Grating precision displacement sensor and measurement system

Abstract

The application discloses a grating precision displacement sensor, and relates to the technical field of grating displacement sensor measurement, comprising a laser generating part, a polarization light splitting part, a polarization state conversion assembly, a reflection assembly, a light splitting detection assembly, a grating assembly, a displacement table and an adjusting assembly; the grating assembly comprises a plurality of gratings, the grating periods of different gratings are different, a grating is detachably arranged on the upper side of the displacement table, and the grating vector direction is parallel to the movement axis direction of the displacement table; the adjusting assembly is connected to the reflection assembly and can adjust the reflection angle of the reflection assembly for the +1 and -1 order diffraction light.The grating precision displacement sensor and the measurement system provided by the application can improve the measurement flexibility and adaptability.The application further provides a measurement system comprising the above grating precision displacement sensor.

Description

Technical Field

[0001] This invention relates to the field of grating displacement sensor measurement technology, and in particular to a grating precision displacement sensor and measurement system. Background Technology

[0002] Grating displacement sensors, as precision optical measuring instruments, are widely used in displacement measurement, surface topography inspection, and optical component manufacturing. Their basic principle is to utilize the diffraction and interference effects of a grating to convert the displacement or deformation of the object under test into detectable changes in interference fringes, thereby achieving high-precision measurement. During the measurement process, the grating period determines the sensor's measurement sensitivity, measurement range, and the smallest resolvable feature size. For example, gratings with smaller periods generally achieve higher measurement accuracy, while gratings with larger periods are more suitable for measuring larger displacements or ranges. However, traditional grating displacement sensors typically use gratings with fixed grating periods as key components, resulting in poor flexibility and adaptability. Summary of the Invention

[0003] The purpose of this invention is to provide a grating precision displacement sensor and measurement system to solve the problems existing in the prior art and improve measurement flexibility and adaptability.

[0004] To achieve the above objectives, the present invention provides the following solution: This invention provides a grating precision displacement sensor, comprising a laser generator, a polarization beam splitter, a polarization state conversion component, a reflection component, a beam splitting detection component, a grating assembly, a displacement stage, and an adjustment component. The laser generator outputs laser light. The polarization state conversion component adjusts the polarization direction of the laser light. The reflection component reflects the laser light, after its polarization direction has been adjusted by the polarization state conversion component, to the grating assembly. It also reflects the ±1st order diffracted light from the grating assembly to the polarization beam splitter, which combines the ±1st order diffracted light into a single beam. The polarization conversion component can also perform polarization state conversion on the ±1st order diffracted light incident on the polarization beam splitter and the combined light emitted from the polarization beam splitter. The beam splitting detection component can split the combined light and detect the signal to obtain an interference signal. The grating component includes a plurality of gratings with different grating periods. A grating is detachably disposed on the upper side of the displacement stage, and the grating vector direction is parallel to the motion axis direction of the displacement stage. The adjustment component is connected to the reflection component and can adjust the reflection angle of the reflection component for the ±1st order diffracted light.

[0005] Preferably, the reflecting assembly includes a first reflector, a second reflector, a third reflector, a fourth reflector, and a fifth reflector; the first reflector is located on the output side of the laser generator, and its reflecting surface forms a 45° angle with the laser emission direction, reflecting the parallel light emitted by the laser as perpendicular light incident on the grating assembly; the perpendicular light incident on the grating surface generates the ±1st order diffracted light; the second and third reflectors are located on different incident sides of the polarizing beam splitter, and the reflecting surfaces of the second and third reflectors are both perpendicular to the emitted light of the laser. Direction; the fourth and fifth reflecting mirrors are both connected to the adjustment assembly and are used to reflect the +1st order diffracted light and the -1st order diffracted light, respectively; the +1st order diffracted light from the fourth reflecting mirror is reflected to the third reflecting mirror, and then reflected by the third reflecting mirror to the polarization state conversion assembly; the incident light and the reflected light on the surface of the third reflecting mirror are orthogonal; the -1st order diffracted light from the fifth reflecting mirror is reflected to the second reflecting mirror, and then reflected by the second reflecting mirror to the polarization state conversion assembly; the incident light and the reflected light on the surface of the second reflecting mirror are orthogonal.

