Heterodyne laser interferometer signal processing link dynamic performance calibration device based on acousto-optic frequency shifter and calibration method thereof

Abstract

The invention discloses a heterodyne laser interferometer signal processing link dynamic performance calibration device based on an acousto-optic frequency shifter and a calibration method of the heterodyne laser interferometer signal processing link dynamic performance calibration device, and relates to the technical field of heterodyne laser interferometer dynamic measurement performance calibration. The calibration result is coupled with the abbe error and cosine error caused by mechanical installation and the like and the data cycle error caused by asynchronous measurement, so that the problem that the dynamic measurement performance of the interferometer in the signal processing link is difficult to evaluate is solved. The calibration device comprises a laser assembly, a first measurement light path, a second measurement light path, an AOFS drive and motor controller light path and a phase meter. The laser assembly emits laser into the beam splitter prism assembly, the beam splitter prism assembly divides incident light into two beams of laser, the two beams of laser enter the first measuring light path and the second measuring light path respectively, and finally the two beams of laser are sent to the phase meter to calculate the phase difference. The device is an equivalent calibration device suitable for dynamic measurement performance of a heterodyne laser interferometer under high-speed movement of a target in a signal processing link.

Description

Technical Field

[0001] The invention relates to the technical field of dynamic measurement performance calibration of heterodyne laser interferometers, and in particular to the technical field of equivalent calibration devices for dynamic measurement performance of a signal processing link of a heterodyne laser interferometer under high-speed target motion. Background Art

[0002] Heterodyne laser interferometers are widely used in ultra-precision CNC machining, microelectronic equipment manufacturing, precision sensor calibration and other fields. With the rapid development of these fields, the dynamic measurement performance of heterodyne laser interferometers has been put forward with high speed and high precision. As the signal processing link that determines the ultimate measurement performance of heterodyne laser interferometers, the calibration of its dynamic measurement performance is also a new challenge.

[0003] During the dynamic measurement of heterodyne laser interferometer, mechanical installation and vibration of the target to be measured will introduce Abbe error and cosine error; temperature changes, humidity fluctuations, and air pressure disturbances caused by m / s-level high-speed motion will introduce air refractive index errors, and the measurement time delay of the interferometer will introduce data period errors. Similarly, these errors still exist in the calibration methods of mainstream laser interferometers and will be coupled into the calibration results, making it impossible to calibrate the measurement performance of the laser interferometer signal processing link, and thus making it difficult to evaluate the extreme dynamic measurement performance of the laser interferometer.

[0004] There are two main calibration methods for heterodyne laser interferometers. The first method is to calibrate each part of the heterodyne interferometer, including temperature, humidity, air pressure sensors, optical lens group, fringe counter, light source, etc., and calculate the calibration results of the overall performance of the interferometer. For example, the Calibration of Displacement Laser Interferometer Systems for Industrial Metrology published on Sensor on September 22, 2019, uses a PZT micro-displacement stage or a heated aluminum tube to test the limit accuracy of the interferometer counting link. However, this method cannot achieve high-speed dynamic calibration, and does not introduce air refractive index errors. Paper published on June 1, 2009: Design of standard test platform for signal processing unit of ultra-precision dynamic laser interferometer. Use electrical signals to simulate the dynamic motion trajectory of the heterodyne laser interferometer to realize the calibration test of the signal processing unit. However, this method is not compatible with the more critical photoelectric conversion part in the signal processing link.

[0005] The second method is to let the interferometer to be calibrated and the high-precision reference interferometer measure the same target on the comparison platform, and determine the performance of the interferometer to be calibrated based on the difference in measurement results. The interferometer calibration specification ASME B89.1.8-2011 is used.

[0006] The method is described and analyzed in detail in the Performance Evaluation of Displacement-Measuring Laser Interferometers. Although this type of calibration method can evaluate the interferometer performance as a whole, its calibration results are coupled with the Abbe error and cosine error caused by mechanical installation, as well as the data period error caused by asynchronous measurement, making it difficult to evaluate the dynamic measurement performance of the interferometer signal processing link. Summary of the invention

[0007] The present invention solves the problem that the existing heterodyne laser interferometer calibration method has a calibration result coupled with Abbe error and cosine error caused by mechanical installation and data period error caused by asynchronous measurement, which makes it difficult to evaluate the dynamic measurement performance of the interferometer signal processing link.

[0008] To achieve the above object, the present invention provides the following solutions:

[0009] The present invention provides a dynamic performance calibration device for a heterodyne laser interferometer signal processing link based on an acousto-optic frequency shifter, the calibration device comprising a laser assembly, a first measurement optical path, a second measurement optical path, an AOFS drive and motor controller optical path and a phase meter;

[0010] The first measuring optical path includes a first reflector, a first AOFS, a first aperture, a first 1 / 2 wave plate, a polarization beam splitter prism PBS, a polarizer and a photodetector PD;

[0011] The second optical path comprises a beam splitter prism assembly, a second AOFS, a second aperture, a second 1 / 2 wave plate, a second reflector and a motor;

[0012] The laser assembly is used to emit laser light, which is injected into the beam splitter prism assembly. The beam splitter prism assembly splits the incident light into two beams of laser light with perpendicular polarization directions, and injects them into the first reflector and the second AOFS respectively;

[0013] The first reflector reflects the incident light into the first AOFS, the first AOFS diffracts the incident light into multi-order diffraction light and injects it into the first aperture, the first aperture selects +1-order diffraction light of the multi-order diffraction light and injects it into the first 1 / 2 wave plate, the first 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction light and injects it into the polarization beam splitter prism PBS, the polarization beam splitter prism PBS injects the incident light into the polarizer, the polarizer converts the incident light into a beat frequency light signal and sends it to the photodetector PD, the photodetector PD converts the beat frequency light signal into an electrical signal and sends it to the phase meter;

[0014] The second AOFS diffracts the light beam into multiple diffraction lights and injects them into the second aperture, the second aperture selects +1-order diffraction lights of the multiple diffraction lights and injects them into the second 1 / 2 wave plate, the second 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction lights and injects them into the second reflector, and the second reflector reflects the incident light to the polarization beam splitter prism PBS;

[0015] The laser assembly is also used to provide a reference optical signal to the AOFS drive and motor controller optical path;

[0016] The AOFS drive and motor controller optical path is used to control the driving frequencies of the first AOFS and the second AOFS respectively, and is also used to control the angle of the second reflector through the motor, and is also used to convert the laser emitted by the laser assembly into a reference electrical signal and send it to the phase meter;

[0017] The phase meter is used to calculate the phase difference according to the received electrical signal.

[0018] Furthermore, in a preferred embodiment, the laser assembly is implemented by a dual-frequency laser having a reference optical signal;

[0019] The above-mentioned beam splitter prism assembly is implemented by a first polarization beam splitter prism PBS;

[0020] The above-mentioned AOFS drive and motor controller optical path includes a depolarizing beam splitter prism NPBS, a second photodetector PD, a third photodetector PD and an AOFS drive and motor controller;

[0021] The dual-frequency laser with the reference light signal emits two laser beams, one laser beam enters the first polarization beam splitter prism PBS, and the other laser beam enters the depolarization beam splitter prism NPBS. The depolarization beam splitter prism NPBS splits the incident light into two linear polarized lights, which are respectively emitted into the second photodetector PD and the third photodetector PD. The second photodetector PD converts the incident light signal into an electrical signal and sends it to the AOFS drive and motor controller. The third photodetector PD converts the incident light signal into an electrical signal and sends it to the phase meter.

[0022] The AOFS drive and motor controller is used to use the received electrical signal as a driving clock to adjust the driving frequencies of the first AOFS and the second AOFS respectively, and is also used to control the motor.

[0023] Furthermore, in a preferred embodiment, the dual-frequency laser with the reference light signal emits two coaxially transmitted laser beams with perpendicular polarization directions and different frequencies.

