CN111289226A - Line laser flatness detection method based on visual measurement technology - Google Patents
Line laser flatness detection method based on visual measurement technology Download PDFInfo
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- CN111289226A CN111289226A CN202010256684.7A CN202010256684A CN111289226A CN 111289226 A CN111289226 A CN 111289226A CN 202010256684 A CN202010256684 A CN 202010256684A CN 111289226 A CN111289226 A CN 111289226A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
- G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
- G01M11/02—Testing optical properties
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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
- G01B11/30—Measuring arrangements characterised by the use of optical techniques for measuring roughness or irregularity of surfaces
Abstract
The invention discloses a line laser flatness detection method based on a vision measurement technology.A plane I is fixedly arranged in front of a line laser to be detected; at least 5 circular targets are arranged on the plane I, and the circular targets are arranged along a straight line approximately and are not overlapped with each other; projecting a laser strip to a plane I by a line laser to be detected, wherein the laser strip can penetrate through all circular targets; collecting images of the laser stripes projected on the circular targets by using a camera, acquiring the central lines of the laser stripes and the centers of the circular targets, and calculating the distance d between the centers of the circular targets and the central lines of the laser stripesiCalculating Point coordinates (x ') of the centerline of the light bar'i，y′i): point coordinates (x ') of all the determined light bar center lines'i，y′i) Performing linear fitting to obtain a maximum fitting residual value serving as an evaluation parameter Q; the method can effectively evaluate and judge the performance of the line laserWhether it meets the measurement requirements.
Description
Technical Field
The invention relates to the field of laser vision measurement, in particular to a line laser flatness detection method based on a vision measurement technology.
Background
The line structured light measurement technology projects line structured light to the surface of a measured object, a camera shoots a laser stripe image, and then a light stripe center extraction algorithm and a camera calibration model jointly calculate three-dimensional coordinate information of the surface of the measured object; with the rapid development of photoelectric sensing technology, computer technology and optical semiconductor technology in recent years, linear structured light measurement is widely applied to the fields of industrial detection, target recognition and reverse engineering due to the characteristics of non-contact efficient real-time measurement.
The line laser is the device that throws line structured light, and under the ideal condition, the laser plane that the line laser throwed is the standard plane of ideal, but because machining error, the assembly error of laser mirror group and semiconductor device's characteristic, the laser plane is not ideal plane, is the curved surface form, handles as the plane with the laser plane in traditional measurement process, can cause the influence to final measurement accuracy, and the measurement visual field is big more, and the influence is big more, and from this can know, the flatness detection to the line laser is the indispensable link of assurance line structured light measurement accuracy.
Disclosure of Invention
Aiming at the problems, the invention provides a line laser flatness detection method based on a visual measurement technology, which can effectively evaluate the performance of a line laser and judge whether the line laser meets the measurement requirements or not.
A line laser flatness detection method based on vision measurement technology, fixedly arranging a plane I in front of a line laser to be detected;
at least 5 circular targets are arranged on the plane I, and the circular targets are arranged along a straight line approximately and are not overlapped with each other;
projecting a laser strip to a plane I by a line laser to be detected, wherein the laser strip can penetrate through all circular targets;
collecting images of the laser stripes projected on the circular targets by using a camera, acquiring the central lines of the laser stripes and the centers of the circular targets, and calculating the distance d between the centers of the circular targets and the central lines of the laser stripesi；
Calculating the point coordinates of the centerline of the light bar (x′i，y′i)：
x′i＝xi+di×cosθ
y′i＝yi+di×sinθ
θ＝arctan(k)
i is 1,2,3 … … m; m is the number of the circular targets; (x)i，yi) Representing the theoretical centre coordinates of each circular target, k represents the coordinates (x) by means ofi，yi) Fitting to obtain the slope of the straight line;
point coordinates (x ') of all the determined light bar center lines'i，y′i) Performing linear fitting to obtain a maximum fitting residual value serving as an evaluation parameter Q; and when the evaluation parameter Q is within the range of the preset value, the line laser to be measured is considered to meet the requirements, otherwise, the line laser to be measured does not meet the requirements.
