Polarized light common-path differential phase-shift measurement system and method

Abstract

The present application relates to the technical field of high-precision relative displacement measurement, and particularly relates to a polarized light common-path differential relative displacement measurement system and method, which can improve the precision of micro relative displacement measurement, effectively enhance the anti-interference ability of the system, and be suitable for more extensive high-precision measurement occasions. By using the polarized light common-path differential measurement technology, the precision and reliability of the traditional laser collimation measurement method are further improved, providing an innovative technical means for high-precision measurement in related fields. Not only can the relative displacement measurement precision of sub-micron level be ensured, but also excellent environmental interference resistance is possessed, thereby ensuring the reliability of ground verification experiments. By combining the laser collimation technology with the polarized light common-path differential measurement technology, high-precision measurement of micro relative displacement is realized. Compared with the traditional measurement method, the present application has higher measurement precision and stronger anti-interference ability.

Description

Technical Field

[0001] This invention relates to the field of high-precision relative displacement measurement technology, specifically to a polarized light common-path differential relative displacement measurement system and method. Background Technology

[0002] With the rapid development of aerospace and high-end manufacturing, certain key components are required to possess specific mechanical properties under vacuum and high / low temperature conditions from the initial design stage. For example, the external support structure of a star sensor is designed to ensure that the relative displacement between the arm and the polyhedron remains within a controllable range under vacuum and high / low temperature conditions. Similarly, in the design of satellite support structures, the relative positional changes of certain key components relative to reference components must be within design limits. To verify that the design parameters meet the requirements, ground-based verification experiments are necessary to determine whether the structural design satisfies the requirements.

[0003] Lasers, with their excellent directionality and linearity, are widely used in geometric measurement. The trajectory of the energy distribution center of a collimated continuous laser beam can be considered a precise geometric straight line, serving as a spatial reference for collimation measurement. This laser collimation technique accurately assesses errors in geometric parameters such as straightness, coaxiality, flatness, parallelism, and perpendicularity by measuring the deviation of the measured object from the reference beam. Currently, laser collimation measurement technology is widely used in high-precision geometric measurements, such as straightness, coaxiality, and flatness. The high directionality of lasers enables them to provide a precise spatial reference, and the deviation of the measured object from the laser beam directly reflects the geometric error. However, with the increasing precision requirements in industry and scientific research, traditional laser collimation measurement methods are insufficient to meet the measurement needs of minute displacements or form and position errors in certain situations. Although traditional laser collimation measurement methods offer high accuracy, when dealing with extremely small displacement measurements, limitations imposed by the laser beam divergence angle and environmental interference, especially air disturbances near the optical path, make it difficult to further improve measurement accuracy and stability. In addition, existing laser interferometry systems also have certain limitations in multi-dimensional measurements, making it 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 minute relative displacement measurement, effectively enhance the anti-interference capability of the system, and is applicable to a wider range of high-precision measurement applications.

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

[0006] A polarized light co-path differential relative displacement measurement system includes a laser head, a measuring head, and a target mirror. The laser head includes a laser, an optical fiber coupler, and a polarization-maintaining fiber. The measuring head includes an optical fiber collimator, a polarization unit, a polarization beam splitter, and two four-quadrant detectors. The target mirror includes two back-reflecting mirrors and a polarization beam splitter prism.

[0007] The linearly polarized light emitted from the laser head is coupled into the polarization-maintaining fiber through the fiber coupler and transmitted. After being collimated by the fiber collimator, the polarization state is adjusted by the polarization unit and split into two beams by the polarization beam splitting unit. The beams are reflected by the two back-reflecting mirrors and then recombined. They are then received by the two four-quadrant detectors to detect the relative displacement of the target object.

[0008] The polarization unit includes a half-wave plate and a linear polarizer.

[0009] 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 deflector, and a Rochon prism.

[0010] The rearward reflecting mirror includes a cornerstone prism, a cat's eye mirror, a hollow cornerstone prism, or a right-angle prism.

[0011] The lasers include He-Ne lasers and semiconductor lasers.

