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

Abstract

This invention relates to a simulation device and method for dynamic interference optical signals of heterodyne laser interferometers based on acousto-optic modulators, and pertains to the field of dynamic performance testing technology for heterodyne laser interferometers. It addresses the problem of difficulty in effectively evaluating the dynamic measurement performance of heterodyne laser interferometers when using electrical signals in existing dynamic performance testing methods. The device uses a CW light source to emit a single-frequency laser, which is split into two linearly polarized beams after being processed by a depolarizing beam splitter. These beams are then directed into a first optical path and a second optical path, respectively. Optical elements, acousto-optic modulators, and apertures in the first and second optical paths process the beams and transmit them to detectors. The detectors convert the optical signals into electrical signals and output them to a phase meter, which calculates the phase difference. A driving component modulates the intensity of the +1st order diffracted light from the acousto-optic modulator. This invention is applicable to the simulation device of interference optical signals in dynamic measurements of heterodyne laser interferometers.

Description

Technical Field

[0001] This invention relates to the field of dynamic performance testing technology for heterodyne laser interferometry. Background Technology

[0002] Heterodyne laser interferometers, with their advantages of high resolution, high measurement speed, and high precision, are widely used in ultra-precision equipment manufacturing, microelectronics processing, and precision metrology. With the rapid development of these fields, the research focus of heterodyne interferometry has shifted from static and quasi-static measurements to high-speed, dynamic measurements, thus placing higher demands on the dynamic measurement performance of heterodyne laser interferometers. Therefore, it is crucial to conduct scientific and effective testing and evaluation of the dynamic measurement performance of heterodyne laser interferometers.

[0003] During dynamic measurements using a heterodyne laser interferometer, mechanical installation and vibration of the target object introduce Abbe and cosine errors; temperature changes, humidity fluctuations, and air pressure disturbances caused by high-speed motion at the m / s level introduce air refractive index errors; and the measurement time delay of the interferometer introduces data periodicity errors. Similarly, mainstream heterodyne laser interferometer calibration specifications often only consider static and quasi-static measurements, failing to analyze and suppress the errors newly introduced in dynamic measurements, thus rendering them unsuitable for dynamic performance testing of heterodyne laser interferometers.

[0004] For example, in the interferometer calibration standard 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 periodic error introduced by asynchrony during dynamic measurements. This makes it difficult to evaluate the dynamic measurement performance of heterodyne laser interferometers.

[0005] To eliminate the aforementioned Abbe error, cosine error, air refractive index error, and data periodicity error, many studies use electrical signals to simulate the motion of the target under test in the dynamic measurement of a heterodyne laser interferometer, thereby evaluating the dynamic measurement performance of the heterodyne laser interferometer. For example, high-speed phase-modulated and frequency-modulated electrical signals are used to test the dynamic measurement performance of the ZMI4000 high-speed ultra-precision laser interferometer. A paper published on June 1, 2009, titled "Design of a Standard Test Platform for the Signal Processing Unit of an Ultra-Precision Dynamic Laser Interferometer," establishes an interference signal model of the moving target and uses electrical signals to simulate the dynamic motion trajectory of the heterodyne laser interferometer to test its dynamic performance. However, this type of method does not include testing the photoelectric conversion part, which, in heterodyne interferometry, is a key factor determining the dynamic measurement performance of the interferometer. Summary of the Invention

[0006] This invention addresses the problem that existing methods use electrical signals to simulate the dynamic motion trajectory of a heterodyne laser interferometer for dynamic performance testing, but do not include testing the photoelectric conversion part, making it difficult to effectively evaluate the dynamic measurement performance of the heterodyne laser interferometer.