[0006] Preferably, the adjustment assembly includes a first rotary motor and a second rotary motor, and the fourth reflector and the fifth reflector are respectively connected to the first rotary motor and the second rotary motor; the first rotary motor and the second rotary motor can drive the fourth reflector and the fifth reflector to rotate, so as to adjust the reflection angle of the reflection assembly for the +1st order diffracted light and the -1st order diffracted light.

[0007] Preferably, the polarization state conversion component includes a half-wave plate, a first quarter-wave plate, a second quarter-wave plate, and a third quarter-wave plate, all capable of allowing light to pass through perpendicularly; the half-wave plate is located between the laser generator and the first reflector, and is used to adjust the polarization direction of the laser; the first quarter-wave plate and the second quarter-wave plate are respectively located on different incident sides of the polarization beam splitter, and the first quarter-wave plate and the second quarter-wave plate can respectively perform polarization state conversion on the +1st order diffracted light and the -1st order diffracted light; the third quarter-wave plate is located on the exit side of the polarization beam splitter, and the third quarter-wave plate can perform polarization state conversion on the combined beam.

[0008] Preferably, the distances from the first quarter-wave plate to the corresponding incident side of the polarizing beam splitter, the distances from the second quarter-wave plate to the corresponding incident side of the polarizing beam splitter, and the distances from the third quarter-wave plate to the exit side of the polarizing beam splitter are all equal; the distances from the center of the fourth mirror to the center of the third mirror and the distances from the center of the fifth mirror to the center of the second mirror are all equal; and the distances from the center of the second mirror to the first quarter-wave plate and the distances from the center of the third mirror to the second quarter-wave plate are all equal.

[0009] Preferably, the beam splitting detection component includes a first photodetector, a second photodetector, a first polarizer, a second polarizer, and a non-polarizing beam splitter; the incident side of the non-polarizing beam splitter is opposite to the exit side of the polarizing beam splitter, and the non-polarizing beam splitter is used to split the combined light into two interference beams of equal intensity, which are incident on the first photodetector and the second photodetector respectively through the two exit sides of the non-polarizing beam splitter; the first polarizer and the second polarizer are both 45° linear polarizers; the first polarizer and the second polarizer are respectively disposed on the two exit sides of the non-polarizing beam splitter; the first photodetector and the second photodetector are respectively disposed on the output sides of the first polarizer and the second polarizer, and both the first photodetector and the second photodetector are used to receive interference light and output interference signals; the distance from the first polarizer to the corresponding exit side of the non-polarizing beam splitter and the distance from the second polarizer to the corresponding exit side of the non-polarizing beam splitter are both equal; the distance from the first photodetector to the output side of the first polarizer and the distance from the second photodetector to the output side of the second polarizer are both equal.

[0010] Preferably, all of the gratings are reflective gratings.

[0011] Preferably, the diffraction angles of the ±1st order diffracted light and the grating period of the grating follow the grating diffraction equation; the grating diffraction equation is: d is the grating period, θ is the diffraction angle, and λ is the laser wavelength.

[0012] Preferably, the laser generator is configured as a laser and used to output linearly polarized light, and the polarization beam splitter is configured as a polarization beam splitter.

[0013] The present invention also provides a grating precision displacement measurement system, including a signal processing module and a grating precision displacement sensor as described above; the signal processing module is used to receive the multi-channel interference signals output by the grating precision displacement sensor and to analyze and process the interference signals to realize displacement measurement.

