Laser displacement sensor automatic calibration device and method

Abstract

The present invention is an automatic calibration device and method for a laser displacement sensor. A laser displacement sensor and a laser interferometer are arranged on both sides of a moving table, and a beam analyzer is arranged on the moving table to realize spot measurement. During calibration, the standard object to be measured is controlled to step from the near end of the range to the far end of the range, and the laser displacement sensor data, laser interferometer data and beam analyzer data at each sampling position are recorded. After completing the full-range scan, the linear deviation is calculated according to the laser displacement sensor readings and laser interferometer readings at different positions to generate a calibration table for calibration; the shape and direction of the measuring beam are fitted according to the cross-sectional spot data at different positions to adjust the focus, direction and other parameters. The present invention can realize the simultaneous measurement of the linear deviation of the laser displacement sensor and the beam shape in a single scan, is suitable for the calibration of laser displacement sensors of various ranges, and can significantly improve the calibration accuracy and production efficiency.

Description

Technical Field

[0001] The present invention relates to the field of precision measurement and sensing technology, and in particular to an automatic calibration device and method for a laser displacement sensor. Background Art

[0002] Laser displacement sensors are widely used in distance measurement, vibration measurement, shape measurement, etc. in the field of industrial automation. Typical applications include dispensing machine positioning, spindle runout measurement, workpiece size measurement, geometric surface measurement, etc. Laser displacement sensors have the excellent characteristics of high speed, high precision, and non-contact. In order to ensure that the laser displacement sensor has good measurement accuracy, its linearity and beam distribution must be calibrated and verified. The laser displacement sensor uses a linear array CMOS sensor to obtain the light spot information on the surface of the object being measured. The nonlinear combined effect of the internal transmitting mirror group, receiving mirror group and CMOS sensor causes the nonlinearity of the measurement data. In addition, the directional deviation and focus position deviation of the emitted laser beam caused by mirror group installation errors, dispensing shrinkage, etc. will affect the measurement accuracy and measurement performance. Therefore, high-precision instruments must be used to calibrate the linear accuracy and beam distribution of the laser displacement sensor. The current calibration equipment can only complete the linear calibration function at a time, so the production efficiency is limited and the laser beam shape cannot be analyzed. In addition, due to the diverse shapes and ranges of laser displacement sensors, it is necessary to calibrate multiple different models of laser displacement sensors on the same device, so the calibration device is also required to have good versatility and adaptability. Summary of the invention

[0003] The purpose of the present invention is to overcome the problems existing in the prior art and to provide a laser displacement sensor automatic calibration device and method.

[0004] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0005] A laser displacement sensor automatic calibration device comprises a horizontal base, on which a laser displacement sensor mounting seat, a motion platform and a laser interferometer mounting seat are sequentially connected along the length direction thereof, a laser displacement sensor is mounted on the laser displacement sensor mounting seat, a laser interferometer is connected to the laser interferometer mounting seat via a laser interferometer adjustment frame, a motion platform is slidably connected to a motion platform, a beam analyzer, and a measured object mounting bracket and a prism mounting plate respectively located on both sides of the beam analyzer are arranged on the motion platform, a standard measured object and a half-reflecting half-mirror are respectively attached to two opposite surfaces of the measured object mounting bracket, the half-reflecting half-mirror is opposite to the laser displacement sensor, and is used to receive a measuring beam of the laser displacement sensor and reflect and irradiate it on the surface of the standard measured object and transmit through the measured object mounting bracket and then irradiate it on the surface of the beam analyzer, a prism mounting plate () is provided with a prism on one side surface relative to the laser interferometer, and a light beam of the laser interferometer is irradiated on the prism to form a return light beam and return to the laser interferometer to generate interference data.

[0006] Furthermore, the measuring beam of the laser displacement sensor, the light-emitting beam and the return beam of the laser interferometer are all parallel to the sliding direction of the moving table, and the measuring beam of the laser displacement sensor and the light-emitting beam of the laser interferometer are collinear.

