A method and apparatus for evaluating the absolute accuracy of a 3D laser profilometer in the z-axis

Abstract

This invention relates to the field of advanced measurement equipment technology, and discloses a method and apparatus for evaluating the absolute accuracy of a 3D laser profilometer in the z-direction. This solves the problem that existing measurement methods and apparatus cannot guarantee accuracy. The evaluation method of this application specifically involves: acquiring x- and z-direction profile data generated when a standard gauge block rotates on a rotary slide using a 3D laser profilometer; selecting two sets of data based on the x- and z-direction profile data; fitting a straight line based on one set of data; calculating the average distance from the other set of data to the fitted straight line; repeating the above steps to obtain profile data at different rotation angles; obtaining the distance between the two sets of data for the standard gauge block at different rotation angles; using the rotation angle as the x-axis and the distance at different rotation angles as the y-axis; fitting a curve between the rotation angle and the distance to obtain the absolute accuracy of the 3D laser profilometer in the z-direction, thereby obtaining accurate absolute accuracy in the z-direction.

Description

Technical Field

[0001] This invention relates to the field of advanced measurement equipment technology, specifically to a method and apparatus for evaluating the absolute accuracy of a 3D laser profilometer in the z-axis. Background Technology

[0002] In industrial applications, the direction of the laser line in a 3D laser profilometer is generally referred to as the x-direction, meaning the line illuminated by the laser is defined as the x-axis, and the height is defined as the z-direction. Data in both the x and z directions can be obtained from a single static photograph, while the direction of motion is typically marked as the y-direction.

[0003] In the measurement industry, the absolute accuracy of a 3D laser profilometer in the z-direction is a crucial indicator of the accuracy of workpiece height measurement. One existing method for measuring absolute accuracy involves placing a standard gauge block on a displacement platform, scanning the gauge block with the 3D laser profilometer to obtain point cloud data from two faces, and then calculating the measured value. This measured value is then compared to the theoretical value. To ensure the accuracy of this calculation, two methods are employed: (1) Calibrate the moving pose of the 3D laser profilometer and the moving platform. However, the accuracy of the moving platform is required to be high during the calibration of the moving pose. But due to the manufacturing process, the accuracy cannot meet the requirements. (2) It is necessary to ensure that the laser plane of the 3D laser profilometer is absolutely perpendicular to the direction of motion of the moving platform, which is difficult to achieve structurally. Summary of the Invention

[0004] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a method and apparatus for evaluating the absolute accuracy of a 3D laser profilometer in the z-axis.

[0005] (II) Technical Solution To address the above problems, the present invention provides the following technical solution: a method for evaluating the absolute accuracy of a 3D laser profilometer in the z-axis, the method specifically comprising: The x- and z-axis contour data generated when a standard block rotates on a rotary slide are obtained using a 3D laser profilometer. Based on the contour data in the x and z directions, two sets of data are selected, and a straight line is fitted based on one set of data. The average distance from the other set of data to the fitted straight line is calculated. Repeat the above steps to obtain contour data at different rotation angles, and obtain the distance between the two sets of data for the standard gauge block at different rotation angles.

[0006] Using the rotation angle as the x-axis and the distance at different rotation angles as the y-axis, a curve is fitted between the rotation angle and the distance to obtain the absolute accuracy of the 3D laser profilometer in the z-direction.

[0007] The present invention also provides a 3D laser profilometer z-axis absolute accuracy evaluation device, the evaluation device comprising: The generation module is used to acquire x- and z-axis contour data generated when a standard block rotates on a rotary slide, based on a 3D laser profilometer. The calculation module is used to select two sets of data based on the contour data in the x and z directions, fit a straight line based on one set of data, and calculate the average distance of the other set of data to the fitted straight line. The repeat module is used to repeat the above steps to obtain contour data at different rotation angles, and to obtain the distance between two sets of data for the standard gauge block at different rotation angles.

[0008] The output module is used to fit a curve between the rotation angle and the distance at different rotation angles as the y-axis, and obtain the absolute accuracy of the 3D laser profilometer in the z-direction.

[0009] (III) Beneficial Effects Compared with the prior art, the present invention provides a method and apparatus for evaluating the absolute accuracy of a 3D laser profilometer in the z-axis, which has the following beneficial effects: The method and apparatus for evaluating the absolute accuracy of a 3D laser profilometer in the z-direction provided in this application obtains the distance between two faces of the standard gauge block by scanning the profile data generated by the 3D laser profilometer scanning the standard gauge block rotating on the rotary slide, and then extracting and calculating the profile data. After multiple rotations, a fitting curve is obtained. The absolute accuracy of the 3D laser profilometer in the z-direction is obtained when the standard gauge block is perpendicular to the 3D laser profilometer, thus ensuring the accuracy of the absolute accuracy. This avoids the problem that the existing measurement methods cannot achieve the required absolute perpendicularity between the laser plane of the 3D laser profilometer and the direction of movement of the mobile platform due to the inaccuracy and structural limitations of the moving platform. This simplifies the requirements of the evaluation method and apparatus and also ensures the accuracy of the absolute accuracy in the z-direction. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the 3D laser profilometer structure of the present invention.

