Laser collimation measurement system and method for digitally compensating light drift angle

Abstract

The invention discloses a laser collimation measurement system and method for a digital compensation light drift angle, and belongs to the technical field of precision measurement, and the system comprises a laser output unit, a collimating lens, a light drift angle measurement unit, a straightness measurement unit, a two-dimensional angle measurement unit and a signal processing unit. The light drift angle measuring unit measures the light drift angle through a light retroreflector, a lens and a photoelectric detector, the straightness and two-dimensional angle measuring unit obtains original measuring signals through an optical splitter and the photoelectric detector, and the signal processing unit receives signals of all the photoelectric detectors. And calculating a real straightness error and a real angle error of the measured object, and performing digital compensation on a measurement error caused by a light drift angle. Through one-way optical path design, common-path compensation and a digital algorithm, the influence of the light drift angle on the measurement precision in long-distance measurement is effectively suppressed, and the method is suitable for high-precision geometric error measurement of large equipment such as a gantry machine tool.

Description

Technical Field

[0001] This application relates to the field of precision optical measurement, and in particular to a laser collimation measurement system and method for digitally compensating for light drift angle. Background Technology

[0002] Currently, in fields such as aerospace, rail transportation, and energy equipment, there is a need to process large workpieces exceeding 2 meters in size, such as aircraft frames, high-speed train heads, and wind turbine blade molds. The processing of these workpieces can only be achieved using gantry milling machines. Therefore, improving the machining accuracy of gantry milling machines is of paramount importance.

[0003] Lasers possess excellent linearity. In industry, lasers are often used as a benchmark for measuring parameters such as straightness / coaxiality, deflection, or pitch angle of large workpieces. However, strictly speaking, lasers are not perfectly linear; they exhibit a certain degree of drift. This drift can be categorized into three types based on the factors causing it: first, laser beam drift caused by the laser itself; second, mechanical displacement of the adjustment mechanism fixing the laser emitter, resulting in slow angular drift; and third, beam bending or jitter caused by uneven air refractive index or air disturbance. These three types of drift are unavoidable in practice, but because their degree is relatively slight, they are generally ignored in industrial measurements.

[0004] Furthermore, laser drift can be categorized into two types: angular drift and parallel drift. Parallel drift can be largely eliminated using a laser with a fiber optic output, and its impact on measurement error is relatively small in long-distance measurements. Angular drift, however, increases significantly with the measurement distance, leading to greater errors in straightness measurements. Therefore, in precision measurements, especially long-distance precision measurements, it is crucial to minimize the influence of angular laser drift on the measurement results.

[0005] Existing technologies, such as patent ZL 200410006321.9, use a cornerstone prism to reflect light back to a fixed end. While this can measure the drift angle, the optical path is twice the measurement distance. Over long distances, air disturbances exacerbate the problem, leading to decreased measurement and compensation accuracy. Another type of hardware compensation method (such as using a PZT-driven mirror) can dynamically correct the drift, but the system is complex, costly, and the compensation and measurement optical paths are not shared, resulting in poor compensation performance. Furthermore, some methods can only compensate for drift caused by the laser itself and cannot effectively address drift caused by air disturbances. Therefore, there is an urgent need for a measurement system and method that is simple in structure, low in cost, and can effectively compensate for light drift angles caused by various factors (especially air disturbances) over long distances. Summary of the Invention

[0006] The purpose of this application is to provide a laser collimation measurement system and method for digitally compensating for light drift angle. It adopts a single-path optical design to reduce the influence of air disturbance. Through a common-path optical model, it uses digital algorithms to accurately decouple and compensate for light drift angle, thereby achieving high-precision straightness and two-dimensional angle (pitch angle, yaw angle) measurement over long distances.

