A kind of line-spectrum confocal sensor calibrating device and calibrating method

Abstract

The application belongs to the technical field of photoelectric detection, and discloses a kind of line spectrum confocal sensor's calibrating device and calibrating method.The device includes integrated standard, displacement generating device, displacement measuring device and driving device, driving device drives displacement generating device to generate vertical displacement, displacement measuring device measures the displacement generated in vertical direction, when displacement generating device occurs displacement in vertical direction, integrated standard is moved in vertical direction;Line spectrum confocal sensor measures the profile displacement of integrated standard in vertical direction, and compares the measured result with the result measured by displacement measuring device, to obtain the extreme position error of line spectrum confocal sensor in vertical measurement plane in transverse and vertical direction, and establishes error model.Through the application, the problems that existing line spectrum confocal sensor is difficult to calibrate and cannot be calibrated are solved.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, and more specifically, relates to a calibration device and calibration method for a line spectrum confocal sensor. Background Technology

[0002] Currently, line spectral confocal sensors are non-contact line profile sensors based on spectral dispersion localization. Their measurement accuracy can reach sub-micron or even nanometer levels. They are insensitive to surface tilt, texture, and surface reflection characteristics, and have strong resistance to stray light. They are important 3D measurement sensors in manufacturing fields such as electronics, new energy, and semiconductors, providing strong support for material surface analysis, quality control, and production process optimization.

[0003] The verification and calibration of line spectral confocal sensors are of great significance for their accuracy analysis and assurance. Currently, the verification of line spectral confocal sensors generally uses length measuring instruments, which are inconvenient and difficult to operate, and cannot verify the lateral positioning error of the sensor. Therefore, there is a need for a set of convenient and easy-to-use dedicated instruments and devices for the effective verification and calibration of this type of sensor. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a calibration device and calibration method for a line spectrum confocal sensor, which solves the problems that existing line spectrum confocal sensors are difficult or impossible to calibrate.

[0005] To achieve the above objectives, according to one aspect of the present invention, a calibration apparatus for a line spectrum confocal sensor is provided. The apparatus includes an integrated standard, a displacement generating device, a displacement measuring device, and a driving device, wherein:

[0006] The driving device is connected to the displacement generating device and is used to drive the displacement generating device to generate vertical displacement. The displacement measuring device is used to measure the vertical displacement generated by the displacement generating device. The integrated standard is set above the displacement generating device. When the displacement generating device generates vertical displacement, it drives the integrated standard to generate vertical displacement. The line spectrum confocal sensor to be tested is used to measure the contour displacement of the integrated standard in the vertical direction and compare the measurement result with the measurement result of the displacement measuring device to obtain the limit positioning error of the line spectrum confocal sensor to be tested in the horizontal and vertical directions.

[0007] The top surface of the integrated standard includes an inclined plane and a horizontal plane. The inclined plane is used to detect the lateral positioning limit error of the spectral sensor to be calibrated, and the horizontal plane is used to detect the vertical positioning limit error of the spectral sensor to be calibrated. Further preferably, the displacement measuring device includes a fixed unit and a moving unit. The fixed unit is fixed in position, and the moving unit is fixedly connected to the displacement generating device. The displacement generating device drives the moving unit to move vertically. The fixed unit captures the movement signal of the moving unit and measures the vertical displacement of the moving unit.

[0008] More preferably, the moving unit includes a displacement stage, a second reflector, and a beam splitter. The displacement stage is disposed at the bottom of the displacement measuring device for contacting the displacement generating device. The second reflector is disposed on one side of the beam splitter in the vertical direction. The horizontal movement of the displacement generating device causes the displacement stage to displace in the vertical direction, that is, the displacement generating device is displaced.

[0009] More preferably, the fixed unit includes a laser, a photodetector, and a first reflector. The laser and the first reflector are respectively disposed on both sides of the beam splitter in the horizontal direction. The laser emits a laser beam, which is split into two beams by the beam splitter: a reference beam and a measurement beam. The reference beam and the measurement beam are reflected by the first reflector and the second reflector, respectively, and then transmitted through the beam splitter. The transmitted light enters the photodetector to form interference fringes. The up-and-down movement of the moving unit changes the position of the interference fringes.