[0011] Figure 2 This is a schematic diagram of the structure of the standard gauge block of the present invention.

[0012] Figure 3 This is a schematic diagram of the structure of the rotary slide of the present invention.

[0013] Figure 4 This is a schematic diagram of the 3D laser profilometer, standard gauge block, and position of the standard gauge block according to the present invention.

[0014] Figure 5This is a schematic diagram showing the positions of face 1 and face 2 of the standard gauge block of the present invention.

[0015] Figure 6 This is a schematic diagram of the outline of the present invention.

[0016] Figure 7 This is a schematic diagram of the fitting curve of the present invention.

[0017] Figure 8 This is a flowchart of the 3D laser profilometer z-axis absolute accuracy evaluation method of the present invention.

[0018] Figure 9 This is a structural diagram of the 3D laser profilometer z-axis absolute accuracy evaluation device of the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Please see Figures 1-8 This invention provides a new technical solution: a method for evaluating the absolute accuracy of a 3D laser profilometer in the z-direction, the method specifically comprising: Step S1: Obtain the x-axis and z-axis contour data generated when the standard block rotates on the rotary slide based on the 3D laser profilometer.

[0021] Specifically, the 3D laser profilometer includes an industrial camera, an industrial lens, a line structured light laser, a laser mounting bracket, a circuit board, a mounting plate, etc. Figure 1 As shown, the contour data of the standard gauge block is obtained by scanning the standard gauge block, wherein the standard gauge block is a special gauge steel, such as... Figure 2 As shown, the selected standard gauge block has a size of 10mm, but other standard sizes can be selected according to the performance of the 3D laser profilometer. The standard gauge block is fixed on the rotary slide, which features high-precision 360° rotation. Figure 3 As shown, the rotary slide includes a toggle handle, fixing screw 2, fixing screw 1, a rotary table, and a micrometer knob.

[0022] Furthermore, the 3D laser profilometer and the rotary slide are fixed on the anti-vibration platform, and the standard gauge block is fixed on the rotary slide. By turning the micrometer knob of the rotary slide, the rotary slide rotates at equal angles. After each rotation of the rotary slide, the 3D laser profilometer scans the standard gauge block and outputs the x-axis and z-axis profile data of the standard gauge block.

[0023] Specifically, the 3D laser profilometer and the rotary slide are fixed to the anti-vibration platform with screws or glue to reduce the impact of external vibrations on the rotary slide. The standard gauge block is fixed to the rotary slide with glue to prevent relative sliding between the two from affecting the measurement. Figure 4 As shown, by turning the micrometer knob on the rotary slide, the rotary slide can be rotated at a constant angle. At the same time, the rotary slide can be rotated from any angle, and the standard gauge block on the rotary slide also rotates accordingly. After each rotation, the standard gauge block is scanned using the 3D laser profilometer to obtain the x-axis and z-axis contour data of the standard gauge block, and the contour data of the x-axis and z-axis are saved. The contour data of the standard gauge block changes after rotation.

[0024] Step S2: Select two sets of data based on the contour data in the x and z directions, fit a straight line based on one set of data, and calculate the average distance of the other set of data to the fitted straight line.

[0025] Specifically, due to interference during the scanning of the standard block by the 3D laser profilometer, errors occur in the contour data in the x and z directions, resulting in the contour data lines not always being straight. Therefore, it is necessary to select the straight contour lines to obtain the contour data on the two faces of the standard block, such as... Figure 5 As shown in the diagram, for surfaces 1 and 2, let the data on one surface be a set of data, then the contour data on the two surfaces will be two sets of data. Fit a straight line to one set of data, and calculate the average distance of the other set of data to the fitted straight line.

[0026] Furthermore, two sets of data are obtained by cropping the ROI region from the contour data, each set of data consisting of several points.

[0027] Specifically, the ROI region is extracted from the contour data obtained by the 3D laser profilometer. The ROI data is the data when the contour line is a straight line, thus obtaining contour data on two surfaces, i.e., obtaining two sets of contour data, such as... Figure 6 As shown, each set of data consists of several points with coordinates (X, Z), where X and Z are the x-axis and z-axis contour data obtained when the standard block is scanned by a 3D laser profilometer, which are the coordinates on the coordinate axes.

