阅读说明：本技术 一种直线导轨六自由度几何误差测量装置及方法 (Linear guide rail six-degree-of-freedom geometric error measuring device and method ) 是由 刘晓军 刁宽 姚贞建 杨文军 刘云峰 汪依思 于 2020-05-22 设计创作，主要内容包括：本发明属于精密加工装备精密测量相关技术领域,其公开了一种直线导轨六自由度几何误差测量装置及方法,其包括固定单元及测量单元,固定单元包括分光棱镜、1/4波片、反射镜,其用于将激光束分裂成三束准直平行光；第四四象限探测器用于接收干涉条纹,继而实现直线导轨位置误差的测量；测量单元包括第一四象限探测器、第二四象限探测器及第三四象限探测器,第一四象限探测器、第二四象限探测器及第三四象限探测器分别用于接收三束准直平行光；对光斑的移动分量进行分离以得到直线导轨的水平直线度误差、垂直直线度误差、滚转角度误差、俯仰角度误差和偏摆角度误差。本发明提高了集成度及测量精度,适用性较强。(The invention belongs to the related technical field of precision measurement of precision machining equipment, and discloses a device and a method for measuring six-degree-of-freedom geometric error of a linear guide rail, wherein the device comprises a fixing unit and a measuring unit, the fixing unit comprises a beam splitter prism, an 1/4 wave plate and a reflector, and the beam splitter prism is used for splitting a laser beam into three beams of collimated parallel light; the fourth four-quadrant detector is used for receiving the interference fringes and further realizing the measurement of the position error of the linear guide rail; the measuring unit comprises a first four-quadrant detector, a second four-quadrant detector and a third four-quadrant detector, and the first four-quadrant detector, the second four-quadrant detector and the third four-quadrant detector are respectively used for receiving three beams of collimated parallel light; and separating the moving components of the light spots to obtain the horizontal linearity error, the vertical linearity error, the rolling angle error, the pitching angle error and the deflection angle error of the linear guide rail. The invention improves the integration level and the measurement precision and has stronger applicability.)

1. The utility model provides a six degree of freedom geometric error measuring device of linear guide which characterized in that:

the measuring device comprises a fixing unit and a measuring unit, wherein the fixing unit comprises a fourth four-quadrant detector (17), the fourth four-quadrant detector (17) is used for receiving interference fringes and then measuring the position error of the linear guide rail according to the interference fringes;

the measuring unit comprises a first four-quadrant detector (14), a second four-quadrant detector (15) and a third four-quadrant detector (16), and the first four-quadrant detector (14), the second four-quadrant detector (15) and the third four-quadrant detector (16) are respectively used for receiving three beams of collimated parallel light from the fixing unit; different errors can cause the relative displacement of the light spots on the detector of the measuring unit, and the horizontal straightness error, the vertical straightness error, the rolling angle error, the pitching angle error and the deflection angle error of the linear guide rail can be obtained by effectively separating the moving components of the light spots.

2. The linear guide six-degree-of-freedom geometric error measuring device according to claim 1, wherein: the fixed unit further comprises a first common beam splitter prism (4), a second common beam splitter prism (5), a first reflecting mirror (10) and a second reflecting mirror (11), wherein the first common beam splitter prism (4) is used for splitting the received laser beam into two beams, transmitted light is marked as P light, refracted light is marked as S light, the first reflecting mirror (10) is used for reflecting the S light to change the light path to form a beam of collimated parallel light, and the collimated parallel light enters the second four-quadrant detector (15); the second common beam splitter prism (5) is used for splitting the P light into two beams again, wherein the transmitted light is marked as P 'light, and the refracted light is marked as S' light; the second reflecting mirror (11) is used for changing the optical path of the S' light to form a bundle of collimated parallel light, and then the collimated parallel light is incident to the first four-quadrant detector (14).

3. The linear guide six-degree-of-freedom geometric error measuring device according to claim 2, wherein: the fixing unit further comprises a polarization beam splitter prism (6), a first wave plate (7), a second wave plate (8), a convex lens (9), a third reflector (12) and a fourth four-quadrant detector (17), wherein the first wave plate (7) and the second wave plate (8) are 1/4 wave plates, and the third reflector (12), the first wave plate (7), the polarization beam splitter prism (6), the convex lens (9) and the fourth four-quadrant detector (17) are arranged in the same vertical direction from top to bottom; the first common beam splitter prism (4), the second common beam splitter prism (5), the polarization beam splitter prism (6) and the second wave plate (8) are sequentially arranged along a first horizontal direction.