[0010] More preferably, the moving unit further includes a third reflector, which is disposed below the beam splitter prism, and the light transmitted from the beam splitter prism is reflected by the third reflector into the photodetector.

[0011] More preferably, the displacement generating device includes a lead screw, a slider, a conversion block, and a guide rail. The lead screw is connected to the driving device and is used to convert the rotation of the output shaft of the driving device into the horizontal movement of the slider on the guide rail. The conversion block is disposed above the slider and fixed to it. When the slider moves horizontally, it drives the conversion block to move horizontally. The conversion block is used to convert the horizontal movement of the slider into the vertical displacement of the moving unit, that is, the displacement generated by the displacement generating device.

[0012] More preferably, the conversion block is an inclined block with an inclined surface on its upper surface. When the conversion block moves horizontally, the moving unit contacts the conversion block, causing the moving unit to displace in the vertical direction.

[0013] According to another aspect of the present invention, a method for calibrating the above-described line spectrum confocal sensor calibration device is provided, characterized in that the method comprises the following steps:

[0014] The driving device described in S1 drives the displacement generating device to move, and the displacement measuring device measures the displacement of the moving unit in the displacement measuring device in the vertical direction and uses the displacement as the standard displacement.

[0015] S2 The confocal spectral sensor to be tested is aligned with the horizontal plane of the integrated standard. The vertical displacement of points at different positions on the horizontal plane is measured. The measured displacement is compared with the standard displacement in step S1 to obtain the vertical error distribution and limit positioning error of the confocal spectral sensor to be tested.

[0016] The S3 line-to-be-tested confocal spectral sensor measures the inclined plane of the integrated standard, and measures the actual vertical height at different positions at the same vertical height on the inclined plane, thereby obtaining the lateral positioning error distribution and limit positioning error of the line-to-be-tested confocal spectral sensor in the vertical direction.

[0017] Based on the vertical and lateral positioning error distributions of the confocal spectral sensor to be tested obtained from S2 and S3, S4 uses a fitting method to obtain the sensor's error model.

[0018] More preferably, in step S2, the vertical limit positioning error is calculated according to the following formula:

[0019]

[0020] Among them, y j标 It is the standard displacement obtained by displacement measuring device. is the actual measured value of the confocal spectral sensor to be tested, i is the number of the point at different positions in the scanning line direction on the horizontal plane, and j is the number of the position at different heights within the vertical height range.

[0021] More preferably, in step S3, the lateral direction limit positioning error is calculated according to the following formula:

[0022] Δx=max{|Δx j |}

[0023]

[0024] Where, Δx j The maximum lateral positioning error at vertical height j, y 测 j max, y 测 jmin represents the maximum and minimum values ​​measured by the line spectral confocal sensor at the corresponding vertical height j, α is the tilt angle of the standard inclined plane, j is the position number at different heights within the vertical height range, and i is the position number at different locations along the scanning line on the inclined plane.

[0025] In summary, the technical solutions conceived by this invention have the following beneficial effects compared with the prior art:

[0026] 1. The integrated standard in the calibration device for the line spectrum confocal sensor provided by the present invention includes two horizontal planes and an inclined plane. Different planes are used to calibrate the positioning error of the line spectrum confocal sensor in different directions. Calibration in two directions can be achieved at one time, and the calibration method is simple and convenient.

[0027] 2. The conversion block in the displacement generating device of the present invention converts horizontal motion into vertical displacement. By adjusting the inclination of the conversion block, the mechanical structure becomes more precise, the resolution of vertical motion is improved, and the functional conversion is achieved through a simple structure, making it highly operable.

[0028] 3. The displacement measuring device provided by this invention uses optical principles to measure the vertical displacement generated by the displacement generating device. The measurement method is perfect, the measurement principle is simple, and it has extremely high accuracy.