[0007] To achieve the above objectives, the present invention provides the following solution:

[0008] This invention provides a dynamic interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator. The simulation device includes a CW light source, a polarization-depolarizing beam splitter (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 beam, which enters the depolarization beam splitter. The depolarization beam splitter splits the incident light into two linearly polarized beams, which enter the first optical element and the second optical element, respectively. The beam processed by the first optical element enters the first acousto-optic modulator (AOM), which diffracts the beam into multi-order diffracted light and enters the third aperture. The third aperture selects the +1st order diffracted light from the multi-order diffracted light and enters 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 injected into the second acousto-optic modulator AOM. The second acousto-optic modulator AOM diffracts the light beam into multi-order diffracted light and injects it into the fourth aperture. The fourth aperture selects the +1 order diffracted light from the multi-order diffracted light and injects it into the second detector. 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 based on the received electrical signal;

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

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

[0016] Furthermore, in a preferred embodiment, the two linearly polarized beams are split equally by an antipolarizing beam splitter NPBS.

[0017] Furthermore, in a preferred embodiment, 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.

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

[0019] Both the first and second apertures are used to reduce the spot diameter of the incident linearly polarized light.

[0020] Furthermore, in a preferred embodiment, the first optical element can also be implemented using a first convex lens, and the second optical element can also be implemented using a second convex lens;

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

[0022] Furthermore, in a preferred embodiment, the first optical element can also be implemented using a first lens group, and the second optical element can also be implemented using a second lens group;

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

[0024] Furthermore, in a preferred embodiment, both the first and second lens groups described above include a convex lens and a concave lens;

[0025] The convex lens is positioned in front of the concave lens, and the rear focal point of the convex lens coincides with the rear focal point of the concave lens.

[0026] Furthermore, in a preferred embodiment, the aforementioned driving component includes a first driver, a second driver, and a driver control board;

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

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

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

[0030] This invention also provides a method for simulating dynamic interference optical signals of a heterodyne laser interferometer based on an acousto-optic modulator. The method is implemented based on the aforementioned device for simulating dynamic interference optical signals of a heterodyne laser interferometer based on an acousto-optic modulator. The simulation method is as follows:

[0031] S1. Pre-measurement: Adjust the frequency, bias 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 measured optical signal and the reference optical signal at different frequencies;

[0032] S2. Measurement initialization: Adjust the frequency, bias and amplitude of the two sinusoidal signals output by the driver control board to make 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 measured 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 measured optical signal and the reference optical signal respectively. Use a phase meter to calculate the phase difference between the simulated measured optical signal and the simulated reference optical signal in real time to perform dynamic performance testing and evaluation of the heterodyne laser interferometer.

[0035] The beneficial effects of this invention are as follows:

[0036] 1. This invention provides a dynamic interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator. It uses optical elements to reduce the spot size and increase the limiting modulation bandwidth of the acousto-optic modulator (AOM). It uses the acousto-optic modulator (AOM) to modulate the intensity of a continuous single-frequency laser to simulate a real beat frequency interference optical signal. It realizes the simulation of heterodyne laser interference signal under high-speed dynamic conditions.

[0037] 2. Existing heterodyne laser interferometers often exhibit various errors in displacement measurement, such as coupling environment error, Abbe error, cosine error, and data period error. This invention provides a dynamic interference optical signal simulation device for heterodyne laser interferometers based on an acousto-optic modulator (AOM). The device directly modulates the light intensity using an AOM to simulate the interference optical signal in heterodyne interferometry, while simultaneously adjusting the power and AC / DC ratio of the simulated interference optical signal. This effectively separates the influence of environmental errors, Abbe errors, cosine errors, and data period errors in the dynamic measurement of the heterodyne interferometer. Simultaneously, two diffracted beams, serving as the measurement and reference optical signals respectively, are received by a first and a second photodetector and then fed into a phase meter to calculate their phase difference. This enables dynamic performance testing and evaluation of the heterodyne laser interferometer, including a photoelectric conversion stage.

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

[0039] This invention is applicable to a simulation device for interfering optical signals in dynamic measurements using a heterodyne laser interferometer. Attached Figure Description

[0040] Figure 1 This is a system diagram of the dynamic interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator as described in Embodiment 1;

[0041] Figure 2 This is a system diagram of the dynamic interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator, which uses an aperture to realize the optical elements as described in Embodiment 5.

