Heterodyne laser interferometer dynamic interference optical signal simulation device based on acousto-optic modulator and simulation method thereof

Abstract

The invention discloses a heterodyne laser interferometer dynamic interference optical signal simulation device based on an acousto-optic modulator and a simulation method thereof, and relates to the technical field of heterodyne laser interference dynamic performance testing. The problem that it is difficult to effectively evaluate the dynamic measurement performance of the heterodyne laser interferometer due to the fact that an electric signal is adopted to test the dynamic performance of the heterodyne laser interferometer in the prior art is solved. The device adopts a CW light source to emit single-frequency laser, the single-frequency laser is processed by a depolarization splitting prism to divide incident light into two beams of linearly polarized light, and the two beams of linearly polarized light are respectively emitted into a first light path and a second light path; optical elements, acousto-optic modulators and diaphragms in the first light path and the second light path respectively process light beams and respectively send the light beams to a detector, the detector respectively converts optical signals into electric signals and outputs the electric signals to a phase meter, and the phase meter calculates a phase difference; the driving assembly modulates the + 1 level diffraction light intensity of the acousto-optic modulator. The device is suitable for simulating interference optical signals of the heterodyne laser interferometer in dynamic measurement.

Description

Technical Field

[0001] The invention relates to the technical field of heterodyne laser interference dynamic performance testing. Background Art

[0002] Heterodyne laser interferometers are widely used in ultra-precision equipment manufacturing, microelectronics processing, precision metrology and testing due to their advantages of high resolution, high speed and high precision. With the rapid development of these fields, the current research focus of heterodyne interferometry has shifted from static and quasi-static measurement to high-speed and dynamic measurement, which has put forward higher requirements for the dynamic measurement performance of heterodyne laser interferometers. Therefore, it is very important to conduct scientific and effective testing and evaluation of the dynamic measurement performance of heterodyne laser interferometers.

[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, in the mainstream heterodyne laser interferometer calibration specifications, since only static and quasi-static measurements are often considered, the newly introduced errors in the dynamic measurement are not analyzed and suppressed, resulting in their inability to be used for dynamic performance testing of heterodyne laser interferometers.

[0004] For example, in the interferometer calibration specification ASME B89.1.8-2011, "Performance Evaluation of Displacement-Measuring Laser Interferometers", the laser interferometer comparison platform used will inevitably have Abbe error, cosine error and data period error introduced by asynchrony in dynamic measurement. It is difficult to evaluate the dynamic measurement performance of heterodyne laser interferometers.

[0005] In order to eliminate the above-mentioned Abbe error, cosine error, air refractive index error and data period error, many studies use electrical signals to simulate the movement of the target to be measured in the dynamic measurement of heterodyne laser interferometer to evaluate the dynamic measurement performance of heterodyne laser interferometer. For example, the dynamic measurement performance of ZMI4000 high-speed ultra-precision laser interferometer is tested by using high-speed phase-modulated and frequency-modulated electrical signals respectively. For example, the paper published on June 1, 2009: Design of standard test platform for signal processing unit of ultra-precision dynamic laser interferometer, which establishes the interference signal model when the target is moving, and uses electrical signals to simulate the dynamic motion trajectory of heterodyne laser interferometer to test the dynamic performance of heterodyne laser interferometer. However, this type of method does not include the test of photoelectric conversion part. However, in heterodyne interferometry measurement, the signal-to-noise ratio of the photoelectric conversion part is the key factor in determining the dynamic measurement of the interferometer. Summary of the invention

[0006] The invention solves the problem that the dynamic performance of a heterodyne laser interferometer is difficult to be effectively evaluated by simulating the dynamic motion trajectory of the heterodyne laser interferometer using an electrical signal, but the test of the photoelectric conversion part is not included.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] The present invention provides a dynamic interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator, the simulation device comprising a CW light source, a depolarizing beam splitter prism NPBS, a first optical path, a second optical path, a phase meter and a driving component;

[0009] The first optical path includes a first optical element, a first acousto-optic modulator AOM, a third aperture and a first detector;

[0010] The second optical path includes a second optical element, a second acousto-optic modulator AOM, a fourth aperture and a second detector;

[0011] The CW light source emits a single-frequency laser, which is incident on the depolarization beam splitter prism. The depolarization beam splitter prism splits the incident light into two beams of linear polarized light, which are respectively incident on the first optical element and the second optical element. The light beam processed by the first optical element is incident on the first acousto-optic modulator AOM. The first acousto-optic modulator AOM diffracts the light beam into multi-order diffracted light, which is incident on the third aperture. The third aperture selects +1-order diffracted light from the multi-order diffracted light, which is incident on the first detector. The first detector converts the optical signal into an electrical signal and outputs it to the phase meter.

