instrument and are respectively stored as standard values, and the precision of the monocular single-line structure optical sensor is evaluated according to the following steps:
1) in an initial pose, the monocular single-line structure optical sensor projects laser to the three-dimensional spherical target, laser bars are formed on the plurality of standard spheres, three-dimensional coordinates of each point on the laser bars under a sensor coordinate system are solved, then space circle fitting is carried out, and the center coordinates and the radius of a space circle where the laser bars are located under the sensor coordinate system are solved; combining the sphere diameter of the standard sphere to obtain the distance between the circle center of the circle where the laser bar is located and the sphere center of the standard sphere, and then deducing the three-dimensional coordinates of the sphere center of the standard sphere under the sensor coordinate system;
2) constructing a reference coordinate system by using three-dimensional coordinates of the sphere center of the reference sphere under the sensor coordinate system;
3) changing the poses of the monocular and single-line structured light for multiple times, repeating the step 1) to obtain the sphere center of the standard sphere, and obtaining the three-dimensional coordinates of the sphere centers of different standard spheres under each sensor coordinate system under each pose;
4) calculating rigid body conversion matrixes of each pose and the initial pose by using three-dimensional coordinates of a plurality of standard sphere centers under different poses and each sensor coordinate system, then acquiring conversion relations of all the poses and a reference coordinate system, converting each point on a laser bar obtained under all the poses to the reference coordinate system, and realizing splicing under the reference coordinate system;
5) and 4) performing ball fitting based on the result of the step 4) to obtain a plurality of spherical equations, respectively calculating the spherical diameter, the sphericity and the spherical center distance, and calculating the difference value between the spherical diameter, the sphericity and the spherical center distance and a standard value, wherein if the three difference values are all in a preset range, the precision of the monocular single-line structure optical sensor meets the requirement, otherwise, the precision does not meet the requirement.
Further, the method for constructing the reference coordinate system in the step 2) is a 3-2-1 system construction.
Furthermore, a high-precision instrument for acquiring the sphere center, the sphere diameter and the sphere center distance of the standard sphere is a three-coordinate measuring machine.
Further, the sphericity is a root mean square error of the fitting sphere, and is calculated by using the following formula:
in the formula: d is the distance of the three-dimensional coordinates of each point on the laser bar obtained in the step 4) in the reference coordinate system and the spherical surface fitted in the step 5);
n is the number of points on the laser strip obtained in the step 4).
The method has no strict requirement on the position where the laser is firstly hit on the ball, does not introduce errors, and can reduce the test difficulty. The accuracy of the single-line structure optical sensor is comprehensively evaluated through the sphericity, the sphere diameter and the sphere center distance, and the evaluation result is more objective.
Drawings
FIG. 1 is a front view of a three-dimensional ball target for use with the present invention;
FIG. 2 is a top view of a three-dimensional ball target for use with the present invention;
fig. 3 is a method for deducing the three-dimensional coordinates of the center of a reference sphere in a sensor coordinate system based on the center and radius of a circle on which a laser bar is located.
Detailed Description
The technical solution of the present invention is described in detail below with reference to the accompanying drawings and examples.
A precision evaluation method of a monocular single-line structure optical sensor is carried out by using a three-dimensional ball target, wherein the three-dimensional ball target is N standard balls fixed on a bottom plate, and the centers of the N standard balls are not collinear; n is more than or equal to 3; as shown in fig. 1, in one embodiment of the present invention, N-3; laser energy projected by the monocular single-line structure light sensor under different bit positions can form laser stripes on at least 3 standard balls;
the sphere centers, the sphere diameters and the sphere center distances of all standard spheres on the three-dimensional sphere target are measured by a high-precision instrument (a three-coordinate measuring machine) and are respectively stored as standard values, and the precision of the monocular single-line structure optical sensor is evaluated according to the following steps:
1) in an initial pose, a monocular single-line structure optical sensor projects laser to a three-dimensional spherical target, laser bars are formed on a plurality of standard spheres, three-dimensional coordinates of each point on the laser bars under a sensor coordinate system are solved, then space circle fitting is carried out, and the center coordinates and the radius of a space circle where the laser bars are located under the sensor coordinate system are solved; combining the sphere diameter of the standard sphere to obtain the distance between the circle center of the circle where the laser bar is located and the sphere center of the standard sphere, and then deducing the three-dimensional coordinates of the sphere center of the standard sphere under the sensor coordinate system;
2) constructing a reference coordinate system by three-dimensional coordinates of the centers of three standard spheres in a sensor coordinate system based on a 3-2-1 method;
3) changing the poses of monocular single-line structured light for multiple times, repeating the step 1) to obtain the sphere center of the standard sphere, and obtaining the three-dimensional coordinates of different sphere centers of the standard sphere under each sensor coordinate system at each pose;
4) calculating rigid body conversion matrixes of each pose and the initial pose by using three-dimensional coordinates of a plurality of standard sphere centers under different poses and each sensor coordinate system, then acquiring conversion relations of all the poses and a reference coordinate system, converting each point on a laser bar obtained under all the poses to the reference coordinate system, and realizing splicing under the reference coordinate system;
5) and 4) performing ball fitting based on the result of the step 4) to obtain a plurality of spherical equations, respectively calculating the spherical diameter, the sphericity and the spherical center distance, and calculating the difference value between the spherical diameter, the sphericity and the spherical center distance and a standard value, wherein if the three difference values are all in a preset range, the precision of the monocular single-line structure optical sensor meets the requirement, otherwise, the precision does not meet the requirement.