[0028] Furthermore, fit a straight line to one set of data as Z = kx + b, and calculate the distance from each point in the other set of data to the fitted line. And calculate the average distance. Where Z is the z-axis data obtained when the 3D laser profilometer scans the standard gauge block, and x is the x-axis data obtained when the 3D laser profilometer scans the standard gauge block. i Let be the distance from another set of data to the fitted line, where i is the number of data points, n is the number of distances, k is the slope of the line, and b is the intercept of the line.

[0029] Specifically, one set of data is fitted to a straight line Z=kx+b, and the distance from the other set of data to the line is calculated using the following formula: , where i is the number of data points, and the average distance is calculated. , average distance The distance between the two faces is represented by two sets of data, where Z is the z-axis data obtained when the 3D laser profilometer scans the standard gauge block, and x is the x-axis data obtained when the 3D laser profilometer scans the standard gauge block. i Let be the distance from another set of data to the fitted line, where i is the number of data points, n is the number of distances, k is the slope of the line, and b is the intercept of the line.

[0030] Step S3: Repeat the above steps to obtain contour data under different rotation angles, and obtain the distance between the two sets of data of the standard gauge block under different rotation angles.

[0031] Specifically, steps S1-S2 above obtain the contour data and the distance between the two faces of the standard gauge block at one rotation angle. By rotating the rotary slide multiple times and using the same method as steps S1-S2, the contour data and the distance between the two faces of the standard gauge block at multiple rotation angles can be obtained.

[0032] Step S4: Using the rotation angle as the x-axis and the distance at different rotation angles as the y-axis, fit the rotation angle and distance to obtain the absolute accuracy of the 3D laser profilometer in the z-direction.

[0033] Specifically, after multiple rotations, the contour data and the distance between the two faces of the standard block at multiple rotation angles are obtained. Then, the rotation angle is taken as the x-axis, and the distance between the two faces at the multiple angles is taken as the y-axis, thereby fitting a curve.

[0034] Furthermore, the fitted curve is d = a0 + a1 cos(w θ)+b1 sin(w θ), where a0, a1, b1, and w are constants.

[0035] Specifically, using the rotation angle as the x-axis, the curve fitted by the distance between the two surfaces at multiple angles as the y-axis is d = a0 + a1. cos(w θ)+b1 sin(w θ), where a0, a1, b1, and w are constants calculated based on the rotation angle and the distance between the two faces at multiple angles.

[0036] Furthermore, the absolute precision D = | |, among which The minimum value of the fitted curve. The true value is obtained by measuring the standard gauge block perpendicular to the laser surface of the 3D laser profilometer.

[0037] Specifically, the absolute precision is the minimum value of the fitted curve. The true value obtained by measuring perpendicularly to the laser surface of the standard gauge block and the 3D laser profilometer. The difference, such as Figure 7 As shown, the absolute accuracy of the 3D laser profilometer in the z-direction is |9.96-10| = 0.04 mm. Compared with existing measurement methods, the accuracy of the absolute accuracy is guaranteed, and the minimum value of the fitted curve is [not specified]. At this time, the standard gauge block is kept perpendicular to the 3D laser profilometer; otherwise, the obtained absolute precision will have errors, thus ensuring the accuracy of the absolute precision.

[0038] This application also provides a device for evaluating the absolute accuracy of a 3D laser profilometer in the z-axis, such as... Figure 9 As shown, the evaluation device includes: The generation module is used to acquire x- and z-axis contour data generated when a standard block rotates on a rotary slide, based on a 3D laser profilometer. The calculation module is used to select two sets of data based on the contour data in the x and z directions, fit a straight line based on one set of data, and calculate the average distance of the other set of data to the fitted straight line. The repeat module is used to repeat the above steps to obtain contour data at different rotation angles, and to obtain the distance between two sets of data for the standard gauge block at different rotation angles.

[0039] The output module is used to fit a curve between the rotation angle and the distance at different rotation angles as the y-axis, and obtain the absolute accuracy of the 3D laser profilometer in the z-direction.

[0040] The generating module is specifically used for: The 3D laser profilometer and the rotary slide are fixed on the anti-vibration platform. The standard gauge block is fixed on the rotary slide. The micrometer knob of the rotary slide is turned so that the rotary slide rotates at equal angles. After each rotation of the rotary slide, the 3D laser profilometer scans the standard gauge block and outputs the x-axis and z-axis profilometer data of the standard gauge block.

[0041] The computing module is specifically used for: Two sets of data are obtained by cropping the ROI region from the contour data, and each set of data consists of several points.