[0012] The light beam processed by the second optical element is incident on the second acousto-optic modulator AOM, the second acousto-optic modulator AOM diffracts the light beam into multi-order diffracted light, and the light beam is incident on the fourth aperture, the fourth aperture selects +1-order diffracted light from the multi-order diffracted light, and the +1-order diffracted light is incident on the second detector, and the second detector converts the optical signal into an electrical signal and outputs it to the phase meter;

[0013] The phase meter is used to calculate the phase difference according to the received electrical signal;

[0014] The driving component is used to modulate the intensity of the +1st order diffracted light of the first AOM and the second AOM respectively.

[0015] Furthermore, in a preferred embodiment, the above-mentioned CW light source is a continuous single-frequency laser light source.

[0016] Furthermore, in a preferred embodiment, the two beams of linearly polarized light are equally divided by a depolarizing beam splitter prism NPBS.

[0017] Furthermore, in a preferred embodiment, the incident angle of the light beam incident on the first acousto-optic modulator AOM and the incident angle of the light beam incident on the second acousto-optic modulator AOM are both Bragg angles.

[0018] Furthermore, in a preferred embodiment, the first optical element is implemented by a first aperture, and the second optical element is implemented by a second aperture;

[0019] The first aperture and the second aperture are both used to reduce the spot diameter of the incident linearly polarized light.

[0020] Furthermore, in another preferred embodiment, the first optical element may be implemented by a first convex lens, and the second optical element may be implemented by a second convex lens;

[0021] The first convex lens and the second convex lens are both used to reduce the spot diameter of the incident linearly polarized light.

[0022] Furthermore, in another preferred embodiment, the first optical element may be realized by a first lens group, and the second optical element may be realized by a second lens group;

[0023] The first mirror group and the second mirror group are both used to reduce the spot diameter of the incident linearly polarized light.

[0024] Furthermore, in a preferred embodiment, the first lens group and the second lens group each include a convex lens and a concave lens;

[0025] The convex lens is arranged in front of the concave lens, and the rear focus of the convex lens coincides with the rear focus of the concave lens.

[0026] Furthermore, in a preferred embodiment, the drive assembly comprises a first drive, a second drive and a drive control board;

[0027] The first driver is used to modulate the intensity of the diffracted light of the first acousto-optic modulator AOM;

[0028] The second driver is used to modulate the intensity of the diffracted light of the second acousto-optic modulator AOM;

[0029] The driver control board is used to send sinusoidal signals to the first driver and the second driver respectively.

[0030] The present invention also provides a method for simulating dynamic interference light signals of a heterodyne laser interferometer based on an acousto-optic modulator, the method being implemented based on any one of the above-mentioned devices for simulating dynamic interference light signals of a heterodyne laser interferometer based on an acousto-optic modulator, and the simulation method is:

[0031] S1. Pre-measurement: adjust the frequency, bias and amplitude of the two sinusoidal signals output by the driver control board to test and record the optical power and AC-DC ratio that the measurement optical signal and the reference optical signal can simulate at different frequencies;

[0032] S2, measurement initialization: adjust the frequency, offset and amplitude of the two sinusoidal signals output by the driver control board, so that the frequency, optical power and AC-DC ratio of the measurement optical signal and the reference optical signal reach the preset values ​​respectively;

[0033] S3, test point selection;

[0034] S4. Adjust the frequency of the two sinusoidal signals output by the driver control board so that the measuring optical signal and the reference optical signal reach the test point. Adjust the bias and amplitude of the two sinusoidal signals output by the driver control board to adjust the optical power and AC-DC ratio of the measuring optical signal and the reference optical signal respectively. Use the phase meter to calculate the phase difference between the simulated measuring optical signal and the simulated reference optical signal in real time to test and evaluate the dynamic performance of the heterodyne laser interferometer.

[0035] The beneficial effects of the present invention are:

[0036] 1. The present invention provides a device for simulating dynamic interference optical signals of heterodyne laser interferometer based on acousto-optic modulator, which uses optical elements to reduce the spot size and improve the limit modulation bandwidth of the acousto-optic modulator AOM; uses the acousto-optic modulator AOM to modulate the intensity of continuous single-frequency laser to simulate a real beat frequency interference optical signal; and realizes the simulation of heterodyne laser interference signals under high-speed dynamic conditions.

[0037] 2. Existing heterodyne laser interferometers often have multiple errors such as coupling environment error, Abbe error, cosine error, data cycle error, etc. in displacement measurement. The present invention provides a heterodyne laser interferometer dynamic interference light signal simulation device based on an acousto-optic modulator, which directly modulates the light intensity through an acousto-optic modulator AOM to simulate the interference light signal in heterodyne interferometry, and simultaneously realizes the adjustment of the light power and AC-DC ratio of the simulated interference light signal, and can effectively separate the influence of environmental error, Abbe error, cosine error, data cycle error and other factors in the dynamic measurement of heterodyne interferometer. At the same time, two beams of diffracted light are respectively received by the first photodetector and the second photodetector as the measurement light signal and the reference light signal, and then enter the phase meter to solve their phase difference, so as to realize the dynamic performance test and evaluation of the heterodyne laser interferometer including the photoelectric conversion link.

