Miniature rotary encoder calibration device based on double-grating interference and calibration method thereof

Abstract

The invention relates to a miniature rotary encoder calibration device based on double-grating interference and a calibration method thereof, the miniature rotary encoder calibration device comprises a double-grating homodyne interference calibration system, a micro-vibration displacement table, a miniature rotary encoder and a receiving system, and the micro-vibration displacement table is provided with a mechanical vibration module provided with two grating adjusting devices. The micro rotary encoder is spliced with one grating adjusting device and is in circuit connection with the single-chip microcomputer control module, the single-chip microcomputer control module receives target parameter information input by an upper computer to control the rotary encoder, drives the micro-vibration displacement table to continuously vibrate in the vector direction and drives the gratings to rotate by a set angle, and the single-chip microcomputer control module controls the micro-vibration displacement table to rotate by a set angle. A double-grating interference signal is output in real time, a cosine angle measurement value generated by grating rotation is calculated, and the cosine angle measurement value is compared with a standard value engraved by the micro rotary encoder until calibration is completed. According to the invention, a double-grating interference comparison calibration form is adopted, high-precision calibration of the micro rotary encoder is realized, the micro rotary encoder can be traced to the definition of'meter ', the stability is high, the traceability chain is short, and the robustness is strong.

Description

Technical Field

[0001] The invention relates to a calibration device for a rotary encoder in the field of optical precision measurement, and in particular discloses a calibration device for a micro rotary encoder based on double grating interference and a calibration method thereof. Background Art

[0002] A rotary encoder is a mechanical device that converts angular displacement into an electrical signal. It is widely used in various automated servo motors, such as moving parts on industrial automation equipment production lines, robotic arms in medical equipment, turbine control systems for aerospace vehicles, etc. With the continuous reduction of integrated circuit characteristic parameters and the size of machined parts, and the integration of ultra-precision instruments and equipment, rotary encoders are gradually developing towards miniaturization and precision. Accurate calibration of the angular displacement of micro rotary encoders is the key to ensuring their high precision and reliability. However, there is currently no clear and fixed specification for the calibration method of micro rotary encoders. Therefore, a device with high-precision online calibration function and the corresponding calibration operation method are technical issues that still need to be solved.

[0003] Grating interferometry and laser interferometry are currently commonly used non-contact ultra-precision displacement measurement technologies. The laser interferometry method uses the laser wavelength as the measurement reference. Its characteristics are large range, ranging from micrometers to hundreds of meters, and the measurement resolution can reach nanometers or even picometers. However, the laser wavelength is extremely sensitive to environmental factors, including changes in parameters such as temperature, humidity, and air refractive index, which requires continuous compensation of the laser interferometer to achieve a stable frequency state. The grating interferometer overcomes the deficiency of the laser interferometer being affected by environmental interference by using the grating spacing as the measurement reference. Therefore, when the grating interferometer is used to measure displacement, the frequency stability of the light source is actually not affected. Its measurement accuracy mainly depends on the characteristics of the grating itself, such as the size of the receiving light surface, the base material of the grating spacing, and the surface coating. If the grating interferometry method is used to calibrate the micro rotary encoder, its high-precision measurement characteristics can be used to improve the calibration accuracy of the micro rotary encoder and the stability of the calibration work. However, there is no relevant calibration device or calibration method in the prior art. Summary of the invention

[0004] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a micro-rotary encoder calibration device and a calibration method based on dual-grating interference, which combines a dual-grating zero-difference interference calibration system with a micro-vibration displacement table to achieve precise calibration of the micro-rotary encoder, while ensuring the calibration accuracy and reducing the production cost, and can also be applied to other equipment that requires high-precision displacement calibration.

[0005] The present invention is implemented as follows: a micro-rotary encoder calibration device based on double grating interference and a calibration method thereof, wherein the micro-rotary encoder calibration device based on double grating interference comprises a double grating homodyne interference calibration system, a micro-vibration displacement stage, a micro-rotary encoder and a receiving system.