[0014] The present invention achieves the following technical effects compared to the prior art: The present invention provides a grating precision displacement sensor, wherein the grating assembly includes several gratings with different grid periods, and the gratings are mounted on the upper side of the displacement stage with the grating vector direction parallel to the direction of the displacement stage's motion axis; a laser generator is used to output laser light; a polarization state conversion assembly can adjust the polarization direction of the laser light to ensure that the incident light meets the beam splitting requirements; a reflection assembly is used to reflect the ±1st order diffracted light reflected at the Littrow angle from the surface of the grating assembly to a polarization beam splitter; the polarization beam splitter is used to separate the ±1st order diffracted light diffracted through the surface of the grating assembly. The beam combining process involves two beams of light carrying opposite phase changes interfering with each other, thus converting the minute displacement of the grating into a high-contrast interference signal that is easy to measure. The polarization state conversion component can also perform polarization state conversion on ±1st order diffracted light and the combined beam emitted after polarization beam splitting, ensuring polarization state stability in the optical path and improving anti-interference capability. The beam splitting detection component is used to split the combined beam and detect the signal, obtaining the interference signal. The multi-path interference signal from the split beam is used to achieve direction discrimination and subdivision by generating orthogonal signals, and interference is suppressed by differential detection. The interference signal is then analyzed... The displacement value of the stage is determined by a single grating, enabling reliable and accurate measurement results even in complex industrial environments. This invention enhances robustness through polarization optics design, achieving high-precision displacement measurement. Furthermore, by adjusting the reflection angle of the reflective component using an adjustment component, it matches gratings with different grid periods for displacement measurement at the same wavelength. Compared to traditional grating interferometers, which can only use a fixed grating period for displacement measurement at the same wavelength, this invention improves measurement flexibility and adaptability. Through optical path transmission and signal linkage, a close correlation is formed, creating a measurement logic of "stage movement → grating synchronous movement → optical path difference change → phase shift," completing the entire measurement process of "laser emission → diffraction → interference → signal detection → displacement calculation." Moreover, by changing gratings with different grid periods and adjusting the reflection angle of the reflective component using the adjustment component, it can also adapt to incident lasers of different wavelengths. Thus, high-precision measurement can be achieved without replacing core modules such as polarization beam splitters, polarization state conversion components, reflection components, or beam splitting detection components, overcoming the inherent defects of traditional equipment such as poor versatility and high operating costs.

[0015] The grating precision displacement measurement system provided by this invention transmits the interference signal measured by the grating precision displacement sensor to the signal processing module for analysis and processing, thereby realizing displacement measurement. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the structure of a grating precision displacement sensor provided in Embodiment 1 of the present invention.

[0018] Figure 2 This is a schematic diagram of the overall optical path of a grating precision displacement sensor provided in Embodiment 1 of the present invention.

[0019] Figure 3 This is a schematic diagram of the +1st order diffraction optical path of a grating precision displacement sensor provided in Embodiment 1 of the present invention.

[0020] Figure 4 This is a schematic diagram of the -1st order diffraction optical path of a grating precision displacement sensor provided in Embodiment 1 of the present invention.

[0021] Figure 5 This is a schematic diagram of a grating precision displacement measurement system provided in Embodiment 2 of the present invention.

[0022] In the figure: 1-Laser generator; 2-Half-wave plate; 3-Polarizing beam splitter; 4-Unpolarizing beam splitter; 501-First quarter-wave plate; 502-Second quarter-wave plate; 503-Third quarter-wave plate; 601-First polarizer; 602-Second polarizer; 701-First mirror; 702-Second mirror; 703-Third mirror; 704-Fourth mirror; 705-Fifth mirror; 801-First photodetector; 802-Second photodetector; 901-First rotary motor; 902-Second rotary motor; 10-Grate; 11-Transmission stage. Detailed Implementation

[0023] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0024] The purpose of this invention is to provide a grating precision displacement sensor and measurement system to solve the problems existing in the prior art and improve measurement flexibility and adaptability.

[0025] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] Example 1 This embodiment provides a grating precision displacement sensor. Please refer to [link / reference]. Figures 1-4 The system includes a laser generator 1, a polarization beam splitter 3, a polarization state conversion component, a reflection component, a beam splitting and detection component, a grating component, a displacement stage 11, and an adjustment component. The laser generator 1 outputs laser light. The polarization state conversion component adjusts the polarization direction of the laser. The reflection component reflects the laser light, after its polarization direction has been adjusted by the polarization state conversion component, to the grating component. It also reflects the ±1st order diffracted light from the grating component to the polarization beam splitter 3. The polarization beam splitter 3 combines the ±1st order diffracted light. The polarization state conversion component also... The beam splitter can perform polarization state conversion on the ±1st order diffracted light incident on the polarization beam splitter 3 and the combined beam emitted from the polarization beam splitter 3. The beam splitting detection component can split the combined beam and detect the signal to obtain the interference signal. The grating component includes several gratings 10 with different grating periods. A grating 10 is detachably mounted on the upper side of the displacement stage 11, and the vector direction of the grating 10 is parallel to the direction of the motion axis of the displacement stage 11. The adjustment component is connected to the reflection component and can adjust the reflection angle of the reflection component for the ±1st order diffracted light.