[0024] Furthermore, in another preferred embodiment, the laser assembly can also be implemented using a dual-frequency laser without a reference optical signal;

[0025] The above-mentioned beam splitter prism assembly can also be implemented by using a first polarization beam splitter prism PBS;

[0026] The above-mentioned AOFS drive and motor controller optical path includes a first depolarizing beam splitter prism NPBS, a second polarizer, a second depolarizing beam splitter prism NPBS, a second photodetector PD, a third photodetector PD and an AOFS drive and motor controller;

[0027] The dual-frequency laser without a reference light signal emits a laser beam, which is incident on the first depolarization beam splitter prism NPBS. The first depolarization beam splitter prism NPBS splits the incident light into two polarized laser beams, which are respectively incident on the first polarization beam splitter prism PBS and the second polarizer. The second polarizer converts the incident light into a beat frequency light signal, which is incident on the second depolarization beam splitter prism NPBS. The second depolarization beam splitter prism NPBS splits the incident light into two linearly polarized lights, which are respectively incident on the second photodetector PD and the third photodetector PD. The second photodetector PD converts the incident light signal into an electrical signal and sends it to the AOFS drive and motor controller. The third photodetector PD converts the incident light signal into an electrical signal and sends it to the phase meter.

[0028] The AOFS drive and motor controller is used to use the received electrical signal as a driving clock to adjust the driving frequencies of the first AOFS and the second AOFS respectively, and is also used to control the motor.

[0029] Furthermore, in a preferred embodiment, the dual-frequency laser without a reference optical signal emits two coaxially transmitted laser beams with vertical polarization directions and different frequencies.

[0030] Furthermore, in another preferred embodiment, the above laser assembly can also be implemented using a single-frequency laser;

[0031] The above-mentioned beam splitter prism assembly can also be implemented by using a second depolarizing beam splitter prism NPBS;

[0032] The AOFS driving and motor controller circuit includes a first depolarizing beam splitter prism NPBS, a third reflector, a third depolarizing beam splitter prism NPBS, a fourth AOFS, a fourth aperture, a fourth 1 / 2 wave plate, a fifth reflector, a fourth reflector, a third AOFS, a third aperture, a third 1 / 2 wave plate, a second polarizing beam splitter prism PBS, a second polarizer, a second photodetector PD and an AOFS driving and motor controller;

[0033] The single-frequency laser emits a laser beam, which is incident on the first depolarization beam splitter prism NPBS. The depolarization beam splitter NPBS splits the incident light into two laser beams, which are respectively incident on the second depolarization beam splitter NPBS and the third reflector;

[0034] The third reflector reflects the incident light to the third depolarizing beam splitter prism NPBS, the depolarizing beam splitter NPBS splits the incident light into two laser beams, which are respectively emitted into the fourth reflector and the fourth AOFS, the fourth reflector reflects the incident light to the third AOFS, the third AOFS diffracts the incident light into multi-order diffraction light and emits it into the third aperture, the third aperture selects +1-order diffraction light of the multi-order diffraction light and emits it into the third 1 / 2 wave plate, the third 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction light and emits it into the second polarizing beam splitter prism PBS, the second polarizing beam splitter prism PBS emits the incident light into the second polarizing plate, the second polarizing plate converts the incident light into a beat frequency light signal and sends it to the second photodetector PD, the second photodetector PD converts the beat frequency light signal into an electrical signal and sends it to the phase meter;

[0035] The fourth AOFS diffracts the incident light into multi-order diffraction light and injects it into the fourth aperture, the fourth aperture selects +1-order diffraction light of the multi-order diffraction light and injects it into the fourth 1 / 2 wave plate, the fourth 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction light and injects it into the fifth reflector, and the fifth reflector reflects the incident light to the second polarization beam splitter prism PBS;

[0036] The AOFS drive and motor controller is used to adjust the driving frequencies of the first AOFS, the second AOFS, the third AOFS and the fourth AOFS respectively, and is also used to control the motor.

[0037] Furthermore, in a preferred embodiment, the above-mentioned single-frequency laser emits a beam of linearly polarized single-frequency light.

[0038] Furthermore, in a preferred embodiment, the depolarizing beam splitter NPBS splits the incident light into two laser beams with the same polarization direction.

[0039] Furthermore, in a preferred embodiment, the AOFS drive and motor controller is used to set the drive signal frequencies of the third AOFS and the fourth AOFS to fixed values.

[0040] The present invention also provides a method for calibrating the dynamic performance of a heterodyne laser interferometer signal processing link based on an acousto-optic frequency shifter. The calibration method is implemented based on any one of the above-mentioned devices for calibrating the dynamic performance of a heterodyne laser interferometer signal processing link based on an acousto-optic frequency shifter. The calibration method is:

[0041] S1. Pre-measurement: respectively adjust the rotation angle of the first 1 / 2 wave plate and the first 1 / 2 wave plate so that the rotation direction is perpendicular to the direction of the optical path, adjust the polarization beam splitter prism PBS, change the optical power of the two laser beams that eventually interfere, adjust the rotation angle of the polarizer so that the rotation direction is perpendicular to the direction of the optical path, respectively adjust the driving frequencies of the first AOFS and the second AOFS, and measure the optical power of the beat frequency optical signal and the adjustable range of the AC-DC ratio and the optical power and AC-DC ratio of the optical signal of the AOFS drive and motor controller circuit clock at different beat frequencies;

[0042] S2, measurement initialization: adjusting the beat frequency of the beat frequency optical signal of the measuring path to a preset value by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS of the first measuring optical path and the second measuring optical path, and adjusting the optical power and AC-DC ratio of the beat frequency optical signal of the measuring path to a preset value by adjusting the rotation angles of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path;

[0043] S3, select test points;

[0044] S4. Start measuring: adjust the two AOFS driving frequencies and the angle of the reflector of the first measuring optical path and the second measuring optical path simultaneously through the AOFS drive and motor controller to make the beat frequency of the measuring path beat frequency optical signal reach the test point, adjust the rotation angles of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path to adjust the optical power and AC-DC ratio of the measuring path beat frequency optical signal, use the phase meter to measure the phase difference between the interference light and the actual simulated motion phase of the target to be measured in real time, and perform dynamic test performance test and calibration of the heterodyne laser interferometer signal processing link.

[0045] The beneficial effects of the present invention are:

[0046] 1. The present invention provides a dynamic performance calibration device for the signal processing link of a heterodyne laser interferometer based on an acousto-optic frequency shifter. The two AOFS driving frequencies and the angle of the reflector of the first measuring optical path and the second measuring optical path are adjusted simultaneously by the AOFS drive and the motor controller so that the beat frequency of the measuring path beat frequency optical signal reaches the test point. The rotation angles of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path are adjusted to adjust the optical power and the AC-DC ratio of the measuring path beat frequency optical signal. The phase difference between the interference light and the actual simulated motion phase of the target to be measured is measured in real time by using the phase meter to be measured, so as to perform dynamic test performance test and calibration of the signal processing link of the heterodyne laser interferometer.

[0047] 2. The present invention provides a dynamic performance calibration device for the signal processing link of a heterodyne laser interferometer based on an acousto-optic frequency shifter. The device is designed based on the basic heterodyne laser interference structure, and uses an AOFS drive and motor controller to simultaneously change the driving frequencies of two acousto-optic frequency shifters AOFS or to keep the driving frequency of one acousto-optic frequency shifter AOFS unchanged and adjust the driving frequency of the other acousto-optic frequency shifter AOFS to continuously modulate the frequency of the final synthesized beat frequency optical signal to simulate different motion modes of the target to be measured. The AOFS drive and motor controller simultaneously drives the motor to adjust the angle of the second reflector so that the two lasers of the first measuring optical path and the second measuring optical path have a good degree of overlap when they are finally synthesized, so as to ensure the quality of the interference optical signal during the modulation process.