[0007] To achieve the above objectives, this application provides the following solution: In a first aspect, this application provides a laser collimation measurement system for digitally compensating for light drift angle, comprising: Laser output unit I, used to generate and output laser light; Collimating lens 201 is mounted on fixed measuring head II and is used to collimate the laser output by laser output unit I into measurement reference light L1; The light drift angle measurement unit III, mounted on the movable measuring head II', includes a light retroreflector 301, a first lens 302, and a first photodetector 303 arranged sequentially along the light propagation direction. The incident light from the light retroreflector 301 is parallel to the retroreflected light L2, and the incident light from the light retroreflector 301 is the measurement reference light L1. The first photodetector 303 is located on the focal plane of the first lens 302 and is used to measure the light drift angle. The straightness measurement unit IV includes a first beam splitter 401 and a second photodetector 402. The first beam splitter 401 is disposed in the optical path of the retroreflected light L2 and is used to split the retroreflected light L2 into two beams. One beam is focused by the first lens 302 and received by the first photodetector 303, and the other beam is received by the second photodetector 402, for measuring the original straightness signal. The two-dimensional angle measurement unit V includes a second beam splitter 501, a second lens 503, and a third photodetector 504 disposed on the fixed measuring head II, and a third beam splitter 502 disposed on the movable measuring head II'. The second beam splitter 501 is disposed in the optical path of the measurement reference light L1, and the third beam splitter 502 is disposed in front of the light retroreflector 301. The light reflected by the third beam splitter 502 is split by the second beam splitter 501, and one beam of light is focused by the second lens 503 onto the third photodetector 504 located on its focal plane for measuring the original two-dimensional angle signal. The signal processing unit is electrically connected to the first photodetector 303, the second photodetector 402 and the third photodetector 504 respectively, and is used to receive and process the signals from each photodetector.

[0008] Optionally, the laser output unit I includes a laser 101 and an optical fiber coupler 102, wherein the laser 101 is connected to the collimating lens 201 via an optical fiber through the optical fiber coupler 102.

[0009] Optionally, the light retroreflector 301 can be any one of a corner prism, a hollow corner prism, a right-angle prism, or a cat's eye reflection system.

[0010] Optionally, the first photodetector 303, the second photodetector 402, and the third photodetector 504 are any one of a quadrant detector (QD), a position-sensitive detector (PSD), a charge-coupled device (CCD), or a complementary metal-oxide-semiconductor (CMOS).

[0011] Optionally, the first beam splitter 401 is configured such that its transmitted light is received by the first photodetector 303 and its reflected light is received by the second photodetector 402; or, its reflected light is received by the first photodetector 303 and its transmitted light is received by the second photodetector 402.

[0012] Optionally, the laser 101 is a 633nm helium-neon laser.

[0013] Secondly, this application provides a laser collimation measurement method for digitally compensating for light drift angle, the method comprising: The laser output unit I generates a laser beam, which is collimated by the collimating lens 201 to form a measurement reference beam L1 that propagates along the X-axis. The measurement reference light L1, after passing through the second beam splitter 501 and the third beam splitter 502, is reflected back by the light retroreflector 301 to form the reflected light L2. The reflected light L2 is split into two beams by the first beam splitter 401. One beam is focused onto the first photodetector 303 by the first lens 302, and the other beam is directly incident onto the second photodetector 402. Meanwhile, the light reflected by the third beam splitter 502 is split by the second beam splitter 501, and one of the beams is focused onto the third photodetector 504 by the second lens 503. The signal processing unit acquires the change in the position of the light spot on the first photodetector 303, the second photodetector 402 and the third photodetector 504 respectively. The signal processing unit calculates the true pitch angle of the object under test based on the change in the position of the light spots of the first photodetector 303 and the third photodetector 504 using a common optical path model. and true sway angle and the ray drift angle around the Y-axis and the ray drift angle around the Z-axis .

[0014] Optionally, the true pitch angle True yaw angle , light drift angle and light drift angle The calculation formula is as follows: ; ; ; ; in, The focal length of the first lens 302 is... The focal length of the second lens 503. , These represent the changes in the position of the light spot in the Y and Z directions of the first photodetector 303, respectively. , These represent the changes in the position of the light spot in the Y and Z directions of the third photodetector 504, respectively.

[0015] Optionally, the signal processing unit is further configured to further adjust the amount of change in the spot position of the second photodetector 402 and the light drift angle based on these parameters. and light drift angle The true straightness error of the measured object in the Y and Z directions is calculated. .

[0016] Optionally, the true straightness error The calculation formula is as follows: ; ; in, This represents the straightness error of the measured object in the Y direction. This represents the straightness error of the measured object in the Z direction. The optical path length between the collimating lens 201 and the second photodetector 402; , These represent the changes in the position of the light spot in the Y and Z directions of the second photodetector 402, respectively. The angle of ray drift around the Y-axis. The angle of ray drift around the Z-axis is denoted as .