[0027] The grating assembly includes several gratings 10 with different grid periods. The gratings 10 are mounted on the upper side of the displacement stage 11 with their vector directions parallel to the axis of motion of the displacement stage. The laser generator 1 outputs laser light. The polarization state conversion assembly adjusts the polarization direction of the laser to ensure that the incident light meets the beam splitting requirements. The reflection assembly reflects the ±1st order diffracted light reflected at the Littrow angle from the surface of the grating assembly to the polarization beam splitter 3. The polarization beam splitter 3 combines the ±1st order diffracted light from the surface of the grating assembly into two beams. Opposite phase changes of light interfere, thus converting the minute displacement of grating 10 into a high-contrast interference signal that is easy to measure. The polarization state conversion component can also perform polarization state conversion on ±1st order diffracted light and the combined light emitted by polarization beam splitter 3, ensuring polarization state stability in the optical path and improving anti-interference capability. The beam splitting detection component is used to split the combined light and detect the signal to obtain the interference signal. The multi-path interference signal of the split beam is used to achieve direction discrimination and subdivision by generating orthogonal signals, and interference is suppressed by differential detection. The displacement is determined by analyzing the interference signal. The displacement value of the stage can still provide reliable and accurate measurement results in complex industrial environments. Thus, this invention enhances robustness by using polarization optics design to achieve high-precision displacement measurement. Moreover, by using adjustment components to adjust the reflection angle of the reflection component, this invention matches gratings 10 with different grating periods for displacement measurement at the same wavelength. Compared with traditional grating interferometers, which can only use a fixed grating period for displacement measurement at the same wavelength, this invention improves measurement flexibility and adaptability. Through optical path transmission and signal linkage, a close correlation is formed, forming a measurement logic of "displacement stage movement → synchronous grating movement → optical path difference change → phase shift", completing the entire measurement process of "laser emission → diffraction → interference → signal detection → displacement calculation". Furthermore, by changing gratings 10 with different grating periods and adjusting the reflection angle of the reflection component with adjustment components, it can also adapt to incident lasers of different wavelengths. Thus, high-precision measurement can be achieved without replacing core modules such as polarization beam splitter 3, polarization state conversion component, reflection component, or beam splitting detection component, thereby overcoming the inherent defects of poor versatility and high operating costs of traditional equipment.

[0028] As an optional implementation, the laser generator 1 is configured as a single-frequency laser and is used to output linearly polarized light; the polarization beam splitter 3 is configured as a polarization beam splitter and is used to combine the ±1st order diffracted light diffracted through the surface of the grating assembly.

[0029] As an optional implementation, all gratings 10 are reflective gratings; the gratings 10 can be gratings with different grid periods, such as 1200 lines / mm, 1800 lines / mm, and other gratings with different grid densities; when performing displacement measurement, gratings with different grid periods can be selected as the measurement reference; the gratings 10 are used for diffraction to realize the change in displacement to optical path difference; wherein, the change in displacement to optical path difference refers to the change in optical path of the diffracted light when the displacement stage 11 moves along the axial direction, and the change in optical path difference of the diffracted light is converted into the phase shift of the interference signal to realize displacement measurement; the axial direction of the displacement stage 11 refers to the direction parallel to the vector direction of the grating 10; the interference signal is used to obtain the displacement value of the displacement stage after analytical processing, as the displacement measurement result.

[0030] As an alternative implementation, the grating 10 is detachably mounted on the upper side of the displacement stage 11, such as by fixing the grating 10 to the upper side of the displacement stage 11 with a peelable adhesive.

[0031] As an optional implementation, the reflective assembly includes a first reflector 701, a second reflector 702, a third reflector 703, a fourth reflector 704, and a fifth reflector 705. The first reflector 701 is located on the output side of the laser generator 1, and its reflective surface forms a 45° angle with the laser emission direction. After reflecting the parallel light emitted from the laser generator 1, it is perpendicularly incident on the grating 10. The perpendicular light incident on the surface of the grating 10 generates ±1st order diffracted light. The second reflector 702 and the third reflector 703 are located on different incident sides of the polarizing beam splitter 3, and the reflective surfaces of the second reflector 702 and the third reflector 703 are both perpendicular to the emission direction of the laser generator 1. The fourth reflector 704 and the fifth reflector 705 are both connected to the adjustment assembly and are used to reflect the +1st order diffracted light and the -1st order diffracted light, respectively.

