Nonlinear error compensation system and method for contact pin contourgraph sensor

Abstract

The invention provides a non-linear error compensation system and method for a stylus contourgraph sensor, and the system comprises a laser light source, an adjustable diaphragm, a beam splitter prism, a focusing lens and a lever which are sequentially arranged along the transmission direction of a light path. An incident light beam emitted by the laser light source is reflected by the lever to form a reflected light beam; the reflected light beam sequentially passes through the focusing lens and the beam splitter prism and then enters the imaging lens; wherein the lever can deflect in the Z direction; the imaging lens, the narrow-band optical filter and the position sensitive detector are sequentially arranged along the transmission direction of the optical path; the position sensitive detector is used for acquiring the position of the center of the reflection light spot in the Z direction before and after the lever deflects in the Z direction; and the control unit is in signal connection with the position sensitive detector. The position change of the reflected light spot in the Z direction is detected, and the angle change of the lever is calculated, so that nonlinear error measurement and dynamic compensation in the X direction and the Z direction are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical detection, and in particular relates to a nonlinear error compensation system and method for a stylus profilometer sensor. Background Art

[0002] The stylus surface topography measurement system plays a vital role in production and scientific research due to its high precision, high resolution, stability, reliability and good dynamic characteristics. It is widely used in precision manufacturing, materials science and biomedicine to detect and analyze the microstructure of various surfaces. However, the lever structure in the stylus sensor will introduce nonlinear errors, especially in large-scale contour measurement, this error will increase significantly, seriously affecting the accuracy of the measurement results. Therefore, effective compensation for nonlinear errors is the key to improving measurement accuracy.

[0003] Traditional nonlinear error compensation methods mainly include methods based on the zero-position tracking principle and polynomial fitting methods. The method based on the zero-position tracking principle uses a high-precision vertical displacement mechanism to keep the sensor lever in the zero-position state, thereby eliminating the nonlinear error caused by the rotation of the lever. Although this method can achieve high-precision compensation in theory, it relies on a high-precision displacement mechanism, and the measurement process is complicated, which affects the measurement efficiency. The polynomial fitting method performs polynomial fitting on the nonlinear error and gives a compensation value during measurement to correct the error. Although this method can improve the measurement accuracy to a certain extent, its compensation effect is limited by the convergence accuracy of the fitting algorithm, and it is difficult to adjust and feedback the error in real time.

[0004] In order to overcome the limitations of traditional methods, a new compensation method is needed that can acquire and compensate for nonlinear errors in real time. The optical lever method is a simple and efficient measurement technology with high sensitivity, strong environmental adaptability, and can perform accurate measurements in a variety of environments. By integrating the optical lever principle into the stylus surface topography measurement system, the nonlinear errors in the X and Z directions can be obtained by real-time monitoring of the changes in the lever angle. This method can not only provide high-precision error measurement, but also achieve rapid response and real-time compensation, thereby significantly improving the overall performance of the system. The present invention combines the optical lever method with advanced data processing technology to design a system for real-time feedback and compensation of nonlinear errors. The system can monitor the angle changes of the lever in real time, and achieve efficient and accurate error compensation by accurately calculating and feeding back errors, providing a new solution for stylus surface topography measurement. Summary of the invention

[0005] The object of the present invention is to provide a nonlinear error compensation system and method for a stylus profilometer sensor, aiming to solve the problems of insufficient accuracy and slow response speed of traditional compensation methods in large-range profilometry.

[0006] To achieve the above object, the present invention proposes a stylus profilometer sensor nonlinear error compensation system and method, including a laser light source, an adjustable aperture, a beam splitter, a focusing lens, a stylus profilometer sensor, an imaging lens, a narrow-band filter, a position sensitive detector, and a computer control and processing system. Its structure is shown in FIG. Figure 1 As shown, where:

[0007] The laser light source, adjustable diaphragm, beam splitter prism and focusing lens are coaxially arranged.

[0008] The laser light source 1, the adjustable aperture 2, the beam splitter prism 3, the focusing lens 4 and the lever 5 are sequentially arranged along the transmission direction of the optical path; the incident light beam emitted by the laser light source 1 is reflected by the lever 5 to form a reflected light beam; the reflected light beam sequentially passes through the focusing lens 4 and the beam splitter prism 3 and enters the imaging lens 6; wherein the lever 5 can be deflected along the Z direction;

[0009] The imaging lens 6, the narrowband filter 7 and the position sensitive detector 8 are sequentially arranged along the transmission direction of the optical path; the position sensitive detector 8 is used to obtain the position of the center of the reflected light spot in the Z direction before and after the lever 5 is deflected in the Z direction;

[0010] And a control unit, which is connected to the position sensitive detector 8 signal.