[0042] Figure 3 This is a system diagram of the dynamic interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator, which uses a convex lens to implement the optical elements described in Embodiment 6.

[0043] Figure 4 This is a system diagram of a heterodyne laser interferometer dynamic interference optical signal simulation device based on an acousto-optic modulator, which uses a mirror group to realize the optical elements described in Embodiment 7. Detailed Implementation

[0044] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

[0045] Implementation Method 1. See [link / reference] Figure 1 This embodiment describes a dynamic interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator. The simulation device includes a CW light source, a polarization-depolarizing beam splitter (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 beam, which enters the depolarization beam splitter. The depolarization beam splitter splits the incident light into two linearly polarized beams, which enter the first optical element and the second optical element, respectively. The beam processed by the first optical element enters the first acousto-optic modulator (AOM), which diffracts the beam into multi-order diffracted light and enters the third aperture. The third aperture selects the +1st order diffracted light from the multi-order diffracted light and enters 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 injected into the second acousto-optic modulator AOM. The second acousto-optic modulator AOM diffracts the light beam into multi-order diffracted light and injects it into the fourth aperture. The fourth aperture selects the +1 order diffracted light from the multi-order diffracted light and injects it into the second detector. 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 based on the received electrical signal;

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

[0052] In practical applications, this implementation method, such as Figure 1As shown, a single-frequency laser beam emitted by a CW light source is split into two linearly polarized beams with the same polarization direction by an antipolarizing beam splitter (NPBS). These two beams are then incident on a first optical element and a second optical element, respectively. Both optical elements limit the spot diameter of the laser beams incident on the corresponding acousto-optic modulators (AOMs) to increase the modulation bandwidth of the AOMs. The two laser beams are diffracted by the AOMs to generate multi-order diffracted light. The +1st order diffracted light is then selected by the third and fourth apertures, respectively. These +1st order diffracted light beams serve as the measurement and reference signals, respectively, and are received by photodetectors 1 and 2, then fed into a phase meter to calculate their phase difference. A driving component is used to modulate the intensity of the diffracted light from the first and second acousto-optic modulators (AOMs), respectively. Specifically, the driving component includes a first driver, a second driver, and a driver control board. The first and second drivers output constant-frequency amplitude-modulated signals, the amplitude of which is modulated by the sinusoidal signal output from the driver control board. Since the diffraction efficiency of the +1st order AOM Bragg diffraction light is positively correlated with the amplitude of the driver output signal, the amplitude-modulated signal output from the driver control board is used to suppress the intensity of the +1st order AOM diffraction light. Because the beat frequency interference signal in a heterodyne laser interferometer is also an intensity-modulated signal, and its modulation frequency is related to the Doppler frequency shift introduced by the motion of the target, the interference light signal in dynamic measurement of a heterodyne laser interferometer can be simulated by suppressing the intensity of the +1st order AOM diffraction light. By adjusting the frequencies of the two sinusoidal signals output from the driver control board, the intensity-modulated 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 heterodyne interferometry. By adjusting the bias and amplitude of the two amplitude modulation 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 optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator. It uses optical elements to reduce the spot size and increase the limiting modulation bandwidth of the acousto-optic modulator (AOM). The AOM is used to modulate the intensity of a continuous single-frequency laser to simulate a real beat frequency interference optical signal, thereby realizing the simulation of heterodyne laser interference signals under high-speed dynamic conditions.

[0054] Existing heterodyne laser interferometers often exhibit various errors in displacement measurement, such as coupling environment error, Abbe error, cosine error, and data period error. This embodiment provides a dynamic interference optical signal simulation device for heterodyne laser interferometers based on an acousto-optic modulator (AOM). The AOM directly modulates the light intensity to simulate the interference optical signal in heterodyne interferometry, while simultaneously adjusting the power and AC / DC ratio of the simulated interference optical signal. This effectively separates the influence of environmental errors, Abbe errors, cosine errors, and data period errors in the dynamic measurement of the heterodyne interferometer. Simultaneously, two diffracted beams, serving as the measurement and reference optical signals respectively, are received by a first and a second photodetector and then fed into a phase meter to calculate their phase difference. This enables dynamic performance testing and evaluation of the heterodyne laser interferometer, including a photoelectric conversion stage.