[0007] Furthermore, a through hole and a wedge-shaped groove are provided on the object mounting bracket, the standard object to be measured is attached to the upper inner surface of the wedge-shaped groove, and the semi-reflecting and semi-mirror lens is attached to the lower inner surface of the wedge-shaped groove. The axial direction of the through hole of the object mounting bracket is consistent with the direction of the measuring light beam. After the measuring light beam is irradiated on the semi-reflecting and semi-mirror lens, a part of the light is reflected onto the standard object to be measured to achieve distance measurement, and the other part of the light passes through the through hole and is irradiated onto the light beam analyzer to achieve spot shape measurement. The height and width of the object mounting bracket are adjusted so that the optical path of the light beam irradiating the standard object to be measured is consistent with that of the light beam irradiated on the light beam analyzer, thereby ensuring that the position of linear calibration and the spot measurement is the same position of the measuring beam.

[0008] Furthermore, the laser interferometer adjustment frame has at least three degrees of freedom adjustment structures of pitch, yaw and height, and the laser interferometer adjustment frame is adjusted so that the light beam of the laser interferometer and the measuring beam of the laser displacement sensor are collinear.

[0009] Furthermore, the laser displacement sensor controls the direction of the measuring light beam by cooperating with the laser displacement sensor mounting base.

[0010] An automatic calibration method for a laser displacement sensor, the specific calibration process of the method is as follows:

[0011] First, install the laser displacement sensor to be tested on the laser displacement sensor mounting base, and then connect the host computer with the laser displacement sensor, beam analyzer, laser interferometer and motion table;

[0012] The host computer controls the motion table to move so that the standard object to be measured is located at the center of the range of the laser displacement sensor, and sets the readings of the laser displacement sensor and the laser interferometer to 0 respectively;

[0013] The host computer controls the motion of the moving table so that the standard object to be measured is located at the starting point of the range of the laser displacement sensor. The step distance d and the motion speed v of the moving table are set. The actual range of the laser displacement sensor is taken as D. Then, the scanning process will take n=D / d positions in the full range of the laser displacement sensor as sampling points.

[0014] The upper computer samples the laser displacement sensor, beam analyzer and laser interferometer at the starting point of the measuring range and saves them in the upper computer. After the sampling is completed, the moving table is controlled to move the step distance d at the far end of the measuring range, and the sampling is performed again. The movement and sampling steps are repeated until the moving table moves to the far end of the measuring range.

[0015] After the sampling is completed, the displacement measurement deviation of the laser displacement sensor and the laser interferometer at each sampling point and the spot data of the beam analyzer are obtained.

[0016] Furthermore, the laser interferometer is used to measure the displacement of the corner cone, and the beam analyzer is used to measure the shape of the cross-section of the measuring beam; the linearity curve of the laser displacement sensor is obtained according to the displacement measurement deviation of all sampling points; the shape of the measuring beam along the optical axis is obtained according to the spot data of all sampling points; and the linear deviation curve and the beam shape are measured more accurately by reducing the step distance d and increasing the number of sampling points n.

[0017] Furthermore, after obtaining the measurement data of the laser displacement sensor and the laser interferometer at all sampling points, the change relationship between the measurement data of the laser displacement sensor and the measurement data of the laser interferometer is quantitatively fitted through a polynomial or spline curve, and then a calibration curve is generated through equal-interval sampling and uploaded to the laser displacement sensor to significantly improve the measurement accuracy of the laser displacement sensor.

[0018] Furthermore, after obtaining the spot shape of the beam cross section at all sampling points, the position of the spot center in two perpendicular directions on the optical axis cross section is fitted by Gaussian function. With spot radius ,in ; Through Perform the least square linear fitting to obtain the deflection angle of the beam in the X direction; The least squares fitting is performed to obtain the deflection angle of the light beam in the Y direction; the focus position of the measurement light beam is obtained by finding the sampling position corresponding to the minimum spot radius; the measurement light beam is calibrated and quickly adjusted according to the measured deflection angle and focus position.