[0048] 3. Existing heterodyne laser interferometers often couple multiple errors such as environmental error, Abbe error, cosine error, data cycle error, etc. in displacement measurement, which will lead to the problem of difficulty in evaluating the dynamic measurement performance of the interferometer signal processing link. The present invention provides a dynamic performance calibration device for heterodyne laser interferometer signal processing link based on an acousto-optic frequency shifter, which generates an interference beat frequency optical signal and adjusts its frequency to simulate the high-speed motion of the target to be measured, and simultaneously realizes the adjustment of the optical power and AC-DC ratio of the beat frequency optical signal, which can effectively avoid the influence of factors such as environmental error, Abbe error, cosine error, data cycle error, etc., and can realize the dynamic performance test and calibration of the heterodyne laser interferometer signal processing link under the high-speed motion of the target.

[0049] 4. The present invention provides a dynamic performance calibration device for the signal processing link of a heterodyne laser interferometer based on an acousto-optic frequency shifter. The device is designed based on a basic heterodyne laser interference structure and can flexibly adjust the optical power, AC-DC ratio and frequency of the interference beat frequency optical signal of the measurement path, and ensure that the interference signals of the measurement path and the reference path are homologous. The device can be used not only for dynamic measurement performance measurement and calibration of the signal processing link of a heterodyne laser interferometer, but also for simulation of the beat frequency optical signal in the dynamic measurement of the heterodyne laser interferometer and adjustment of its optical power, AC-DC ratio and frequency.

[0050] The invention is applicable to an equivalent calibration device for the dynamic measurement performance of a signal processing link of a heterodyne laser interferometer under high-speed target motion. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a system diagram of the dynamic performance calibration device of the heterodyne laser interferometer signal processing link based on the acousto-optic frequency shifter described in the first embodiment;

[0052] Figure 2 It is a system diagram of a dynamic performance calibration device for a heterodyne laser interferometer signal processing link, in which the laser assembly described in the second embodiment is implemented by a dual-frequency laser having a reference light signal and the beam splitter prism assembly is implemented by a first polarization beam splitter prism PBS;

[0053] Figure 3 It is a system diagram of a dynamic performance calibration device for a signal processing link of a heterodyne laser interferometer in which the laser assembly described in the fourth embodiment is implemented by a dual-frequency laser without a reference light signal and the beam splitter prism assembly is implemented by a first polarization beam splitter prism PBS;

[0054] Figure 4 It is a system diagram of a dynamic performance calibration device for a signal processing link of a heterodyne laser interferometer in which the laser component described in Embodiment 6 is implemented by a single-frequency laser and the beam splitter prism component is implemented by a second depolarizing beam splitter prism NPBS. DETAILED DESCRIPTION

[0055] The specific implementation mode of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

[0056] Implementation method 1. See Figure 1 This embodiment is described. This embodiment provides a dynamic performance calibration device for a heterodyne laser interferometer signal processing link based on an acousto-optic frequency shifter. The calibration device includes a laser assembly, a first measurement optical path, a second measurement optical path, an AOFS drive and motor controller optical path, and a phase meter.

[0057] The first measuring optical path includes a first reflector, a first AOFS, a first aperture, a first 1 / 2 wave plate, a polarization beam splitter prism PBS, a polarizer and a photodetector PD;

[0058] The second optical path comprises a beam splitter prism assembly, a second AOFS, a second aperture, a second 1 / 2 wave plate, a second reflector and a motor;

[0059] The laser assembly is used to emit laser light, which is injected into the beam splitter prism assembly. The beam splitter prism assembly splits the incident light into two beams of laser light with perpendicular polarization directions, and injects them into the first reflector and the second AOFS respectively;

[0060] The first reflector reflects the incident light into the first AOFS, the first AOFS diffracts the incident light into multi-order diffraction light and injects it into the first aperture, the first aperture selects +1-order diffraction light of the multi-order diffraction light and injects it into the first 1 / 2 wave plate, the first 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction light and injects it into the polarization beam splitter prism PBS, the polarization beam splitter prism PBS injects the incident light into the polarizer, the polarizer converts the incident light into a beat frequency light signal and sends it to the photodetector PD, the photodetector PD converts the beat frequency light signal into an electrical signal and sends it to the phase meter;

[0061] The second AOFS diffracts the light beam into multiple diffraction lights and injects them into the second aperture, the second aperture selects +1-order diffraction lights of the multiple diffraction lights and injects them into the second 1 / 2 wave plate, the second 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction lights and injects them into the second reflector, and the second reflector reflects the incident light to the polarization beam splitter prism PBS;

[0062] The laser assembly is also used to provide a reference optical signal to the AOFS drive and motor controller optical path;

[0063] The AOFS drive and motor controller optical path is used to control the driving frequencies of the first AOFS and the second AOFS respectively, and is also used to control the angle of the second reflector through the motor, and is also used to convert the laser emitted by the laser assembly into a reference electrical signal and send it to the phase meter;

[0064] The phase meter is used to calculate the phase difference according to the received electrical signal.

[0065] In practical application, if Figure 1As shown, the laser assembly is used to emit laser light, which is injected into the beam splitter prism assembly. The beam splitter prism assembly splits the incident light into two laser beams with perpendicular polarization directions, realizes the separation of the two laser beams with perpendicular polarization directions, and injects them into the first reflector and the second AOFS respectively; wherein, a laser beam is reflected by the first reflector and then injected into the first acousto-optic frequency shifter AOFS, the first acousto-optic frequency shifter AOFS diffracts the incident light to generate multi-order diffraction light, which is injected into the first aperture, the first aperture selects the +1st order diffraction light of the multi-order diffraction light and injects it into the first 1 / 2 wave plate to adjust the polarization direction of the light beam and inject it into The second acousto-optic frequency shifter AOFS diffracts the incident light to generate multi-order diffracted light, which is then injected into the second aperture. The second aperture selects the +1st order diffracted light of the multi-order diffracted light and injects it into the second 1 / 2 wave plate to adjust the polarization direction of the light beam and then injects it into the second reflector. The second reflector emits the light beam to the polarization beam splitter prism PBS. The polarization beam splitter prism PBS emits the received light beam to the polarizing plate to generate a beat frequency light signal, which is received by the photodetector PD to generate an electrical signal and enters the phase meter for further processing. The laser assembly is also used to provide a reference light signal to the AOFS drive and motor controller optical path; the AOFS drive and motor controller optical path is used to control the driving frequencies of the first AOFS and the second AOFS respectively, and is also used to control the angle of the second reflector through the motor, and is also used to convert the laser emitted by the laser assembly into a reference electrical signal and send it to the phase meter; the phase meter is used to calculate the phase difference based on the received electrical signal. The invention solves the problem that the existing heterodyne laser interferometer calibration method is difficult to evaluate the dynamic measurement performance of the interferometer signal processing link due to the coupling of the Abbe error and cosine error caused by mechanical installation and the data period error caused by asynchronous measurement.

[0066] The present embodiment provides a dynamic performance calibration device for the signal processing link of a heterodyne laser interferometer based on an acousto-optic frequency shifter. The two AOFS driving frequencies and the reflector angles of the first measuring optical path and the second measuring optical path are adjusted simultaneously through the AOFS drive and motor controller to make the beat frequency of the measuring path beat frequency optical signal reach the test point. The rotation angles of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path are adjusted to adjust the optical power and AC-DC ratio of the measuring path beat frequency optical signal. The phase difference between the interference light and the actual simulated motion phase of the target to be measured is measured in real time using the phase meter to be measured, and the dynamic test performance test and calibration of the signal processing link of the heterodyne laser interferometer are performed.

[0067] This embodiment provides a dynamic performance calibration device for the signal processing link of a heterodyne laser interferometer based on an acousto-optic frequency shifter. It is designed based on the basic heterodyne laser interference structure, and uses an AOFS drive and motor controller to simultaneously change the driving frequencies of two acousto-optic frequency shifters AOFS or keep the driving frequency of one acousto-optic frequency shifter AOFS unchanged and adjust the driving frequency of the other acousto-optic frequency shifter AOFS to continuously modulate the frequency of the final synthesized beat frequency optical signal to simulate different motion modes of the target to be measured. The AOFS drive and motor controller simultaneously drives the motor to adjust the angle of the second reflector so that the two lasers of the first measurement optical path and the second measurement optical path have a good degree of overlap when they are finally synthesized, so as to ensure the quality of the interference optical signal during the modulation process.