[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 simple optical path, few components, high test bandwidth and low coupling error. It can not only be used for dynamic measurement performance testing and calibration of heterodyne laser interferometer, but also realize the adjustment and real-time detection of optical power, AC / DC ratio and frequency of interference optical signal of heterodyne laser interferometer.

[0056] Implementation Method 2. This implementation method 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 Implementation Method 1. The CW light source is a continuous single-frequency laser light source.

[0057] In practical applications, this implementation method firstly ensures that the single-frequency light source has a single optical frequency, preventing interference between multiple optical frequencies; secondly, the polarization direction of the single-frequency light source is fixed, avoiding fluctuations in diffraction efficiency due to changes in polarization direction; and finally, the single-frequency light source has a large optical power, ensuring that there is still sufficient optical power to simulate actual interference signals after diffraction.

[0058] Implementation Method 3. This implementation method illustrates the beam splitting method of two linearly polarized beams in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in Implementation Method 1. The two linearly polarized beams are split equally by the depolarizing beam splitter NPBS.

[0059] In practical applications, this embodiment uses a polarization-depolarizing beam splitter (NPBS) to divide the light source of a single-frequency laser into equal parts. This avoids fluctuations in the intensity of the two polarized beams caused by changes in the polarization direction of the light source, thereby ensuring the stability of the final simulated interference signal intensity.

[0060] Implementation Method 4. This implementation method illustrates the incident angles of the light beam into the first acousto-optic modulator (AOM) and the second acousto-optic modulator (AOM) in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in Implementation Method 1. Both the incident angles of the light beam into the first acousto-optic modulator (AOM) and the incident angles of the light beam into the second acousto-optic modulator (AOM) are Bragg angles.

[0061] In practical applications, when the incident light is incident at the Bragg angle, the diffracted light only has the 0th order and the +1 or -1 order. At this time, the +1 or -1 order diffraction efficiency is the highest, thus providing sufficient optical power for interference signal simulation.

[0062] Implementation Method 5. See also Figure 2 This embodiment is described by way of example, illustrating the first and second optical elements in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in Embodiment 1. The first optical element is implemented using a first aperture, and the second optical element is implemented using a second aperture.

[0063] Both the first and second apertures are used to reduce the spot diameter of the incident linearly polarized light.

[0064] In practical application, as shown in Figure 2, the CW light source is a continuous single-frequency laser source. The CW light source emits a single-frequency laser beam, which is split into two linearly polarized beams with the same polarization direction by the depolarizing beam splitter NPBS. These two linearly polarized beams are respectively incident on the first and second apertures. Both the first and second apertures limit the spot diameter of the two laser beams incident on the corresponding acousto-optic modulators (AOMs) to increase the modulation bandwidth of the AOMs. The two laser beams are diffracted by the AOMs to generate multi-order diffracted light, which is then selected by the third and fourth apertures to select the +1st order diffracted light. The two +1st order diffracted light beams serve as the measurement and reference light signals, respectively, and are received by photodetectors 1 and 2, and then enter a phase meter to calculate their phase difference. The driving component is used to modulate the intensity of the diffracted light from the first and second acousto-optic modulators (AOMs), respectively. Specifically, the driving component includes a first driver, a second driver, and a driver control board. The first and second drivers output constant-frequency amplitude-modulated signals, the amplitude of which is modulated by the sinusoidal signal output from the driver control board. Since the diffraction efficiency of the +1st order AOM Bragg diffraction light is positively correlated with the amplitude of the driver output signal, the amplitude-modulated signal output from the driver control board is used to suppress the intensity of the +1st order AOM diffraction light. Because the beat frequency interference signal in a heterodyne laser interferometer is also an intensity-modulated signal, and its modulation frequency is related to the Doppler frequency shift introduced by the motion of the target, the interference light signal in dynamic measurement of a heterodyne laser interferometer can be simulated by suppressing the intensity of the +1st order AOM diffraction light. By adjusting the frequencies of the two sinusoidal signals output from the driver control board, the intensity-modulated 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 heterodyne interferometry. By adjusting the bias and amplitude of the two amplitude modulation 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 six. See also Figure 3 This embodiment is described by way of example of the first and second optical elements in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in Embodiment 1. 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] Both the first convex lens and the second convex lens are used to reduce the spot diameter of the incident linearly polarized light.