[0019] The beneficial effects of the present invention are:

[0020] The present invention integrates the linear calibration device and the beam measuring device of the laser displacement sensor into the same device, which not only realizes the high-precision calibration of the linearity of the laser displacement sensor, but also realizes the simultaneous calibration of the beam distribution, which significantly reduces the calibration process. The linearity calibration result can generate a calibration table for the linear accuracy compensation of the laser displacement sensor, and the beam distribution calibration result can provide guidance for the installation and adjustment of the laser displacement sensor, thereby greatly improving the calibration efficiency and effectively ensuring the calibration accuracy. In addition, by combining sensor mounting bases and motion modules of different specifications, the calibration of various types of laser displacement sensors can be realized on the same device, which has universality and practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the principle of automatic calibration of linearity and beam distribution of the laser displacement sensor of the present invention;

[0022] Figure 2 It is a schematic diagram of the automatic calibration device for the linearity and beam distribution of the laser displacement sensor of the present invention;

[0023] Figure 3 This is a schematic diagram of the laser displacement sensor of the present invention measuring the angle deviation of the light beam;

[0024] Figure 4 It is a schematic diagram of the shape of the measuring beam of the laser displacement sensor of the present invention;

[0025] Figure 5 It is a linear deviation diagram of a 500 mm range laser displacement sensor in the present invention.

[0026] Explanation of the numbers in the figure: 1. Horizontal base, 2. Laser displacement sensor mounting base, 3. Laser displacement sensor, 4. Measuring beam, 5. Standard object to be measured, 6. Semi-reflective and semi-mirror, 7. Object mounting bracket, 8. Beam analyzer, 9. Cube mirror mounting plate, 10. Cube mirror, 11. Outgoing light beam, 12. Returning light beam, 13. Laser interferometer, 14. Laser interferometer adjustment frame, 15. Laser interferometer mounting base, 16. Moving table, 17. Moving table, 18. Host computer, 19. Position of the center point of the light spot, 20. Sampling position, 21. Theoretical light emitting direction, 22. Actual light emitting direction, 23. Light spot shape, 24. Reference position, 25. Actual light emitting beam. DETAILED DESCRIPTION

[0027] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0028] like Figure 1 and Figure 2 As shown, a laser displacement sensor automatic calibration device comprises a horizontal base 1, on which a laser displacement sensor mounting seat 2, a motion platform 17 and a laser interferometer mounting seat 15 are sequentially connected along the length direction thereof, a laser displacement sensor 3 is mounted on the laser displacement sensor mounting seat 2, a laser interferometer 13 is connected to the laser interferometer mounting seat 15 via a laser interferometer adjustment frame 14, a motion table 16 is slidably connected to the motion platform 17, a beam analyzer 8, and a measured object mounting bracket 7 and a corner cube mounting plate 9 are respectively arranged on the two opposite surfaces of the measured object mounting bracket 7. A standard object to be measured 5 and a half-reflecting half-mirror 6 are attached. The half-reflecting half-mirror 6 is opposite to the laser displacement sensor 3 and is used to receive the measuring light beam 4 of the laser displacement sensor 3 and reflect it to illuminate the surface of the standard object to be measured 5 and transmit it through the object mounting bracket 7 to illuminate the surface of the beam analyzer 8. A corner mirror 10 is provided on the side surface of the corner mirror mounting plate 9 relative to the laser interferometer 13. The light beam 11 of the laser interferometer 13 is irradiated on the corner mirror 10 to form a return light beam 12 and return to the laser interferometer 13 to generate interference data. The laser displacement sensor 3, the beam analyzer 8, the laser interferometer 13 and the moving table 16 are respectively electrically connected to the host computer 18 for drive control and data transmission.

[0029] The measuring beam 4 of the laser displacement sensor 3 , the outgoing beam 11 and the returning beam 12 of the laser interferometer 13 are all parallel to the sliding direction of the moving table 16 , and the measuring beam 4 of the laser displacement sensor 3 is collinear with the outgoing beam 11 of the laser interferometer 13 .

