Polarized light common-path differential relative displacement measurement system and method

Abstract

The invention relates to the technical field of high-precision relative displacement measurement, in particular to a polarized light common-path differential relative displacement measurement system and method, which can improve the precision of tiny relative displacement measurement, effectively enhance the anti-interference capability of the system and are suitable for wider high-precision measurement occasions. By using a polarized light common-path differential measurement technology, the precision and reliability of a traditional laser collimation measurement method are further improved, and an innovative technical means is provided for high-precision measurement in related fields. The submicron-level relative displacement measuring precision can be guaranteed, the excellent environment interference resisting capacity is achieved, and therefore the reliability of a ground verification experiment is guaranteed. Through combination of a laser collimation technology and a polarized light common-path differential measurement technology, high-precision measurement of tiny relative displacement is realized. Compared with a traditional measurement method, the method has higher measurement precision and stronger anti-interference capability.

Description

Technical Field

[0001] The present invention relates to the technical field of high-precision relative displacement measurement, and in particular to a polarized light common-path differential relative displacement measurement system and method. Background Art

[0002] With the rapid development of aerospace and high-end manufacturing industries, some key components are required to have certain mechanical properties under vacuum and high-temperature environmental conditions at the beginning of their design. For example, the external support structure of the star sensor is required to have the relative displacement change between the arm and the polyhedron within a controllable range under vacuum and high-temperature conditions at the beginning of its design. In the design process of the satellite bracket structure, the relative position change of certain key parts relative to the reference part is required to be within the design range. In order to verify that the design parameters meet the requirements. Ground verification experiments are required to determine whether the design of the structure meets the requirements.

[0003] Lasers are widely used in geometric measurement due to their excellent directivity and linearity. The trajectory of the energy distribution center of a collimated continuous laser beam can be regarded as an accurate geometric straight line, which serves as a spatial reference for collimation measurement. This laser collimation technology can accurately evaluate the errors of geometric parameters such as straightness, coaxiality, flatness, parallelism, and perpendicularity by measuring the deviation of the measured object relative to the reference beam. At present, laser collimation measurement technology has been widely used in high-precision measurement of geometric quantities, such as straightness, coaxiality, and flatness. The high directivity of the laser enables it to provide an accurate spatial reference, and the deviation of the measured object relative to the laser beam can directly reflect the error of the geometric quantity. However, with the continuous improvement of the accuracy requirements in the industrial and scientific research fields, the traditional laser collimation measurement method has been difficult to meet the measurement requirements of small displacements or form and position errors in some occasions. Although the traditional laser collimation measurement method has high accuracy, it is limited by the divergence angle of the laser beam and environmental interference, especially the air disturbance near the optical path, when facing extremely small displacement measurements, the measurement accuracy and stability are difficult to further improve. In addition, the existing laser interferometry measurement system also has certain limitations in multi-dimensional measurement, and it is difficult to achieve high-precision simultaneous measurement of multiple parameters. Summary of the invention

[0004] In view of this, the present invention provides a polarized light common-path differential relative displacement measurement system and method, which can improve the accuracy of tiny relative displacement measurement, effectively enhance the anti-interference ability of the system, and is suitable for a wider range of high-precision measurement occasions.

[0005] To achieve the above purpose, the technical solution of the present invention is as follows:

[0006] A polarized light common-path differential relative displacement measurement system, the system comprising a laser head, a measuring head and a target mirror, the laser head comprising a laser, a fiber coupler and a polarization-maintaining fiber; the measuring head comprising a fiber collimator, a polarization unit, a polarization beam splitting unit and two four-quadrant detectors; the target mirror comprising two retroreflectors and a polarization beam splitting prism;

[0007] The linearly polarized light emitted by the laser head is coupled into the polarization-maintaining optical fiber through the optical fiber coupler for transmission, is collimated by the optical fiber collimator, and then the polarization state is adjusted by the polarization unit, and is divided into two beams by the polarization splitting unit, which are respectively reflected by the two retroreflectors and then recombined, and are received by the two four-quadrant detectors for detecting the relative displacement of the target object.

[0008] Wherein, the polarization unit includes a half-wave plate and a linear polarizer.

[0009] The polarization splitting unit includes a polarization splitting prism, a Wollaston prism, a Glan laser polarization prism, a Glan-laser calcite polarizer, a Glan-Taylor calcite polarizer, a yttrium vanadate (YVO4) beam shifter and a Rochon prism.

[0010] Wherein, the retroreflector includes a corner cube prism, a cat's eye prism, a hollow corner cube prism or a right-angle prism.

[0011] Wherein, the laser includes He-Ne laser and semiconductor laser.

[0012] The present invention also provides a polarized light common-path differential relative displacement measurement method, which is implemented using the polarized light common-path differential relative displacement measurement system of the present invention, and includes the following steps:

[0013] Adjust the position and angle of the half-wave plate to ensure that the two beams of light generated by the polarization beam splitter prism have equal energy;

[0014] Recording the position change of the light spot on the four-quadrant detector and calculating the relative displacement of the target object;

[0015] The data detected by the four-quadrant detector is used to calculate the relative displacement change of the target object in two directions using a mathematical model; the mathematical model is:

[0016]

[0017] Where ΔX QD1 and ΔX QD2 They represent the relative position change of the light spot on QD1 and QD2 along the horizontal direction, ΔZ QD1 and ΔZ QD2They represent the relative position changes of the light spot on QD1 and QD2 along the vertical direction, δ y is the relative displacement change between CCR1 and CCR2 in the horizontal direction, δ z is the relative displacement change between CCR1 and CCR2 in the vertical direction.