Further, the theoretical center coordinates (x)i，yi) Obtained by the following method: respectively obtaining the circle center coordinates (x) of each circular target by using a close-range photogrammetric systemi，yi,zi) (ii) a Two-dimensional coordinates (x) thereini，yi) And recording as a theoretical circle center coordinate.
Further, noting that the distance between the two circular targets that are farthest apart is s, s satisfies the following relationship:
L≥s≥2/3L
wherein, L is 2 xdw×tanβ，
Theta' is the fan angle of the line laser, dwIs the distance between plane I and the line laser.
Further, dwD is the working distance of the line laser, preferably Dw＝D。
Preferably, the distance between the centers of two adjacent circular targets is 5(R1+ R2) < H < 15(R1+ R2), wherein R1 and R2 are the radii of the two circular targets respectively
For the convenience of calculation, the sizes of the circular targets are consistent, and the centers of the circles are approximately on the same straight line.
Further, the working distance D of the line laser is 3 to 10m, and the radius of each circular target is 5 to 15 cm.
Preferably, in order to obtain more accurate calculation results, the flatness of the plane I is less than 3mm, and the circular target is a concentric target.
Further, a close-range photogrammetry system is used for repeatedly measuring a single target for multiple times to obtain the coordinate (x) of the center of the target circleij，yij，zij) Wherein i is 1,2,3, … … m, j is 1,2,3, … … n; n is the number of repeated measurements; then the center of a circle coordinate (x)i，yi,zi) Obtaining by taking the mean:
further, in order to enable the laser bar to cover all the circular targets, the circular targets are adjusted as follows:
before the circular targets are not placed, the line laser to be detected projects laser stripes to the plane I, and each circular target is roughly positioned according to the positions of the laser stripes; putting the circular targets, projecting the laser bar to the plane I again by the line laser to be detected, observing whether the laser bar covers all the circular targets or not by a camera or human eyes, and if not, adjusting the positions of the corresponding circular targets until the laser bar can cover all the circular targets; the position of each circular target is fixed.
According to the method, the coordinate point on the center of the line laser light stripe is accurately obtained in a mode of combining the circular target with the photogrammetry system, the line data of the laser stripe is represented by the coordinate point, the fitting residual is obtained, the planeness of the laser ray of the line laser is evaluated by the maximum residual value, the performance of the line laser is effectively evaluated, and whether the measurement requirement is met or not is judged.
Drawings
FIG. 1 is a schematic diagram showing the relationship between the position of a line laser, a camera, a photogrammetric system and a plane I in the embodiment;
FIG. 2 is a schematic diagram of the projection range of a line laser in an embodiment;
FIG. 3 is a schematic diagram showing the positional relationship between the light plane and each circular target in the embodiment;
FIG. 4 is a schematic diagram showing the positional relationship between the light plane and each circular target in another embodiment;
fig. 5 is an image of a laser bar passing through a circular target in an image acquired by a single camera in an embodiment.
Detailed Description
A method for detecting flatness of a line laser based on a vision measurement technology is disclosed, as shown in figure 1, a plane I is fixedly arranged in front of a line laser 1 to be detected;
at least 5 circular targets are arranged on the plane I, and the circular targets 5 are arranged along a substantially straight line (as shown in FIG. 3 or FIG. 4) and do not overlap with each other;
projecting a laser strip 2 to the plane I by the line laser to be detected, wherein the laser strip can penetrate through all circular targets;
the camera 3 is used for collecting the image (as shown in fig. 5) of the laser stripe projected on each circular target, obtaining the central line of the laser stripe and the circle center of the circular target, and calculating the distance d between the circle center of each circular target and the central line of the laser stripei；
Calculating Point coordinates (x ') of centerline of light bar'i，y′i)：
x′i＝xi+di×cosθ
y′i＝yi+di×sinθ
θ＝arctan(k)
i is 1,2,3 … … m; m is the number of the circular targets; (x)i，yi) Representing the theoretical centre coordinates of each circular target, k represents the coordinates (x) by means ofi，yi) The fitting is carried out by the user,the slope of the resulting line;
point coordinates (x ') of all the determined light bar center lines'i，y′i) Performing linear fitting to obtain a maximum fitting residual value serving as an evaluation parameter Q; and when the evaluation parameter Q is within the range of the preset value, the line laser to be measured is considered to meet the requirements, otherwise, the line laser to be measured does not meet the requirements.