[0038] 3. The present invention provides a device for simulating dynamic interference optical signals of a heterodyne laser interferometer based on an acousto-optic modulator. The device has the advantages of a simple optical path, few components, high test bandwidth and little coupling error. It can not only be used for dynamic measurement performance testing and calibration of heterodyne laser interferometers, but also can realize the adjustment and simulation of optical power, AC-DC ratio and frequency of dynamic interference optical signals of heterodyne laser interferometers.

[0039] The invention is suitable for a simulation device for interfering light signals of a heterodyne laser interferometer in dynamic measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 1 is a system diagram of a dynamic interference optical signal simulation device of a heterodyne laser interferometer based on an acousto-optic modulator according to the first embodiment;

[0041] Figure 2 It is a system diagram of a dynamic interference optical signal simulation device of a heterodyne laser interferometer based on an acousto-optic modulator, in which the optical element described in the fifth embodiment is realized by using an aperture;

[0042] Figure 3 It is a system diagram of a dynamic interference optical signal simulation device of a heterodyne laser interferometer based on an acousto-optic modulator, in which the optical element described in Embodiment 6 is realized by using a convex lens;

[0043] Figure 4 It is a system diagram of a dynamic interference optical signal simulation device of a heterodyne laser interferometer based on an acousto-optic modulator, in which the optical element described in Embodiment 7 is realized by using a mirror group. DETAILED DESCRIPTION

[0044] 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.

[0045] Implementation method 1. See Figure 1 This embodiment is described. This embodiment provides a dynamic interference optical signal simulation device of a heterodyne laser interferometer based on an acousto-optic modulator. The simulation device includes a CW light source, a depolarizing beam splitter prism NPBS, a first optical path, a second optical path, a phase meter, and a driving component.

[0046] The first optical path includes a first optical element, a first acousto-optic modulator AOM, a third aperture and a first detector;

[0047] The second optical path includes a second optical element, a second acousto-optic modulator AOM, a fourth aperture and a second detector;

[0048] The CW light source emits a single-frequency laser, which is incident on the depolarization beam splitter prism. The depolarization beam splitter prism splits the incident light into two beams of linear polarized light, which are respectively incident on the first optical element and the second optical element. The light beam processed by the first optical element is incident on the first acousto-optic modulator AOM. The first acousto-optic modulator AOM diffracts the light beam into multi-order diffracted light, which is incident on the third aperture. The third aperture selects +1-order diffracted light from the multi-order diffracted light, which is incident on the first detector. The first detector converts the optical signal into an electrical signal and outputs it to the phase meter.

[0049] The light beam processed by the second optical element is incident on the second acousto-optic modulator AOM, the second acousto-optic modulator AOM diffracts the light beam into multi-order diffracted light, and the light beam is incident on the fourth aperture, the fourth aperture selects +1-order diffracted light from the multi-order diffracted light, and the +1-order diffracted light is incident on the second detector, and the second detector converts the optical signal into an electrical signal and outputs it to the phase meter;

[0050] The phase meter is used to calculate the phase difference according to the received electrical signal;

[0051] The driving component is used to modulate the intensity of the +1st order diffracted light of the first AOM and the second AOM respectively.

[0052] In practical application, if Figure 1As shown, a CW light source emits a single-frequency laser beam which is divided into two linearly polarized lights with the same polarization direction by a depolarizing beam splitter prism NPBS. The two linearly polarized lights are respectively incident into a first optical element and a second optical element. The first optical element and the second optical element are used to limit the spot diameter of the two laser beams incident on the corresponding acousto-optic modulator AOM to improve the modulation bandwidth of the acousto-optic modulator AOM. The two laser beams are diffracted by the acousto-optic modulator AOM to generate multi-order diffracted lights, and the +1st order diffracted lights of the two multi-order diffracted lights are selected by the third aperture and the fourth aperture respectively. The two +1st order diffracted lights are received by the photodetector 1 and the photodetector 2 as the measurement light signal and the reference light signal respectively, and then enter the phase meter to resolve the phase difference. The driving component is used to modulate the diffracted light intensity of the first acousto-optic modulator AOM and the second acousto-optic modulator AOM respectively. Specifically, the drive assembly includes a first driver, a second driver, and a driver control board; the first driver and the second driver output an amplitude modulated signal with a constant frequency, and its amplitude is modulated by the sinusoidal signal output by the driver control board. Since the diffraction efficiency of the acousto-optic modulator AOM Bragg diffraction +1-order diffraction light is positively correlated with the amplitude of the driver output signal, the driver control board outputs an amplitude modulated signal to achieve light intensity modulation of the AOM+1-order diffraction light. Since the beat frequency interference signal in the heterodyne laser interferometer is also a light intensity modulation signal, and its modulation frequency is related to the Doppler frequency shift introduced by the motion of the target to be measured. Therefore, the interference light signal in the dynamic measurement of the heterodyne laser interferometer can be simulated by modulating the light intensity of the AOM+1-order diffraction light. By adjusting the frequency of the two sinusoidal signals output by the driver control board, the light intensity modulation frequencies of the measurement light signal and the reference light signal can be adjusted respectively, thereby simulating the frequency of the interference light signal in the heterodyne interferometry. By adjusting the bias and amplitude of the two-way AM signals output by the driver control board, the modulation depth and modulation amplitude of the measurement optical signal and the reference optical signal can be adjusted respectively, thereby simulating the optical power and AC-DC ratio of the interference optical signal in heterodyne interferometry.