4. The linear guide six-degree-of-freedom geometric error measuring device according to claim 3, wherein: the polarization beam splitter prism (6) is used for splitting the P 'light into two beams again, wherein the transmitted light is represented as P' light, the refracted light is represented as S 'light, the S' light passes through the first wave plate (7), is reflected by the third reflector (12) and returns back, and passes through the first wave plate (7), the polarization beam splitter prism (6) and the convex lens (9) again to be incident on the fourth four-quadrant detector (17) as reference light.

5. The linear guide six-degree-of-freedom geometric error measuring device according to claim 4, wherein: the measuring unit further comprises a semi-transmission and semi-reflection mirror (13), and the semi-transmission and semi-reflection mirror (13) is positioned between the second wave plate (8) and the third four-quadrant detector (16); p' light is transmitted to the semi-transmission semi-reflection mirror (13) after passing through the second wave plate (8), one beam of reflected laser is reflected in the original path under the action of the semi-transmission semi-reflection mirror (13), the light passes through the second wave plate (8) and the polarization beam splitter prism (6) again and then is used as measuring light to finally enter the fourth four-quadrant detector (17), reference light and the measuring light are converged on the fourth four-quadrant detector (17) to form interference fringes, and the light transmitted by the semi-transmission semi-reflection mirror (13) enters the third four-quadrant detector (16).

6. The linear guide six-degree-of-freedom geometric error measuring apparatus according to any one of claims 1 to 5, wherein: the measuring device further comprises a frequency stabilization helium-neon laser (1), a single mode fiber (2) and a collimator (3), wherein two ends of the single mode fiber (2) back to back are respectively connected with the frequency stabilization helium-neon laser (1) and the collimator (3).

7. The linear guide six-degree-of-freedom geometric error measuring device according to claim 6, wherein: the helium neon laser is used for emitting laser beams, the laser beams are transmitted to the collimator (3) through the single mode fiber (2), the collimator (3) is used for collimating and amplifying the laser beams, and the collimated and amplified laser beams enter the fixing unit.

8. A method for measuring six-degree-of-freedom geometric error of a linear guide rail is characterized by comprising the following steps: firstly, providing a six-degree-of-freedom geometric error measuring device of a linear guide rail as defined in any one of claims 1 to 7, and installing the fixed unit on a fixed plane of a numerical control machine tool while installing the measuring unit on a movable slide block of the linear guide rail of the numerical control machine tool; then, after the light path of the measuring device is adjusted, the numerical control machine tool is started, and a four-quadrant detector is used for collecting position data of a group of light spots at intervals of a preset distance; and then, obtaining error information of the partition of the linear guide rail according to the position of the light spot in each preset distance.

9. The linear guide six-degree-of-freedom geometric error measurement method according to claim 8, characterized in that: the calculation formula of the position error is:

ΔL＝L_m-L_r

in the formula, L_mThe measured displacement is obtained; l is_rTheoretical displacement;n is the number of changes in the interference fringes;the non-integral multiple variable quantity of the interference fringe; λ is the laser wavelength.

10. The linear guide six-degree-of-freedom geometric error measurement method according to claim 8, characterized in that: the calculation formulas of the horizontal straightness error, the vertical straightness error, the rolling angle error, the pitching angle error and the deflection angle error are respectively as follows:

in the formula I₁And l₂The distance of detector QD1 and detector QD2 from the central axis of rotation, respectively;andthe vertical components of detector QD1 and detector QD2, respectively; l₃The distance of the detector QD3 from the axis of rotation,the relative movement distance of the light spot in the vertical direction of the detector is obtained; h is^QD1、h^QD2、h^QD3The relative movement distances of the light spot in the horizontal direction of the detector QD1, the detector QD2 and the detector QD3 are respectively.

Technical Field

The invention belongs to the technical field related to precision measurement of precision machining equipment, and particularly relates to a device and a method for measuring six-degree-of-freedom geometric error of a linear guide rail.

Background

The linear guide rail is widely applied to a precise numerical control machine tool and a precise measuring instrument, and in the process of linear motion along the guide rail, the guide rail has six geometric errors due to manufacturing and mounting errors of the guide rail, so that the machining quality and the measuring precision are greatly influenced. Therefore, the method has important significance for six-term motion error and compensation of the guide rail.