[0029] 4. The calibration method provided by this invention uses a driving device to induce a minute displacement of the plane of an integrated standard, which can be used to detect the vertical positioning error of each point on the sensor along the scan line. Considering the lateral positioning error present at each point along the sensor's line length, the inclined surface of the integrated standard reflects this lateral positioning error in the vertical direction, thus demonstrating the sensor's lateral positioning error. Simultaneously, a fitting method can be used to obtain vertical and lateral positioning error models of each point along the sensor's scan line length within the vertical range, forming a calibration and verification method for the sensor. The standard values ​​of this calibration device are directly traceable to a length reference, possessing stable, high-precision, fast, and convenient calibration capabilities. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of a calibration device for a line spectrum confocal sensor constructed according to a preferred embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the specific structure of the calibration device for a line spectrum confocal sensor constructed according to a preferred embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of a structure constructed according to a preferred embodiment of the present invention to replace the standard;

[0033] Figure 4 This is a partial schematic diagram of a standard displacement generating device constructed according to a preferred embodiment of the present invention;

[0034] Figure 5 This is a schematic diagram of a standard displacement measurement system constructed according to a preferred embodiment of the present invention;

[0035] Figure 6 This is a schematic diagram of the planar error distribution obtained by constructing the ideal contour displacement and the measured contour displacement according to a preferred embodiment of the present invention.

[0036] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0037] 1-Base, 2-Motor mount, 3-Drive device, 4-Reducer, 5-Right bearing mount, 6-Lead screw, 7-Support seat, 8-Support plate, 9-Laser, 10-Photodetector, 11-Displacement stage, 12-Third reflector, 13-Beam splitter prism support frame, 14-Beam splitter prism, 15-Second reflector, 16-Second reflector mount, 17-Integrated standard, 18-Column, 19-First reflector, 20-First reflector support mount, 21-Conversion block, 22-Slider, 23-Guide rail, 24-Left bearing mount. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0039] This invention provides a calibration device and method for a line spectrum confocal sensor, such as... Figure 1 As shown, the line spectrum confocal sensor calibration device consists of three parts: a standard plane and a standard inclined plane integrated standard 17, a standard displacement generating device 110, and a standard displacement measuring device 120.

[0040] The integrated standard device 17, consisting of a standard plane and a connected standard inclined plane, possesses high plane accuracy and surface quality, respectively. The integrated standard device is connected to the displacement stage 11 of the standard displacement generator, outputting the standard displacement to the sensor to be verified and calibrated.

[0041] The standard displacement generating device 110 includes a base 1, a guide rail 23, a slider 22, a conversion block 21, a displacement stage 11, a column 18, a lead screw 6, and an integrated standard device 17. The conversion block 22 is fixed on the slider 22, and the slider 22 and the guide rail 23 form an x-axis linear motion pair. The guide rail 23 is fixed to the base 1. The lead screw 6 passes through the center of the slider 22 and is fixed to both the right bearing seat 5 and the left bearing seat 24. Furthermore, the upper surface of the conversion block 21 is inclined. The displacement stage 11 and the guide rail 23 fixed on the column 18 form a z-axis linear motion pair, and the column 18 is connected to the base 1. This structure can convert x-axis displacement into z-axis displacement and achieve high-precision microstepping control. In this embodiment, the drive device 3 uses a stepper motor, which is mounted on the motor base 2, and the output shaft of the drive device 3 is connected to the reducer 4.