[0018] Beneficial effects:

[0019] 1. The system of the present invention further improves the accuracy and reliability of the traditional laser alignment measurement method by utilizing the polarized light common-path differential measurement technology, and provides an innovative technical means for high-precision measurement in related fields. It can not only ensure the sub-micron level of relative displacement measurement accuracy, but also has excellent ability to resist environmental interference, thereby ensuring the reliability of ground verification experiments. By combining laser alignment technology with polarized light common-path differential measurement technology, high-precision measurement of tiny relative displacements is achieved. Compared with traditional measurement methods, the present invention has higher measurement accuracy and stronger anti-interference ability.

[0020] 2. The present invention further combines the collimation characteristics of laser with the differential measurement technology of polarized light to achieve high-precision measurement of small relative displacements. It has broad application prospects in metrology and testing, and is particularly suitable for high-precision geometric measurement, such as relative displacement monitoring between two points in high space, relative displacement changes between the arm of a star-sensitive bracket and a polyhedron, and relative displacement change measurement between two points in a satellite structure during high-temperature and vacuum cycle changes.

[0021] 3. In the ground verification experiment of the star sensor bracket, the present invention can provide sub-micron relative displacement measurement accuracy in a complex environment, significantly improving the measurement accuracy and reliability of the two-degree-of-freedom relative displacement between two positions to be measured in the star sensor. In the ground verification experiment of the satellite structure in a vacuum high and low temperature environment, the present invention effectively reduces the impact of ambient temperature changes on the measurement results, ensuring the stability and consistency of the measurement. In addition, in the measurement of the straightness error of the linear axis of a high-precision CNC machine tool, the present invention can significantly improve the ability of the measurement system to resist environmental interference.

[0022] 4. The present invention not only shows significant advantages in the existing high-precision measurement field, but also its innovative measurement method has wide application potential in other occasions that require high-precision displacement measurement. This technology can be used in many fields such as precision manufacturing, engineering monitoring and scientific research, and is expected to greatly promote the development of measurement technology in these fields and has broad market prospects.

[0023] 5. The use of the system of the present invention can significantly reduce the maintenance cost of the measurement system and extend the service life of the equipment. At the same time, the high accuracy and reliability of the technology can help reduce production losses caused by measurement errors and improve overall production efficiency, which is expected to bring significant economic benefits to related companies. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the optical principle of the polarized light common-path differential relative displacement measurement system of the present invention.

[0025] Figure 2 It is a schematic diagram of measuring the two-dimensional relative displacement change between corner cube prism CCR2 and CCR1 with corner cube prism CCR1 as a reference.

[0026] Figure 3 It is a schematic diagram of measuring the two-dimensional relative displacement change between corner cube prism CCR1 and CCR2 with corner cube prism CCR2 as a reference.

[0027] Figure 4 Schematic diagram of the change in the two-degree-of-freedom relative displacement between CCR1 and CCR2.

[0028] Figure 5 Schematic diagram of polarized light common-path differential relative displacement measurement by changing the optical path structure by adding a reflector. DETAILED DESCRIPTION

[0029] The present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0030] The present invention significantly improves the measurement accuracy and stability by introducing polarized light common-path differential technology into traditional laser measurement technology, providing a reliable and efficient solution for high-precision geometric measurement, and has great promotion and application value.

[0031] The optical principle diagram of the polarized light common-path differential relative displacement measurement system of the present invention is as follows: Figure 1 As shown. The system includes a laser head, a measuring head and a target mirror. The laser head includes a He-Ne laser, a fiber coupler and a polarization-maintaining fiber; the measuring head includes a fiber collimator, a half-wave plate, a polarization beam splitter and two four-quadrant detectors; the target mirror includes two corner cube prisms and a polarization beam splitter.

[0032] Specifically, the linearly polarized light with stable frequency, stable optical power and stable polarization direction output by the He-Ne laser is coupled into the single-mode polarization-maintaining optical fiber through the fiber coupler for transmission. Thanks to the spatial filtering effect of the optical fiber, after the measurement light output by the optical fiber passes through the collimator, the energy distribution of the light spot presents a relatively ideal Gaussian distribution, which is conducive to improving the measurement accuracy of the relative displacement. In addition, due to the use of fiber coupling technology, the He-Ne laser is isolated from the measuring head, thereby avoiding the influence of the heat of the laser on the measurement optical path. The collimated measurement light passes through the half-wave plate, and by adjusting the angle between the half-wave plate and the optical axis of the polarization beam splitter prism PBS1, the energy of the transmitted light and the reflected light through PBS1 are roughly equal. The transmitted light of PBS1, that is, the "P" light, is reflected by the corner cube prism CCR2 and then returns to the beam splitting surface of PBS1 and is transmitted; the reflected light of PBS1, that is, the "S" light, is reflected by the corner cube prism CCR1 and then returns to the beam splitting surface of PBS1 and is reflected. The measuring light reflected by the two corner cube prisms returns to the measuring head again after passing through PBS1 and enters PBS2, wherein the reflected light of CCR2 is received by the four-quadrant detector QD1 after passing through PBS2, and the reflected light of CCR1 is received by the four-quadrant detector QD2 after passing through PBS2.