[0006] The dual-grating homodyne interference calibration system comprises a single-frequency laser light source, a first self-traceable grating interference optical path and a second self-traceable grating interference optical path arranged on both sides of the micro-vibration displacement stage, and a photoelectric receiving device for receiving signals of the two self-traceable grating interference optical paths, wherein the light source is respectively subjected to the action of the transmission surface and the reflection surface of the polarization splitter prism to form an incident light source of the two self-traceable grating interference optical paths, and the photoelectric receiving device is used to convert the received light signal into a digital signal, a mechanical vibration module is provided at the middle position of the displacement base of the micro-vibration displacement stage, and two grating adjustment devices are provided above the mechanical vibration module, each of the grating adjustment devices comprises a grating fixing frame installed on the grating adjustment frame, the grating fixing frame is used to clamp the grating, and the grating adjustment frame is used to adjust the position of the grating, the micro-rotary encoder and the micro-rotary encoder in the receiving system are arranged between the two gratings, and are spliced ​​with one of the two grating adjustment devices, and are connected to the single-chip control module circuit, and the single-chip control module is connected to the host computer using a universal serial bus.

[0007] The single-chip control module is used to receive the target parameter information input by the host computer to control the rotary encoder, and drive the micro-vibration displacement stage to vibrate continuously along the vector direction, while driving the grating to rotate a set angle perpendicular to the movement direction of the micro-vibration displacement stage. The micro-rotary encoder calibration device synchronously displays and records the actual rotation cosine angle measurement value of the grating through the host computer, and compares it with the standard value of the engraved angle of the micro-rotary encoder to complete the calibration of the micro-rotary encoder to meet the standard value range.

[0008] The single-frequency laser light source comprises a driving power supply, a single-frequency laser, an optical fiber jumper and an optical fiber connector. One end of the optical fiber jumper is connected to the corresponding interface of the single-frequency laser, and the other end is inserted into the matching optical fiber connector and locked. The single-frequency laser outputs 405 nm linear polarized light and is coupled to the optical fiber connector via the optical fiber jumper. The optical fiber connector is used to provide a propagation direction with multiple degrees of freedom for the light source and is installed on the optical air floating platform using a connecting rod. The two grating adjustment devices are used to adjust the clamped double gratings to maintain relative parallelism and ensure that the double gratings are parallel to the micro-vibration displacement stage along the vector motion direction.

[0009] The first self-traceable grating interference optical path includes a first half-wave plate, a second reflector, and a second polarization beam splitter prism in sequence, and is divided into two paths after the second polarization beam splitter prism, one path includes a first 1 / 4 wave plate and a fourth reflector in sequence, and the other path includes a second 1 / 4 wave plate and a fifth reflector in sequence. The second self-traceable grating interference optical path includes a second half-wave plate, a third reflector, and a third polarization beam splitter prism in sequence, and is divided into two paths after the third polarization beam splitter prism, one path includes a third 1 / 4 wave plate and a sixth reflector in sequence, and the other path includes a fourth 1 / 4 wave plate and a seventh reflector in sequence. The photoelectric receiving device includes a first photodetector and a second photodetector. The first photodetector is arranged outside the first self-traceable grating interference optical path and is coaxial with the second polarization beam splitter prism. The second photodetector is arranged outside the second self-traceable grating interference optical path and is coaxial with the third polarization beam splitter prism. Each component in the optical path is installed on the optical air floating table using its corresponding connecting rod and clamp.

[0010] The linearly polarized light output by the single-frequency laser is decomposed into two light beams in equal proportion after passing through the transmission surface and reflection surface of the polarization beam splitter prism and entering two self-traceable grating interference light paths. The light beam in the first self-traceable grating interference light path passes through a half-wave plate, a reflector and a polarization beam splitter prism in sequence and is decomposed into two light beams again. The two light beams then pass through a quarter-wave plate and a reflector in sequence and are incident on the corresponding grating surface to be diffracted.

[0011] The second self-traceable grating interference optical path structure and light beam propagation path are the same as those of the first self-traceable grating interference optical path. The four light beams that are finally incident on the corresponding grating surface are all incident on the grating at the Littrow angle, and the diffracted light returns along the original path and converges to interfere, and the optical interference signal is collected by a photoelectric receiving device.

[0012] The photoelectric receiving device includes two photoelectric detectors and a data acquisition card and a signal processing system connected to the two photoelectric detector circuits. The photoelectric detectors are used to convert the received optical interference signals into electrical signals in real time and transmit them to the signal processing system through the data acquisition card.