[0053] This embodiment provides a dynamic interference light signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator, which uses optical elements to reduce the spot size and improve the limit modulation bandwidth of the acousto-optic modulator AOM; uses the acousto-optic modulator AOM to modulate the intensity of a continuous single-frequency laser to simulate a real beat frequency interference light signal; and realizes the simulation of heterodyne laser interference signals under high-speed dynamic conditions.

[0054] Existing heterodyne laser interferometers often have multiple errors such as coupling environment error, Abbe error, cosine error, data cycle error, etc. in displacement measurement. This embodiment provides a heterodyne laser interferometer dynamic interference light signal simulation device based on an acousto-optic modulator, which directly modulates the light intensity through the acousto-optic modulator AOM to simulate the interference light signal in the heterodyne interferometry measurement, and at the same time realizes the adjustment of the light power and AC-DC ratio of the simulated interference light signal, which can effectively separate the influence of environmental error, Abbe error, cosine error, data cycle error and other factors in the dynamic measurement of the heterodyne interferometer. At the same time, two beams of diffracted light are received by the first photodetector and the second photodetector as the measurement light signal and the reference light signal respectively, and then enter the phase meter to solve their phase difference, so as to realize the dynamic performance test and evaluation of the heterodyne laser interferometer including the photoelectric conversion link.

[0055] This embodiment provides a dynamic interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator. The simulation device has the advantages of a simple optical path, fewer components, a high test bandwidth and less coupling error. It can not only be used for dynamic measurement performance testing and calibration of the heterodyne laser interferometer, but also can realize the adjustment and real-time detection of the optical power, AC-DC ratio and frequency of the interference optical signal of the heterodyne laser interferometer.

[0056] Embodiment 2. This embodiment is an example of the CW light source in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in Embodiment 1. The CW light source is a continuous single-frequency laser light source.

[0057] In actual application of this embodiment, firstly, the optical frequency of the single-frequency light source is single, and interference between multiple optical frequencies will not occur; secondly, the polarization direction of the single-frequency light source is fixed, avoiding the fluctuation of diffraction efficiency caused by the change of polarization direction; finally, the optical power of the single-frequency light source is large, which can ensure that there is still enough optical power after diffraction to simulate the actual interference signal.

[0058] Embodiment 3. This embodiment is an example of the splitting method of two beams of linearly polarized light in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in Embodiment 1. The two beams of linearly polarized light are equally divided by the depolarizing beam splitter prism NPBS.

[0059] In practical applications, this embodiment uses a depolarization beam splitter NPBS to equally divide the light source of a single-frequency laser, thereby avoiding fluctuations in the intensity of the two equally divided polarized light beams caused by changes in the polarization direction of the light source, thereby ensuring the stability of the intensity of the final simulated interference signal.

[0060] Embodiment 4. This embodiment is to illustrate the incident angle of the light beam entering the first acousto-optic modulator AOM and the incident angle of the light beam entering the second acousto-optic modulator AOM in the heterodyne laser interferometer dynamic interference light signal simulation device based on acousto-optic modulator described in embodiment 1 by taking an example. The incident angle of the light beam entering the first acousto-optic modulator AOM and the incident angle of the light beam entering the second acousto-optic modulator AOM are both Bragg angles.

[0061] In actual application of this embodiment, when the incident light is incident at the Bragg angle, the diffracted light has only 0th order and +1st or -1st order. At this time, the +1st or -1st order diffraction efficiency is the highest, thus being able to provide sufficient optical power for interference signal simulation.

[0062] Implementation method 5. See Figure 2 This embodiment is described. This embodiment is an example of the first optical element and the second optical element in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in the first embodiment. The first optical element is implemented by a first aperture, and the second optical element is implemented by a second aperture.

[0063] The first aperture and the second aperture are both used to reduce the spot diameter of the incident linearly polarized light.