[0067] In practical application, as shown in Figure 3, the CW light source is a continuous single-frequency laser source. The CW light source emits a single-frequency laser beam, which is split into two linearly polarized beams with the same polarization direction by the depolarizing beam splitter NPBS. These two linearly polarized beams are respectively incident on a first convex lens and a second convex lens. Both the first and second convex lenses are used to reduce the spot diameter of the laser beams incident on the corresponding acousto-optic modulators (AOMs), thereby increasing the modulation bandwidth of the AOMs. The focal point of the convex lens is the incident point of the AOM to reduce the spot diameter of the laser beam incident on the AOM. The two laser beams are diffracted by the acousto-optic modulators (AOMs) to generate multi-order diffracted light. The +1st order diffracted light of the two multi-order diffracted beams is selected by the third and fourth apertures, respectively. These two +1st order diffracted beams are used as measurement and reference light signals, respectively, and are received by photodetectors 1 and 2, and then enter a phase meter to calculate their phase difference. The driving component is used to modulate the intensity of the diffracted light from the first and second acousto-optic modulators (AOMs), respectively. Specifically, the driving component includes a first driver, a second driver, and a driver control board. The first and second drivers output constant-frequency amplitude-modulated signals, the amplitude of which is modulated by the sinusoidal signal output from the driver control board. Since the diffraction efficiency of the +1st order AOM Bragg diffraction light is positively correlated with the amplitude of the driver output signal, the amplitude-modulated signal output from the driver control board is used to suppress the intensity of the +1st order AOM diffraction light. Because the beat frequency interference signal in a heterodyne laser interferometer is also an intensity-modulated signal, and its modulation frequency is related to the Doppler frequency shift introduced by the motion of the target, the interference light signal in dynamic measurement of a heterodyne laser interferometer can be simulated by suppressing the intensity of the +1st order AOM diffraction light. By adjusting the frequencies of the two sinusoidal signals output from the driver control board, the intensity-modulated 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 heterodyne interferometry. By adjusting the bias and amplitude of the two amplitude modulation 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 Seven. See also Figure 4 This embodiment is described by way of example of the first and second optical elements in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the 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] Both the first and second mirror groups are used to reduce the spot diameter of the incident linearly polarized light.