[0017] According to the specific embodiments provided in this application, this application has the following technical effects: This application provides a laser collimation measurement system and method for digitally compensating for light drift angle, which has the following significant advantages: High measurement accuracy: The use of a single-path optical path for straightness measurement effectively reduces the adverse effects of air disturbance on measurement accuracy over long distances.

[0018] Excellent compensation effect: The optical path for measuring the light drift angle is completely shared with the optical paths for measuring straightness and two-dimensional angle, which enables the digital compensation algorithm to accurately decouple and compensate for the light drift angle caused by all factors such as the laser itself and air disturbances.

[0019] The system is low in cost and simple in structure: by using digital compensation instead of complex hardware compensation mechanisms such as PZT, the system structure is simplified, reducing manufacturing costs and errors introduced by the system itself.

[0020] Easy installation: The system only requires one measuring head to be installed at the fixed end and one at the mobile end, without the need for an additional feedback platform, which reduces the complexity of installation and debugging.

[0021] Precise and consistent formulas: By clearly defining the coordinate system and positive and negative directions, the calculation formulas do not require manual judgment of positive and negative signs, which improves the automation and reliability of data processing. .Attached Figure Description To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of a laser collimation measurement system for digital compensation of light drift angle in Embodiment 1 of this application; Figure 2 This is a schematic diagram of the composition of the laser four-degree-of-freedom measurement system with automatic measurement of light drift angle in Embodiment 2 of this application; Figure 3 This is a schematic diagram of the composition of the laser four-degree-of-freedom measurement system with automatic measurement of light drift angle in Embodiment 3 of this application; Figure 4 This is a schematic diagram of the composition of the laser straightness measurement system with automatic compensation for light drift angle in Embodiment 4 of this application. Detailed Implementation

[0024] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] In the XYZ spatial coordinate system of this invention, when an object moves along any one of the X, Y, and Z directions, there is a "six-degree-of-freedom geometric error". This "six-degree-of-freedom geometric error" includes three linear errors related to translation along the X, Y, and Z directions. , , And the three angular errors of rotation around the X, Y, and Z coordinate axes. , , .

[0026] In subsequent embodiments, the emission direction of laser beam L1 is defined as the X-axis, the vertically upward direction as the Z-axis, and the Y-axis. This coordinate system is set as the reference coordinate system. At this point, the six-degree-of-freedom geometric error of the linear guide rail translating along the X-axis— For positioning error, , For straightness error, , , In order, they are roll angle, pitch angle, and yaw angle.

[0027] After converting the incident light rays onto the first photodetector 303 back to the reference coordinate system along with the first photodetector 303, the first photodetector 303 is located in the YOZ plane, with its two directions being the Y-axis and Z-axis, respectively, and the positive directions of the Y-axis and Z-axis being positive. Similarly, the second photodetector 402 and the third photodetector 504 are placed, and their Y-axis and Z-axis directions are defined.

[0028] After converting the incident light rays incident on the first photodetector 303 back to the reference coordinate system along with the first photodetector 303, when the incident light rotates around the Y-axis... Then, when the incident light is projected onto the Z-axis and points in the positive direction of the Z-axis, the angle is positive; when the incident light rotates around the Z-axis... Then, when the incident light projects onto the Y-axis and points in the positive direction of the Z-axis, the angle is considered positive. Similarly, the sign of the angle measured by the second photodetector 402 and the third photodetector 504 is defined.

[0029] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1 Figure 1 This is a schematic diagram of a laser collimation measurement system for digitally compensating for light drift angle according to an embodiment of this application. See also... Figure 1 The system includes: a laser output unit I, a collimating lens 201, a light drift angle measurement unit III, a straightness measurement unit IV, a two-dimensional angle measurement unit V, and a signal processing unit; Among them, the laser output unit I is used to generate and output laser; the laser output unit I specifically includes: laser 101 and fiber coupler 102, and the fiber coupler 102 is connected to the collimating lens 201 through an optical fiber.

[0031] The collimating lens 201 is mounted on the fixed measuring head II and is used to collimate the laser output by the laser output unit I into the measurement reference light L1.