[0013] The micro-vibration displacement stage is connected to the displacement stage driving system by a communication cable, and the vibration digital signal of the target parameter information input by the host computer is converted into a voltage signal through a signal generator to drive the micro-vibration displacement stage to vibrate continuously along the vector direction.

[0014] The two gratings use one-dimensional chromium self-traceable gratings directly traced to natural constants, and the grating spacing is 212.8 nm. The accuracy and consistency of the one-dimensional chromium self-traceable grating used in the present invention is 0.001 nm. Under the condition of high line density, its surface shape is sinusoidal, and the line density can reach 4700 lines / mm. Its spacing value is 212.8nm, which is half of the wavelength of the laser standing wave field, and completely corresponds to the transition frequency of the chromium atom.

[0015] The calibration method of the micro rotary encoder calibration device based on double grating interference is characterized in that the calibration method includes the following calibration process: The micro rotary encoder is spliced ​​into one of the grating fixing frames of the calibration device to ensure that the initial positions of the double grating lines and grating surfaces are relatively parallel, the laser light source is turned on and the real-time interference signal is received by the photoelectric receiving device, one of the gratings is kept stationary, and the other grating is controlled to rotate clockwise from 0° to 90° perpendicular to the movement direction of the micro-vibration displacement stage through mutual communication among the host computer, the single-chip control module, and the micro rotary encoder, and the phase difference between the rotated grating and the stationary grating is obtained based on the relationship between the light intensity and the grating displacement, the phase difference ratio is calculated, and the inverse cosine operation is performed to solve the cosine angle generated by the grating rotation, and the measured value of the cosine angle of every 10° is recorded in real time on the host computer through the photoelectric receiving device, and the angle value engraved on the rotary encoder is used as the standard value to determine whether the measured value of the cosine angle of every 10° meets the standard value range, until the calibration of the micro rotary encoder is finally completed.

[0016] The beneficial effects of the present invention are: 1. The micro rotary encoder calibration device and calibration method based on dual grating interference proposed in the present invention trace the grating period to the definition of "meter", and have the characteristics of high stability, short traceability chain and strong robustness, which provides a new idea for the calibration of micro rotary encoders.

[0017] 2. The present invention adopts the form of dual-grating interference comparison calibration, combines the dual-grating zero-difference interference calibration system with a micro-vibration displacement stage, and places the two gratings on the same displacement stage for synchronous movement. Therefore, the displacement changes of the two gratings are the same and the grating spacing is also the same. The measurement of angular displacement can be completed by simply outputting the phase of the dual-grating interference signal and performing real-time calculation.

[0018] 3. The overall structure of the micro rotary encoder calibration device based on dual grating interference proposed in the present invention adopts a modular design. Each module component is designed as an independent individual and placed on an optical air flotation table, so that each module component can be quickly disassembled and assembled, thereby improving the efficiency of the calibration work. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1It is a schematic diagram of the structure of the present invention.

[0020] Figure 2 It is a schematic diagram of the three-dimensional structure of the present invention.

[0021] Figure 3 It is a schematic diagram of light path propagation of the present invention.

[0022] Figure 4 It is a schematic diagram of the installation structure relationship between the grating adjustment device and the micro-vibration displacement stage in the present invention.

[0023] Figure 5 It is a schematic diagram of an example of a double grating interference signal of the present invention.

[0024] In the figure: 1. Double grating homodyne interferometry calibration system; 2. Micro-vibration displacement stage; 3. Micro rotary encoder and receiving system; 4. Optical air floating stage; 5. Single frequency laser; 6. Fiber jumper; 7. Fiber connector; 8. First reflector; 9. Second reflector; 10. Third reflector; 11. Fourth reflector; 12. Fifth reflector; 13. Sixth reflector; 14. Seventh reflector; 15. First polarization beam splitter prism; 16. Second polarization beam splitter prism; 17. Third polarization beam splitter prism; 18. First half-wave plate; 19. Second half-wave plate; 20. First 1 / 4 wave plate; 21. Second 1 / 4 wave plate; 22. Third 1 / 4 wave plate; 23. Fourth 1 / 4 wave plate; 24. First photodetector; 25. Second photodetector; 26. Connecting rod; 27. Clamp; 28. Fastening bolt; 29. ​​Upper computer; 101. laser light source; 102. first self-traceable grating interference optical path; 103. second self-traceable grating interference optical path; 104. photoelectric receiving device; 201, grating adjustment frame; 202, grating fixing frame; 203, first self-traceable grating; 204, second self-traceable grating; 205, displacement base; 206, mechanical vibration module; 207, rectangular block; 208, short-circuit rod; 209, fixing screw; 210, through hole; 211, small clamping claw; 212, hexagonal bolt; 301. Micro rotary encoder; 302. Single chip microcomputer control module. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. All other embodiments obtained by ordinary technicians in the field without making creative work based on the embodiments of the present invention shall fall within the scope of protection of the present invention.