[0068] Existing heterodyne laser interferometers often couple multiple errors such as environmental error, Abbe error, cosine error, data cycle error, etc. in displacement measurement, which will lead to the problem of difficulty in evaluating the dynamic measurement performance of the interferometer signal processing link. This embodiment provides a dynamic performance calibration device for the heterodyne laser interferometer signal processing link based on an acousto-optic frequency shifter, which generates an interference beat frequency optical signal and adjusts its frequency to simulate the high-speed motion of the target to be measured, and simultaneously realizes the adjustment of the optical power and AC-DC ratio of the beat frequency optical signal, which can effectively avoid the influence of factors such as environmental error, Abbe error, cosine error, data cycle error, etc., and can realize the dynamic performance test and calibration of the heterodyne laser interferometer signal processing link under the high-speed motion of the target.

[0069] The present embodiment provides a dynamic performance calibration device for the signal processing link of a heterodyne laser interferometer based on an acousto-optic frequency shifter. The device is designed based on a basic heterodyne laser interference structure and can flexibly adjust the optical power, AC-DC ratio and frequency of the interference beat frequency optical signal of the measurement path, and ensure that the interference signals of the measurement path and the reference path are homologous. The device can be used not only for dynamic measurement performance measurement and calibration of the signal processing link of a heterodyne laser interferometer, but also for simulation of the beat frequency optical signal in the dynamic measurement of the heterodyne laser interferometer and adjustment of its optical power, AC-DC ratio and frequency.

[0070] Implementation method 2. See Figure 2 This embodiment is described. This embodiment is to illustrate the laser component, the beam splitter prism component and the AOFS drive and motor controller optical path in the dynamic performance calibration device of the heterodyne laser interferometer signal processing link based on the acousto-optic frequency shifter described in the first embodiment. The laser component is implemented by a dual-frequency laser with a reference light signal; the beam splitter prism component is implemented by a first polarization beam splitter prism PBS;

[0071] The AOFS drive and motor controller optical path includes a depolarizing beam splitter prism NPBS, a second photodetector PD, a third photodetector PD and an AOFS drive and motor controller;

[0072] The dual-frequency laser with the reference light signal emits two laser beams, one laser beam enters the first polarization beam splitter prism PBS, and the other laser beam enters the depolarization beam splitter prism NPBS. The depolarization beam splitter prism NPBS splits the incident light into two linear polarized lights, which are respectively emitted into the second photodetector PD and the third photodetector PD. The second photodetector PD converts the incident light signal into an electrical signal and sends it to the AOFS drive and motor controller. The third photodetector PD converts the incident light signal into an electrical signal and sends it to the phase meter.

[0073] The AOFS drive and motor controller is used to use the received electrical signal as a driving clock to adjust the driving frequencies of the first AOFS and the second AOFS respectively, and is also used to control the motor.

[0074] In practical application, if Figure 2 As shown, the laser component is implemented by a dual-frequency laser with a reference light signal, and the beam splitter component is implemented by a first polarization beam splitter prism PBS; the AOFS drive and motor controller optical path includes a depolarization beam splitter prism NPBS, a second photodetector PD, a third photodetector PD and an AOFS drive and motor controller. A dual-frequency laser with a reference light signal outputs two coaxially transmitted laser beams with vertical polarization directions and different frequencies, which are vertically incident on the first polarization beam splitter PBS to separate the two laser beams with vertical polarization directions. One laser beam is reflected by the first reflector and enters the first acousto-optic frequency shifter AOFS and the second acousto-optic frequency shifter AOFS respectively with the other laser beam to generate multi-order diffraction light after diffraction, and the first aperture and the second aperture select the +1 order diffraction light of the two laser beams respectively. The two diffracted lights are respectively adjusted in polarization direction by the first 1 / 2 wave plate and the second 1 / 2 wave plate 2, and then converged at the polarization beam splitter PBS by the second reflector. A beat frequency light signal is generated by the interference of the polarizers and is received by the photodetector PD to generate a measurement electrical signal that enters the phase meter for further processing.

[0075] Since the reference optical signal of the dual-frequency laser is a beat optical signal formed by the interference of two coaxially transmitted laser beams with different frequencies, the reference optical signal is divided into two paths after being processed by the depolarizing beam splitter NPBS. One path is converted into a reference electrical signal by the third photodetector PD and enters the phase meter for further processing, and the other path is converted into an electrical signal by the second photodetector PD and used as the driving clock of the AOFS drive and motor controller to ensure that the measurement is homologous to the reference interference signal. The AOFS drive and motor controller simulates different motion modes of the target to be measured by changing two AOFS drive frequencies at the same time or keeping one AOFS drive frequency unchanged and adjusting the other AOFS drive frequency to continuously modulate the frequency of the final synthesized beat optical signal.

[0076] This embodiment modulates the frequency of the final synthesized beat frequency optical signal by controlling the driving frequency of the first acousto-optic frequency shifter AOFS to remain unchanged and adjusting the driving frequency of the second acousto-optic frequency shifter AOFS. Since changing the driving frequency of the acousto-optic frequency shifter AOFS will cause the emission angle of the +1st order diffraction light to change, the AOFS drive and motor controller simultaneously drives the motor to adjust the angle of the second reflector, so that the two lasers of the first measuring optical path and the second measuring optical path have a good degree of overlap when they are finally synthesized, so as to ensure the quality of the interference optical signal during the modulation process.

[0077] This embodiment provides a dynamic performance calibration device for the signal processing link of a heterodyne laser interferometer based on an acousto-optic frequency shifter. It is designed based on the basic heterodyne laser interference structure, and uses an AOFS drive and motor controller to simultaneously change the driving frequencies of two acousto-optic frequency shifters AOFS or keep the driving frequency of one acousto-optic frequency shifter AOFS unchanged and adjust the driving frequency of the other acousto-optic frequency shifter AOFS to continuously modulate the frequency of the final synthesized beat frequency optical signal to simulate different motion modes of the target to be measured. The AOFS drive and motor controller simultaneously drives the motor to adjust the angle of the second reflector so that the two lasers of the first measurement optical path and the second measurement optical path have a good degree of overlap when they are finally synthesized, so as to ensure the quality of the interference optical signal during the modulation process.

[0078] The specific implementation steps of this embodiment in practical application are:

[0079] Step 1, pre-measurement: Before initializing the measurement, it is necessary to measure the applicable range of the calibration device in advance. By adjusting the rotation angle of the two 1 / 2 wave plates of the first measuring optical path and the second measuring optical path so that the rotation direction is perpendicular to the optical path direction, the polarization directions of the two laser lines in the first measuring optical path and the second measuring optical path can be changed respectively, and then the optical powers of the two laser beams that finally interfere are changed by the polarization beam splitter prism PBS. By adjusting the rotation angle of the polarizer in the first measuring optical path so that the rotation direction is perpendicular to the optical path direction, the interference degree of the two laser beams in the measuring path, that is, the AC-DC ratio, can be changed. By adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS in the first measuring optical path and the second measuring optical path, the frequency of the synthetic beat frequency optical signal in the measuring path can be adjusted. Therefore, by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS, the 1 / 2 wave plate and the rotation angle of the polarizer, the optical power of the beat frequency optical signal and the adjustable range of the AC-DC ratio under different beat frequencies can be measured; the optical power and AC-DC ratio of the reference optical signal and the optical signal that provides the AOFS drive and the motor controller clock are measured and recorded.