[0064] In actual application of this embodiment, as shown in Figure 2, the CW light source is a continuous single-frequency laser light source. The CW light source emits a single-frequency laser beam, which is divided into two linearly polarized lights with the same polarization direction by a depolarizing beam splitter NPBS. The two linearly polarized lights are respectively incident into the first aperture and the second aperture. The first aperture and the second aperture are used to limit the spot diameter of the two laser beams incident on the corresponding acousto-optic modulator AOM to improve the modulation bandwidth of the acousto-optic modulator AOM. The two laser beams are diffracted by the acousto-optic modulator AOM to generate multi-order diffracted lights, and the +1st order diffracted lights of the two multi-order diffracted lights are selected by the third aperture and the fourth aperture respectively. The two +1st order diffracted lights are received by the photodetector 1 and the photodetector 2 as the measurement light signal and the reference light signal, and then enter the phase meter to resolve the phase difference. The driving component is used to modulate the diffracted light intensity of the first acousto-optic modulator AOM and the second acousto-optic modulator AOM respectively. Specifically, the drive assembly includes a first driver, a second driver, and a driver control board; the first driver and the second driver output an amplitude modulated signal with a constant frequency, and its amplitude is modulated by the sinusoidal signal output by the driver control board. Since the diffraction efficiency of the acousto-optic modulator AOM Bragg diffraction +1-order diffraction light is positively correlated with the amplitude of the driver output signal, the driver control board outputs an amplitude modulated signal to achieve light intensity modulation of the AOM+1-order diffraction light. Since the beat frequency interference signal in the heterodyne laser interferometer is also a light intensity modulation signal, and its modulation frequency is related to the Doppler frequency shift introduced by the motion of the target to be measured. Therefore, the interference light signal in the dynamic measurement of the heterodyne laser interferometer can be simulated by modulating the light intensity of the AOM+1-order diffraction light. By adjusting the frequency of the two sinusoidal signals output by the driver control board, the light intensity modulation frequencies of the measurement light signal and the reference light signal can be adjusted respectively, thereby simulating the frequency of the interference light signal in the heterodyne interferometry. By adjusting the bias and amplitude of the two-way AM signals output by the driver control board, the modulation depth and modulation amplitude of the measurement optical signal and the reference optical signal can be adjusted respectively, thereby simulating the optical power and AC-DC ratio of the interference optical signal in heterodyne interferometry.

[0065] Implementation method 6. See Figure 3 This embodiment is described. This embodiment is an example of the first optical element and the second optical element in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in the first embodiment. The first optical element can also be implemented by a first convex lens, and the second optical element can also be implemented by a second convex lens.

[0066] The first convex lens and the second convex lens are both used to reduce the spot diameter of the incident linearly polarized light.

[0067] In actual application of this embodiment, as shown in Figure 3, the CW light source is a continuous single-frequency laser light source. The CW light source emits a beam of single-frequency laser light, which is divided into two beams of linearly polarized light with the same polarization direction by a depolarizing beam splitter prism NPBS. The two beams of linearly polarized light are respectively incident into the first convex lens and the second convex lens. The first convex lens and the second convex lens are used to reduce the spot diameter of the two laser beams incident on the corresponding acousto-optic modulator AOM to improve the modulation bandwidth of the acousto-optic modulator AOM, wherein the focus of the convex lens is the AOM incident point to reduce the spot diameter of the AOM incident laser. The two laser beams are diffracted by the acousto-optic modulator AOM to generate multi-order diffracted light, and the +1-order diffracted light of the two multi-order diffracted light beams is selected by the third aperture and the fourth aperture respectively. The two +1-order diffracted light beams are received by the photodetector 1 and the photodetector 2 as the measurement light signal and the reference light signal, and then enter the phase meter to resolve their phase difference. The driving component is used to modulate the diffracted light intensity of the first acousto-optic modulator AOM and the second acousto-optic modulator AOM respectively. Specifically, the drive assembly includes a first driver, a second driver, and a driver control board; the first driver and the second driver output an amplitude modulated signal with a constant frequency, and its amplitude is modulated by the sinusoidal signal output by the driver control board. Since the diffraction efficiency of the acousto-optic modulator AOM Bragg diffraction +1-order diffraction light is positively correlated with the amplitude of the driver output signal, the driver control board outputs an amplitude modulated signal to achieve light intensity modulation of the AOM+1-order diffraction light. Since the beat frequency interference signal in the heterodyne laser interferometer is also a light intensity modulation signal, and its modulation frequency is related to the Doppler frequency shift introduced by the motion of the target to be measured. Therefore, the interference light signal in the dynamic measurement of the heterodyne laser interferometer can be simulated by modulating the light intensity of the AOM+1-order diffraction light. By adjusting the frequency of the two sinusoidal signals output by the driver control board, the light intensity modulation frequencies of the measurement light signal and the reference light signal can be adjusted respectively, thereby simulating the frequency of the interference light signal in the heterodyne interferometry. By adjusting the bias and amplitude of the two-way AM signals output by the driver control board, the modulation depth and modulation amplitude of the measurement optical signal and the reference optical signal can be adjusted respectively, thereby simulating the optical power and AC-DC ratio of the interference optical signal in heterodyne interferometry.