Wherein, the sphericity is the root mean square error of the fitting sphere and is calculated by using the following formula:
in the formula: d is the distance between the three-dimensional coordinates of each point on the laser bar obtained in the step 4) in the reference coordinate system and the spherical surface fitted in the step 5);
n is the number of points on the laser strip obtained in the step 4).
The method has no strict requirement on the position where the laser is firstly hit on the ball, does not introduce errors, and can reduce the test difficulty. The accuracy of the single-line structure optical sensor is comprehensively evaluated through the sphericity, the sphere diameter and the sphere center distance, and the evaluation result is more objective.
The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. The foregoing description is not intended to be exhaustive or to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and its practical application to enable others skilled in the art to make and use various exemplary embodiments of the invention and various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the following claims and their equivalents.
Claims (4)
1. A precision evaluation method of a monocular single line structure optical sensor is characterized in that: the method comprises the following steps of (1) using a three-dimensional ball target, wherein the three-dimensional ball target is N standard balls fixed on a bottom plate, and the centers of the N standard balls are not collinear; n is more than or equal to 3; laser energy projected by the monocular single-line structure light sensor under different positions can form laser stripes on at least 3 standard balls;
the sphere centers, the sphere diameters and the sphere center distances of all standard spheres on the three-dimensional sphere target are measured by a high-precision instrument and are respectively stored as standard values, and the precision of the monocular single-line structure optical sensor is evaluated according to the following steps:
1) in an initial pose, the monocular single-line structure optical sensor projects laser to the three-dimensional spherical target, laser bars are formed on the plurality of standard spheres, three-dimensional coordinates of each point on the laser bars under a sensor coordinate system are solved, then space circle fitting is carried out, and the center coordinates and the radius of a space circle where the laser bars are located under the sensor coordinate system are solved; combining the sphere diameter of the standard sphere to obtain the distance between the circle center of the circle where the laser bar is located and the sphere center of the standard sphere, and then deducing the three-dimensional coordinates of the sphere center of the standard sphere under the sensor coordinate system;
2) constructing a reference coordinate system by using three-dimensional coordinates of the sphere center of the reference sphere under the sensor coordinate system;
3) changing the poses of monocular single-line structured light for multiple times, repeating the step 1) to obtain the sphere center of the standard sphere, and obtaining the three-dimensional coordinates of different sphere centers of the standard sphere under each sensor coordinate system at each pose;
4) calculating rigid body conversion matrixes of each pose and the initial pose by using three-dimensional coordinates of a plurality of standard sphere centers under different poses and each sensor coordinate system, then acquiring conversion relations of all the poses and a reference coordinate system, converting each point on a laser bar obtained under all the poses to the reference coordinate system, and realizing splicing under the reference coordinate system;
5) and 4) performing ball fitting based on the result of the step 4) to obtain a plurality of spherical equations, respectively calculating the spherical diameter, the sphericity and the spherical center distance, and calculating the difference value between the spherical diameter, the sphericity and the spherical center distance and a standard value, wherein if the three difference values are all in a preset range, the precision of the monocular single-line structure optical sensor meets the requirement, otherwise, the precision does not meet the requirement.
2. The accuracy evaluation method of the monocular single-line structured light sensor according to claim 1, characterized in that: and 2) constructing a system for 3-2-1 by using a method for constructing a reference coordinate system.
3. The accuracy evaluation method of the monocular single-line structured light sensor according to claim 1, characterized in that: the high-precision instrument for obtaining the sphere center, the sphere diameter and the sphere center distance of the standard sphere is a three-coordinate measuring machine.
4. The accuracy evaluation method of the monocular single-line structured light sensor according to claim 1, characterized in that: the sphericity is the root mean square error of the fitting sphere and is calculated by using the following formula:
in the formula: d is the distance of the three-dimensional coordinates of each point on the laser bar obtained in the step 4) in the reference coordinate system and the spherical surface fitted in the step 5);
n is the number of points on the laser strip obtained in the step 4).
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Citations (3)
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| KR20130050691A (en) * | 2011-11-08 | 2013-05-16 | 한국건설기술연구원 | Method for automatic registration of 3-dimensional scan data for intelligent excavation system |
| CN110017770A (en) * | 2019-04-18 | 2019-07-16 | 天津工业大学 | A kind of vision-based detection scaling method applied to three coordinate measuring machine |
| CN111256592A (en) * | 2020-03-13 | 2020-06-09 | 易思维（杭州）科技有限公司 | External parameter calibration device and method for structured light sensor |
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|---|---|---|---|---|
| KR20130050691A (en) * | 2011-11-08 | 2013-05-16 | 한국건설기술연구원 | Method for automatic registration of 3-dimensional scan data for intelligent excavation system |
| CN110017770A (en) * | 2019-04-18 | 2019-07-16 | 天津工业大学 | A kind of vision-based detection scaling method applied to three coordinate measuring machine |
| CN111256592A (en) * | 2020-03-13 | 2020-06-09 | 易思维（杭州）科技有限公司 | External parameter calibration device and method for structured light sensor |
Non-Patent Citations (1)
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| 解则晓, 张成国, 张国雄: "线结构光测头外参数的精确标定方法", 机械工程学报, no. 08 * |
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Address after: Room 495, building 3, 1197 Bin'an Road, Binjiang District, Hangzhou City, Zhejiang Province 310051 Patentee after: Yi Si Si (Hangzhou) Technology Co.,Ltd. Address before: Room 495, building 3, 1197 Bin'an Road, Binjiang District, Hangzhou City, Zhejiang Province 310051 Patentee before: ISVISION (HANGZHOU) TECHNOLOGY Co.,Ltd. |