[0080] Step 2, measurement initialization: adjust the beat frequency of the beat frequency optical signal of the measurement path to a preset value by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS of the first measurement optical path and the second measurement optical path, and adjust the optical power and AC-DC ratio of the beat frequency optical signal of the measurement path to a preset value by adjusting the rotation angles of the two 1 / 2 wave plates and the polarizer of the first measurement optical path and the second measurement optical path;

[0081] Step 3, test point selection: select the test point by using the mapping relationship between the moving speed of the target to be measured in the heterodyne laser interferometer displacement measurement system and the frequency of the beat frequency optical signal measured by the equivalent measurement device;

[0082] Step 4, start measurement: adjust the two AOFS drive frequencies and the reflector angle of the first measuring optical path and the second measuring optical path simultaneously through the AOFS drive and motor controller to make the beat frequency of the measuring path beat frequency optical signal reach the test point, and adjust the rotation angle of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path as needed to adjust the optical power and AC-DC ratio of the measuring path beat frequency optical signal, and use the phase meter to measure the phase difference between the interference light and the actual simulated motion phase of the target to be measured in real time, and perform dynamic test performance test and calibration of the heterodyne laser interferometer signal processing link.

[0083] Embodiment 3. This embodiment is an example of the dual-frequency laser with a reference light signal in the dynamic performance calibration device of the signal processing link of the heterodyne laser interferometer based on the acousto-optic frequency shifter described in Embodiment 2. The dual-frequency laser with a reference light signal emits two coaxially transmitted laser beams with vertical polarization directions and different frequencies.

[0084] Implementation method 4. See Figure 3 This embodiment is described. This embodiment is an example of the laser component, the beam splitter prism component and the AOFS drive and motor controller optical path in the dynamic performance calibration device of the heterodyne laser interferometer signal processing link based on the acousto-optic frequency shifter described in the first embodiment. The laser component can also be implemented by a dual-frequency laser without a reference optical signal.

[0085] The beam splitter assembly is implemented by a first polarization beam splitter prism PBS;

[0086] The AOFS drive and motor controller optical path includes a first depolarizing beam splitter prism NPBS, a second polarizer, a second depolarizing beam splitter prism NPBS, a second photodetector PD, a third photodetector PD and an AOFS drive and motor controller;

[0087] The dual-frequency laser without a reference light signal emits a laser beam, which is incident on the first depolarization beam splitter prism NPBS. The first depolarization beam splitter prism NPBS splits the incident light into two polarized laser beams, which are respectively incident on the first polarization beam splitter prism PBS and the second polarizer. The second polarizer converts the incident light into a beat frequency light signal, which is incident on the second depolarization beam splitter prism NPBS. The second depolarization beam splitter prism NPBS splits the incident light into two linearly polarized lights, which are respectively incident on the second photodetector PD and the third photodetector PD. The second photodetector PD converts the incident light signal into an electrical signal and sends it to the AOFS drive and motor controller. The third photodetector PD converts the incident light signal into an electrical signal and sends it to the phase meter.

[0088] The AOFS drive and motor controller is used to use the received electrical signal as a driving clock to adjust the driving frequencies of the first AOFS and the second AOFS respectively, and is also used to control the motor.

[0089] In practical application, if Figure 3 As shown, the laser assembly can also be implemented by a dual-frequency laser without a reference light signal; the beam splitter assembly is implemented by a first polarization beam splitter prism PBS; the AOFS drive and motor controller optical path includes a first depolarization beam splitter prism NPBS, a second polarizer, a second depolarization beam splitter prism NPBS, a second photodetector PD, a third photodetector PD and an AOFS drive and motor controller. The dual-frequency laser is a dual-frequency laser without a reference light signal; the measurement light signal, the reference light signal and the light signal providing the AOFS drive and motor controller clock are all generated by two coaxially transmitted laser beams output by the dual-frequency laser, with vertical polarization directions and different frequencies.

[0090] The laser beam output by the dual-frequency laser is processed by the first depolarizing beam splitter prism NPBS and then divided into two laser beams, one of which is processed by the first polarizing beam splitter prism PBS to generate a measurement light signal; the other laser beam is interfered by the second polarizer to generate a beat frequency light signal, which is then separated into two laser beams by the second depolarizing beam splitter prism NPBS and generates a reference light signal and a light signal for providing the AOFS drive and motor controller clock respectively. The light signal for the AOFS drive and motor controller clock is generated by the reference laser. The AOFS drive and motor controller use the clock provided by the beat frequency light signal of the laser as a reference to generate the AOFS drive signal to ensure that the measurement light signal and the reference light signal clock are of the same source.

[0091] The AOFS drive and motor controller is used to drive the acousto-optic frequency shifter AOFS and the motor of the first measuring optical path and the second measuring optical path, by simultaneously changing the driving frequencies of the two acousto-optic frequency shifters AOFS of the first measuring optical path and the second measuring optical path or keeping the driving frequency of one acousto-optic frequency shifter AOFS unchanged and adjusting the driving frequency of the other acousto-optic frequency shifter AOFS to continuously modulate the beat frequency of the final synthesized beat frequency optical signal to simulate different motion modes of the target to be measured. In this embodiment, the beat frequency of the final synthesized beat frequency optical signal is modulated by controlling the driving frequency of the first acousto-optic frequency shifter AOFS unchanged and adjusting the driving frequency of the second acousto-optic frequency shifter AOFS. Since changing the driving frequency of the acousto-optic frequency shifter AOFS will cause the emission angle of the +1-order diffraction light to change, the controller simultaneously drives the motor to adjust the angle of the second reflector so that the two lasers of the first measuring optical path and the second measuring optical path have a good degree of overlap when they are finally synthesized, so as to ensure the quality of the interference optical signal during the modulation process.

[0092] The specific implementation steps of this embodiment in practical application are:

[0093] Step 1, pre-measurement: Before initializing the measurement, it is necessary to measure the applicable range of the calibration device in advance. By adjusting the rotation angle of the two 1 / 2 wave plates of the first measuring optical path and the second measuring optical path so that the rotation direction is perpendicular to the optical path direction, the polarization directions of the two laser lines in the first measuring optical path and the second measuring optical path can be changed respectively, and then the optical powers of the two laser beams that finally interfere are changed by the polarization beam splitter prism PBS. By adjusting the rotation angle of the polarizer in the first measuring optical path so that the rotation direction is perpendicular to the optical path direction, the interference degree of the two laser beams in the measuring path, that is, the AC-DC ratio, can be changed. By adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS in the first measuring optical path and the second measuring optical path, the frequency of the synthetic beat frequency optical signal in the measuring path can be adjusted. Therefore, by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS, the 1 / 2 wave plate and the rotation angle of the polarizer, the optical power of the beat frequency optical signal and the adjustable range of the AC-DC ratio under different beat frequencies can be measured; the optical power and AC-DC ratio of the reference optical signal and the optical signal that provides the AOFS drive and the motor controller clock are measured and recorded.

[0094] Step 2, measurement initialization: adjust the beat frequency of the beat frequency optical signal of the measurement path to a preset value by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS of the first measurement optical path and the second measurement optical path, and adjust the optical power and AC-DC ratio of the beat frequency optical signal of the measurement path to a preset value by adjusting the rotation angles of the two 1 / 2 wave plates and the polarizer of the first measurement optical path and the second measurement optical path;

[0095] Step 3, test point selection: select the test point by using the mapping relationship between the moving speed of the target to be measured in the heterodyne laser interferometer displacement measurement system and the frequency of the beat frequency optical signal measured by the equivalent measurement device;

[0096] Step 4, start measurement: adjust the two AOFS drive frequencies and the reflector angle of the first measuring optical path and the second measuring optical path simultaneously through the AOFS drive and motor controller to make the beat frequency of the measuring path beat frequency optical signal reach the test point, and adjust the rotation angle of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path as needed to adjust the optical power and AC-DC ratio of the measuring path beat frequency optical signal, and use the phase meter to measure the phase difference between the interference light and the actual simulated motion phase of the target to be measured in real time, and perform dynamic test performance test and calibration of the heterodyne laser interferometer signal processing link.