[0068] Implementation method 7. See Figure 4 This embodiment is described. This embodiment is an example of the first optical element and the second optical element in the dynamic interference optical signal simulation device of heterodyne laser interferometer based on acousto-optic modulator described in Embodiment 1. The first optical element can also be implemented by a first mirror group, and the second optical element can also be implemented by a second mirror group.

[0069] The first mirror group and the second mirror group are both used to reduce the spot diameter of the incident linearly polarized light.

[0070] In practical application, if Figure 4As shown, the CW light source is a continuous single-frequency laser light source. The CW light source emits a single-frequency laser beam which is divided into two linearly polarized lights with the same polarization direction by a depolarizing beam splitter NPBS. The two linearly polarized lights are respectively incident into the first mirror group and the second mirror group. The first mirror group and the second mirror group are used to reduce the spot diameter of the two laser beams incident on the corresponding acousto-optic modulator AOM to improve the modulation bandwidth of the acousto-optic modulator AOM. The first mirror group and the second mirror group are used to reduce the spot diameter of the incident laser beam of the acousto-optic modulator AOM while maintaining laser alignment. The two laser beams are diffracted by the acousto-optic modulator AOM to generate multi-order diffracted light, and the +1st order diffracted light of the two multi-order diffracted light beams is selected by the third aperture and the fourth aperture respectively. The two +1st order diffracted lights are received by the photodetector 1 and the photodetector 2 as the measurement light signal and the reference light signal respectively and then enter the phase meter to resolve the phase difference. The driving component is used to modulate the diffracted light intensity of the first acousto-optic modulator AOM and the second acousto-optic modulator AOM respectively. Specifically, the drive assembly includes a first driver, a second driver, and a driver control board; the first driver and the second driver output an amplitude modulated signal with a constant frequency, and its amplitude is modulated by the sinusoidal signal output by the driver control board. Since the diffraction efficiency of the acousto-optic modulator AOM Bragg diffraction +1-order diffraction light is positively correlated with the amplitude of the driver output signal, the driver control board outputs an amplitude modulated signal to achieve light intensity modulation of the AOM+1-order diffraction light. Since the beat frequency interference signal in the heterodyne laser interferometer is also a light intensity modulation signal, and its modulation frequency is related to the Doppler frequency shift introduced by the motion of the target to be measured. Therefore, the interference light signal in the dynamic measurement of the heterodyne laser interferometer can be simulated by modulating the light intensity of the AOM+1-order diffraction light. By adjusting the frequency of the two sinusoidal signals output by the driver control board, the light intensity modulation frequencies of the measurement light signal and the reference light signal can be adjusted respectively, thereby simulating the frequency of the interference light signal in the heterodyne interferometry. By adjusting the bias and amplitude of the two-way AM signals output by the driver control board, the modulation depth and modulation amplitude of the measurement optical signal and the reference optical signal can be adjusted respectively, thereby simulating the optical power and AC-DC ratio of the interference optical signal in heterodyne interferometry.

[0071] Embodiment 8. This embodiment is an example of the first mirror group and the second mirror group in the dynamic interference light signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in Embodiment 1, wherein the first mirror group and the second mirror group each include a convex lens and a concave lens;

[0072] The convex lens is arranged in front of the concave lens, and the focus of the convex lens coincides with the focus of the concave lens.

[0073] In actual application of this embodiment, the internal structure of the first mirror group and the second mirror group is a convex lens plus a concave lens, the convex lens is in front and the concave lens is in the back, and the rear focus of the convex lens coincides with the rear focus of the concave lens, thereby achieving the reduction of the spot size while ensuring the collimation of the light beam. The purpose of the first mirror group and the second mirror group is to reduce the spot diameter of the incident laser of the acousto-optic modulator AOM while maintaining the laser collimation.

[0074] Embodiment 9. This embodiment is an example of the driving component in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in embodiment 1, wherein the driving component includes a first driver, a second driver and a driver control board;

[0075] The first driver is used to modulate the intensity of the diffracted light of the first acousto-optic modulator AOM;

[0076] The second driver is used to modulate the intensity of the diffracted light of the second acousto-optic modulator AOM;

[0077] The driver control board is used to send sinusoidal signals to the first driver and the second driver respectively.