[0042] The computing module is more specifically used for: Fit a straight line to one set of data as Z = kx + b, and calculate the distance from each point in the other set of data to the fitted line. And calculate the average distance. Where Z is the z-axis data obtained when the 3D laser profilometer scans the standard gauge block, and x is the x-axis data obtained when the 3D laser profilometer scans the standard gauge block. i is the distance from the other set of data to the fitted line, i is the number of data points, n is the number of distances, k is the slope of the line, and b is the intercept of the line.

[0043] The output module is specifically used for: The fitted curve is d=a0+a1 cos(w θ)+b1 sin(w θ), where a0, a1, b1, and w are constants.

[0044] The output module is more specifically used for: The absolute precision D=| |, among which The minimum value of the fitted curve. The true value is obtained by measuring the standard gauge block perpendicular to the laser surface of the 3D laser profilometer.

[0045] The 3D laser profilometer z-axis absolute accuracy evaluation device provided in this application embodiment can realize all the processes of the above-described 3D laser profilometer z-axis absolute accuracy evaluation method embodiment and achieve the same technical effect. To avoid repetition, it will not be described again here.

[0046] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for evaluating the absolute accuracy of a 3D laser profilometer in the z-axis, characterized in that: The method specifically includes: The x- and z-axis contour data generated when a standard block rotates on a rotary slide are obtained using a 3D laser profilometer. Based on the contour data in the x and z directions, two sets of data are selected. A straight line is fitted based on one set of data, and the average distance from the other set of data to the fitted line is calculated. Specifically, the fitted line for one set of data is: Z = kx + b. The distance from each point in the other set of data to the fitted line is calculated. And calculate the average distance. Where Z is the z-axis data obtained when the 3D laser profilometer scans the standard gauge block, and x is the x-axis data obtained when the 3D laser profilometer scans the standard gauge block. i Let i be the distance from another set of data to the fitted line, n be the number of data points, k be the slope of the line, and b be the intercept of the line. Repeat the above steps to obtain contour data at different rotation angles, and obtain the distance between the two sets of data of the standard block at different rotation angles; Using the rotation angle as the x-axis and the distance at different rotation angles as the y-axis, a fitting curve is formed between the rotation angle and the distance to obtain the absolute accuracy of the 3D laser profilometer in the z-direction; wherein, the fitting curve is d=a0+a1. cos(w θ)+b1 sin(w θ), where a0, a1, b1, and w are constants.

2. The method for evaluating the absolute accuracy of a 3D laser profilometer in the z-direction according to claim 1, characterized in that: The method of acquiring x- and z-axis contour data of a standard gauge block when it rotates on a rotary slide using a 3D laser profilometer includes: The 3D laser profilometer and the rotary slide are fixed on the anti-vibration platform. The standard gauge block is fixed on the rotary slide. The micrometer knob of the rotary slide is turned so that the rotary slide rotates at equal angles. After each rotation of the rotary slide, the 3D laser profilometer scans the standard gauge block and outputs the x-axis and z-axis profilometer data of the standard gauge block.

3. The method for evaluating the absolute accuracy of a 3D laser profilometer in the z-direction according to claim 1, characterized in that: The contour data based on the x and z directions is selected from two sets of data, including: Two sets of data are obtained by cropping the ROI region from the contour data, and each set of data consists of several points.

4. The method for evaluating the absolute accuracy of a 3D laser profilometer in the z-direction according to claim 1, characterized in that: The rotation angle and distance are fitted to a curve to obtain the absolute accuracy of the 3D laser profilometer in the z-direction, including: The absolute precision D=| |, among which The minimum value of the fitted curve. The true value is obtained by measuring the standard gauge block perpendicular to the laser surface of the 3D laser profilometer.

5. A device for evaluating the absolute accuracy of a 3D laser profilometer in the z-direction, used to implement the method for evaluating the absolute accuracy of a 3D laser profilometer in the z-direction as described in any one of claims 1-4, characterized in that: The evaluation device includes: The generation module is used to acquire x- and z-axis contour data generated when a standard block rotates on a rotary slide, based on a 3D laser profilometer. The calculation module is used to select two sets of data based on the contour data in the x and z directions, fit a straight line based on one set of data, and calculate the average distance of the other set of data to the fitted straight line. The repeat module is used to repeat the above steps to obtain contour data under different rotation angles, and to obtain the distance between two sets of data of the standard block under different rotation angles. The output module is used to fit a curve between the rotation angle and the distance at different rotation angles as the y-axis, and obtain the absolute accuracy of the 3D laser profilometer in the z-direction.

Images