[0012] This invention also provides a method for measuring polarized light common-path differential relative displacement, implemented using the polarized light common-path differential relative displacement measurement system described in this invention, comprising 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 polarizing beam splitter have equal energy;

[0014] Record the position changes of the light spot on the four-quadrant detector and calculate the relative displacement of the target object;

[0015] Using the data detected by the four-quadrant detector, the relative displacement changes of the target object in two directions are calculated using a mathematical model; the mathematical model is as follows:

[0016]

[0017] Where, ΔX QD1 and ΔX QD2 Let ΔZ represent the relative changes in the horizontal position of the light spot on QD1 and QD2, respectively. QD1 and ΔZ QD2δ represents the relative change in position of the light spot along the vertical direction on QD1 and QD2, respectively. y δ represents the relative displacement change between CCR1 and CCR2 along the horizontal direction. z This represents the relative displacement change between CCR1 and CCR2 along the vertical direction.

[0018] Beneficial effects:

[0019] 1. This invention utilizes polarized light common-path differential measurement technology to further improve the accuracy and reliability of traditional laser collimation measurement methods, providing an innovative technical means for high-precision measurement in related fields. It not only ensures sub-micron level relative displacement measurement accuracy but also possesses excellent resistance to environmental interference, thus guaranteeing the reliability of ground-based verification experiments. By combining laser collimation technology with polarized light common-path differential measurement technology, high-precision measurement of minute relative displacements is achieved. Compared to traditional measurement methods, this invention offers higher measurement accuracy and stronger anti-interference capabilities.

[0020] 2. This invention further combines the collimation characteristics of laser with the differential measurement technology of polarized light to achieve high-precision measurement of minute relative displacements. It has broad application prospects in metrology and testing, and is particularly suitable for measuring geometric quantities with high precision requirements, such as monitoring the relative displacement between two points in high space, the relative displacement change between the arm and polyhedron of a star-sensor support, and measuring the relative displacement change between two points of a satellite structure during vacuum high and low temperature cycles.

[0021] 3. In ground verification experiments on star sensor brackets, this invention provides sub-micron level relative displacement measurement accuracy under complex environments, significantly improving the measurement accuracy and reliability of two-degree-of-freedom relative displacement between two measured positions in the star sensor. In ground verification experiments on satellite structures under vacuum and high / low temperature environments, this invention effectively reduces the impact of environmental temperature changes on measurement results, ensuring measurement stability and consistency. Furthermore, in the measurement of linear axis straightness error on high-precision CNC machine tools, this invention significantly enhances the measurement system's resistance to environmental interference.

[0022] 4. This invention not only demonstrates significant advantages in existing high-precision measurement fields, but its innovative measurement method also has broad application potential in other situations requiring high-precision displacement measurement. This technology can be used in multiple fields such as precision manufacturing, engineering monitoring, and scientific research, and is expected to significantly promote the development of measurement technologies in these fields, with broad market prospects.

[0023] 5. The system of this 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 precision and reliability of this technology help reduce production losses caused by measurement errors, improve overall production efficiency, and are expected to bring significant economic benefits to relevant enterprises. Attached Figure Description

[0024] Figure 1 This 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 This is a schematic diagram showing the two-dimensional relative displacement change between corner prism CCR2 and CCR1, with corner prism CCR1 as the reference.

[0026] Figure 3 This is a schematic diagram showing the two-dimensional relative displacement change between corner prism CCR1 and CCR2, with corner prism CCR2 as the reference.

[0027] Figure 4 This is a schematic diagram showing the relative displacement changes between CCR1 and CCR2 with two degrees of freedom.

[0028] Figure 5 This is a schematic diagram of polarized light common-path differential relative displacement measurement by adding a reflector to change the optical path structure. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] This invention significantly improves the accuracy and stability of measurements 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 value for promotion and application.

[0031] The optical principle diagram of the polarization light common-path differential relative displacement measurement system of this 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, an optical fiber coupler, and a polarization-maintaining fiber; the measuring head includes an optical fiber collimator, a half-wave plate, a polarization beam splitter, and two four-quadrant detectors; the target mirror includes two cornerstone prisms and one polarization beam splitter.

