A line laser two-dimensional positioning method based on laser triangulation ranging

Abstract

The application discloses a line laser two-dimensional positioning method based on laser triangulation, and the method utilizes a measuring device which comprises an image acquisition module, a mounting frame, a laser projector and a control processing system; the image acquisition module, the mounting frame and the laser projector form a measuring probe, and the method uses two measuring probes and one control processing system in total. The method comprises the following steps: a calibration block is placed at a target position, and the calibration block is in a triangular relationship with the two measuring devices; the control processing system completes calibration of the target position according to the image of a current laser line; the calibration block is removed, and a target positioning object is moved in for positioning; during the positioning process, the relative distance from the target object to the target position is obtained based on laser triangulation through real-time calculation of the image of the current laser line. When the method is used for positioning the target object, complex equipment, complicated positioning procedures and target material requirements are not needed, and two-dimensional accurate positioning of the object to be positioned can be realized according to an auxiliary laser line and an image processing algorithm.

Description

Technical Field

[0001] This invention belongs to the field of measurement technology, specifically relating to a linear laser two-dimensional positioning method based on laser triangulation. Background Technology

[0002] Common laser triangulation methods use point lasers and image receiving units, which can only locate targets in one dimension. However, in most applications, we are not satisfied with one-dimensional target location; we need to determine the relative coordinates in two dimensions. Furthermore, in practical industrial applications, relying solely on data for location is risky; we expect to obtain data along with real-world images for mutual verification. Finally, point lasers cannot detect the lateral displacement of large targets, a problem that can be effectively addressed using line lasers. Summary of the Invention

[0003] The purpose of this invention is to overcome the above-mentioned defects and provide a linear laser two-dimensional positioning method based on laser triangulation.

[0004] The technical solution adopted in this invention is: a line laser two-dimensional positioning method based on laser triangulation, comprising the following steps:

[0005] Step A. Fix the laser projector and image acquisition module at a certain angle using the mounting frame to form a measurement module. Place the two measurement modules at a suitable angle, forming a triangular relationship with the target positioning position.

[0006] Step B. Before positioning, use a calibration piece to place at the target position for calibration. During positioning, the control system judges the relative coordinates of the object to be positioned to the target position in real time. The calibration piece needs to be consistent with the shape of the target object, and the target object needs to be a cylindrical object.

[0007] Step C. Extract the grayscale center line of the laser line, solve for the centroid of the grayscale center line, and use this as a basis to determine the relative distance between the object being measured and the measuring probe. Then, based on the relative distance between the target position and the two measuring modules, obtain the relative coordinates between the object being measured and the target position.

[0008] The specific method for step C is as follows: First, acquire an image containing laser lines, and perform filtering and grayscale thresholding to obtain an image without noise and with grayscale values ​​greater than the threshold. Then, calculate the grayscale centroid points of the light stripe regions column by column. Let the horizontal and vertical coordinates of the pixels be variables x and y, respectively. (x,y) This is the grayscale value of the pixel with coordinates (x, y). Let the non-zero interval of column x be [y1, y2], then the grayscale centroid of column x is x0. c for:

[0009]

[0010] Let the horizontal non-zero interval of the laser center line be [x1, x2], then the longitudinal coordinate L of the laser line center is c

[0011]

[0012] The longitudinal coordinate L of the laser line center is c The displacement cc' on the camera imaging plane and the distance pp' between the calibration plane and the measurement plane conform to the Snell law, and the formula can be obtained by combining the similar triangle formula:

[0013]

[0014] In the formula, α is the included angle between the camera optical axis and the imaging plane, β is the included angle between the camera optical axis and the calibration plane, gc and gp are the distances of the lens g along the optical axis to the imaging plane and the calibration plane respectively, and can be obtained by calibration. According to the above formula, when the displacement cc' of the laser line on the image is known, the distance pp' from the measurement plane to the calibration plane can be solved.

[0015] According to the Heron theorem, the formula is obtained:

[0016]

[0017] In the formula, q is half of the perimeter of triangle ap1p2, am is the height of triangle ap1p2, ap1 is the distance from target a to camera p1, ap2 is the distance from target a to camera p2, and p1p2 is the distance from camera p1 to camera p2. As described above, ap1 and ap2 can be solved according to the displacement of the laser line on the image, and p1p2 is a fixed parameter, so the coordinates (p1m, am) of the measured object can be solved. The relative coordinates of the measured object to the target position are the difference between the coordinates of the measured object and the target coordinates.

[0018] The beneficial effects of the present application are:

[0019] When the above-mentioned linear laser two-dimensional positioning method is used to position the measured object, the relative coordinates of the measured object to the target position can be positioned in two dimensions. This method can observe the positioning situation with the naked eye while positioning, and can identify the small displacement in the parallel direction using only one measurement module, so that high-precision target positioning can be achieved. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a device schematic diagram of a linear laser two-dimensional positioning method based on laser triangulation of the present application;

[0021] Figure 2 is a flow chart of a linear laser two-dimensional positioning method based on laser triangulation of the present application;

[0022] ​Figure 3 is a schematic diagram of the principle of laser triangulation of a line laser two-dimensional positioning method based on laser triangulation ranging;

[0023] Figure 4 is a schematic diagram of the principle of two-dimensional positioning of a line laser two-dimensional positioning method based on laser triangulation ranging;

[0024] In the figure, the reference numeral is: 1 is an image acquisition module, 2 is a mounting frame, 3 is a laser projector, 4 is a control processing system. DETAILED DESCRIPTION

[0025] The present application will be further described below in conjunction with specific examples and drawings:

[0026] As Figure 1 shown, a device of a line laser two-dimensional positioning method based on laser triangulation ranging includes: an image acquisition module 1, a mounting frame 2, a laser projector 3, and a control processing system 4. The image acquisition module 1 is used to acquire image data; the laser projector 3 is used to emit a line laser; the mounting frame 2 is used to fix the image acquisition module 1 and the laser projector 3; and the control processing system 4 is connected to the mounting frame 2 for interaction and power supply with the image acquisition module 1 and the laser projector 3;

[0027] As Figure 2 shown, the above-mentioned line laser two-dimensional positioning method based on laser triangulation ranging includes the following steps:

[0028] Step A. The laser projector 3 and the image acquisition module 1 are fixed at a certain angle by the mounting frame 2 to form a measurement module, and two measurement modules are placed at a suitable angle in a triangular relationship with the target positioning position;

[0029] Step B. Before positioning, a calibration piece is placed at the target position for calibration, and the control system judges the relative coordinates of the object to be positioned to the target position in real time during positioning. The calibration piece needs to be consistent with the shape of the target object, and the target object needs to be a columnar object;

[0030] Step C. Extract the gray center line of the laser line, solve the gravity center of the gray center line, and judge the relative distance of the measured object to the measurement probe based on this, and then obtain the relative coordinates of the measured object to the target position according to the relative distance of the target position to the two measurement modules.

[0031] The specific method of step C is: first, acquire an image containing a laser line, and perform filtering and gray threshold segmentation processing to obtain an image without noise and with a gray level greater than a threshold. Then, calculate the gray gravity points of the light stripe area column by column, set the horizontal and vertical coordinates of the pixel point as variables x and y, and I (x,y)is the gray value of the pixel point with coordinate (x, y). Let the non-zero interval of x column be [y1, y2], then the gray gravity center x c is:

[0032]

[0033] Let the horizontal non-zero interval of the laser center line be [x1, x2], then the vertical coordinate L c of the laser line center is:

[0034]

[0035] The vertical coordinate L c of the laser line center is:

[0036]

[0037] In the formula, α is the angle between the camera optical axis and the imaging plane, β is the angle between the camera optical axis and the calibration plane, gc and gp are the distances of the lens g along the optical axis to the imaging plane and the calibration plane respectively, which can be obtained by calibration. According to the above formula, when the offset cc' of the laser line on the image is known, the distance pp' of the measurement plane to the calibration plane can be solved.

[0038] According to Heron's formula, the formula is obtained:

[0039]

[0040] In the formula, q is half the perimeter of triangle ap1p2, am is the height of triangle ap1p2, ap1 is the distance from target a to camera p1, ap2 is the distance from target a to camera p2, and p1p2 is the distance from camera p1 to camera p2. As described above, ap1 and ap2 can be solved according to the offset of the laser line on the image, and p1p2 is a fixed parameter, so the coordinates (p1m, am) of the measured object can be solved. The relative coordinates of the measured object to the target position are the difference between the coordinates of the measured object and the target coordinates.

[0041] The actual effect of the technology is affected by many factors such as the angle between the two measurement modules, the camera resolution, the angle between the camera and the laser, the camera focal length, etc. The core is the positioning accuracy of the measurement module. A 500 million pixel industrial camera and a 55mm fixed focus lens are tested, and the positioning accuracy of a 1m distance target object is higher than 0.1mm.

[0042] Those skilled in the art can easily understand that the above description is only the preferred embodiment of the present application, and is not intended to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A linear laser two-dimensional positioning method based on laser triangulation, characterized in that: Includes the following steps: Step A. Fix the laser projector and image acquisition module at a certain angle using the mounting frame to form a measurement module. Place the two measurement modules at a suitable angle, forming a triangular relationship with the target positioning position. Step B. Before positioning, use a calibration piece to place at the target position for calibration. During positioning, the control system judges the relative coordinates of the object to be positioned to the target position in real time. The calibration piece needs to be consistent with the shape of the target object, and the target object needs to be a cylindrical object. Step C. Extract the grayscale center line of the laser line, solve for the centroid of the grayscale center line, and use this as a basis to determine the relative distance between the object being measured and the measuring probe. Then, based on the relative distance between the target position and the two measuring modules, obtain the relative coordinates between the object being measured and the target position. The specific method of step C is as follows: First, acquire an image containing laser lines, and perform filtering and grayscale thresholding to obtain an image without noise and with grayscale values ​​greater than the threshold; then, calculate the grayscale centroid points of the light stripe regions column by column, setting the horizontal and vertical coordinates of the pixels as variables. and variables , The coordinates are The grayscale value of the pixel; let The non-zero interval of the column is ,but Grayscale center of gravity of the column for: Let the horizontal non-zero interval of the laser centerline be... Then the ordinate of the center of the laser line for: The vertical coordinate of the center of the laser line Displacement on the camera's imaging plane and the distance between the calibration plane and the measurement plane It conforms to Snell's law, and combined with the formula for similar triangles, we can obtain the following formula: In the formula The angle between the camera's optical axis and the imaging plane. The angle between the camera's optical axis and the calibration plane. , Lenses The distances along the optical axis to the imaging plane and calibration plane are obtained through calibration; according to the above formula, when the offset of the laser line on the image is known... The distance from the measuring plane to the calibration plane can then be calculated. ; According to Heron's theorem, the formula is: In the formula Let am be half the perimeter of triangle ap1p2, where am is the height of triangle ap1p2, ap1 is the distance from target a to camera p1, ap2 is the distance from target a to camera p2, and p1p2 is the distance from camera p1 to camera p2. ap1 and ap2 can be calculated based on the offset of the laser line in the image. Since p1p2 is a fixed parameter, the coordinates (p1m, am) of the measured object can be calculated. The relative coordinates of the measured object to the target position are the difference between the coordinates of the measured object and the target coordinates.

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