[0026] According to the attached Figure 1The present invention provides a micro rotary encoder calibration device based on double grating interference and a calibration method thereof, comprising: a double grating homodyne interference calibration system 1, a micro-vibration displacement stage 2 and a micro rotary encoder and receiving system 3.

[0027] The dual-grating homodyne interference calibration system 1 includes a single-frequency laser light source 101, a first self-traceable grating interference optical path 102 and a second self-traceable grating interference optical path 103 arranged on both sides of a micro-vibration displacement stage 2, and a photoelectric receiving device 104 for receiving signals of the two self-traceable grating interference optical paths, wherein the light sources are respectively subjected to the action of the transmission surface and the reflection surface of a polarization splitter prism to form incident light sources of two self-traceable grating interference optical paths, and the photoelectric receiving device converts the received optical signals into digital signals.

[0028] According to the attached Figure 2 With attached Figure 4 A mechanical vibration module 206 is provided at the middle position of the displacement base 205 of the micro-vibration displacement stage 2, and two grating adjustment devices are provided above the mechanical vibration module 206. The two grating adjustment devices are respectively arranged on the surfaces of two identical rectangular blocks 207. The rectangular block 207 is connected and fixed to the mechanical vibration module 206 through two connecting short-circuit rods 208. The two connecting short-circuit rods 208 are respectively clamped by their respective corresponding small clamps 211, and the fixing screws are screwed into the through holes 210 of the mechanical vibration module 206 to achieve a fixed connection between the connecting short-circuit rods 208 and the mechanical vibration module 206. Grating adjustment frames 201 are respectively arranged above the two rectangular blocks 207, and are respectively connected and fixed by hexagonal bolts 212. The two grating adjustment frames 201 are arranged back to back, and grating fixing frames 202 are respectively installed on the sides. The first self-traceable grating 203 and the second self-traceable grating 204 are respectively clamped by the two grating fixing frames 202.

[0029] The micro-rotary encoder 301 in the micro-rotary encoder and receiving system 3 is arranged between two self-traceable gratings, and is spliced ​​with one of the two grating adjustment devices, and is connected to the single-chip control module 302 circuit.

[0030] According to the attached Figure 2 As a technical optimization solution of the present invention, the dual-grating interference micro-rotary encoder calibration device is an integrated structure and adopts a modular design. Each structural module is placed on the optical air floating table 4 in the form of an independent individual and can be quickly disassembled and assembled.

[0031] Reference Figure 2 With attached Figure 4As an optimization solution of the present invention, the single-frequency laser light source 101 includes a single-frequency laser 5, a fiber jumper 6 and a fiber connector 7. One end of the fiber jumper 6 is connected to the corresponding interface of the single-frequency laser 5, and the other end is inserted into the matching fiber connector 7 and locked. The fiber connector 7 is used to provide the light source with multiple degrees of freedom in propagation direction. The first self-traceable grating interference optical path 102 includes a first half-wave plate 18, a second reflector 9 and a second polarization beam splitter prism 16 in sequence, and is divided into two paths after the second polarization beam splitter prism 16, one path includes a first 1 / 4 wave plate 20 and a fourth reflector 11 in sequence, and the other path includes a second 1 / 4 wave plate 21 and a fifth reflector 12 in sequence. The second self-traceable grating interference optical path 103 includes a second half-wave plate 19, a third reflector 10 and a third polarization beam splitter prism 17 in sequence, and is divided into two paths after the third polarization beam splitter prism 17, one path includes a third 1 / 4 wave plate 22 and a sixth reflector 13 in sequence, and the other path includes a fourth 1 / 4 wave plate 23 and a seventh reflector 14 in sequence. The photoelectric receiving device 104 includes a first photodetector 24 and a second photodetector 25 and a data acquisition card and a signal processing system connected to the two photodetector circuits. The photodetector is used to convert the received optical interference signal into an electrical signal in real time and transmit it to the signal processing system through the data acquisition card. The first photodetector 24 is arranged outside the first self-traceable grating interference optical path 102 and is coaxial with the second polarization beam splitter prism 16. The second photodetector 25 is arranged outside the second self-traceable grating interference optical path 103 and is coaxial with the third polarization beam splitter prism 17.