[0011] The laser light source 1 is a highly stable He-Ne laser or diode laser, which has the characteristics of high brightness, high stability and long life, and is used to generate a high-brightness and high-stability light beam.

[0012] The light beam emitted by the laser light source passes through the adjustable aperture, the beam splitter prism and the focusing lens in sequence, and is finally focused on the lever of the stylus profiler sensor.

[0013] The adjustable aperture 2 is located on the image focal plane of the focusing lens, and its diameter can be adjusted to meet the needs of different light fluxes during the measurement process, while being able to suppress stray light beams and improve the uniformity of the light source and the measurement accuracy.

[0014] The beam splitting prism 3 has a beam splitting ratio of 50:50 and is used to evenly split the incident light beam into two parts, one part is used to illuminate the lever, and the other part is used to reflect the path of the light beam.

[0015] The focusing lens can accurately focus the light beam emitted by the laser light source onto the lever of the stylus profiler sensor, ensuring the concentration and focusing quality of the light beam.

[0016] After the reflected light beam is reflected from the lever, it passes through the beam splitter prism. The PSD detects the position of the reflected light spot in real time and feeds the data back to the computing processing system.

[0017] The imaging lens can clearly image the reflected light beam on the PSD, ensuring that the position change of the light spot can be accurately detected.

[0018] The optical filter is used to filter out stray light and only allow light beams of specific wavelengths to pass through, further improving the signal-to-noise ratio and measurement accuracy of the system.

[0019] PSD can accurately detect the position of the reflected light spot and feed the data back to the computer processing system in real time. The computer processing system calculates the angle change of the lever based on the position change output by PSD. Through the established relationship model between angle and position change, the system can obtain the nonlinear error in the X and Z directions in real time. These error data will be fed back to the processing system in real time for dynamic compensation, thereby improving the measurement accuracy and reliability.

[0020] The control unit comprises:

[0021] The angle change calculation unit, the displacement change calculation unit and the compensated coordinate calculation unit are signal-connected in sequence.

[0022] The computer control and processing system is used to control the operation of the entire system, including: adjusting and controlling the output power and stability of the laser light source; receiving data fed back by the PSD; calculating the angle change of the stylus profiler sensor lever; acquiring the nonlinear errors in the X and Z directions in real time and performing dynamic compensation; and data processing and storage to ensure the accuracy and reliability of the measurement results.

[0023] Through the above components and functions, the present invention provides a simple and efficient stylus profilometer sensor nonlinear error compensation system and method, which is suitable for fields such as precision manufacturing, material science and biomedicine.

[0024] The angle variation calculation unit is:

[0025]

[0026] The displacement variation calculation unit is:

[0027] ΔX=l2 sin(Δθ)+l1[cos(Δθ)-1]

[0028] ΔZ=l2[1-cos(Δθ)]+l1 sin(Δθ)

[0029] The coordinate calculation unit after compensation is:

[0030]

[0031] Wherein, Δθ-positive rotation angle of the lever along the Z direction;

[0032] X - X coordinate of the stylus before the lever 5 is turned;

[0033] Y - Y coordinate of the stylus before the lever 5 is turned;

[0034] l2- stylus length; l1- distance from the stylus fixed end to the lever fulcrum;

[0035] f1-focal length of focusing lens, Z3-vertical displacement of lever;

[0036] f2-focal length of imaging lens, d-distance from imaging focus to PSD, Z1-position of the center of the light spot on PSD.