At present, a commercial laser interferometer is often adopted as a main measuring instrument for single-item error measurement, but the main measuring instrument has the defects of complex process, long time consumption, low efficiency, high cost and the like. The grating diffraction has better resolution and higher measurement precision in the measurement of angle errors, but the measurement of position errors and horizontal straightness errors cannot be carried out; the laser collimation can realize the measurement of angle errors and straightness errors, but cannot realize the measurement of position errors, and the method combining the laser collimation and the laser interference generally has the defects of complex device structure, crosstalk among various errors, great influence on the measurement precision and the like.

Disclosure of Invention

Aiming at the defects or the improvement requirements of the prior art, the invention provides a device and a method for measuring the six-degree-of-freedom geometric error of the linear guide rail, which establish an error full decoupling algorithm through the analysis of the change relation of light spots on a detector, realize the separation of six geometric errors of the linear guide rail, and finally achieve the simultaneous measurement of the six-degree-of-freedom geometric error of the linear guide rail.

In order to achieve the above object, according to one aspect of the present invention, there is provided a linear guide six-degree-of-freedom geometric error measurement apparatus, the measurement apparatus includes a fixing unit and a measurement unit, the fixing unit includes a fourth four-quadrant detector for receiving interference fringes and then measuring a position error of the linear guide according to the interference fringes;

the measuring unit comprises a first four-quadrant detector, a second four-quadrant detector and a third four-quadrant detector, and the first four-quadrant detector, the second four-quadrant detector and the third four-quadrant detector are respectively used for receiving three beams of collimated parallel light; different errors can cause the relative displacement of the light spots on the detector of the measuring unit, and the horizontal straightness error, the vertical straightness error, the rolling angle error, the pitching angle error and the deflection angle error of the linear guide rail can be obtained by effectively separating the moving components of the light spots.

Further, the fixed unit further includes a first ordinary splitting prism, a second ordinary splitting prism, a first reflecting mirror and a second reflecting mirror, the first ordinary splitting prism is configured to split the received laser beam into two beams, wherein the transmitted light is P light, and the refracted light is S light, the first reflecting mirror is configured to reflect the S light to change a light path to form a bundle of collimated parallel light, and the collimated parallel light is incident to the second four-quadrant detector; the second common beam splitter prism is used for splitting the P light into two beams again, wherein the transmitted light is marked as P 'light, and the refracted light is marked as S' light; the second reflecting mirror is used for changing the light path of the S' light to form a beam of collimated parallel light, and then the collimated parallel light is incident to the first four-quadrant detector.

Furthermore, the fixing unit further comprises a polarization beam splitter prism, a first wave plate, a second wave plate, a convex lens, a third reflector and a fourth four-quadrant detector, wherein the first wave plate and the second wave plate are 1/4 wave plates, and the third reflector, the first wave plate, the polarization beam splitter prism, the convex lens and the fourth four-quadrant detector are arranged along the same vertical direction from top to bottom; the first common beam splitter prism, the second common beam splitter prism, the polarization beam splitter prism and the second wave plate are sequentially arranged along a first horizontal direction.

Further, the polarization beam splitter prism is configured to split the P' light into two beams again, where the transmitted light is denoted as P "light, the refracted light is denoted as S" light, the S "light passes through the first wave plate, is reflected by the third mirror and returns back, and passes through the first wave plate, the polarization beam splitter prism and the convex lens again to be incident on the fourth four-quadrant detector as reference light.

Furthermore, the measuring unit also comprises a semi-transmission and semi-reflection mirror, and the semi-transmission and semi-reflection mirror is positioned between the second wave plate and the third four-quadrant detector; the P' light is transmitted to the semi-transmission semi-reflection mirror after passing through the second wave plate, a beam of reflected laser is reflected in a primary path under the action of the semi-transmission semi-reflection mirror, passes through the second wave plate and the polarization beam splitter prism again and then is used as measuring light to finally enter the fourth four-quadrant detector, the reference light and the measuring light are converged on the fourth four-quadrant detector to form interference fringes, and the light transmitted by the semi-transmission semi-reflection mirror enters the third four-quadrant detector.

Furthermore, the measuring device also comprises a frequency stabilization helium-neon laser, a single-mode optical fiber and a collimator, wherein two ends of the single-mode optical fiber, which are opposite to each other, are respectively connected with the frequency stabilization helium-neon laser and the collimator.

Furthermore, the he-ne laser is configured to emit a laser beam, the laser beam is transmitted to the collimator through the single-mode fiber, the collimator is configured to collimate and amplify the laser beam, and the collimated and amplified laser beam enters the fixing unit.