[0032] As an optimization scheme of the present invention, a first polarization beam splitter prism 15 is used to form two paths of incident light of self-tracing grating interference light paths after the light source of the single-frequency laser light source 101 passes through the transmission surface and the reflection surface, wherein the transmission surface is arranged coaxially with the incident surface of the first half-wave plate 18 and the second reflector 9, and the reflection surface is arranged coaxially with the incident surface of the second half-wave plate 19 and the third reflector 10. The transmission surface of the second polarization beam splitter prism 16 is arranged coaxially with the incident surface of the first 1 / 4 wave plate 20, the fourth reflector 11 and the receiving surface of the first photodetector 24, and the reflection surface is arranged coaxially with the incident surface of the second 1 / 4 wave plate 21 and the fifth reflector 12. The transmission surface of the third polarization beam splitter prism 17 is arranged coaxially with the incident surface of the third 1 / 4 wave plate 22, the sixth reflector 13 and the receiving surface of the second photodetector 25, and the reflection surface is arranged coaxially with the incident surface of the fourth 1 / 4 wave plate 23 and the seventh reflector 14.

[0033] As an optimization solution of the present invention, the optical and mechanical components of the dual-grating homodyne interferometry calibration system 1 are all mounted on the optical air-floating platform 4 using connecting rods 26 and fixed by clamping claws 27 and fastening bolts 28 at the bottom of the connecting rods 26 .

[0034] As an optimization scheme of the present invention, the micro-vibration displacement stage 2 is connected to the displacement stage drive system by a communication cable, the host computer 29 inputs the target parameters and issues a vibration command, the vibration digital signal is converted into a voltage signal through a signal generator, and the single-chip microcomputer control module controls the rotary encoder according to the target parameter information received from the host computer, and drives the micro-vibration displacement stage 2 to vibrate continuously along the vector direction, driving the grating spliced ​​with the micro-rotary encoder to rotate a certain angle perpendicular to the movement direction of the micro-vibration displacement stage 2. At the same time, the output angle of the micro-rotary encoder and the actual rotation angle of the grating are synchronously displayed on the host computer, and compared with the standard value of the engraved angle of the rotary encoder until the calibration of the micro-rotary encoder is completed.

[0035] Reference Figures 1 to 4 The specific optical path propagation process of the double grating homodyne interferometry calibration system 1 and the micro-vibration displacement stage 2 is as follows: In this embodiment, in order to make the layout of each structural module arranged on the optical air-floating platform 4 more reasonable and compact, a first reflector 8 is provided at the incident end of the first polarization beam splitter prism 15, and the first reflector 8 is also installed on the optical air-floating platform 4 by using a connecting rod 26 and a clamp 27. The single-frequency laser 5 emits a laser, and the output is a 405 nm linear polarized light, which is coupled to the optical fiber connector 7 through the optical fiber jumper 6 and then incident on the first reflector 8. After being reflected by the first reflector 8, it enters the first polarization beam splitter prism 15, and is decomposed into a first horizontal polarized light and a first vertical polarized light by the first polarization beam splitter prism 15. The first horizontal polarized light enters the first self-traceable grating interference optical path 102, and is reflected by the first half-wave plate 18 and the second reflector 9 to the second polarization beam splitter prism 16, and is decomposed into two polarized lights again. The second vertical polarized light passes through the first 1 / 4 wave plate 20 and the fourth reflector 11 convert it into left-handed circularly polarized light, and the second horizontally polarized light is converted into right-handed circularly polarized light through the second 1 / 4 wave plate 21 and the fifth reflector 12. The left-handed circularly polarized light and the right-handed circularly polarized light are respectively incident on the surface of the first self-traceable grating 203 at the Littrow angle and diffracted. The two -1 order diffracted lights return along the original path and converge at the second polarization splitter prism 16 to form the first self-traceable grating 203 optical interference signal, which is received by the first photodetector 24. The first vertical polarized light enters the second self-traceable grating interference optical path 103, is reflected by the second half-wave plate 19 and the third reflector 10 to the third polarization beam splitter prism 17, and is decomposed into two polarized lights again. The third vertical polarized light is converted into left-handed circularly polarized light by the third 1 / 4 wave plate 22 and the sixth reflector 13, and the third horizontal polarized light is converted into right-handed circularly polarized light by the fourth 1 / 4 wave plate 23 and the seventh reflector 14. The left-handed circularly polarized light and the right-handed circularly polarized light are respectively incident on the surface of the second self-traceable grating 204 at the Littrow angle and diffracted. The two -1 order diffracted lights return along the original path and converge at the third polarization beam splitter prism 17 to form the second self-traceable grating 204 optical interference signal, which is received by the second photodetector 25.