[0037] A method for compensating a nonlinear error of a stylus profilometer sensor comprises the following steps:

[0038] Step 1. Initialization:

[0039] Start the laser light source 1 and ensure that it is stable; then adjust the size of the adjustable aperture 2 to control the diameter of the light beam;

[0040] Then, the beam splitter prism 3 is calibrated; at the same time, the focusing lens 4 is adjusted to ensure that the incident light beam emitted from the laser light source 1 is focused on the lever 5 of the stylus profiler sensor before and after the lever 5 is deflected by Δθ, and the reflected light beam is imaged on the position sensitive detector 8;

[0041] Step 2: Light path preparation:

[0042] The laser light source 1 generates a stable laser beam, which is finally focused on the lever 5 of the stylus profiler sensor via the adjustable aperture 2, the beam splitter prism 3 and the focusing lens 4;

[0043] The reflected light beam of the lever passes through the beam splitter prism 3 again, and the light beam converges after passing through the imaging lens 6, and reaches the position sensitive detector 8 after filtering out the stray light through the narrow band filter 7;

[0044] Step 3: Measurement error;

[0045] Step 4, the position sensitive detector 8 outputs a signal to the control unit, and the control unit calculates the nonlinear errors in the X direction and the Z direction;

[0046] Step 5: Error compensation:

[0047] The control unit adjusts the system measurement results according to the calculated nonlinear errors ΔX and ΔZ to perform dynamic compensation.

[0048] Compared with the prior art, the advantages of the present invention are:

[0049] The system structure of the invention is simple and easy to integrate. The position of the center of the reflected light spot in the Z direction is detected in real time by PSD, and the angle change of the lever is calculated, thereby realizing nonlinear error measurement and dynamic compensation in the X and Z directions, and solving the technical problems of insufficient accuracy and slow response speed of the existing compensation method in large-range contour measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 Schematic diagram of the error compensation system.

[0051] Figure 2 Schematic diagram for calculating the nonlinear error of the stylus surface topography measurement system.

[0052] Figure 3 Schematic diagram of the measurement method based on optical lever.

[0053] Figure 4 Flow chart of the error compensation method.

[0054] Among them, 1-laser light source, 2-adjustable aperture, 3-beam splitter prism, 4-focusing lens, 5-lever, 6-imaging lens, 7-narrow band filter, 8-position sensitive detector, 9-computer control and processing system. DETAILED DESCRIPTION

[0055] The nonlinear error compensation system and method of the stylus profilometer sensor of the present invention will be described in more detail below in conjunction with a schematic diagram, wherein a preferred embodiment of the present invention is shown, and it should be understood that those skilled in the art may modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as being broadly known to those skilled in the art and not as a limitation of the present invention.

[0056] Figure 1 It is a schematic diagram of the error compensation system of the present invention, including a laser light source 1, an adjustable aperture 2, a beam splitter prism 3, a focusing lens 4, a lever 5 of a stylus profilometer sensor, an imaging lens 6, a narrow-band filter 7, a position sensitive detector 8, and a computer control and processing system 9. The position sensitive detector 8 is a PSD.

[0057] The light beam emitted by the laser light source 1 passes through the adjustable aperture 2, the beam splitter prism 3 and the focusing lens 4 in sequence, and is finally focused on the lever 5 of the stylus profilometer sensor.

[0058] After being reflected from the lever, the reflected light beam passes through the beam splitter prism 3, and then passes through the imaging lens 6 and the narrow-band filter 7 to filter out stray light, and finally forms an image on the position sensitive detector PSD.

[0059] Specifically, (1) when the lever 5 is in a horizontal position along the X direction, the formation process of the optical path G1 and the optical path G2 is as follows:

[0060] (1) The lever 5 is kept in a horizontal state, and the formation process of the optical path G1 and the optical path G2 is as follows:

[0061] The light beam emitted by the laser light source 1 passes through the adjustable aperture 2, the beam splitter prism 3 and the focusing lens 4 in sequence, and is finally focused on the lever 5 at the dotted line position, thereby forming an optical path G1.

[0062] After the reflected light beam is reflected from the lever at the dotted line position, it is split into two parts by the beam splitter prism 3. One part of the light beam continues to return along the original path, while the other part of the light beam passes through the imaging lens 6 and the narrow-band filter 7 to filter out stray light, and finally forms an image on the position sensitive detector PSD in the form of a reflected light spot, thus forming an optical path G2.

[0063] (2) When the lever 5 rotates by an angle Δθ, the formation process of the optical path G1 and the optical path G3 is as follows:

[0064] The light beam emitted by the laser light source 1 passes through the adjustable aperture 2, the beam splitter prism 3 and the focusing lens 4 in sequence, and is finally focused on the deflected lever 5, thereby forming an optical path G1.