[0032] The +1st order diffracted light from the fourth mirror 704 is reflected to the third mirror 703, and then reflected by the third mirror 703 to the polarization state conversion component; the incident light and the reflected light on the surface of the third mirror 703 are orthogonal; the -1st order diffracted light from the fifth mirror 705 is reflected to the second mirror 702, and then reflected by the second mirror 702 to the polarization state conversion component; the incident light and the reflected light on the surface of the second mirror 702 are orthogonal.

[0033] As an optional implementation, the adjustment assembly includes a first rotary motor 901 and a second rotary motor 902, with a fourth reflector 704 and a fifth reflector 705 respectively connected to the first rotary motor 901 and the second rotary motor 902; the drive ends of the first rotary motor 901 and the second rotary motor 902 can be fixedly connected to the bases of the fourth reflector 704 and the fifth reflector 705 by bolts, so as to be able to drive the fourth reflector 704 and the fifth reflector 705 to rotate respectively (e.g., Figure 1(The direction of rotation drive indicated by the arrow) is used to adjust the reflection angle of the reflective component for the +1st order diffracted light and the -1st order diffracted light.

[0034] Furthermore, it should be noted that the adjustment component is not limited to the aforementioned rotary motor method; any component capable of driving the fourth reflector 704 and the fifth reflector 705 to rotate is acceptable.

[0035] As an optional implementation, the polarization state conversion component includes a half-wave plate 2, a first quarter-wave plate 501, a second quarter-wave plate 502, and a third quarter-wave plate 503, all capable of allowing light to pass through perpendicularly. The half-wave plate 2 is located between the laser generator 1 and the first reflector 701, and is used to adjust the polarization direction of the laser to ensure that the incident light meets the beam splitting requirements. The first quarter-wave plate 501 and the second quarter-wave plate 502 are located on different incident sides of the polarization beam splitter 3 (i.e., the fourth and third adjacent sides of the polarization beam splitter). The first quarter-wave plate 501 and the second quarter-wave plate 502 can respectively convert the polarization state of the +1st order diffracted light and the -1st order diffracted light, realizing the conversion between linearly polarized light and circularly polarized light, and ensuring the stability of the polarization state in the optical path. The third quarter-wave plate 503 is located on the exit side of the polarization beam splitter 3 (i.e., the second side of the polarization beam splitter). The third quarter-wave plate 503 can convert the polarization state of the combined beam, realizing the conversion between linearly polarized light and circularly polarized light, and ensuring the stability of the polarization state in the optical path.

[0036] As an optional implementation, the distances from the first quarter-wave plate 501 to the fourth side of the polarizing beam splitter 3, the distances from the second quarter-wave plate 502 to the third side of the polarizing beam splitter 3, and the distances from the third quarter-wave plate 503 to the second side of the polarizing beam splitter 3 are all equal; the distances from the center of the fourth reflector 704 to the center of the third reflector 703 and the distances from the center of the fifth reflector 705 to the center of the second reflector 702 are all equal; the distances from the center of the second reflector 702 to the first quarter-wave plate 501 and the distances from the center of the third reflector 703 to the second quarter-wave plate 502 are all equal; by controlling the above distances to be the same, the interference from factors other than the movement of the displacement stage 11 during the transmission interference of the +1st order diffracted light and -1st order diffracted light can be reduced, thus reducing the impact on the detection accuracy.

[0037] As an optional implementation, the beam splitting detection assembly includes a first photodetector 801, a second photodetector 802, a first polarizer 601, a second polarizer 602, and a non-polarizing beam splitter 4. Both the first polarizer 601 and the second polarizer 602 are 45° linear polarizers. The incident side (fourth side) of the non-polarizing beam splitter 4 is opposite to the second side of the polarizing beam splitter 3. The non-polarizing beam splitter 4 is used to split the combined optical signal into two beams of interference light of equal intensity, which are respectively incident on the first photodetector 801 and the second photodetector 802. The first polarizer 601 and the second polarizer 602 are respectively disposed on the two exit sides of the non-polarizing beam splitter 4 (i.e., the adjacent first and second sides of the non-polarizing beam splitter 4). The first photodetector 801 and the second photodetector 802 are respectively disposed on the output sides of the first polarizer 601 and the second polarizer 602. Both the first photodetector 801 and the second photodetector 802 are used to receive the interference light and output the interference signal.