According to another aspect of the invention, a method for measuring a six-degree-of-freedom geometric error of a linear guide rail is provided, and the method comprises the following steps: firstly, providing a six-degree-of-freedom geometric error measuring device of a linear guide rail as defined in any one of claims 1 to 7, and installing the fixed unit on a fixed plane of a numerical control machine tool while installing the measuring unit on a movable slide block of the linear guide rail of the numerical control machine tool; then, after the light path of the measuring device is adjusted, the numerical control machine tool is started, and a four-quadrant detector is used for collecting position data of a group of light spots at intervals of a preset distance; and then, obtaining error information of the partition of the linear guide rail according to the position of the light spot in each preset distance.

Further, the calculation formula of the position error is:

ΔL＝L_m-L_r

in the formula, L_mThe measured displacement is obtained; l is_rTheoretical displacement;n is the number of changes in the interference fringes;the non-integral multiple variable quantity of the interference fringe; λ is the laser wavelength.

Further, the calculation formulas of the horizontal straightness error, the vertical straightness error, the roll angle error, the pitch angle error and the yaw angle error are respectively as follows:

in the formula I₁And l₂The distance of detector QD1 and detector QD2 from the central axis of rotation, respectively;andthe vertical components of detector QD1 and detector QD2, respectively; l₃The distance of the detector QD3 from the axis of rotation,the light spot is in the vertical direction of the detectorAn upward relative movement distance; h is^QD1、h^QD2、h^QD3The relative movement distances of the light spot in the horizontal direction of the detector QD1, the detector QD2 and the detector QD3 are respectively.

Generally, compared with the prior art, the device and the method for measuring the six-degree-of-freedom geometric error of the linear guide rail, which are provided by the invention, have the following beneficial effects:

1. the measuring speed is high/the efficiency is high: the method combining laser collimation and laser interference is adopted, the simultaneous measurement of the six-degree-of-freedom geometric errors of the linear guide rail can be realized, compared with the traditional single-degree-of-freedom detection method, the measurement efficiency can be greatly improved, and the problem of non-uniform measurement reference caused by the replacement of measurement components with different error items can be solved; in addition, the efficient measurement efficiency can provide a favorable error compensation reference for the machine tool during the use process, thereby improving the processing quality of products.

2. The measurement accuracy is high: the invention adopts an error decoupling algorithm, can effectively reduce the problem that error crosstalk generally existing on a multi-degree-of-freedom simultaneous measurement device/method has great influence on a measurement result, fundamentally realizes the separation of errors and improves the measurement precision.

3. The measuring range is large and the implementation is convenient: the invention adopts the laser interference method to measure the position error, and compared with the grating ruler measurement method, the measurement range is larger; meanwhile, the measuring unit with a simpler structure is adopted, so that the installation and debugging are convenient to carry out in the limited operation space of the moving work of the machine tool, and the measurement can be completed only by one-time installation and debugging.

4. The measuring device and the method can realize the simultaneous measurement of six-degree-of-freedom errors of the linear guide rail, have the advantages of simple and compact structure, capability of error decoupling, high measuring precision, high measuring speed and the like, and the rapid detection method provides favorable data support for the error compensation of the machine tool.

Drawings

FIG. 1 is a schematic structural diagram of a linear guide six-degree-of-freedom geometric error measuring device provided by the invention;

FIG. 2 is a schematic view of a part of the structure of the linear guide six-degree-of-freedom geometric error measuring device in FIG. 1 for measuring position degree errors;

FIG. 3 is a schematic structural diagram of the linear guide rail six-degree-of-freedom geometric error measuring device in FIG. 1 for analyzing linearity errors;

FIG. 4 is a schematic structural diagram of the linear guide six-degree-of-freedom geometric error measuring device in FIG. 1 for analyzing roll angle errors;

FIG. 5 is a schematic structural diagram of the linear guide rail six-degree-of-freedom geometric error measuring device in FIG. 1 for measuring pitch angle error;