[0030] The object mounting bracket 7 is provided with a through hole and a 45-degree wedge-shaped groove, the standard object 5 is attached to the upper inner surface of the wedge-shaped groove, the semi-reflective mirror 6 is attached to the lower inner surface of the wedge-shaped groove, the through hole axis direction of the object mounting bracket 7 is consistent with the direction of the measuring light beam 4, after the measuring light beam 4 is irradiated on the semi-reflective mirror 6, part of the light is reflected onto the standard object 5 to achieve distance measurement, and the other part of the light passes through the through hole and irradiates the light beam analyzer 8 to achieve spot shape measurement, the height and width of the object mounting bracket 7 are adjusted so that the optical path of the light beam irradiated on the standard object 5 is consistent with that irradiated on the light beam analyzer 8, thereby ensuring that the position of linear calibration and spot measurement is the same position of the measuring light beam 4.

[0031] The laser interferometer adjustment frame 14 has at least three degrees of freedom adjustment structures of pitch, yaw and height. By adjusting the laser interferometer adjustment frame 14, the light beam 11 of the laser interferometer 13 and the measuring beam 4 of the laser displacement sensor 3 are made collinear.

[0032] The laser displacement sensor 3 controls the direction of the measuring beam 4 by cooperating with the laser displacement sensor mounting base 2. In this embodiment, when it is necessary to calibrate laser displacement sensors 3 of different ranges, the laser displacement sensor mounting base 2 can be replaced to adapt to the sizes of different models. In addition, the motion base 17 of a specific stroke can meet the calibration of laser displacement sensors with a range smaller than its stroke. When it is necessary to calibrate a laser displacement sensor of a larger range, the calibration requirement can be met by replacing the motion base 17 with a larger stroke.

[0033] An automatic calibration method for a laser displacement sensor, the specific calibration process of the method is as follows:

[0034] First, the laser displacement sensor 3 to be tested is mounted on the laser displacement sensor mounting base 2, and then the host computer 18 is connected with the laser displacement sensor 3, the beam analyzer 8, the laser interferometer 13 and the motion table 16;

[0035] The host computer 18 controls the motion table 16 to move so that the standard object 5 is located at the center of the range of the laser displacement sensor 3, and sets the readings of the laser displacement sensor 3 and the laser interferometer 13 to 0 respectively;

[0036] The host computer 18 controls the motion table 16 to move so that the standard object 5 is located at the starting point of the range of the laser displacement sensor 3, sets the stepping distance d and the motion speed v of the motion table 16, and takes the actual range of the laser displacement sensor 3 as D. Then, the scanning process will take n=D / d positions in the full range of the laser displacement sensor 3 as sampling points;

[0037] The upper computer 18 samples the laser displacement sensor 3, the beam analyzer 8 and the laser interferometer 13 at the starting point of the measuring range and saves the samples in the upper computer 18. After the sampling is completed, the moving table 16 is controlled to move the step distance d to the far end of the measuring range and sample again. The movement and sampling steps are repeated until the moving table 16 moves to the far end of the measuring range.

[0038] After the sampling is completed, the displacement measurement deviation of the laser displacement sensor 3 and the laser interferometer 13 at each sampling point and the spot data of the beam analyzer 8 are obtained.

[0039] The laser interferometer 13 is used to measure the displacement of the corner conic mirror 10, and the beam analyzer 8 is used to measure the shape of the cross section of the measuring beam 4; the linearity curve of the laser displacement sensor 3 is obtained according to the displacement measurement deviation of all sampling points; the shape of the measuring beam 4 along the optical axis is obtained according to the spot data of all sampling points; by reducing the step distance d and increasing the number of sampling points n, the linear deviation curve and the beam shape can be measured more accurately.