[0042] The standard displacement measuring device has the following structure: a laser 9 and a beam splitter 14 split the light emitted by the laser 9 into two paths. One path is directed to a first reflecting mirror 19 located on a column 18 as a reference path, and the other path is directed to a second reflecting mirror 15 on a displacement stage 11 as a measurement path. The two returning beams pass through a third reflecting mirror 12 and are directed to a photodetector 10, which is located on the axis of the beam emitted from the third reflecting mirror 12. The laser 9 is mounted on a support plate 8, which is mounted on a support base 7. The second reflecting mirror 15 is mounted on a second reflecting mirror base 16, and the first reflecting mirror 19 is mounted on a first reflecting mirror base 20. The beam splitter 14 and the third reflecting mirror 12 are mounted on a beam splitter support frame 13, which is mounted on the support plate 8. The light emitted from the laser 9 passes through the beam splitter 14. One beam is directed to the first reflector 19 mounted on the support plate 8, and the other beam is directed to the second reflector 15 mounted on the displacement stage. The two returning beams meet at the first reflector 12 after passing through the beam splitter 14, causing interference. The interference signal is received by the photodetector 10 and input into the subsequent processing circuit to obtain the change in the optical path difference between the two interference beams, i.e., the displacement measurement of the displacement stage. This yields the real-time standard displacement information of the integrated standard instrument 17 for the standard plane and standard inclined plane.

[0043] An integrated standard device 17, a standard displacement generator 110, and a standard displacement measuring device 120 constitute a line-spectrum confocal sensor calibration device. The standard displacement generator 110 generates a high-resolution, wide-range displacement, which, combined with the real-time, high-precision measurement of this displacement by the standard displacement measuring device 120, forms a standard displacement. This standard displacement is input to the integrated standard device 17, generating standard planar and inclined plane translational motions. The standard translational motions are output as standards to the line-spectrum confocal sensor. The sensor's measured results are compared with the standard motions, and, based on corresponding algorithms and modeling, the sensor is calibrated and verified. The standard values ​​of this calibration device are directly traceable to a length reference, possessing stable, high-precision, fast, and convenient calibration capabilities.

[0044] The displacement usually expressed is the displacement of a point. The contour displacement mentioned in this invention refers to the overall displacement of a contour line within a horizontal or inclined plane, also known as contour displacement. Specifically, the light emitted by the line spectrum confocal sensor forms a vertical light plane. This vertical plane intersects with the integrated standard to form a straight line, called the contour line. When the integrated standard moves vertically, it intersects with the light plane emitted by the line spectrum sensor and the integrated standard in the vertical direction to form multiple contour lines. Ideally, the contour line is a horizontal straight line. Figure 6 The left side shows several ideal contour lines, i.e., standard contour lines. In this invention, the line spectrum confocal sensor measures the contour displacement generated by the translational motion of the horizontal and inclined planes of the integrated standard within the vertical measurement range. This contour displacement is defined as the standard contour displacement, such as... Figure 6 As shown, the contour displacement produces a series of horizontal straight lines arranged at standard intervals in the vertical plane; however, due to sensor error, what is actually measured are curves with errors.

[0045] The specific working process is as follows: The computer sends a displacement signal to drive the drive device 3 to rotate, thereby driving the lead screw 6 to rotate. Through the action of the screw pair, the lead screw 6 nut moves in the corresponding direction. Driven by the lead screw and guided by the guide rail 23, the conversion block 22 realizes the movement along the x-direction. The conversion block 22 converts the x-direction movement of the guide rail into the z-direction linear movement of the displacement stage 11, thereby driving the z-direction standard displacement movement of the integrated standard device 17 of the standard plane and standard inclined plane.

[0046] In summary, the standard displacement generating device 110 achieves high resolution through electronic subdivision of the stepper motor and mechanical subdivision of the wedge block, driving the integrated standard to perform large-range, high-resolution translational motion. The standard displacement measuring device 120 is based on the measurement principle of a laser interferometer, obtaining the standard value of the large-range, high-resolution translational motion of the standard in real time. The standard displacement is input to the sensor, and the comparison and relationship modeling with the actual sensor measurements enable sensor verification and calibration. This verification device can be used to verify the accuracy characteristics of a line-spectral confocal sensor, including the linearity and accuracy of vertical height measurement at various points along the line length, and the uncertainty in the lateral positioning of the sensor measurement points.