[0065] The rotation of the lever 5 is due to the slight angle change that occurs naturally when the stylus sweeps across the measured surface. The high-precision bearing and mechanical inertia ensure that the lever remains stable after the rotation.

[0066] After the reflected light beam is reflected from the deflected lever, the stray light is filtered out by the imaging lens 6 and the narrow-band filter 7, and finally the image is formed on the position sensitive detector PSD in the form of a reflected light spot, thereby forming an optical path G3. At this time, the angle between the optical path G1 and the optical path G3 is 2Δθ.

[0067] The PSD can accurately detect the position of the reflected light spot and feed back the data to the computer control and processing system 9 (i.e., the control unit) in real time. The computer control and processing system calculates the angle change of the lever according to the position Z1 output by the PSD through formula 6.

[0068] Through the relationship model between angle and position change (i.e., formulas 1-2) established in the computer control and processing system 9, the computer control and processing system 9 can obtain the nonlinear errors in the X direction and the Z direction in real time according to formula 6, and perform dynamic compensation according to formula 3. These error data will be fed back to the processing system in real time for dynamic compensation, thereby improving the measurement accuracy and reliability.

[0069] From the above, the computer control and processing system 9 integrates formulas 1 to 3 and formula 6.

[0070] The laser light source 1, the adjustable aperture 2, the beam splitter prism and the focusing lens 4 are coaxially arranged.

[0071] The laser light source is a high-stability He-Ne laser or diode laser, which has the characteristics of high brightness, high stability and long life, and is used to generate a high-brightness and high-stability light beam.

[0072] The adjustable aperture 2 is located on the image focal plane of the focusing lens 4, and its diameter can be adjusted to meet the needs of different light fluxes during the measurement process, while being able to suppress stray light beams and improve the uniformity of the light source and the measurement accuracy.

[0073] The splitting ratio of the beam splitting prism 3 is 50:50.

[0074] The focusing lens can accurately focus the light beam emitted by the laser light source onto the lever of the stylus profiler sensor, ensuring the concentration and focus quality of the light beam.

[0075] Computer control and processing systems are used to control the operation of the entire system, including:

[0076] Adjust and control the output power and stability of laser light sources;

[0077] Receive data fed back by PSD;

[0078] Calculate the angle change of the stylus profilometer sensor lever;

[0079] Acquire the nonlinear errors in the X and Z directions in real time and perform dynamic compensation;

[0080] Data processing and storage ensure the accuracy and reliability of measurement results.

[0081] Figure 2 This is a schematic diagram for calculating the nonlinear error of the stylus surface topography measurement system. l2 is the stylus length; l1 is the distance from the stylus fixed end to the lever fulcrum. The lever and stylus are fixed at 90 degrees. The coordinate system XOZ is established with the lever fulcrum as the origin.

[0082] OA represents the lever before deflection; AP represents the stylus before deflection;

[0083] OA′ represents the lever after deflection, and A′P′ represents the stylus after deflection;

[0084] A and A′ both represent the fixed ends of the stylus, and P and P′ represent the free ends of the stylus;

[0085] The blue dotted lines are auxiliary lines, which are parallel to OA and AP respectively. The intersection point of one auxiliary line with OA is B, and the intersection point with the other auxiliary line is C.

[0086] As shown in the figure, when the lever rotates in the positive direction of the Z direction by an angle Δθ, the actual position of the free end of the stylus changes from point P to point P′.

[0087] The displacement of the stylus along the X direction can be expressed as l2 sin(Δθ).

[0088] Due to the rotation of the lever, the displacement of the lever in the Z direction will also produce a component in the X direction of the stylus, which can be expressed as l1[cos(Δθ)-1].

[0089] Therefore, the total X-direction measurement error can be expressed as:

[0090] ΔX=l2 sin(Δθ)+l1[cos(Δθ)-1] (1)

[0091] The change in displacement of the stylus in the Z direction due to the rotation of the lever can be expressed as:

[0092] ΔZ=l2[1-cos(Δθ)]+l1 sin(Δθ) (2)

[0093] The derivation process of formula (1) is as follows:

[0094] P′C=l2 sin(Δθ)

[0095] AB=l1-l1 cos(Δθ)

[0096] ΔX=P′C-AB=l2 sin(Δθ)+l1[cos(Δθ)-1]

[0097] The derivation process of formula (2) is as follows:

[0098] AP=l2

[0099] A′B=l1 sin(Δθ)

[0100] A′C=l2 cos(Δθ)

[0101] ΔZ=AP+A′BA′C=l2+l1 sin(Δθ)-l2 cos(Δθ)

[0102] The compensated contour coordinates can be expressed as:

[0103]

[0104] Therefore, by calculating the nonlinear errors in the X and Z directions, the measured coordinates (X, Z) can be compensated to obtain the actual coordinates (X', Z').