[0040] After obtaining the measurement data of the laser displacement sensor 3 and the laser interferometer 13 at all sampling points, the change relationship between the measurement data of the laser displacement sensor 3 and the measurement data of the laser interferometer 13 is quantitatively fitted through a polynomial or spline curve, and then a calibration curve is generated through equal-interval sampling and uploaded to the laser displacement sensor 3 to significantly improve the measurement accuracy of the laser displacement sensor 3.

[0041] After obtaining the spot shape of the beam cross section at all sampling points, the position of the spot center in two perpendicular directions on the optical axis section is fitted by Gaussian function. With spot radius ,in ; Through Perform the least square linear fitting to obtain the deflection angle of the beam in the X direction; The least squares fitting is performed to obtain the deflection angle of the light beam in the Y direction; the focusing position of the measuring light beam 4 is obtained by finding the sampling position corresponding to the minimum spot radius; the calibration and rapid adjustment of the measuring light beam 4 are realized according to the measured deflection angle and focusing position.

[0042] like Figure 3 As shown, there is a certain deviation between the actual light emitting direction 22 of the laser displacement sensor 3 and the theoretical light emitting direction 21. By measuring the center point position 19 of the light spot at different sampling positions 20, the actual light emitting direction 22 can be fitted by the least squares method, thereby providing a reference for adjusting the light emitting direction.

[0043] like Figure 4 As shown, the actual output light beam 25 of the laser displacement sensor 3 is a Gaussian waist-shaped light beam. By measuring the spot shape 23 at different sampling positions 20, the shape of the entire light beam can be restored, and the reference position 24 corresponding to the minimum spot can be found.

[0044] like Figure 5 As shown, after measuring the data of the laser displacement sensor and the laser interferometer at different positions, the linear residual of the data at each sampling position can be obtained. With the measured distance as the horizontal axis and the linear residual as the vertical axis, a linear deviation graph can be drawn to complete the calibration and verification of the linear deviation of the laser displacement sensor.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A laser displacement sensor automatic calibration device, characterized in that: The invention comprises a horizontal base (1), on which a laser displacement sensor mounting seat (2), a motion platform (17) and a laser interferometer mounting seat (15) are sequentially connected along the length direction thereof; a laser displacement sensor (3) is mounted on the laser displacement sensor mounting seat (2); a laser interferometer (13) is connected to the laser interferometer mounting seat (15) via a laser interferometer adjustment frame (14); a motion platform (16) is slidably connected to the motion platform (17); a beam analyzer (8) is arranged on the motion platform (16); and a measured object mounting bracket (7) and a corner cube mounting plate (9) are respectively located on both sides of the beam analyzer (8); A standard object to be measured (5) and a half-reflecting half-mirror (6) are respectively attached to two opposite surfaces of the mounting bracket (7); the half-reflecting half-mirror (6) is opposite to the laser displacement sensor (3) and is used to receive a measuring light beam (4) of the laser displacement sensor (3) and reflect and irradiate the surface of the standard object to be measured (5) and transmit through the object mounting bracket (7) to irradiate the surface of the beam analyzer (8); a corner mirror (10) is provided on a side surface of the corner mirror mounting plate (9) opposite to the laser interferometer (13); an outgoing light beam (11) of the laser interferometer (13) is irradiated on the corner mirror (10) to form a return light beam (12) and return to the laser interferometer (13) to generate interference data; The measuring light beam (4) of the laser displacement sensor (3), the light output light beam (11) and the return light beam (12) of the laser interferometer (13) are all parallel to the sliding direction of the moving table (16), and the measuring light beam (4) of the laser displacement sensor (3) and the light output light beam (11) of the laser interferometer (13) are collinear; The object mounting bracket (7) is provided with a through hole and a 45-degree wedge-shaped groove, the standard object (5) is attached to the upper inner surface of the wedge-shaped groove, the semi-reflective semi-mirror (6) is attached to the lower inner surface of the wedge-shaped groove, the through hole axis direction of the object mounting bracket (7) is consistent with the direction of the measuring light beam (4), after the measuring light beam (4) is irradiated on the semi-reflective semi-mirror (6), a part of the light is reflected to the standard object (5) to achieve distance measurement, and the other part of the light passes through the through hole and is irradiated on the beam analyzer (8) to achieve spot shape measurement, and the height and width of the object mounting bracket (7) are adjusted so that the optical path of the light beam irradiated on the standard object (5) and the light beam irradiated on the beam analyzer (8) are consistent, thereby ensuring that the position of linear calibration and spot measurement is the same position of the measuring light beam (4); The laser interferometer adjustment frame (14) has at least an adjustment structure with three degrees of freedom: pitch, yaw and height. By adjusting the laser interferometer adjustment frame (14), the light beam (11) of the laser interferometer (13) and the measuring beam (4) of the laser displacement sensor (3) are made collinear.