[0047] When specifically applied to sensor verification and calibration, a computer sends a drive displacement signal to drive a standard displacement generator to push the integrated standard device 17 (standard plane and standard inclined plane) to a designated position. The standard displacement measuring device 120 measures the standard displacement output, compares it with the measured value of the line spectrum confocal displacement sensor 100, and obtains the verification result and an error calibration model through fitting. When testing the axial accuracy of the line spectrum confocal displacement sensor, the line is aligned with the standard plane portion; when testing the lateral inaccuracy of the line spectrum confocal displacement sensor, it is aligned with the inclined plane portion of the standard.

[0048] The specific evaluation process is as follows:

[0049] When calibrating the accuracy of vertical measurements using a line-fed spectral confocal displacement sensor, the vertical limit positioning error is calculated according to the following formula:

[0050]

[0051] The maximum value Δy of the positioning error of each point in each line length direction within the entire height measurement range is obtained, which reflects the limit error of the sensor in the entire range, and the accuracy characteristics of the sensor can be analyzed and judged accordingly.

[0052] Based on the positioning errors of each line length direction point within the entire height measurement range, an error model in the entire vertical plane is constructed, which can be used as a sensor calibration model.

[0053] When detecting inaccuracies in the lateral measurement point positioning of the line spectrum confocal sensor, the measurement line of the line spectrum confocal sensor 100 is located at the standard inclined plane. The measurement value of the line spectrum confocal sensor 100 is read, and the measurement results of each point along the line length direction of the line spectrum confocal sensor are compared to obtain the straightness of the focal line at each vertical height and the flatness of the focal plane at the entire height, thereby obtaining the calibration result.

[0054] The maximum lateral positioning error at height j is

[0055]

[0056] Among them, y 测 j max, y 测 j `min` represents the maximum and minimum values ​​measured by the line-spectral confocal sensor at the corresponding vertical height `j`, where `α` is the inclination angle of the standard inclined plane, `j` is the position number at different heights within the vertical height range, and `i` is the position number at different locations along the scanning line on the inclined plane. The maximum value of the lateral positioning error within the entire height range is the lateral positioning limit error, Δx = max{|Δx| ... j |}.

[0057] The positioning error of each point along the line length direction within the entire height measurement range is obtained by a series of standard profile displacements generated by the sensor-integrated standard device under test.

[0058]

[0059] Therefore, i can be used as the x-axis and j*h as the y-axis. For the output, surface fitting is used to construct an error model covering the entire vertical plane. Here, h represents the standard profile displacement step. This error model can be used for error compensation in profile measurement by the sensor throughout its entire vertical measurement range.

[0060] Similarly, a lateral positioning error model for each point in the contour measurement of the sensor can be obtained throughout the entire vertical measurement range.

[0061] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A calibration device for a line spectrum confocal sensor, characterized in that, The device includes an integrated standard (17), a displacement generator (110), a displacement measuring device (120), and a drive device (3), wherein: The driving device (3) is connected to the displacement generating device (110) and is used to drive the displacement generating device (110) to generate vertical displacement. The displacement measuring device (120) is used to measure the vertical displacement generated by the displacement generating device (110). The integrated standard (17) is set above the displacement generating device (110). When the displacement generating device (110) generates vertical displacement, it drives the integrated standard (17) to generate vertical displacement. The line spectrum confocal sensor to be tested is used to measure the contour displacement of the integrated standard (17) in the vertical direction and compare the measurement result with the measurement result of the displacement measuring device (120) to obtain the limit positioning error of the line spectrum confocal sensor to be tested in the horizontal and vertical directions. The top surface of the integrated standard (17) includes an inclined plane and a horizontal plane. The inclined plane is used to detect the lateral positioning limit error of the spectral sensor to be tested, and the horizontal plane is used to detect the vertical positioning limit error of the spectral sensor to be tested. The displacement measuring device (120) includes a fixed unit and a moving unit. The fixed unit is fixed in position, and the moving unit is fixedly connected to the displacement generating device (110). The displacement generating device (110) drives the moving unit to move in the vertical direction. The fixed unit captures the movement signal of the moving unit and measures the displacement of the moving unit in the vertical direction. The displacement generating device (110) includes a lead screw (6), a slider (22), a conversion block (21), and a guide rail (23). The lead screw (6) is connected to the drive device (3) and is used to convert the rotation of the output shaft of the drive device (3) into the horizontal movement of the slider (22) on the guide rail (23). The conversion block (21) is set above the slider (22) and fixed to it. When the slider (22) moves horizontally, it drives the conversion block (21) to move horizontally. The conversion block (21) is used to convert the horizontal movement of the slider (22) into the vertical displacement of the moving unit, that is, the displacement generated by the displacement generating device. The conversion block (21) is an inclined block with an inclined surface on its upper surface. When the conversion block (21) moves horizontally, the moving unit contacts the conversion block (21), causing the moving unit to be displaced in the vertical direction.