Wherein, the theoretical center coordinates (x)i，yi) Obtained by the following method: the circle center coordinates (x) of each circular target are respectively obtained by using the close-range photogrammetric system 4i，yi,zi) (ii) a Two-dimensional coordinates (x) thereini，yi) And recording as a theoretical circle center coordinate.
Specifically, as shown in fig. 2, if the distance between two circular targets that are farthest apart is s, s satisfies the following relationship:
L≥s≥2/3L
wherein, L is 2 xdw×tanβ，
Theta' is the fan angle of the line laser, dwIs the distance between plane I and the line laser.
dwD is the working distance of the line laser, preferably Dw＝D。
In this embodiment, the working distance D of the line laser is 3m to 10m, and since the working distance is relatively long, the size of the laser bar image is large, a camera is required to shoot images of each circular target and the light bar at different positions, a single image includes images of 1 to 3 circular targets through which the laser bar passes (as shown in fig. 5), and the radius of each circular target is 5cm to 15 cm. Respectively calculating the distance d between the circle center of each circular target and the central line of the light stripi；
In order to facilitate photographing and improve the accuracy of subsequent calculation, the distance and the number of the circular targets should be properly arranged, the distance between the centers of two adjacent circular targets is 5(R1+ R2) < H < 15(R1+ R2), wherein R1 and R2 are the radiuses of the two circular targets respectively;
as a preferred embodiment: the sizes of all the circular targets are consistent, and the centers of all the circular targets are approximately on the same straight line (as shown in FIG. 3); the planeness of the plane I is less than 3mm, the circular target is a concentric circular target, and the plane I can be a wall surface with high planeness or a plane of a finish-machined glass plate.
When calculating the coordinates of the theoretical circle center, repeatedly measuring the single target for multiple times by using the close-range photogrammetry system 4 to obtain the coordinates (x) of the circle center of the targetij，yij，zij) Wherein i is 1,2,3, … … m, j is 1,2,3, … … n; n is the number of repeated measurements;
then the center of a circle coordinate (x)i，yi,xi) Obtaining by taking the mean:
in order to enable the laser bar to cover all circular targets, before the measurement is formally started, the following preparation is carried out: adjusting the circular target:
before the circular targets are not placed, the line laser to be detected projects laser stripes to the plane I, and each circular target is roughly positioned according to the positions of the laser stripes; putting the circular targets, projecting the laser bar to the plane I again by the line laser to be detected, observing whether the laser bar covers all the circular targets or not by a camera or human eyes, and if not, adjusting the positions of the corresponding circular targets until the laser bar can cover all the circular targets; the position of each circular target is fixed.