[0032] Specifically, the linearly polarized light output from the He-Ne laser, characterized by stable frequency, stable optical power, and stable polarization direction, is coupled into a single-mode polarization-maintaining fiber via an optical fiber coupler. Thanks to the spatial filtering effect of the fiber, the energy distribution of the measurement beam output from the fiber, after passing through the collimator, exhibits a relatively ideal Gaussian distribution, which is beneficial for improving the measurement accuracy of relative displacement. Furthermore, due to the use of fiber coupling technology, the He-Ne laser is isolated from the measurement head, thus avoiding the influence of laser heat on the measurement optical path. After collimation, the measurement beam passes through a half-wave plate. By adjusting the angle between the half-wave plate and the optical axis of the polarizing beam splitter prism PBS1, the energy of the transmitted and reflected light passing through PBS1 is made approximately equal. The transmitted light from PBS1—the "P" beam—is reflected by the cornerstone prism CCR2 and returns to the beam splitting surface of PBS1 before being transmitted again; the reflected light from PBS1—the "S" beam—is reflected by the cornerstone prism CCR1 and returns to the beam splitting surface of PBS1 before being reflected again. The measurement light, after being reflected by the two pyramidal prisms, returns to the measurement head after passing through PBS1 and enters PBS2. The reflected light from CCR2 is received by the four-quadrant detector QD1 after passing through PBS2, and the reflected light from CCR1 is received by the four-quadrant detector QD2 after passing through PBS2.

[0033] Figure 2 This is a schematic diagram showing the two-dimensional relative displacement change between corner prism CCR2 and CCR1, with corner prism CCR1 as the reference. Figure 3 This is a schematic diagram showing the two-dimensional relative displacement change between corner prism CCR1 and CCR2, with corner prism CCR2 as the reference. Figure 4 This is a schematic diagram showing the relative displacement changes between CCR1 and CCR2 with two degrees of freedom. Figure 5 This is a schematic diagram of polarized light common-path differential relative displacement measurement by adding a reflector to change the optical path structure.

[0034] Furthermore, the half-wave plate (HWP) can be replaced with a linear polarizer, and the polarizing beam splitter (PBS) can be replaced with optical or electrical components or systems with polarization splitting capabilities, such as Wollaston prisms, Glan laser polarizing prisms, Glan-laser calcite polarizers, Glan-Taylor calcite polarizers, yttrium vanadate (YVO4) beam deflectors, yttrium vanadate (YVO4) beam deflectors, and Rochon prisms.

[0035] The corner cube prism (CCR) can also be replaced by optical elements or systems with back reflection capabilities, such as cat's eye lenses, hollow corner cubes, and right-angle prisms.

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

[0037] This invention also provides a polarization-guided co-path differential relative displacement measurement method. Based on the system implementation of this invention, the polarization-guided co-path differential relative displacement measurement method can realize the two-degree-of-freedom relative displacement measurement function between CCR1 and CCR2. The measurement formula is shown below:

[0038]

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

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

Claims

1. A polarized light common-path differential relative displacement measurement system, characterized in that, The system includes a laser head, a measuring head, and a target mirror. The laser head includes a laser, an optical fiber coupler, and a polarization-maintaining fiber. The measuring head includes an optical fiber collimator, a polarization unit, a polarization beam splitter, and two four-quadrant detectors. The target mirror includes two back-facing mirrors and a polarization beam splitter prism. The linearly polarized light emitted from the laser head is coupled into the polarization-maintaining fiber through the fiber coupler and transmitted. After being collimated by the fiber collimator, the polarization state is adjusted by the polarization unit and split into two beams by the polarization beam splitting unit. The beams are reflected by the two back-reflecting mirrors and then recombined. They are received by the two four-quadrant detectors to detect the relative displacement of the target object. The polarization unit includes a half-wave plate and a linear polarizer; 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 deflector, and a Rochon prism; the back mirror includes a corner cube prism, a cat's eye mirror, a hollow corner cube mirror, or a right-angle prism; the laser includes a He-Ne laser and a semiconductor laser.

2. A method for measuring polarized light co-path differential relative displacement, characterized in that, The polarization-guided differential relative displacement measurement system according to claim 1 is used to achieve this, 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 polarizing beam splitter have equal energy; Record the position changes of the light spot on the four-quadrant detector and calculate the relative displacement of the target object; Using the data detected by the four-quadrant detector, the relative displacement changes of the target object in two directions are calculated using a mathematical model; the mathematical model is as follows: in, and These represent the relative changes in the horizontal position of the light spot on QD1 and QD2, respectively. and These represent the relative changes in the vertical position of the light spot on QD1 and QD2, respectively. This represents the relative displacement change between CCR1 and CCR2 along the horizontal direction. This represents the relative displacement change between CCR1 and CCR2 along the vertical direction.

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