[0038] Specifically, the distances from the first polarizer 601 to the first side of the unpolarized beam splitter 4 and the second polarizer 602 to the second side of the unpolarized beam splitter 4 are both equal; similarly, the distances from the first photodetector 801 to the output side of the first polarizer 601 and the second photodetector 802 to the output side of the second polarizer 602 are also equal. By controlling these distances to be identical, the detection accuracy can be reduced due to interference from factors other than the movement of the displacement stage 11 during the transmission interference of the +1st and -1st order diffracted light.

[0039] As an optional implementation, the diffraction angles of the ±1st order diffracted light are related to the grating period of grating 10 and follow the grating diffraction equation, which is: d is the grating period, θ is the diffraction angle, and λ is the laser wavelength.

[0040] Specifically, the specific cooperation relationship between the components of the grating precision displacement sensor provided in this embodiment is as follows: Laser generator 1 is located on the input side of half-wave plate 2; laser generator 1 is used to emit a laser beam; the installation direction of half-wave plate 2 is perpendicular to the emitted light of laser generator 1; the reflecting surface of first reflector 701 is parallel to the first side of polarizing beam splitter 3 and is located on the output side of half-wave plate 2; first rotary motor 901 and second rotary motor 902 are axially symmetrically located on the center line of first reflector 701; fourth reflector 704 and fifth reflector 705 are respectively fixed to the upper sides of first rotary motor 901 and second rotary motor 902; second reflector 702 is parallel to half-wave plate 2 and is located on the input side of first quarter-wave plate 501; third reflector 703 is parallel to half-wave plate 2 and is located on the input side of second quarter-wave plate 501. The input side of the quarter-wave plate 502; the output side of the first quarter-wave plate 501 and the fourth side of the polarizing beam splitter 3 are opposite; the output side of the second quarter-wave plate 502 and the third side of the polarizing beam splitter 3 are opposite; the input side of the third quarter-wave plate 503 and the second side of the polarizing beam splitter 3 are opposite; the fourth side of the unpolarizing beam splitter 4 and the output side of the third quarter-wave plate 503 are opposite; the first polarizer 601 and the second polarizer 602 are located on the first side and the second side of the unpolarizing beam splitter 4, respectively; the first photodetector 801 is located on the output side of the first polarizer 601; the second photodetector 802 is located on the output side of the second polarizer 602.

[0041] like Figure 2 As shown, the overall optical path is illustrated. The grating 10 is mounted on the upper side of the displacement stage 11 with the grating vector direction parallel to the motion axis of the displacement stage 11. At this time, the parallel light emitted from the laser generator 1 is incident on the surface of the grating 10 through the first reflecting mirror 701, generating ±1st order diffraction light on the surface of the grating 10. The fourth reflecting mirror 704 and the fifth reflecting mirror 705 are adjusted by the first rotary motor 901 and the second rotary motor 902. The reflected light from the fourth reflecting mirror 704 and the fifth reflecting mirror 705 is reflected to the third reflecting mirror 703 and the second reflecting mirror 702, respectively, and then incident perpendicularly on the second quarter-wave plate 502 and the first quarter-wave plate 501, respectively, and then combined by the polarization beam splitter 3. The combined light is split into two interference signals with a 90° phase difference by the non-polarization beam splitter 4, which are received by the first photodetector 801 and the second photodetector 802, respectively.

[0042] Figure 3The optical path of the +1st order diffracted light is shown. The emitted light from the laser generator 1 passes through the half-wave plate 2 and is perpendicularly incident on the surface of the grating 10. The generated +1st order diffracted light is reflected by the fourth mirror 704 and the third mirror 703 to the second quarter-wave plate 502. After passing through the second quarter-wave plate 502, it becomes left-hand circularly polarized light. After passing through the polarizing beam splitter 3, the left-hand circularly polarized light becomes P-beam (parallel light). After passing through the third quarter-wave plate 503, it becomes right-hand circularly polarized light. After passing through the unpolarizing beam splitter 4, it is split into two right-hand circularly polarized beams of equal intensity and are respectively incident on the first polarizer 601 and the second polarizer 602.