[0078] In actual application, the driving component of this embodiment includes a first driver, a second driver and a driver control board; the output of the first driver and the second driver is an amplitude modulated signal with a constant frequency, and its amplitude is modulated by the sinusoidal signal output by the driver control board. Since the diffraction efficiency of the acousto-optic modulator AOM Bragg diffraction +1-order diffraction light is positively correlated with the amplitude of the driver output signal, the driver control board outputs an amplitude modulated signal to achieve light intensity modulation of the AOM+1-order diffraction light. Since the beat frequency interference signal in the heterodyne laser interferometer is also a light intensity modulation signal, and its modulation frequency is related to the Doppler frequency shift introduced by the motion of the target to be measured. Therefore, the interference light signal in the dynamic measurement of the heterodyne laser interferometer can be simulated by modulating the light intensity of the AOM+1-order diffraction light. By adjusting the frequency of the two sinusoidal signals output by the driver control board, the light intensity modulation frequencies of the measurement light signal and the reference light signal can be adjusted respectively, thereby simulating the frequency of the interference light signal in the heterodyne interferometry. By adjusting the bias and amplitude of the two-way AM signals output by the driver control board, the modulation depth and modulation amplitude of the measurement optical signal and the reference optical signal can be adjusted respectively, thereby simulating the optical power and AC-DC ratio of the interference optical signal in heterodyne interferometry.

[0079] Embodiment 10. This embodiment provides a method for simulating dynamic interference light signals of a heterodyne laser interferometer based on an acousto-optic modulator. The method is implemented based on the dynamic interference light signal simulation device of a heterodyne laser interferometer based on an acousto-optic modulator described in any one of embodiments 1 to 9. The simulation method is:

[0080] S1. Pre-measurement: adjust the frequency, bias and amplitude of the two sinusoidal signals output by the driver control board to test and record the optical power and AC-DC ratio that the measurement optical signal and the reference optical signal can simulate at different frequencies;

[0081] S2, measurement initialization: adjust the frequency, offset and amplitude of the two sinusoidal signals output by the driver control board, so that the frequency, optical power and AC-DC ratio of the measurement optical signal and the reference optical signal reach the preset values ​​respectively;

[0082] S3, test point selection;

[0083] S4. Adjust the frequency of the two sinusoidal signals output by the driver control board so that the measuring optical signal and the reference optical signal reach the test point. Adjust the bias and amplitude of the two sinusoidal signals output by the driver control board to adjust the optical power and AC-DC ratio of the measuring optical signal and the reference optical signal respectively. Use the phase meter to calculate the phase difference between the simulated measuring optical signal and the simulated reference optical signal in real time to test and evaluate the dynamic performance of the heterodyne laser interferometer.

[0084] When this implementation method is actually applied, the specific implementation steps are as follows:

[0085] Step 1: Pre-measurement: Before initializing the measurement and conducting the experiment, it is necessary to measure the applicable range of the simulation device in advance, adjust the frequency, offset and amplitude of the two sinusoidal signals output by the driver control board, and test and record the optical power and AC-DC ratio that can be simulated by the measurement optical signal and the reference optical signal at different frequencies;

[0086] Step 2, measurement initialization: adjust the frequency, offset and amplitude of the two sinusoidal signals output by the driver control board, so that the frequency, optical power and AC-DC ratio of the measurement optical signal and the reference optical signal reach the preset values ​​respectively;

[0087] Step 3: Test point selection: Use the high-speed motion of the target to be measured in the laser interferometer displacement measurement system and the simulation device to measure the mapping relationship between the optical signal modulation frequency, modulation depth, and modulation amplitude, and select the test point;

[0088] Step 4. Start measuring: adjust the frequency of the sinusoidal signal output by the driver control board so that the measuring light signal and the reference light signal reach the test point. Adjust the bias and amplitude of the two sinusoidal signals output by the driver control board as needed to adjust the optical power and AC / DC ratio of the measuring light signal and the reference light signal respectively. 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 to test and evaluate the dynamic performance of the heterodyne laser interferometer.

[0089] This embodiment adopts a heterodyne laser interferometer dynamic interference light signal simulation device based on an acousto-optic modulator to realize a heterodyne laser interferometer dynamic interference light signal simulation method based on an acousto-optic modulator. The simulation device has the advantages of simple optical path, few components, high test bandwidth and small coupling error. It can not only be used for dynamic measurement performance test and calibration of heterodyne laser interferometer, but also can realize the adjustment and simulation of optical power, AC-DC ratio and frequency of heterodyne laser interferometer dynamic interference light signal. The simulation of heterodyne laser interferometer dynamic interference light signal is realized by using four steps: pre-measurement, measurement initialization, test point selection and start measurement.

[0090] 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.

[0091] 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.