[0036] As a technical optimization solution of the present invention, the angle between the fast axis of the half-wave plate and the 1 / 4 wave plate and the light incident plane is 45°, wherein the half-wave plate is used to make the polarization direction of the incident laser be 45° with the incident plane and proportionally adjust the split light intensity of the first polarization splitter prism 16, and the 1 / 4 wave plate is used to convert linear polarized light into circularly polarized light.

[0037] As a technical optimization solution of the present invention, the grating adjustment frame 201 in the two grating adjustment devices has a three-axis adjustment knob. By rotating the three-axis knobs respectively, the grating fixing frame 202 drives the first self-traceable grating 203 and the second self-traceable grating 204 to keep the grating lines parallel to the grating surface, and keep the vector motion directions of the two self-traceable gratings consistent with the micro-vibration displacement stage 2. The two self-traceable gratings are both one-dimensional chromium self-traceable gratings, and the grating spacing is 212.8 nm, which can be directly traced to natural constants without measurement.

[0038] Reference Figures 1 to 3 The micro-rotary encoder and receiving system 3 includes a micro-rotary encoder 301 and a single-chip control system 302. The front end of the micro-rotary encoder 301 is inserted into the corresponding interface of the grating fixing frame 202 of the first self-traceable grating 203, and the rear end is connected to the single-chip control system 302 through a wire. The single-chip control system 302 is connected to the host computer through a USB serial port for communication.

[0039] The micro rotary encoder calibration method based on double grating interference described in the present invention has the following specific calibration process: Firstly, the dual-grating homodyne interferometer calibration system 1, the micro-vibration displacement stage 2, the micro-rotary encoder and the receiving system 3 are respectively assembled and constructed according to the optical path structure, the center position of the optomechanical component is adjusted to be consistent with the center position of the grating surface and the height of the photodetector receiving surface, the angle between the fast axis of the half-wave plate and the quarter-wave plate and the light incident plane is adjusted to be 45°, the micro-rotary encoder 301 is spliced ​​to the grating fixing frame 202 of the first self-traceable grating 203, and the two grating adjustment frames are adjusted to keep the two grating surfaces, grating lines and the vector motion direction of the micro-vibration displacement stage 2 parallel.

[0040] Further, the single-frequency laser 5 and the micro-vibration displacement stage 2 are powered on and the motion parameters are set. The linear polarized light with a wavelength of 405 nm enters the optical fiber connector 7. The optical fiber connector 7 is adjusted to collimate the light beam and enter the first polarization beam splitter prism 15. The first horizontal polarized light and the first vertical polarized light decomposed by the first polarization beam splitter prism 15 enter the first self-traceable grating interference optical path 102 and the second self-traceable grating interference optical path 103 respectively. Two interference signals are formed according to the optical path propagation process, and are received by the first photodetector 24 and the second photodetector 25 to the data acquisition card respectively, and then transmitted to the host computer 29.

[0041] Furthermore, the second self-traceable grating 204 is kept stationary without any angular deflection, and communication is performed with the single-chip control module 302 via the host computer 29, and the angle rotation command is transmitted to the micro rotary encoder 301 to control the first self-traceable grating 203 to rotate clockwise from the 0° position to the 90° position perpendicular to the movement direction of the micro-vibration displacement stage, and the cosine angle measurement value displayed in real time on the host computer 29 is recorded every time the first self-traceable grating 203 rotates 10°.