[0097] Implementation method five. This implementation method is to illustrate the dual-frequency laser without a reference light signal in the dynamic performance calibration device of the heterodyne laser interferometer signal processing link based on the acousto-optic frequency shifter described in implementation method four. 5. The dual-frequency laser without a reference light signal emits two coaxially transmitted laser beams with vertical polarization directions and different frequencies.

[0098] Implementation method 6. See Figure 4 This embodiment is described. This embodiment is to illustrate the laser component, the beam splitter prism component and the AOFS drive and motor controller optical path in the dynamic performance calibration device of the heterodyne laser interferometer signal processing link based on the acousto-optic frequency shifter described in the first embodiment. The laser component can also be implemented by a single-frequency laser; the beam splitter prism component can also be implemented by a second depolarizing beam splitter prism NPBS;

[0099] The AOFS driving and motor controller circuit includes a first depolarizing beam splitter prism NPBS, a third reflector, a third depolarizing beam splitter prism NPBS, a fourth AOFS, a fourth aperture, a fourth 1 / 2 wave plate, a fifth reflector, a fourth reflector, a third AOFS, a third aperture, a third 1 / 2 wave plate, a second polarizing beam splitter prism PBS, a second polarizer, a second photodetector PD and an AOFS driving and motor controller;

[0100] The single-frequency laser emits a laser beam, which is incident on the first depolarization beam splitter prism NPBS. The depolarization beam splitter NPBS splits the incident light into two laser beams, which are respectively incident on the second depolarization beam splitter NPBS and the third reflector;

[0101] The third reflector reflects the incident light to the third depolarizing beam splitter prism NPBS, the depolarizing beam splitter NPBS splits the incident light into two laser beams, which are respectively emitted into the fourth reflector and the fourth AOFS, the fourth reflector reflects the incident light to the third AOFS, the third AOFS diffracts the incident light into multi-order diffraction light and emits it into the third aperture, the third aperture selects +1-order diffraction light of the multi-order diffraction light and emits it into the third 1 / 2 wave plate, the third 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction light and emits it into the second polarizing beam splitter prism PBS, the second polarizing beam splitter prism PBS emits the incident light into the second polarizing plate, the second polarizing plate converts the incident light into a beat frequency light signal and sends it to the second photodetector PD, the second photodetector PD converts the beat frequency light signal into an electrical signal and sends it to the phase meter;

[0102] The fourth AOFS diffracts the incident light into multi-order diffraction light and injects it into the fourth aperture, the fourth aperture selects +1-order diffraction light of the multi-order diffraction light and injects it into the fourth 1 / 2 wave plate, the fourth 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction light and injects it into the fifth reflector, and the fifth reflector reflects the incident light to the second polarization beam splitter prism PBS;

[0103] The AOFS drive and motor controller is used to adjust the driving frequencies of the first AOFS, the second AOFS, the third AOFS and the fourth AOFS respectively, and is also used to control the motor.

[0104] In practical application, if Figure 4 As shown, the laser assembly is implemented by a single-frequency laser; the beam splitter assembly is implemented by a second depolarizing beam splitter prism NPBS; the AOFS drive and motor controller circuit includes a first depolarizing beam splitter prism NPBS, a third reflector, a third depolarizing beam splitter prism NPBS, a fourth AOFS, a fourth aperture, a fourth 1 / 2 wave plate, a fifth reflector, a fourth reflector, a third AOFS, a third aperture, a third 1 / 2 wave plate, a second polarizing beam splitter prism PBS, a second polarizer, a second photodetector PD and an AOFS drive and motor controller.

[0105] The laser adopts a single-frequency laser. The single-frequency laser outputs a beam of linearly polarized single-frequency light, which is divided into two beams of laser light with the same polarization direction after passing through the first depolarizing beam splitter prism NPBS. One beam of laser light is divided into a first measuring optical path and a second measuring optical path by the second depolarizing beam splitter prism NPBS to generate a measuring optical signal. The other beam has the same optical path as the first beam and generates a reference optical signal after being processed.

[0106] The AOFS drive and motor controller clock reference signal is generated by its own clock generation circuit. Since both the measurement optical signal and the reference optical signal are generated by the controller driving the acousto-optic frequency shifter AOFS, it can be ensured that the measurement optical signal and the reference optical signal are of the same source.

[0107] The AOFS drive and motor controller is used to drive the first acousto-optic frequency shifter AOFS, the second acousto-optic frequency shifter AOFS and the motor, by simultaneously changing the driving frequencies of the two acousto-optic frequency shifters AOFS or keeping the driving frequency of one acousto-optic frequency shifter AOFS unchanged and adjusting the driving frequency of the other acousto-optic frequency shifter AOFS to continuously modulate the beat frequency of the final synthesized beat frequency optical signal to simulate different motion modes of the target to be measured. In this embodiment, the frequency of the final synthesized beat frequency optical signal of the measurement path is modulated by controlling the driving frequency of the first acousto-optic frequency shifter AOFS unchanged and adjusting the driving frequency of the second acousto-optic frequency shifter AOFS. Since changing the driving frequency of the acousto-optic frequency shifter AOFS will cause the +1 order diffraction light to change its exit angle, the controller simultaneously drives the motor to adjust the angle of the second reflector so that the two lasers of the measurement path have a better degree of overlap when they are finally synthesized, so as to ensure the quality of the interference light signal during the modulation process. The reference path beat frequency optical signal operates at a pre-set beat frequency. The AOFS drive and motor controller sets the driving signal frequencies of the third acousto-optic frequency shifter AOFS and the fourth acousto-optic frequency shifter AOFS of the reference path to fixed values. Since the AOFS driving frequency does not need to be continuously adjusted, the reference path does not need a motor to continuously adjust the mirror angle.

[0108] The specific implementation steps of this embodiment in practical application are:

[0109] Step 1, pre-measurement: Before initializing the measurement, it is necessary to measure the applicable range of the calibration device in advance. By adjusting the rotation angle of the two 1 / 2 wave plates of the first measuring optical path and the second measuring optical path so that the rotation direction is perpendicular to the optical path direction, the polarization directions of the two laser lines in the first measuring optical path and the second measuring optical path can be changed respectively, and then the optical powers of the two laser beams that finally interfere are changed by the polarization beam splitter prism PBS. By adjusting the rotation angle of the polarizer in the first measuring optical path so that the rotation direction is perpendicular to the optical path direction, the interference degree of the two laser beams in the measuring path, that is, the AC-DC ratio, can be changed. By adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS in the first measuring optical path and the second measuring optical path, the frequency of the synthetic beat frequency optical signal in the measuring path can be adjusted. Therefore, by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS, the 1 / 2 wave plate and the rotation angle of the polarizer, the optical power of the beat frequency optical signal and the adjustable range of the AC-DC ratio under different beat frequencies can be measured; the optical power and AC-DC ratio of the reference optical signal and the optical signal that provides the AOFS drive and the motor controller clock are measured and recorded.

[0110] Step 2, measurement initialization: adjust the beat frequency of the beat frequency optical signal of the measurement path to a preset value by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS of the first measurement optical path and the second measurement optical path, and adjust the optical power and AC-DC ratio of the beat frequency optical signal of the measurement path to a preset value by adjusting the rotation angles of the two 1 / 2 wave plates and the polarizer of the first measurement optical path and the second measurement optical path;

[0111] Step 3, test point selection: select the test point by using the mapping relationship between the moving speed of the target to be measured in the heterodyne laser interferometer displacement measurement system and the frequency of the beat frequency optical signal measured by the equivalent measurement device;

[0112] Step 4, start measurement: adjust the two AOFS drive frequencies and the reflector angle of the first measuring optical path and the second measuring optical path simultaneously through the AOFS drive and motor controller to make the beat frequency of the measuring path beat frequency optical signal reach the test point, and adjust the rotation angle of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path as needed to adjust the optical power and AC-DC ratio of the measuring path beat frequency optical signal, and use the phase meter to measure the phase difference between the interference light and the actual simulated motion phase of the target to be measured in real time, and perform dynamic test performance test and calibration of the heterodyne laser interferometer signal processing link.