[0105] The measurement coordinates (X, Z) refer to the coordinates of the stylus before the lever 5 rotates by an angle Δθ, and are measured by the stylus sensor and the x-direction sensing unit of the profilometer structure.

[0106] Figure 3This is a schematic diagram of the measurement method based on the optical lever. The lever rotation angle is calculated by detecting the position change of the reflected light spot through PSD, thereby obtaining the nonlinear error in the X and Z directions.

[0107] As shown in the figure, when the lever rotates slightly, the following geometric relationship is satisfied:

[0108]

[0109] Among them, f1 is the focal length of the focusing lens, Z2 is the vertical offset of the light beam along the Z direction during the propagation process of the beam splitter prism and the imaging lens, and Z3 is the vertical displacement of the lever.

[0110] From the similarity relationship we can get:

[0111]

[0112] Among them, f2 is the focal length of the imaging lens, d is the distance from the imaging focus to the PSD, and Z1 is the position of the center of the light spot on the PSD.

[0113] Combining formulas (4) and (5), we can get that the angle change Δθ satisfies:

[0114]

[0115] Substituting equation (6) into equations (1) and (2) and merging them into equation (3), we can obtain (X', Z').

[0116] The derivation process of formula (6) is as follows:

[0117]

[0118] -2Z3 2 +2f1Z3-Z2l1=0

[0119]

[0120] Considering the small deflection:

[0121]

[0122] Substituting the first equation into formula (4), we can get:

[0123]

[0124] Figure 4 Flow chart of the error compensation method of the present invention. Specifically comprising the following steps:

[0125] Step 1: Initialize the system.

[0126] In the process of measuring errors and compensating errors, the system is first initialized.

[0127] Start the laser light source and ensure it is stable;

[0128] The size of the aperture is then adjusted to effectively control the diameter of the beam.

[0129] Next, calibrate the beam splitter to ensure it can achieve a 50:50 beam splitting ratio.

[0130] At the same time, the focusing lens is adjusted to ensure that the light beam emitted from the light source can be accurately focused on the lever 5 of the stylus profilometer sensor before and after the lever 5 is deflected by Δθ, and the reflected light beam can be clearly imaged on the PSD.

[0131] On this basis, the stylus profilometer sensor is initialized to facilitate subsequent data collection.

[0132] In addition, the imaging lens and narrow-band filters are calibrated to optimize the imaging quality.

[0133] Finally, the computer control and processing system is started to begin receiving and processing the position data from the sensor.

[0134] Step 2: Prepare the optical path.

[0135] The laser light source generates a stable laser beam, which is finally focused onto the lever of the stylus profiler sensor via an adjustable aperture, a beam splitter and a focusing lens.

[0136] Step 3: Error measurement.

[0137] When the lever 5 is in a horizontal position along the X direction, the reflected light beam of the lever passes through the beam splitter prism again, and part of the light beam returns along the original path and does not participate in the error measurement. The other part of the light beam converges after passing through the imaging lens 6, and reaches the PSD after filtering out stray light through the narrow-band filter.

[0138] After the lever 5 rotates by an angle Δθ, the reflected light beam of the lever passes through the beam splitter prism again, and the light beam converges after passing through the imaging lens 6, and reaches the PSD after the stray light is filtered out by the narrow-band filter.

[0139] Step 4: Data collection and processing.

[0140] The PSD detects the position change of the reflected light spot and sends the position data to the computer control and processing system. These data reflect the tiny displacement of the stylus profilometer sensor lever. By analyzing these data, the computer control and processing system can calculate the angular change Δθ of the lever.

[0141] Then, according to the angle change Δθ, the nonlinear errors ΔX and ΔZ in the X direction and the Z direction are calculated by formula (1) and formula (2).

[0142] Step 5: Error compensation.