[0032] The light drift angle measurement unit III, mounted on the movable measuring head II', includes a light retroreflector 301, a first lens 302, and a first photodetector 303 arranged sequentially along the light propagation direction. The incident light from the light retroreflector 301 is parallel to the reflected light L2, and the incident light from the light retroreflector 301 is the measurement reference light L1. The first photodetector 303 is located on the focal plane of the first lens 302 and is used to measure the light drift angle. The first lens 302 and the first photodetector 303 are located on the reflected light L2, with the first photodetector 303 positioned on the focal plane of the first lens 302, i.e., they are spaced apart. The first photodetector 303 is connected to the signal processing unit to directly measure the magnitude of the light drift angle caused by various factors.

[0033] The straightness measurement unit IV includes a first beam splitter 401 and a second photodetector 402. The first beam splitter 401 is disposed in the optical path of the retroreflected light L2 and is used to split the retroreflected light L2 into two beams. One beam is focused by the first lens 302 and received by the first photodetector 303, and the other beam is received by the second photodetector 402, for measuring the original straightness signal. Figure 1 The diagram shows the transmitted portion being received by the first photodetector 303, and the reflected portion L3 being received by the second photodetector 402. In practice, the first lens 302 and the first photodetector 303 can also be positioned on the reflected light L3, and the second photodetector 402 on the transmitted light, achieving the same effect. The second photodetector 402 is connected to the signal processing unit, which, combined with the measurement signal from the first photodetector 303, calculates the two-dimensional straightness error.

[0034] The two-dimensional angle measurement unit V includes a second beam splitter 501, a second lens 503, and a third photodetector 504 disposed on the fixed measuring head II, and a third beam splitter 502 disposed on the movable measuring head II'. The second beam splitter 501 is disposed in the optical path of the measurement reference light L1, and the third beam splitter 502 is disposed in front of the light retroreflector 301. The light reflected by the third beam splitter 502 is split by the second beam splitter 501, and one beam of light is focused by the second lens 503 onto the third photodetector 504 located on its focal plane, for measuring the original two-dimensional angle signal, namely the two-dimensional angle error and the pitch and yaw angle errors.

[0035] The signal processing unit is electrically connected to the first photodetector 303, the second photodetector 402 and the third photodetector 504 respectively, and is used to receive and process the signals from each photodetector.

[0036] The first photodetector 303, the second photodetector 402 and the third photodetector 504 mentioned above are any one of a quadrant detector (QD), a position-sensitive detector (PSD), a charge-coupled device (CCD) or a complementary metal-oxide-semiconductor (CMOS).

[0037] The above measurement system, except for the laser output unit I, is mechanically connected to form two parts: a fixed measuring head II and a movable measuring head II'.

[0038] To obtain a stable collimated beam within the measurement range, this embodiment uses a 633nm helium-neon laser as the laser source. A focusing lens or microscope objective is used as the fiber coupler 102, paired with an optical fiber with a mode field diameter of 4.0~4.5μm. Through a collimating lens 201 with a focal length of 15~20mm, a collimated beam with a diameter of 3.02~3.58mm, a full divergence angle of 0.015~0.013°, and a beam waist position of 5.5~8m can be obtained. Within the range of 0-20 meters, the spot diameter varies from 3mm to 7.1mm, meeting the measurement requirements.

[0039] By selecting photodetectors with a resolution of 0.5~1μm as the first photodetector 303 and the third photodetector 504, and lenses with a focal length of 200~500mm as the first lens 302 and the second lens 503, a resolution of about 0.2"~1" for light drift angle and two-dimensional angle measurement can be achieved.

[0040] A lens group consisting of a convex lens with a focal length of 150-175mm and a concave lens with a focal length of -20 to -30mm is selected to replace the single first lens 302 and second lens 503. When the distance from the positive lens to the focal plane of the combined lens is between 150mm and 300mm, the combined focal length is about 200mm to 1000mm. Increasing the focal length improves the measurement resolution, while shortening the distance from the positive lens to the first photodetector 303 and the third photodetector 504, thereby reducing the size of the measuring heads II and II', increasing portability, and reducing the installation difficulty.

[0041] Example 2 Another implementation of the active measuring head II' is, for example Figure 2 As shown, compared to Figure 1 In this embodiment 2, the optical path removes the light retroreflector 301 and consists only of the first lens 302 and the first photodetector 303 to form the light drift angle measurement unit III'. Figure 1 The advantage of the optical path is that the light L2 is reflected back by the light returner 301, and after adding a beam splitter to split a beam of light back to the fixed measuring head II, the interferometric length measurement module can be integrated into the fixed measuring head II to achieve 5-degree-of-freedom measurement. Figure 2 The advantage of the optical path is that the movable measuring head II' reduces one component, thus reducing cost and weight, and simplifying installation.