fig. 6 is a schematic structural diagram of the linear guide six-degree-of-freedom geometric error measuring device in fig. 1 for analyzing a yaw angle error.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: 1-frequency stabilized He-Ne laser, 2-single mode fiber, 3-collimator, 4-first common beam splitter prism, 5-second common beam splitter prism, 6-polarization beam splitter prism, 7-first wave plate, 8-second wave plate, 9-convex lens, 10-first reflector, 11-second reflector, 12-third reflector, 13-semi-transmission semi-reflector, 14-first four-quadrant detector, 15-second four-quadrant detector, 16-third four-quadrant detector and 17-fourth four-quadrant detector.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Referring to fig. 1 and 2, the measuring device for six-degree-of-freedom geometric errors of a linear guide rail provided by the invention comprises a laser light source, a fixing unit and a measuring unit, wherein the laser light source is used for emitting laser beams to the fixing unit, the fixing unit is used for splitting the laser beams into three collimated parallel light beams and detecting interference fringes so as to measure position errors, the measuring unit is used for receiving the three collimated parallel light beams, different errors can cause relative displacement of light spots on a detector of the measuring unit, and moving components of the light spots are effectively separated so as to obtain horizontal straightness errors, vertical straightness errors, rolling angle errors, pitching angle errors and deflection angle errors.

The laser light source comprises a frequency stabilization helium-neon laser 1, a single mode fiber 2 and a collimator 3, wherein two ends of the single mode fiber 2, which are back to back, are respectively connected with the frequency stabilization helium-neon laser 1 and the collimator 3. The frequency stabilized he-ne laser 1 can effectively reduce the fluctuation change of the wavelength, thereby improving the measurement precision of the position error. The single-mode optical fiber 2 can separate the helium-neon laser 1 from a measuring unit and conduct laser to the measuring unit, and laser thermal drift caused by the helium-neon laser 1 is effectively eliminated. When the laser machine tool works, the laser light source is arranged outside the machine tool; the fixing unit is fixed on a fixing plane of the machine tool; the measuring unit is mounted on a moving slide of a linear guide of the machine tool. The collimator is used for collimating and amplifying laser spots, and the required spot size can be obtained by selecting a proper collimator.

During operation, helium neon laser 1 sends the laser beam, the laser beam via single mode fiber 2 transmits to collimator 3, collimator 3 is used for to the laser beam carries out collimation and amplification, after the collimation and amplification the laser beam gets into fixed unit.

The fixed unit includes first ordinary beam splitter prism 4, the ordinary beam splitter prism 5 of second, polarization beam splitter prism 6, first wave plate 7, second wave plate 8, convex lens 9, first speculum 10, second speculum 11, third speculum 12 and fourth four-quadrant detector 17, first ordinary beam splitter prism 4 the ordinary beam splitter prism 5 of second polarization beam splitter prism 6 second wave plate 8, half transmission half mirror 13 and third four-quadrant detector 16 set up along first horizontal direction in proper order. The first reflecting mirror 10 is located below the first ordinary beam splitter prism 4, and the second reflecting mirror 11 is located above the second ordinary beam splitter prism 5. The third reflector 12, the first wave plate 7, the polarization beam splitter prism 6, the convex lens 9 and the fourth four-quadrant detector 17 are arranged along the same vertical direction from top to bottom. In this embodiment, the first wave plate 7 and the second wave plate 8 are both 1/4 wave plates; said fourth four-quadrant detector 17 is abbreviated QD 4.

The first ordinary beam splitter prism 4 splits the laser beam from the laser light source into two beams, wherein the transmitted light is denoted as P light, the refracted light is denoted as S light, and the S light is reflected by the first reflector 10 to change the light path and then enters the measuring unit. The P light continues to travel forward and is split into two beams again by the second ordinary splitting prism 5, wherein the transmitted light is denoted as P ' light, the refracted light is denoted as S ' light, and the S ' light is incident to the measuring unit after the optical path is changed by the second reflecting mirror 11. The P' light continues to propagate forward and is split into two beams again under the action of the polarization beam splitter prism 6, wherein the transmitted light is denoted as P "light, the refracted light is denoted as S" light, the S "light is reflected by the third reflector 12 after passing through the first wave plate 7 and returns back, and the light passes through the first wave plate 7, the polarization beam splitter prism 6 and the convex lens 9 again and then is incident on the fourth four-quadrant detector 17 as reference light. The P "light continues to propagate forward and, after passing through the second wave plate 8, to the measurement unit.

The measuring unit comprises a semi-transmission semi-reflecting mirror 13, a first four-quadrant detector 14, a second four-quadrant detector 15 and a third four-quadrant detector 16, and the semi-transmission semi-reflecting mirror 13 and the third four-quadrant detector 16 are arranged along the horizontal direction. The collimated parallel light transmitted through the second wave plate 8 passes through the half-mirror 13 and is received and detected by the third four-quadrant detector 16. The light of S' changes its optical path under the action of the second reflecting mirror 11 to form collimated parallel light to be received and detected by the first four-quadrant detector 14. The S light is reflected by the first reflector 10 to form collimated parallel light to be incident on the second four-quadrant detector 15. The three beams of collimated parallel light are used for measuring straightness errors and angle errors.