[0042] Based on the relationship between light intensity and grating displacement, the phase difference between the rotated first self-traceable grating 203 and the stationary second self-traceable grating 204 is obtained, the phase difference ratio is calculated and the inverse cosine operation is performed to solve the cosine angle generated by the grating rotation. The cosine angle output value is recorded in real time on the host computer through the photoelectric receiving device and linear fitting is performed to obtain the cosine angle output curve. When the grating does not rotate, the light intensity expressions of the two interference signals are respectively expressed as: , , where I 1 ,I 2 are the interference light intensities of the first self-traceable grating 203 and the second self-traceable grating 204, d 1 is the spacing of the first self-traceable grating 203, d 2 is the spacing of the second self-traceable grating 204, and d 1 = d 2 , x(t) is the displacement. When the grating rotates by angle γ, the light intensity expression becomes: , , the relationship between the phase difference and displacement of the interference signal is expressed as: , , the two expressions can be combined to obtain the value of the rotation angle γ: According to the attached Figure 5 The figure shows two self-traceable grating interference signals, wherein the solid line is the first self-traceable grating interference signal curve, and the dotted line is the second self-traceable grating interference signal curve. The grating rotates clockwise from the 0° position to the 90° position, and the real-time measurement value of the rotation angle γ is recorded every 10°. The angle value engraved on the rotary encoder is used as the standard value, and it is determined whether the cosine angle measurement value of each 10° meets the standard value range, thereby completing the calibration of the micro rotary encoder 301.

[0043] Although the embodiments of the present invention have been shown and described, those skilled in the art will find that there may be changes in the specific implementation and scope of application based on the concept of the present invention. In summary, the contents of this specification should not be understood as limiting the present invention.

Claims

1. A micro rotary encoder calibration device based on double grating interference, characterized in that: Including double grating homodyne interferometry calibration system, micro vibration displacement stage and micro rotary encoder and receiving system, The dual-grating homodyne interference calibration system comprises a single-frequency laser light source, a first self-traceable grating interference optical path and a second self-traceable grating interference optical path arranged on both sides of the micro-vibration displacement stage, and a photoelectric receiving device for receiving signals of the two self-traceable grating interference optical paths, wherein the light source is respectively subjected to the action of the transmission surface and the reflection surface of the polarization beam splitter prism to form an incident light source of the two self-traceable grating interference optical paths, and the photoelectric receiving device is used to convert the received optical signal into a digital signal. A mechanical vibration module is provided at the middle position of the displacement base of the micro-vibration displacement stage, and two grating adjustment devices are provided above the mechanical vibration module. Each of the grating adjustment devices comprises a grating fixing frame installed on the grating adjustment frame, the grating fixing frame is used to clamp the grating, and the grating adjustment frame is used to adjust the position of the grating. The micro-rotary encoder and the micro-rotary encoder in the receiving system are arranged between the two gratings, and are spliced ​​with one of the two grating adjustment devices, and are connected to the single-chip control module circuit. The single-chip control module is connected to the host computer using a universal serial bus.

2. The micro rotary encoder calibration device based on double grating interference according to claim 1 is characterized in that: The single-chip control module is used to receive the target parameter information input by the host computer to control the rotary encoder, and drive the micro-vibration displacement stage to vibrate continuously along the vector direction, while driving the grating to rotate a set angle perpendicular to the movement direction of the micro-vibration displacement stage. The micro-rotary encoder calibration device synchronously displays and records the actual rotation cosine angle measurement value of the grating through the host computer, and compares it with the standard value of the engraved angle of the micro-rotary encoder to complete the calibration of the micro-rotary encoder to meet the standard value range.

3. The micro rotary encoder calibration device based on double grating interference according to claim 1 is characterized in that: The single-frequency laser light source comprises a driving power supply, a single-frequency laser, an optical fiber jumper and an optical fiber connector. One end of the optical fiber jumper is connected to the corresponding interface of the single-frequency laser, and the other end is inserted into the matching optical fiber connector and locked. The single-frequency laser outputs 405 nm linear polarized light and is coupled to the optical fiber connector via the optical fiber jumper. The optical fiber connector is used to provide a propagation direction with multiple degrees of freedom for the light source and is installed on the optical air floating platform using a connecting rod. The two grating adjustment devices are used to adjust the clamped double gratings to maintain relative parallelism and ensure that the double gratings are parallel to the micro-vibration displacement stage along the vector motion direction.