[0143] The computer control and processing system adjusts the system measurement results according to the calculated nonlinear errors ΔX and ΔZ, and performs dynamic compensation, that is, compensating the calculated nonlinear errors to the actual measurement results.

[0144] Step 6: Output the results.

[0145] The computer control and processing system outputs the final measurement results and stores and records the measurement data for subsequent analysis.

[0146] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any technician in the relevant technical field, without departing from the scope of the technical solution of the present invention, makes any form of equivalent replacement or modification to the technical solution and technical content disclosed in the present invention, which does not depart from the content of the technical solution of the present invention and still falls within the protection scope of the present invention.

Claims

1. A nonlinear error compensation system for a stylus profilometer sensor, characterized in that: include: A laser light source (1), an adjustable aperture (2), a beam splitter prism (3), a focusing lens (4) and a lever (5) are arranged in sequence along the transmission direction of the optical path; an incident light beam emitted by the laser light source (1) is reflected by the lever (5) to form a reflected light beam; the reflected light beam passes through the focusing lens (4) and the beam splitter prism (3) in sequence and then enters an imaging lens (6); wherein the lever (5) can be deflected along the Z direction; The imaging lens (6), the narrowband filter (7) and the position sensitive detector (8) are arranged in sequence along the transmission direction of the light path; the position sensitive detector (8) is used to obtain the position of the center of the reflected light spot in the Z direction before and after the lever (5) is deflected in the Z direction; and a control unit connected to the position sensitive detector (8) by signal.

2. The nonlinear error compensation system of the stylus profilometer sensor according to claim 1, characterized in that: The laser light source (1) is a highly stable He-Ne laser or a diode laser.

3. The nonlinear error compensation system of the stylus profilometer sensor according to claim 1, characterized in that: The adjustable diaphragm (2) is located on the image focal plane of the focusing lens (4).

4. The nonlinear error compensation system for a stylus profilometer sensor according to claim 1, characterized in that: The splitting ratio of the beam splitting prism (3) is 50:

50.

5. The nonlinear error compensation system for a stylus profilometer sensor according to claim 1, characterized in that: The control unit comprises: The angle change calculation unit, the displacement change calculation unit and the compensated coordinate calculation unit are signal-connected in sequence.

6. The nonlinear error compensation system for a stylus profilometer sensor according to claim 5, characterized in that: The angle variation calculation unit is: The displacement variation calculation unit is: ΔX=l2 sin(Δθ)+l1[cos(Δθ)-1] ΔZ=l2[1-cos(Δθ)]+l1 sin(Δθ) The coordinate calculation unit after compensation is: Wherein, Δθ-positive rotation angle of the lever along the Z direction; X - X coordinate of the stylus before the lever 5 is turned; Y - Y coordinate of the stylus before the lever 5 is turned; l2- stylus length; l1- distance from the stylus fixed end to the lever fulcrum; f1-focal length of focusing lens, Z3-vertical displacement of lever; f2-focal length of imaging lens, d-distance from imaging focus to PSD, Z1-position of the center of the light spot on PSD.

7. A nonlinear error compensation method for a stylus profilometer sensor, based on the nonlinear error compensation system for a stylus profilometer sensor according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1. Initialization: Start the laser light source (1) and ensure that it is stable; Then the size of the adjustable diaphragm (2) is adjusted to control the diameter of the light beam; Then, the beam splitter prism (3) is calibrated; at the same time, the focusing lens (4) is adjusted to ensure that the incident light beam emitted from the laser light source (1) is focused on the lever (5) of the stylus profiler sensor before and after the lever (5) is deflected by Δθ, and the reflected light beam is imaged on the position sensitive detector (8); Step 2: Light path preparation: The laser light source (1) generates a stable laser beam, which is finally focused on the lever (5) of the stylus profiler sensor via an adjustable aperture (2), a beam splitter (3) and a focusing lens (4); The reflected light beam from the lever passes through the beam splitter prism (3) again, and the light beam converges after passing through the imaging lens 6, and reaches the position sensitive detector (8) after passing through the narrow band filter (7) to filter out stray light; Step 3: Measurement error; Step 4, the position sensitive detector (8) outputs a signal to the control unit, and the control unit calculates the nonlinear errors in the X direction and the Z direction; Step 5: Error compensation: The control unit adjusts the system measurement results according to the calculated nonlinear errors ΔX and ΔZ to perform dynamic compensation.

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