[0042] Example 3 Because the beam splitter 401 only serves to split the light, the transmitted and reflected light it separates has no substantial difference in terms of light drift and two-dimensional straightness measurement. This can be utilized... Figure 1 , Figure 2 In this implementation method, transmitted light is used to measure light drift, and reflected light is used to measure two-dimensional straightness. Alternatively, it can utilize... Figure 3 , Figure 4 In this implementation method, transmitted light is used to measure two-dimensional straightness, and reflected light is used to measure light drift.

[0043] Example 4 This application provides a laser collimation measurement method for digitally compensating for light drift angle. This method is applied to the laser collimation measurement system for digitally compensating for light drift angle in Example 1. The method includes: Step 101: The laser output unit I generates laser light, which is collimated by the collimating lens 201 to form a measurement reference light L1 that propagates along the X-axis. Step 102: The measurement reference light L1, after passing through the second beam splitter 501 and the third beam splitter 502, is reflected back by the light retroreflector 301 to form the reflected light L2; Step 103: The reflected light L2 is split into two beams by the first beam splitter 401. One beam is focused onto the first photodetector 303 by the first lens 302, and the other beam is directly incident onto the second photodetector 402. Step 104: At the same time, the light reflected by the third beam splitter 502 is split by the second beam splitter 501, and one of the beams is focused onto the third photodetector 504 by the second lens 503. Step 105: The signal processing unit acquires the change in the position of the light spot on the first photodetector 303, the second photodetector 402 and the third photodetector 504 respectively; Step 106: The signal processing unit calculates the true pitch angle of the object under test based on the change in the position of the light spots of the first photodetector 303 and the third photodetector 504 using a common optical path model. and true sway angle and the ray drift angle around the Y-axis and the ray drift angle around the Z-axis .

[0044] Specifically, the true pitch angle True yaw angle , light drift angle and light drift angle The calculation formula is as follows: ; ; ; ; in, The focal length of the first lens 302 is... The focal length of the second lens 503. , These represent the changes in the position of the light spot in the Y and Z directions of the first photodetector 303, respectively. , These represent the changes in the position of the light spot in the Y and Z directions of the third photodetector 504, respectively.

[0045] The signal processing unit is further configured to further analyze the change in the position of the light spot of the second photodetector 402 and the light drift angle. and light drift angle The true straightness error of the measured object in the Y and Z directions is calculated. .

[0046] The true straightness error The calculation formula is as follows: ; ; in, This represents the straightness error of the measured object in the Y direction. This represents the straightness error of the measured object in the Z direction. The optical path length between the collimating lens 201 and the second photodetector 402; , These represent the changes in the position of the light spot in the Y and Z directions of the second photodetector 402, respectively. The angle of ray drift around the Y-axis. The angle of ray drift around the Z-axis is denoted as .

[0047] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0048] This document uses specific examples to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. Furthermore, those skilled in the art will recognize that, based on the ideas of this application, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A laser collimation measurement system for digitally compensating for light drift angle, characterized in that, The digitally compensated laser collimation measurement system for the light drift angle includes: Laser output unit (I) is used to generate and output laser light; A collimating lens (201) is mounted on a fixed measuring head (II) and is used to collimate the laser output by the laser output unit (I) into a measurement reference light (L1). A light drift angle measurement unit (III) is mounted on a movable measuring head (II') and includes a light retroreflector (301), a first lens (302), and a first photodetector (303) arranged sequentially along the light propagation direction. The incident light of the light retroreflector (301) is parallel to the retroreflected light (L2), and the incident light of the light retroreflector (301) is the measurement reference light (L1). The first photodetector (303) is located on the focal plane of the first lens (302) and is used to measure the light drift angle. The straightness measurement unit (IV) includes a first beam splitter (401) and a second photodetector (402). The first beam splitter (401) is disposed in the optical path of the reflected light (L2) and is used to split the reflected light (L2) into two beams. One beam is focused by the first lens (302) and received by the first photodetector (303), and the other beam is received by the second photodetector (402) for measuring the original straightness signal. The two-dimensional angle measurement unit (V) includes a second beam splitter (501), a second lens (503), and a third photodetector (504) disposed on the fixed measuring head (II), and a third beam splitter (502) disposed on the movable measuring head (II'). The second beam splitter (501) is disposed in the optical path of the measurement reference light (L1), and the third beam splitter (502) is disposed in front of the light retroreflector (301). The light reflected by the third beam splitter (502) is split by the second beam splitter (501), and one beam of light is focused by the second lens (503) onto the third photodetector (504) located on its focal plane for measuring the original two-dimensional angle signal. The signal processing unit is electrically connected to the first photodetector (303), the second photodetector (402) and the third photodetector (504) respectively, and is used to receive and process the signals from each photodetector.