[0070] In practical applications, this implementation method, such as Figure 4As shown, the CW light source is a continuous single-frequency laser source. The CW light source emits a single-frequency laser beam, which is split into two linearly polarized beams with the same polarization direction by the depolarizing beam splitter NPBS. These two linearly polarized beams are respectively incident on a first mirror group and a second mirror group. Both the first and second mirror groups are used to reduce the spot diameter of the laser beams incident on the corresponding acousto-optic modulator (AOM), thereby increasing the modulation bandwidth of the AOM. The purpose of the first and second mirror groups is to maintain laser collimation while reducing the spot diameter of the laser beam incident on the AOM. The two laser beams are diffracted by the AOM to generate multi-order diffracted light, and the +1st order diffracted light is selected by the third and fourth apertures respectively. These two +1st order diffracted light beams are used as measurement and reference light signals, respectively, and are received by photodetectors 1 and 2, and then enter a phase meter to calculate their phase difference. The driving component is used to modulate the intensity of the diffracted light from the first and second acousto-optic modulators (AOM). Specifically, the driving component includes a first driver, a second driver, and a driver control board. The first and second drivers output constant-frequency amplitude-modulated signals, the amplitude of which is modulated by the sinusoidal signal output from the driver control board. Since the diffraction efficiency of the +1st order AOM Bragg diffraction light is positively correlated with the amplitude of the driver output signal, the amplitude-modulated signal output from the driver control board is used to suppress the intensity of the +1st order AOM diffraction light. Because the beat frequency interference signal in a heterodyne laser interferometer is also an intensity-modulated signal, and its modulation frequency is related to the Doppler frequency shift introduced by the motion of the target, the interference light signal in dynamic measurement of a heterodyne laser interferometer can be simulated by suppressing the intensity of the +1st order AOM diffraction light. By adjusting the frequencies of the two sinusoidal signals output from the driver control board, the intensity-modulated 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 heterodyne interferometry. By adjusting the bias and amplitude of the two amplitude modulation 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] Implementation Method 8. This implementation method is an example of the first and second mirror groups in the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator described in Implementation Method 1. Both the first and second mirror groups include a convex lens and a concave lens.

[0072] The convex lens is positioned in front of the concave lens, and the focal point of the convex lens coincides with the focal point of the concave lens.

[0073] In practical applications, the internal structure of the first and second mirror groups is a convex lens and a concave lens, with the convex lens in front and the concave lens behind, and the rear focal point of the convex lens coincides with the rear focal point of the concave lens. This achieves the reduction of the spot size while ensuring the collimation of the beam. The purpose of the first and second mirror groups is to reduce the spot diameter of the incident laser of the acousto-optic modulator (AOM) while maintaining laser collimation.

[0074] Implementation Method Nine. This implementation method 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 Implementation Method One. 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 from the first acousto-optic modulator AOM;

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

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

[0078] In practical applications, the driving components of this embodiment include a first driver, a second driver, and a driver control board. The outputs of the first and second drivers are amplitude-modulated signals with constant frequencies, whose amplitudes are modulated by the sinusoidal signal output from the driver control board. Since the diffraction efficiency of the +1st order AOM Bragg diffraction light is positively correlated with the amplitude of the driver output signal, the intensity modulation of the +1st order AOM diffraction light is achieved by outputting the amplitude-modulated signal from the driver control board. Because the beat frequency interference signal in a heterodyne laser interferometer is also an intensity modulation signal, and its modulation frequency is related to the Doppler frequency shift introduced by the motion of the target, the interference light signal in dynamic measurement of a heterodyne laser interferometer can be simulated by intensity modulation of the +1st order AOM diffraction light. By adjusting the frequencies of the two sinusoidal signals output from the driver control board, the 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 heterodyne interferometry. By adjusting the bias and amplitude of the two amplitude modulation 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] Implementation Method 10. This implementation method provides a method for simulating dynamic interference optical signals of a heterodyne laser interferometer based on an acousto-optic modulator. The method is implemented based on the dynamic interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator described in any one of Implementation Methods 1 to 9. The simulation method is as follows:

[0080] S1. Pre-measurement: Adjust the frequency, bias 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 measured optical signal and the reference optical signal at different frequencies;

[0081] S2. Measurement initialization: Adjust the frequency, bias and amplitude of the two sinusoidal signals output by the driver control board to make 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 measured 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 measured optical signal and the reference optical signal respectively. Use a phase meter to calculate the phase difference between the simulated measured optical signal and the simulated reference optical signal in real time to perform dynamic performance testing and evaluation of the heterodyne laser interferometer.

[0084] In practical applications, the specific implementation steps of this embodiment 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, bias 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 respectively.

[0086] Step 2, Measurement Initialization: Adjust the frequency, bias, and amplitude of the two sinusoidal signals output by the driver control board to make 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: Utilize the high-speed motion simulation device of the target under test in the laser interferometric displacement measurement system to measure the mapping relationship between the modulation frequency, modulation depth, and modulation amplitude of the optical signal, and select test points accordingly.