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 (10)
1. A line laser flatness detection method based on vision measurement technology is characterized in that a plane I is fixedly arranged in front of a line laser to be detected;
at least 5 circular targets are arranged on the plane I, and the circular targets are arranged along a straight line approximately and are not overlapped with each other;
projecting a laser strip to a plane I by a line laser to be detected, wherein the laser strip can penetrate through all circular targets;
collecting images of the laser stripes projected on the circular targets by using a camera, acquiring the central lines of the laser stripes and the centers of the circular targets, and calculating the distance d between the centers of the circular targets and the central lines of the laser stripesi；
Calculating Point coordinates (x ') of centerline of light bar'i，y′i)：
x′i＝xi+di×cosθ
y′i＝yi+di×sinθ
θ＝arctan(k)
1,2, 3.. m; m is the number of the circular targets; (x)i，yi) Representing the theoretical centre coordinates of each circular target, k represents the coordinates (x) by means ofi，yi) Fitting to obtain the slope of the straight line;
point coordinates (x ') of all the determined light bar center lines'i，y′i) Performing linear fitting to obtain a maximum fitting residual value serving as an evaluation parameter Q; and when the evaluation parameter Q is within the range of the preset value, the line laser to be measured is considered to meet the requirements, otherwise, the line laser to be measured does not meet the requirements.
2. The line laser flatness detection method based on vision measurement technique as claimed in claim 1, wherein: the theoretical center coordinates (x)i，yi) Obtained by the following method: respectively obtaining the circle center coordinates (x) of each circular target by using a close-range photogrammetric systemi，yi，zi) (ii) a Two-dimensional coordinates (x) thereini，yi) And recording as a theoretical circle center coordinate.
3. The line laser flatness detection method based on vision measurement technique as claimed in claim 1, wherein: noting the distance between the two circular targets that are farthest apart as s, s satisfies the following relationship:
L≥s≥2/3L
wherein, L is 2 xdw×tanβ，
Theta' is the fan angle of the line laser, dwIs the distance between plane I and the line laser.
4. The line laser flatness detection method based on vision measurement technique as claimed in claim 3, wherein: dwD is the working distance of the line laser, preferably Dw＝D。
5. The line laser flatness detection method based on vision measurement technique as claimed in claim 1, wherein: the distance between the centers of two adjacent circular targets is 5(R1+ R2) < H < 15(R1+ R2), wherein R1 and R2 are the radiuses of the two circular targets respectively.
6. The line laser flatness detection method based on vision measurement technique as claimed in claim 1, wherein: the sizes of the circular targets are consistent, and the centers of the circles are approximately on the same straight line.
7. The line laser flatness detection method based on vision measurement technique as claimed in claim 6, wherein: the working distance D of the line laser is 3-10 m, and the radius of each circular target is 5-15 cm.
8. The line laser flatness detection method based on vision measurement technique as claimed in claim 1, wherein: the planeness of the plane I is less than 3mm, and the circular target is a concentric target.
9. The line laser flatness detection method based on vision measurement technique as claimed in claim 2, wherein: repeatedly measuring a single target for multiple times by using a close-range photogrammetry system to obtain the coordinate (x) of the center of the target circleij，yij，zij) Wherein i 1,2,3,.. to m, j 1,2,3,. to n; n is the number of repeated measurements;
then the center of a circle coordinate (x)i，yi，zi) Obtaining by taking the mean:
10. the line laser flatness detection method based on vision measurement technique as claimed in claim 1, wherein: in order to enable the laser bar to cover all circular targets, the circular targets are adjusted as follows:
before the circular targets are not placed, the line laser to be detected projects laser stripes to the plane I, and each circular target is roughly positioned according to the positions of the laser stripes; putting the circular targets, projecting the laser bar to the plane I again by the line laser to be detected, observing whether the laser bar covers all the circular targets or not by a camera or human eyes, and if not, adjusting the positions of the corresponding circular targets until the laser bar can cover all the circular targets; the position of each circular target is fixed.
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| CN112611340A (en) * | 2020-11-19 | 2021-04-06 | 易思维（杭州）科技有限公司 | Method for adjusting laser light plane in vision sensor |
| CN113701639A (en) * | 2021-10-21 | 2021-11-26 | 易思维（杭州）科技有限公司 | Method for acquiring laser light plane and application |
| CN114354137A (en) * | 2021-12-28 | 2022-04-15 | 中国航空工业集团公司北京长城航空测控技术研究所 | Line laser nonstandard performance detection platform and line laser characteristic parameter detection method |
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Application publication date: 20200616 |