[0092] 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 interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator, characterized in that: The simulation device includes a CW light source, a depolarization beam splitter prism NPBS, a first optical path, a second optical path, a phase meter and a driving component; The first optical path includes a first optical element, a first acousto-optic modulator AOM, a third aperture and a first detector; The second optical path includes a second optical element, a second acousto-optic modulator AOM, a fourth aperture and a second detector; The CW light source emits a single-frequency laser, which is incident on the depolarization beam splitter prism. The depolarization beam splitter prism splits the incident light into two beams of linear polarized light, which are respectively incident on the first optical element and the second optical element. The light beam processed by the first optical element is incident on the first acousto-optic modulator AOM. The first acousto-optic modulator AOM diffracts the light beam into multi-order diffracted light, which is incident on the third aperture. The third aperture selects +1-order diffracted light from the multi-order diffracted light, which is incident on the first detector. The first detector converts the optical signal into an electrical signal and outputs it to the phase meter. The light beam processed by the second optical element is incident on the second acousto-optic modulator AOM, the second acousto-optic modulator AOM diffracts the light beam into multi-order diffracted light, and the light beam is incident on the fourth aperture, the fourth aperture selects +1-order diffracted light from the multi-order diffracted light, and the +1-order diffracted light is incident on the second detector, and the second detector converts the optical signal into an electrical signal and outputs it to the phase meter; The phase meter is used to calculate the phase difference according to the received electrical signal; The driving component is used to modulate the intensity of the +1st order diffracted light of the first AOM and the second AOM respectively.

2. The dynamic interference optical signal simulation device of heterodyne laser interferometer based on acousto-optic modulator according to claim 1, characterized in that: The CW light source is a continuous single-frequency laser light source.

3. The dynamic interference optical signal simulation device of heterodyne laser interferometer based on acousto-optic modulator according to claim 1, characterized in that: The two linearly polarized lights are equally divided by a depolarizing beam splitter prism NPBS.

4. The dynamic interference optical signal simulation device of heterodyne laser interferometer based on acousto-optic modulator according to claim 1, characterized in that: The incident angle of the light beam incident on the first acousto-optic modulator AOM and the incident angle of the light beam incident on the second acousto-optic modulator AOM are both Bragg angles.

5. The dynamic interference optical signal simulation device of heterodyne laser interferometer based on acousto-optic modulator according to claim 1, characterized in that: The first optical element is realized by a first aperture, and the second optical element is realized by a second aperture; The first aperture and the second aperture are both used to reduce the spot diameter of the incident linearly polarized light.

6. The dynamic interference optical signal simulation device of heterodyne laser interferometer based on acousto-optic modulator according to claim 1, characterized in that: The first optical element may also be implemented by a first convex lens, and the second optical element may also be implemented by a second convex lens; The first convex lens and the second convex lens are both used to reduce the spot diameter of the incident linearly polarized light.

7. The dynamic interference optical signal simulation device of heterodyne laser interferometer based on acousto-optic modulator according to claim 1, characterized in that: The first optical element may also be realized by using a first lens group, and the second optical element may also be realized by using a second lens group; The first mirror group and the second mirror group are both used to reduce the spot diameter of the incident linearly polarized light.

8. The dynamic interference optical signal simulation device of heterodyne laser interferometer based on acousto-optic modulator according to claim 1, characterized in that: The first lens group and the second lens group each include a convex lens and a concave lens; The convex lens is arranged in front of the concave lens, and the rear focus of the convex lens coincides with the rear focus of the concave lens.

9. The dynamic interference optical signal simulation device of heterodyne laser interferometer based on acousto-optic modulator according to claim 1, characterized in that: The drive assembly includes a first drive, a second drive and a drive control board; The first driver is used to modulate the intensity of the diffracted light of the first acousto-optic modulator AOM; The second driver is used to modulate the intensity of the diffracted light of the second acousto-optic modulator AOM; The driver control board is used to send sinusoidal signals to the first driver and the second driver respectively.

10. A method for simulating dynamic interference optical signals of a heterodyne laser interferometer based on an acousto-optic modulator, characterized in that: The method is implemented based on the dynamic interference optical signal simulation device of heterodyne laser interferometer based on acousto-optic modulator according to any one of claims 1 to 9, and the simulation method is: S1. Pre-measurement: adjust the frequency, bias and amplitude of the two sinusoidal signals output by the driver control board to test and record the optical power and AC-DC ratio that the measurement optical signal and the reference optical signal can simulate at different frequencies; S2, measurement initialization: adjust the frequency, offset and amplitude of the two sinusoidal signals output by the driver control board, so that the frequency, optical power and AC-DC ratio of the measurement optical signal and the reference optical signal reach the preset values ​​respectively; S3, test point selection; S4. Adjust the frequency of the two sinusoidal signals output by the driver control board so that the measuring optical signal and the reference optical signal reach the test point. Adjust the bias and amplitude of the two sinusoidal signals output by the driver control board to adjust the optical power and AC-DC ratio of the measuring optical signal and the reference optical signal respectively. Use the phase meter to calculate the phase difference between the simulated measuring optical signal and the simulated reference optical signal in real time to test and evaluate the dynamic performance of the heterodyne laser interferometer.

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