[0043] Figure 4 The optical path of the -1st order diffracted light is shown. The emitted light from the laser generator 1 passes through the half-wave plate 2 and is perpendicularly incident on the surface of the grating 10. The generated -1st order diffracted light is reflected by the fifth mirror 705 and the second mirror 702 to the first quarter-wave plate 501. After passing through the first quarter-wave plate 501, it becomes right-hand circularly polarized light. After passing through the polarization beam splitter 3, the right-hand circularly polarized light becomes S-beam (perpendicular light). After passing through the third quarter-wave plate 503, it becomes left-hand circularly polarized light. After passing through the unpolarized beam splitter 4, it is split into two left-hand circularly polarized beams of equal intensity and are incident on the first polarizer 601 and the second polarizer 602, respectively.

[0044] The ±1st order diffracted light is combined in the polarization beam splitter 3; the combined beam exits from the second side of the polarization beam splitter 3, and after passing through the third quarter-wave plate 503, it becomes left-handed circularly polarized light and right-handed circularly polarized light, respectively; the left-handed circularly polarized light and right-handed circularly polarized light are combined in the unpolarization beam splitter 4 to become first polarized light and second polarized light of equal intensity; the first polarized light is perpendicularly incident on the first polarizer 601 and interferes to obtain the first interference light, and the second polarized light is perpendicularly incident on the second polarizer 602 and interferes to obtain the second interference light; the first photodetector 801 receives the first interference light to obtain the first signal; the second photodetector 802 receives the second interference light to obtain the second signal; the first signal and the second signal are sinusoidal wave signals with a 90-degree phase difference; the signal processing module processes the first interference signal and the second interference signal to realize displacement measurement.

[0045] Example 2 This embodiment also provides a grating precision displacement measurement system, such as Figure 5 As shown, it includes a signal processing module and the grating precision displacement sensor provided in Embodiment 1; the signal processing module is used to receive the multi-channel interference signals output by the grating precision displacement sensor, and to analyze and process the interference signals to realize displacement measurement.

[0046] As an optional implementation, the signal processing module includes a signal conditioning unit and a data processing unit; wherein, the signal conditioning unit is used to amplify, filter and compensate the interference signal to obtain the conditioned interference signal; the data processing unit is used to perform phase analysis calculation on the conditioned interference signal and obtain the displacement value by combining the grating parameters.

[0047] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, 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 invention.

Claims

1. A grating precision displacement sensor characterized by: It includes a laser generator, a polarization beam splitter, a polarization state conversion assembly, a reflection assembly, a beam splitting and detection assembly, a grating assembly, a displacement stage, and an adjustment assembly; The laser generator is used to output laser light. The polarization state conversion component can adjust the polarization direction of the laser light. The reflection component can reflect the laser light after its polarization direction has been adjusted by the polarization state conversion component to the grating component, and can reflect the ±1st order diffracted light diffracted by the grating component to the polarization beam splitter respectively. The polarization beam splitter can combine the ±1st order diffracted light. The polarization state conversion component can also perform polarization state conversion on the ±1st order diffracted light incident on the polarization beam splitter and the combined light emitted from the polarization beam splitter. The beam splitting detection component can split the combined light and detect the signal to obtain an interference signal. The grating assembly includes several gratings with different grating periods. A grating is detachably disposed on the upper side of the displacement stage, and the vector direction of the grating is parallel to the direction of the movement axis of the displacement stage. The adjustment assembly is connected to the reflection assembly and can adjust the reflection angle of the reflection assembly for the ±1st order diffracted light.

2. The grating precision displacement sensor according to claim 1, characterized in that: The reflective assembly includes a first reflector, a second reflector, a third reflector, a fourth reflector, and a fifth reflector; The first reflector is located on the output side of the laser generator, and its reflective surface forms a 45° angle with the laser emission direction, reflecting the parallel light emitted by the laser generator as perpendicular light incident on the grating assembly; the perpendicular light incident on the grating surface generates the ±1st order diffracted light; the second and third reflectors are located on different incident sides of the polarizing beam splitter, and the reflective surfaces of the second and third reflectors are both perpendicular to the emission direction of the laser generator; the fourth and fifth reflectors are both connected to the adjustment assembly and are used to reflect the +1st order diffracted light and the -1st order diffracted light, respectively; The +1st order diffracted light is reflected by the fourth mirror to the third mirror, and then reflected by the third mirror to the polarization state conversion component; The incident light and the reflected light on the surface of the third reflecting mirror are orthogonal; The -1st order diffracted light from the fifth mirror is reflected to the second mirror, and then reflected by the second mirror to the polarization state conversion component; the incident light and the reflected light on the surface of the second mirror are orthogonal.