2. The calibration device for a line spectrum confocal sensor as described in claim 1, characterized in that, The moving unit includes a displacement stage (11), a second reflector (15), and a beam splitter (14). The displacement stage (11) is located at the bottom of the displacement measuring device (120) and is used to contact the displacement generating device (110). The second reflector (15) is located on one side of the beam splitter (14) in the vertical direction. The horizontal movement of the displacement generating device (110) causes the displacement stage (11) to generate displacement in the vertical direction.

3. The calibration device for a line spectrum confocal sensor as described in claim 2, characterized in that, The fixed unit includes a laser (9), a photodetector (10), and a first reflector (19). The laser (9) and the first reflector (19) are respectively disposed on both sides of the beam splitter (14) in the horizontal direction. The laser (9) emits laser light, which is split into two beams by the beam splitter (14). One beam is a reference beam and the other is a measurement beam. The reference beam and the measurement beam are reflected by the first reflector (19) and the second reflector (15) respectively, and then enter the beam splitter (14) for transmission. The transmitted light enters the photodetector (10) to form interference fringes. The up and down movement of the moving unit changes the position of the interference fringes.

4. The calibration device for a line spectrum confocal sensor as described in claim 3, characterized in that, The moving unit also includes a third reflector (12), which is disposed below the beam splitter (14). Light transmitted from the beam splitter (14) is reflected by the third reflector (12) into the photodetector (10).

5. A method for calibrating a line-spectral confocal sensor using the calibration apparatus according to any one of claims 1-4, characterized in that, The method includes the following steps: The driving device described in S1 drives the displacement generating device to move, and the displacement measuring device measures the displacement of the moving unit in the displacement measuring device in the vertical direction and uses the displacement as the standard displacement. S2 The confocal spectral sensor to be tested is aligned with the horizontal plane of the integrated standard. The vertical displacement of points at different positions on the horizontal plane is measured. The measured displacement is compared with the standard displacement in step S1 to obtain the vertical error distribution and limit positioning error of the confocal spectral sensor to be tested. The S3 line spectrum confocal sensor under test measures the inclined plane of the integrated standard, and measures the actual vertical height at different positions at the same vertical height on the inclined plane, thereby obtaining the lateral positioning error distribution and limit positioning error of the line spectrum confocal sensor under test. Based on the vertical and lateral positioning error distributions of the confocal spectral sensor to be tested obtained from S2 and S3, S4 fits and obtains the sensor's error model.

6. The method as described in claim 5, characterized in that, In step S2, the vertical limit positioning error is calculated according to the following formula: in, It is the standard displacement obtained by measuring the vertical height position j using a displacement measuring device. The confocal spectral sensor to be tested is located at the corresponding vertical height j and The actual measured value of the scan line position on the inclined plane, j is the position number of different heights within the vertical height range, and i is the position number of different points in the direction of the scan line on the horizontal plane.

7. The method as described in claim 5, characterized in that, In step S3, the lateral direction limit positioning error is calculated according to the following formula: in, It is the lateral positioning error at the vertical height j. , These represent the maximum and minimum values ​​measured by the line-spectral confocal sensor at the corresponding vertical height j, respectively. is the standard inclined plane angle, and j is the position number at different heights within the vertical height range.

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