[0113] Embodiment 7. This embodiment is an example of the single-frequency laser in the dynamic performance calibration device of the heterodyne laser interferometer signal processing link based on the acousto-optic frequency shifter described in Embodiment 6, and the single-frequency laser emits a beam of linearly polarized single-frequency light.

[0114] Embodiment 8. This embodiment is an example of the depolarizing beam splitter prism NPBS in the dynamic performance calibration device of the heterodyne laser interferometer signal processing link based on the acousto-optic frequency shifter described in Embodiment 6. The depolarizing beam splitter prism NPBS splits the incident light into two laser beams with the same polarization direction.

[0115] Implementation method nine. This implementation method is to illustrate the AOFS drive and motor controller in the dynamic performance calibration device of the heterodyne laser interferometer signal processing link based on the acousto-optic frequency shifter described in implementation method six, and the AOFS drive and motor controller are used to set the drive signal frequency of the third AOFS and the fourth AOFS to a fixed value.

[0116] Embodiment 10. This embodiment provides a method for calibrating the dynamic performance of a heterodyne laser interferometer signal processing link based on an acousto-optic frequency shifter. The calibration method is implemented based on the dynamic performance calibration device for a heterodyne laser interferometer signal processing link based on an acousto-optic frequency shifter described in any one of embodiments 1 to 9. The calibration method is:

[0117] S1. Pre-measurement: respectively adjust the rotation angle of the first 1 / 2 wave plate and the first 1 / 2 wave plate so that the rotation direction is perpendicular to the direction of the optical path, adjust the polarization beam splitter prism PBS, change the optical power of the two laser beams that eventually interfere, adjust the rotation angle of the polarizer so that the rotation direction is perpendicular to the direction of the optical path, respectively adjust the driving frequencies of the first AOFS and the second AOFS, and measure the optical power of the beat frequency optical signal and the adjustable range of the AC-DC ratio and the optical power and AC-DC ratio of the optical signal of the AOFS drive and motor controller circuit clock at different beat frequencies;

[0118] S2, measurement initialization: adjusting the beat frequency of the beat frequency optical signal of the measuring path to a preset value by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS of the first measuring optical path and the second measuring optical path, and adjusting the optical power and AC-DC ratio of the beat frequency optical signal of the measuring path to a preset value by adjusting the rotation angles of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path;

[0119] S3, select test points;

[0120] S4. Start measuring: adjust the two AOFS driving frequencies and the angle of the reflector of the first measuring optical path and the second measuring optical path simultaneously through the AOFS drive and motor controller to make the beat frequency of the measuring path beat frequency optical signal reach the test point, adjust the rotation angles of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path to adjust the optical power and AC-DC ratio of the measuring path beat frequency optical signal, use the phase meter to measure the phase difference between the interference light and the actual simulated motion phase of the target to be measured in real time, and perform dynamic test performance test and calibration of the heterodyne laser interferometer signal processing link.

[0121] In actual application of this embodiment, step 1, pre-measurement: before initializing the measurement, it is necessary to pre-measure the applicable range of the calibration device, and by adjusting the rotation angle of the two 1 / 2 wave plates of the first measuring optical path and the second measuring optical path so that the rotation direction is perpendicular to the optical path direction, the polarization directions of the two laser lines in the first measuring optical path and the second measuring optical path can be changed respectively, and then the optical powers of the two laser beams that finally interfere are changed by the polarization beam splitter prism PBS, and by adjusting the rotation angle of the polarizer in the first measuring optical path so that the rotation direction is perpendicular to the optical path direction, the interference degree of the two laser beams in the measuring path, that is, the AC-DC ratio, can be changed, and the frequency of the synthetic beat frequency optical signal in the measuring path can be adjusted by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS in the first measuring optical path and the second measuring optical path, thereby measuring the optical power of the beat frequency optical signal and the adjustable range of the AC-DC ratio at different beat frequencies by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS, the 1 / 2 wave plate and the rotation angle of the polarizer; measuring and recording the optical power and AC-DC ratio of the reference optical signal and the optical signal that provides the AOFS drive and the motor controller clock.

[0122] Step 2, measurement initialization: adjust the beat frequency of the beat frequency optical signal of the measurement path to a preset value by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS of the first measurement optical path and the second measurement optical path, and adjust the optical power and AC-DC ratio of the beat frequency optical signal of the measurement path to a preset value by adjusting the rotation angles of the two 1 / 2 wave plates and the polarizer of the first measurement optical path and the second measurement optical path;

[0123] Step 3, test point selection: select the test point by using the mapping relationship between the moving speed of the target to be measured in the heterodyne laser interferometer displacement measurement system and the frequency of the beat frequency optical signal measured by the equivalent measurement device;

[0124] Step 4, start measurement: adjust the two AOFS drive frequencies and the reflector angle of the first measuring optical path and the second measuring optical path simultaneously through the AOFS drive and motor controller to make the beat frequency of the measuring path beat frequency optical signal reach the test point, and adjust the rotation angle of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path as needed to adjust the optical power and AC-DC ratio of the measuring path beat frequency optical signal, and use the phase meter to measure the phase difference between the interference light and the actual simulated motion phase of the target to be measured in real time, and perform dynamic test performance test and calibration of the heterodyne laser interferometer signal processing link.

[0125] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0126] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0127] The above description is only an embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may be subject to various modifications and variations. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the scope of the claims of the present invention.

Claims

1. A dynamic performance calibration device for the signal processing link of a heterodyne laser interferometer based on an acousto-optic frequency shifter, characterized in that: The calibration device includes a laser assembly, a first measurement optical path, a second measurement optical path, an AOFS drive and motor controller optical path, and a phase meter; The first measuring optical path includes a first reflector, a first AOFS, a first aperture, a first 1 / 2 wave plate, a polarization beam splitter prism PBS, a polarizer and a photodetector PD; The second optical path comprises a beam splitter prism assembly, a second AOFS, a second aperture, a second 1 / 2 wave plate, a second reflector and a motor; The laser assembly is used to emit laser light, which is injected into the beam splitter prism assembly. The beam splitter prism assembly splits the incident light into two beams of laser light with perpendicular polarization directions, and injects them into the first reflector and the second AOFS respectively; The first reflector reflects the incident light into the first AOFS, the first AOFS diffracts the incident light into multi-order diffraction light and injects it into the first aperture, the first aperture selects +1-order diffraction light of the multi-order diffraction light and injects it into the first 1 / 2 wave plate, the first 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction light and injects it into the polarization beam splitter prism PBS, the polarization beam splitter prism PBS injects the incident light into the polarizer, the polarizer converts the incident light into a beat frequency light signal and sends it to the photodetector PD, the photodetector PD converts the beat frequency light signal into an electrical signal and sends it to the phase meter; The second AOFS diffracts the light beam into multiple diffraction lights and injects them into the second aperture, the second aperture selects +1-order diffraction lights of the multiple diffraction lights and injects them into the second 1 / 2 wave plate, the second 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction lights and injects them into the second reflector, and the second reflector reflects the incident light to the polarization beam splitter prism PBS; The laser assembly is also used to provide a reference optical signal to the AOFS drive and motor controller optical path; The AOFS drive and motor controller optical path is used to control the driving frequencies of the first AOFS and the second AOFS respectively, and is also used to control the angle of the second reflector through the motor, and is also used to convert the laser emitted by the laser assembly into a reference electrical signal and send it to the phase meter; The phase meter is used to calculate the phase difference according to the received electrical signal.