[0033] Figure 2 It is a schematic diagram of measuring the two-dimensional relative displacement change between corner cube prism CCR2 and CCR1 with corner cube prism CCR1 as a reference. Figure 3 It is a schematic diagram of measuring the two-dimensional relative displacement change between corner cube prism CCR1 and CCR2 with corner cube prism CCR2 as a reference. Figure 4 Schematic diagram of the change in the two-degree-of-freedom relative displacement between CCR1 and CCR2. Figure 5 Schematic diagram of polarized light common-path differential relative displacement measurement by changing the optical path structure by adding a reflector.

[0034] Furthermore, the half-wave plate (HWP) can also be replaced by a linear polarizer, and the polarization beam splitter (PBS) can also be replaced by an optical or electrical element or system with polarization splitting capability, such as a Wollaston prism, a Glan laser polarization prism, a Glan-laser calcite polarizer, a Glan-Taylor calcite polarizer, a yttrium vanadate (YVO4) beam shifter, a yttrium vanadate (YVO4) beam shifter, or a Rochon prism.

[0035] The corner cube prism CCR can also be replaced by cat's eye glasses, hollow corner cubes, right-angle prisms and other optical elements or systems with retroreflective capabilities.

[0036] He-Ne lasers can also be light sources such as semiconductor lasers.

[0037] The present invention also provides a polarized light common path differential relative displacement measurement method. Based on the system implementation of the present invention, the polarized light common path differential relative displacement measurement method of the present invention can realize the two-degree-of-freedom relative displacement measurement function between CCR1 and CCR2. The measurement formula is shown in the following formula:

[0038]

[0039] Where ΔX QD1 and ΔX QD2 They represent the relative position change of the light spot on QD1 and QD2 along the horizontal direction, ΔZ QD1 and ΔZ QD2 They represent the relative position changes of the light spot on QD1 and QD2 along the vertical direction, δ y is the relative displacement change between CCR1 and CCR2 along the horizontal direction (Y axis of the coordinate system), δ z It is the relative displacement change between CCR1 and CCR2 along the vertical direction (Z axis of the coordinate system).

[0040] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A polarized light common-path differential relative displacement measurement system, characterized in that: The system comprises a laser head, a measuring head and a target mirror, wherein the laser head comprises a laser, a fiber coupler and a polarization-maintaining fiber; the measuring head comprises a fiber collimator, a polarization unit, a polarization beam splitting unit and two four-quadrant detectors; the target mirror comprises two retroreflectors and a polarization beam splitting prism; The linearly polarized light emitted by the laser head is coupled into the polarization-maintaining optical fiber through the optical fiber coupler for transmission, is collimated by the optical fiber collimator, and then the polarization state is adjusted by the polarization unit, and is divided into two beams by the polarization splitting unit, which are respectively reflected by the two retroreflectors and then recombined, and are received by the two four-quadrant detectors for detecting the relative displacement of the target object.

2. The measuring system according to claim 1, characterized in that The polarization unit includes a half-wave plate and a linear polarization plate.

3. The measuring system according to claim 2, characterized in that The polarization beam splitting unit includes a polarization beam splitting prism, a Wollaston prism, a Glan laser polarization prism, a Glan-laser calcite polarizer, a Glan-Taylor calcite polarizer, a yttrium vanadate (YVO4) beam shifter and a Rochon prism.

4. The measuring system according to claim 1, characterized in that The retroreflector includes a corner cube prism, a cat's eye prism, a hollow corner cube prism or a right-angle prism.

5. The measuring system according to any one of claims 1 to 4, characterized in that: The lasers include He-Ne lasers and semiconductor lasers.

6. A method for measuring relative displacement of polarized light common-path differential, characterized in that: The method is implemented by using the polarized light common-path differential relative displacement measurement system according to any one of claims 1 to 5, comprising the following steps: Adjust the position and angle of the half-wave plate to ensure that the two beams of light generated by the polarization beam splitter prism have equal energy; Recording the position change of the light spot on the four-quadrant detector and calculating the relative displacement of the target object; The data detected by the four-quadrant detector is used to calculate the relative displacement change of the target object in two directions using a mathematical model; the mathematical model is: Where ΔX QD1 and ΔX QD2 They represent the relative position change of the light spot on QD1 and QD2 along the horizontal direction, ΔZ QD1 and ΔZ QD2 They represent the relative position changes of the light spot on QD1 and QD2 along the vertical direction, δ y is the relative displacement change between CCR1 and CCR2 in the horizontal direction, δ z is the relative displacement change between CCR1 and CCR2 in the vertical direction.

Images