In this embodiment, the first four-quadrant detector 14, the second four-quadrant detector 15, and the third four-quadrant detector 16 are abbreviated as QD1, QD2, and QD3, respectively; the P ″ light continuously propagates forward, and propagates to the semi-transmission semi-reflection mirror 13 after passing through the second wave plate 8, a beam of reflected laser returns as a primary path under the action of the semi-transmission semi-reflection mirror 13, and finally enters the fourth four-quadrant detector 17 as measurement light after passing through the second wave plate 8 and the polarization beam splitter prism 6 again, the reference light and the measurement light are converged on the fourth four-quadrant detector 17 to form interference fringes, the light transmitted by the semi-transmission semi-reflection mirror 13 enters the third four-quadrant detector 16, and the position change of a light spot is detected by the third four-quadrant detector 16.

The three beams of collimated parallel light should be ensured to be parallel, the installation positions of the four-quadrant detectors in the measuring unit should be determined, and the distances among the four-quadrant detectors are accurately known; the collimator 3 can make the laser spot size and the effective photosensitive surface of the detector form an optimal proportional size.

The invention also provides a method for measuring the six-degree-of-freedom geometric error of the linear guide rail, which mainly comprises the following steps:

(1) and providing the measuring device, and opening the frequency stabilization helium-neon laser 1 for preheating for 30 minutes before starting so that the frequency stabilization helium-neon laser 1 can reach a stable state.

(2) The measuring device is arranged on a numerical control machine tool, the optical path is adjusted, so that three beams of collimated parallel light are in a parallel state, and the center of a light spot is basically coincided with the center of a detector through adjustment of a multi-degree-of-freedom micro-adjusting mechanism on the measuring unit.

(3) And starting the numerical control machine tool to enable the movable worktable to do linear motion along the linear guide rail, and acquiring position data of a group of light spots at intervals of a preset distance by using a four-quadrant detector.

(4) And obtaining error information of the partition of the linear guide rail according to the position of the light spot in each section of preset distance.

The error information includes a position error, a horizontal straightness error, a vertical straightness error, a yaw angle error, a pitch angle error and a roll angle error, and as shown in fig. 2, the calculation formula of the position is as follows:

the position error is then:

ΔL＝L_m-L_r

wherein N is the variation number of the interference fringes;the non-integral multiple variable quantity of the interference fringe; λ is the laser wavelength; l is_mThe measured displacement is obtained; l is_rIs the theoretical displacement.

The first four-quadrant detector 14, the second four-quadrant detector 15 and the third four-quadrant detector 16 are fixed on a guide rail sliding block, and along with the linear movement of the sliding block along the guide rail, the guide rail has installation errors and manufacturing deviations, so that the center position of a light spot is changed on the detector according to the laser auto-collimation principle, and the generated movement amount is the concrete expression caused by the linearity errors and the angle errors.

As shown in fig. 3, the straightness error can be expressed as:

in the formula, Δ v and Δ h represent the amount of change of the probe in the vertical direction and the horizontal direction, respectively.

As shown in fig. 4, the roll angle error may be expressed as:

in the formula I₁And l₂Distances of detectors QD1 and QD2 from the central axis of rotation, respectively;andthe vertical components of detectors QD1 and QD2, respectively.

As shown in fig. 5, the pitch angle error can be expressed as:

in the formula I₃The distance of the detector QD3 from the axis of rotation,is the relative movement distance of the light spot in the vertical direction of the detector.

As shown in fig. 6, the yaw angle error can be expressed as:

in the formula I₃The distance of the detector QD3 from the axis of rotation,is the relative movement distance of the light spot in the horizontal direction of the detector.

In the actual measurement process, different error terms can jointly cause relative movement of the light spots on the detector, the moving components of the light spots need to be effectively separated, in the step (4), the horizontal straightness error can be influenced by the rolling angle error and the yaw angle error, the vertical straightness error can be influenced by the rolling angle error and the pitch angle error, and an error decoupling equation is established according to a relation model among the components.

For the first four-quadrant detector of the measuring unit, there are:

for the second four-quadrant detector, then:

for the third four-quadrant detector, there are:

and when various errors exist simultaneously, the horizontal straightness error, the vertical straightness error, the rolling angle error, the pitching angle error and the deflection angle error can be output according to the following equations:

it will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.