2. The dynamic performance calibration device for signal processing link of heterodyne laser interferometer based on acousto-optic frequency shifter according to claim 1, characterized in that: The laser assembly is implemented using a dual-frequency laser with a reference optical signal; The beam splitter assembly is implemented by a first polarization beam splitter prism PBS; The AOFS drive and motor controller optical path includes a depolarizing beam splitter prism NPBS, a second photodetector PD, a third photodetector PD and an AOFS drive and motor controller; The dual-frequency laser with the reference light signal emits two laser beams, one laser beam enters the first polarization beam splitter prism PBS, and the other laser beam enters the depolarization beam splitter prism NPBS. The depolarization beam splitter prism NPBS splits the incident light into two linear polarized lights, which are respectively emitted into the second photodetector PD and the third photodetector PD. The second photodetector PD converts the incident light signal into an electrical signal and sends it to the AOFS drive and motor controller. The third photodetector PD converts the incident light signal into an electrical signal and sends it to the phase meter. The AOFS drive and motor controller is used to use the received electrical signal as a driving clock to adjust the driving frequencies of the first AOFS and the second AOFS respectively, and is also used to control the motor.

3. The dynamic performance calibration device for signal processing link of heterodyne laser interferometer based on acousto-optic frequency shifter according to claim 2, characterized in that: The dual-frequency laser with a reference light signal emits two coaxially transmitted laser beams with vertical polarization directions and different frequencies.

4. The dynamic performance calibration device for signal processing link of heterodyne laser interferometer based on acousto-optic frequency shifter according to claim 1, characterized in that: The laser assembly can also be implemented using a dual-frequency laser without a reference optical signal; The beam splitter assembly can also be implemented using a first polarization beam splitter prism PBS; The AOFS drive and motor controller optical path includes a first depolarizing beam splitter prism NPBS, a second polarizer, a second depolarizing beam splitter prism NPBS, a second photodetector PD, a third photodetector PD and an AOFS drive and motor controller; The dual-frequency laser without a reference light signal emits a laser beam, which is incident on the first depolarization beam splitter prism NPBS. The first depolarization beam splitter prism NPBS splits the incident light into two polarized laser beams, which are respectively incident on the first polarization beam splitter prism PBS and the second polarizer. The second polarizer converts the incident light into a beat frequency light signal, which is incident on the second depolarization beam splitter prism NPBS. The second depolarization beam splitter prism NPBS splits the incident light into two linearly polarized lights, which are respectively incident on the second photodetector PD and the third photodetector PD. The second photodetector PD converts the incident light signal into an electrical signal and sends it to the AOFS drive and motor controller. The third photodetector PD converts the incident light signal into an electrical signal and sends it to the phase meter. The AOFS drive and motor controller is used to use the received electrical signal as a driving clock to adjust the driving frequencies of the first AOFS and the second AOFS respectively, and is also used to control the motor.

5. The dynamic performance calibration device for signal processing link of heterodyne laser interferometer based on acousto-optic frequency shifter according to claim 4, characterized in that: The dual-frequency laser without a reference light signal emits two coaxially transmitted laser beams with vertical polarization directions and different frequencies.

6. The dynamic performance calibration device for signal processing link of heterodyne laser interferometer based on acousto-optic frequency shifter according to claim 1, characterized in that: The laser assembly can also be implemented using a single-frequency laser; The beam splitter assembly can also be implemented using a second depolarizing beam splitter prism NPBS; The AOFS driving and motor controller circuit includes a first depolarizing beam splitter prism NPBS, a third reflector, a third depolarizing beam splitter prism NPBS, a fourth AOFS, a fourth aperture, a fourth 1 / 2 wave plate, a fifth reflector, a fourth reflector, a third AOFS, a third aperture, a third 1 / 2 wave plate, a second polarizing beam splitter prism PBS, a second polarizer, a second photodetector PD and an AOFS driving and motor controller; The single-frequency laser emits a laser beam, which is incident on the first depolarization beam splitter prism NPBS. The depolarization beam splitter NPBS splits the incident light into two laser beams, which are respectively incident on the second depolarization beam splitter NPBS and the third reflector; The third reflector reflects the incident light to the third depolarizing beam splitter prism NPBS, the depolarizing beam splitter NPBS splits the incident light into two laser beams, which are respectively emitted into the fourth reflector and the fourth AOFS, the fourth reflector reflects the incident light to the third AOFS, the third AOFS diffracts the incident light into multi-order diffraction light and emits it into the third aperture, the third aperture selects +1-order diffraction light of the multi-order diffraction light and emits it into the third 1 / 2 wave plate, the third 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction light and emits it into the second polarizing beam splitter prism PBS, the second polarizing beam splitter prism PBS emits the incident light into the second polarizing plate, the second polarizing plate converts the incident light into a beat frequency light signal and sends it to the second photodetector PD, the second photodetector PD converts the beat frequency light signal into an electrical signal and sends it to the phase meter; The fourth AOFS diffracts the incident light into multi-order diffraction light and injects it into the fourth aperture, the fourth aperture selects +1-order diffraction light of the multi-order diffraction light and injects it into the fourth 1 / 2 wave plate, the fourth 1 / 2 wave plate adjusts the polarization direction of the +1-order diffraction light and injects it into the fifth reflector, and the fifth reflector reflects the incident light to the second polarization beam splitter prism PBS; The AOFS drive and motor controller is used to adjust the driving frequencies of the first AOFS, the second AOFS, the third AOFS and the fourth AOFS respectively, and is also used to control the motor.

7. The dynamic performance calibration device for signal processing link of heterodyne laser interferometer based on acousto-optic frequency shifter according to claim 6, characterized in that: The single-frequency laser emits a beam of linearly polarized single-frequency light.

8. The dynamic performance calibration device for signal processing link of heterodyne laser interferometer based on acousto-optic frequency shifter according to claim 6, characterized in that: The depolarization beam splitter NPBS splits the incident light into two laser beams with the same polarization direction.

9. The dynamic performance calibration device for signal processing link of heterodyne laser interferometer based on acousto-optic frequency shifter according to claim 6, characterized in that: The AOFS driving and motor controller is used to set the driving signal frequencies of the third AOFS and the fourth AOFS to fixed values.

10. A method for calibrating the dynamic performance of a heterodyne laser interferometer signal processing link based on an acousto-optic frequency shifter, characterized in that: The calibration method is implemented based on the dynamic performance calibration device for the signal processing link of a heterodyne laser interferometer based on an acousto-optic frequency shifter according to any one of claims 1 to 9, and the calibration method is: S1. Pre-measurement: respectively adjust the rotation angle of the first 1 / 2 wave plate and the first 1 / 2 wave plate so that the rotation direction is perpendicular to the direction of the optical path, adjust the polarization beam splitter prism PBS, change the optical power of the two laser beams that eventually interfere, adjust the rotation angle of the polarizer so that the rotation direction is perpendicular to the direction of the optical path, respectively adjust the driving frequencies of the first AOFS and the second AOFS, and measure the optical power of the beat frequency optical signal and the adjustable range of the AC-DC ratio and the optical power and AC-DC ratio of the optical signal of the AOFS drive and motor controller circuit clock at different beat frequencies; S2, measurement initialization: adjusting the beat frequency of the beat frequency optical signal of the measuring path to a preset value by adjusting the driving frequencies of the two acousto-optic frequency shifters AOFS of the first measuring optical path and the second measuring optical path, and adjusting the optical power and AC-DC ratio of the beat frequency optical signal of the measuring path to a preset value by adjusting the rotation angles of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path; S3, select test points; S4. Start measuring: adjust the two AOFS driving frequencies and the angle of the reflector of the first measuring optical path and the second measuring optical path simultaneously through the AOFS drive and motor controller to make the beat frequency of the measuring path beat frequency optical signal reach the test point, adjust the rotation angles of the two 1 / 2 wave plates and the polarizer of the first measuring optical path and the second measuring optical path to adjust the optical power and AC-DC ratio of the measuring path beat frequency optical signal, use the phase meter to measure the phase difference between the interference light and the actual simulated motion phase of the target to be measured in real time, and perform dynamic test performance test and calibration of the heterodyne laser interferometer signal processing link.

Images