2. The automatic calibration device for laser displacement sensor according to claim 1, characterized in that: The laser displacement sensor (3) controls the direction of the measuring light beam (4) by cooperating with the laser displacement sensor mounting seat (2).

3. A calibration method for an automatic calibration device for a laser displacement sensor according to any one of claims 1 to 2, characterized in that: The specific calibration process of this method is as follows: First, a laser displacement sensor (3) to be tested is mounted on a laser displacement sensor mounting base (2), and then a host computer (18) is connected to the laser displacement sensor (3), a beam analyzer (8), a laser interferometer (13) and a motion table (16); The upper computer (18) controls the motion table (16) to move so that the standard object to be measured (5) is located at the center of the range of the laser displacement sensor (3), and the readings of the laser displacement sensor (3) and the laser interferometer (13) are respectively set to 0; The upper computer (18) controls the motion table (16) to move so that the standard object to be measured (5) is located at the starting point of the range of the laser displacement sensor (3), and the step distance d and the motion speed v of the motion table (16) are set. The actual range of the laser displacement sensor (3) is taken as D. Then, in the scanning process, n=D / d positions are taken as sampling points in the full range of the laser displacement sensor (3); The upper computer (18) samples the laser displacement sensor (3), the beam analyzer (8) and the laser interferometer (13) at the starting point of the measuring range and stores the samples in the upper computer (18). After the sampling is completed, the moving table (16) is controlled to move a step distance d to the far end of the measuring range and sample again. The movement and sampling steps are repeated until the moving table (16) moves to the far end of the measuring range. After the sampling is completed, the displacement measurement deviation of the laser displacement sensor (3) and the laser interferometer (13) at each sampling point and the spot data of the beam analyzer (8) are obtained; The laser interferometer (13) is used to measure the displacement of the corner cube (10), and the beam analyzer (8) is used to measure the shape of the cross section of the measurement beam (4); the linearity curve of the laser displacement sensor (3) is obtained according to the displacement measurement deviation of all sampling points; the shape of the measurement beam (4) along the optical axis is obtained according to the spot data of all sampling points; and the linear deviation curve and the beam shape are measured more accurately by reducing the step distance d and increasing the number of sampling points n; After obtaining the measurement data of the laser displacement sensor (3) and the laser interferometer (13) at all sampling points, quantitatively fitting the change relationship between the measurement data of the laser displacement sensor (3) and the measurement data of the laser interferometer (13) through a polynomial or spline curve, and then generating a calibration curve through equal-interval sampling, and uploading it to the laser displacement sensor (3), so as to significantly improve the measurement accuracy of the laser displacement sensor (3); After obtaining the spot shape of the beam cross section at all sampling points, the position of the spot center in two perpendicular directions on the optical axis section is fitted by Gaussian function. With spot radius ,in ; Through Perform the least square linear fitting to obtain the deflection angle of the beam in the X direction; The least squares fitting is performed to obtain the deflection angle of the light beam in the Y direction; the focus position of the measurement light beam (4) is obtained by finding the sampling position corresponding to the minimum spot radius; and the measurement light beam (4) is calibrated and quickly adjusted according to the measured deflection angle and focus position.

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