4. The micro rotary encoder calibration device based on double grating interference according to claim 1 is characterized in that: The first self-traceable grating interference optical path includes a first half-wave plate, a second reflector, and a second polarization beam splitter prism in sequence, and is divided into two paths after the second polarization beam splitter prism, one path includes a first 1 / 4 wave plate and a fourth reflector in sequence, and the other path includes a second 1 / 4 wave plate and a fifth reflector in sequence. The second self-traceable grating interference optical path includes a second half-wave plate, a third reflector, and a third polarization beam splitter prism in sequence, and is divided into two paths after the third polarization beam splitter prism, one path includes a third 1 / 4 wave plate and a sixth reflector in sequence, and the other path includes a fourth 1 / 4 wave plate and a seventh reflector in sequence. The photoelectric receiving device includes a first photodetector and a second photodetector. The first photodetector is arranged outside the first self-traceable grating interference optical path and is coaxial with the second polarization beam splitter prism. The second photodetector is arranged outside the second self-traceable grating interference optical path and is coaxial with the third polarization beam splitter prism. Each component in the optical path is installed on the optical air floating table using its corresponding connecting rod and clamp.

5. The micro rotary encoder calibration device based on double grating interference according to claim 4 is characterized in that: The linearly polarized light output by the single-frequency laser is decomposed into two light beams in equal proportion after passing through the transmission surface and reflection surface of the polarization beam splitter prism and entering two self-traceable grating interference light paths. The light beam in the first self-traceable grating interference light path passes through a half-wave plate, a reflector and a polarization beam splitter prism in sequence and is decomposed into two light beams again. The two light beams then pass through a quarter-wave plate and a reflector in sequence and are incident on the corresponding grating surface to be diffracted.

6. The micro rotary encoder calibration device based on double grating interference according to claim 4 is characterized in that: The second self-traceable grating interference optical path structure and light beam propagation path are the same as those of the first self-traceable grating interference optical path. The four light beams that are finally incident on the corresponding grating surface are all incident on the grating at the Littrow angle, and the diffracted light returns along the original path and converges to interfere, and the optical interference signal is collected by a photoelectric receiving device.

7. The micro rotary encoder calibration device based on double grating interference according to claim 1 or 4, characterized in that: The photoelectric receiving device includes two photoelectric detectors and a data acquisition card and a signal processing system connected to the two photoelectric detector circuits. The photoelectric detectors are used to convert the received optical interference signals into electrical signals in real time and transmit them to the signal processing system through the data acquisition card.

8. The micro rotary encoder calibration device based on double grating interference according to claim 1 or 3, characterized in that: The micro-vibration displacement stage is connected to the displacement stage driving system by a communication cable, and the vibration digital signal of the target parameter information input by the host computer is converted into a voltage signal through a signal generator to drive the micro-vibration displacement stage to vibrate continuously along the vector direction.

9. The micro rotary encoder calibration device based on double grating interference according to claim 1, 4, 5 or 6, characterized in that: The two gratings are one-dimensional chromium self-traceable gratings directly traced to natural constants, and the grating spacing is 212.8nm.

10. A calibration method for a micro rotary encoder calibration device based on double grating interference, used in the micro rotary encoder calibration device based on double grating interference as claimed in any one of claims 1 to 9, characterized in that The calibration method includes the following calibration process: The micro rotary encoder is spliced ​​into one of the grating fixing frames of the calibration device to ensure that the initial positions of the double grating lines and grating surfaces are relatively parallel, the laser light source is turned on and the real-time interference signal is received by the photoelectric receiving device, one of the gratings is kept stationary, and the other grating is controlled to rotate clockwise from 0° to 90° perpendicular to the movement direction of the micro-vibration displacement stage through mutual communication among the host computer, the single-chip control module, and the micro rotary encoder, and the phase difference between the rotated grating and the stationary grating is obtained based on the relationship between the light intensity and the grating displacement, the phase difference ratio is calculated, and the inverse cosine operation is performed to solve the cosine angle generated by the grating rotation, and the measured value of the cosine angle of every 10° is recorded in real time on the host computer through the photoelectric receiving device, and the angle value engraved on the rotary encoder is used as the standard value to determine whether the measured value of the cosine angle of every 10° meets the standard value range, until the calibration of the micro rotary encoder is finally completed.

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