2. The laser collimation measurement system for digital compensation of light drift angle according to claim 1, characterized in that, The laser output unit (I) includes a laser (101) and an optical fiber coupler (102). The laser (101) is connected to the collimating lens (201) via the optical fiber through the optical fiber coupler (102).

3. The laser collimation measurement system for digital compensation of light drift angle according to claim 1, characterized in that, The light retroreflector (301) can be any one of a corner prism, a hollow corner prism, a right-angle prism, or a cat's eye reflection system.

4. The laser collimation measurement system for digital compensation of light drift angle according to claim 1, characterized in that, The first photodetector (303), the second photodetector (402), and the third photodetector (504) are any one of a quadrant detector (QD), a position-sensitive detector (PSD), a charge-coupled device (CCD), or a complementary metal-oxide-semiconductor (CMOS).

5. The laser collimation measurement system for digital compensation of light drift angle according to claim 1, characterized in that, The first beam splitter (401) is configured such that its transmitted light is received by the first photodetector (303) and its reflected light is received by the second photodetector (402); or, its reflected light is received by the first photodetector (303) and its transmitted light is received by the second photodetector (402).

6. The laser collimation measurement system for digital compensation of light drift angle according to claim 2, characterized in that, The laser (101) is a 633nm helium-neon laser.

7. A laser collimation measurement method for digitally compensated light drift angle based on the laser collimation measurement system for digitally compensated light drift angle according to any one of claims 1-6, characterized in that, The laser collimation measurement method for digitally compensated light drift angle includes: The laser output unit (I) generates a laser beam, which is collimated by the collimating lens (201) to form a measurement reference beam (L1) that propagates along the X-axis. The measurement reference light (L1) is reflected back by the light retroreflector (301) after passing through the second beam splitter (501) and the third beam splitter (502) to form the reflected light (L2). The reflected light (L2) is split into two beams by the first beam splitter (401). One beam is focused onto the first photodetector (303) by the first lens (302), and the other beam is directly incident onto the second photodetector (402). Meanwhile, the light reflected by the third beam splitter (502) is split by the second beam splitter (501), and one of the beams is focused onto the third photodetector (504) by the second lens (503); The signal processing unit acquires the change in the position of the light spot on the first photodetector (303), the second photodetector (402), and the third photodetector (504), respectively; The signal processing unit calculates the true pitch angle of the object under test based on the change in the position of the light spots of the first photodetector (303) and the third photodetector (504) using a common optical path model. and true sway angle and the ray drift angle around the Y-axis and the ray drift angle around the Z-axis .

8. The laser collimation measurement method for digitally compensated light drift angle according to claim 7, characterized in that, The true pitch angle True yaw angle , light drift angle and light drift angle The calculation formula is as follows: ； ； ； ； in, The focal length of the first lens (302) is... The focal length of the second lens (503) is... , These represent the changes in the position of the light spot in the Y and Z directions of the first photodetector (303), respectively. , These represent the changes in the position of the light spot in the Y and Z directions of the third photodetector (504), respectively.

9. The laser collimation measurement method for digitally compensated light drift angle according to claim 7, characterized in that, The signal processing unit is further configured to further adjust the signal based on the change in the position of the light spot of the second photodetector (402) and the light drift angle. and light drift angle The true straightness error of the measured object in the Y and Z directions is calculated. ).

10. The laser collimation measurement method for digitally compensated light drift angle according to claim 9, characterized in that, The true straightness error ( The calculation formula for ) is as follows: ； ； in, This represents the straightness error of the measured object in the Y direction. This represents the straightness error of the measured object in the Z direction. The optical path length between the collimating lens (201) and the second photodetector (402); , These represent the changes in the position of the light spot in the Y and Z directions of the second photodetector (402), respectively. The angle of ray drift around the Y-axis. The angle of ray drift around the Z-axis is denoted as .

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