3. The grating precision displacement sensor according to claim 2, characterized in that: The adjustment assembly includes a first rotary motor and a second rotary motor, and the fourth reflector and the fifth reflector are respectively connected to the first rotary motor and the second rotary motor; The first rotary motor and the second rotary motor can drive the fourth reflector and the fifth reflector to rotate, respectively, so as to adjust the reflection angle of the reflective component for the +1st order diffracted light and the -1st order diffracted light.

4. The grating precision displacement sensor of claim 2, wherein: The polarization state conversion component includes a half-wave plate, a first quarter-wave plate, a second quarter-wave plate, and a third quarter-wave plate, all of which allow light to pass through perpendicularly. The half-wave plate is located between the laser generator and the first reflector, and is used to adjust the polarization direction of the laser. The first quarter-wave plate and the second quarter-wave plate are located on different incident sides of the polarization beam splitter, and the first quarter-wave plate and the second quarter-wave plate can respectively convert the polarization state of the +1st order diffracted light and the -1st order diffracted light. The third quarter-wave plate is located on the exit side of the polarization beam splitter, and the third quarter-wave plate can convert the polarization state of the combined light.

5. The grating precision displacement sensor according to claim 4, characterized in that: The distances from the first quarter-wave plate to the corresponding incident side of the polarizing beam splitter, the distances from the second quarter-wave plate to the corresponding incident side of the polarizing beam splitter, and the distances from the third quarter-wave plate to the exit side of the polarizing beam splitter are all equal. The distance from the center of the fourth reflector to the center of the third reflector and the distance from the center of the fifth reflector to the center of the second reflector are both equal; the distance from the center of the second reflector to the first quarter-wave plate and the distance from the center of the third reflector to the second quarter-wave plate are both equal.

6. The grating precision displacement sensor of claim 1, wherein: The beam splitting detection component includes a first photodetector, a second photodetector, a first polarizer, a second polarizer, and a non-polarizing beam splitter; The incident side of the unpolarized beam splitter is opposite to the exit side of the polarized beam splitter. The unpolarized beam splitter is used to split the combined beam into two interference beams of equal intensity, which are then incident on the first photodetector and the second photodetector respectively through the two exit sides of the unpolarized beam splitter. The first polarizer and the second polarizer are both 45° linear polarizers. The first polarizer and the second polarizer are respectively disposed on the two exit sides of the unpolarized beam splitter. The first photodetector and the second photodetector are respectively disposed on the output sides of the first polarizer and the second polarizer. Both the first photodetector and the second photodetector are used to receive the interference light and output the interference signal. The distance from the first polarizer to the corresponding exit side of the unpolarized beam splitter and the distance from the second polarizer to the corresponding exit side of the unpolarized beam splitter are both equal; the distance from the first photodetector to the output side of the first polarizer and the distance from the second photodetector to the output side of the second polarizer are both equal.

7. The grating precision displacement sensor of claim 1, wherein: All of the gratings are reflective gratings.

8. The grating precision displacement sensor of claim 1, wherein: The ±1st order diffracted light has a diffraction angle and the grating period of the grating follows the grating diffraction equation; The grating diffraction equation is , d is the grating period, θ is the diffraction angle, and λ is the laser wavelength.

9. The grating precision displacement sensor of claim 1, wherein: The laser generator is configured as a laser and is used to output linearly polarized light, and the polarization beam splitter is configured as a polarization beam splitter.

10. A precision displacement measurement system for gratings, characterized by: Includes a signal processing module and the grating precision displacement sensor as described in any one of claims 1-9; The signal processing module is used to receive the multi-channel interference signals output by the grating precision displacement sensor, and to analyze and process the interference signals to achieve displacement measurement.

Images