[0088] Step 4: Start Measurement: Adjust the frequency of the sinusoidal signal output by the driver control board to ensure that the measurement optical signal and the reference optical signal reach the test point. As needed, 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 measurement optical signal and the reference optical signal respectively. Use the phase meter under test to measure the phase difference between the interference light and the actual simulated target motion phase in real time to perform dynamic performance testing and evaluation of the heterodyne laser interferometer.

[0089] This embodiment employs a dynamic interference optical signal simulation device for a heterodyne laser interferometer based on an acousto-optic modulator, realizing a method for simulating dynamic interference optical signals of a heterodyne laser interferometer based on an acousto-optic modulator. The simulation device possesses advantages such as a simple optical path, few components, high test bandwidth, and low coupling error. It can be used not only for dynamic measurement performance testing and calibration of heterodyne laser interferometers, but also for adjusting and simulating the optical power, AC / DC ratio, and frequency of the dynamic interference optical signal of a heterodyne laser interferometer. The simulation of the dynamic interference optical signal of a heterodyne laser interferometer is achieved through four steps: pre-measurement, measurement initialization, test point selection, and measurement start.

[0090] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0091] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0092] The above description is merely an embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within 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 comprises a CW light source, a depolarization beam splitter prism NPBS, a first light path, a second light path, a phase meter and a driving assembly; The first light path comprises a first optical element, a first acousto-optic modulator AOM, a third light barrier and a first detector; The second light path comprises a second optical element, a second acousto-optic modulator AOM, a fourth light barrier and a second detector; The CW light source emits monochromatic laser, which is incident into the depolarization beam splitter prism. The depolarization beam splitter prism divides the incident light into two linearly polarized lights, which are respectively incident into the first optical element and the second optical element. The light beam processed by the first optical element is incident into the first acousto-optic modulator AOM. The first acousto-optic modulator AOM diffracts the light beam into multiple levels of diffracted light, which is incident into the third light barrier. The third light barrier selects the +1 level of diffracted light from the multiple levels of diffracted light and is incident into the first detector. The first detector converts the optical signal into an electrical signal and outputs the electrical signal to the phase meter. The light beam processed by the second optical element is incident into the second acousto-optic modulator AOM. The second acousto-optic modulator AOM diffracts the light beam into multiple levels of diffracted light, which is incident into the fourth light barrier. The fourth light barrier selects the +1 level of diffracted light from the multiple levels of diffracted light and is incident into the second detector. The second detector converts the optical signal into an electrical signal and outputs the electrical signal to the phase meter. The phase meter is used to calculate the phase difference according to the received electrical signal. The driving assembly is used to modulate the +1 level of diffracted light intensity of the first acousto-optic modulator AOM and the second acousto-optic modulator AOM respectively. The driving assembly comprises a first driver, a second driver and a driver control board card. The first driver is used to modulate the diffracted light intensity of the first acousto-optic modulator AOM. The second driver is used to modulate the diffracted light intensity of the second acousto-optic modulator AOM. The driver control board card is used to send sinusoidal signals to the first driver and the second driver respectively. The frequencies of the two sinusoidal signals output by the driver control board card are adjusted to respectively adjust the light intensity modulation frequencies of the measurement light signal and the reference light signal, thereby simulating the frequency of the interference light signal in the heterodyne interference measurement. The bias and amplitude of the two amplitude modulation signals output by the driver control board card are adjusted to respectively adjust the modulation depth and modulation amplitude of the measurement light signal and the reference light signal, thereby simulating the optical power and AC / DC ratio of the interference light signal in the heterodyne interference measurement.

2. The dynamic interferometric optical signal simulation apparatus based on a heterodyne laser interferometer with acousto-optic modulators according to claim 1, characterized in that, The CW light source is a continuous single-frequency laser light source.

3. The dynamic heterodyne laser interferometer dynamic interference light signal simulation apparatus based on an acousto-optic modulator according to claim 1, characterized in that, The two linearly polarized lights are equally divided by the depolarization beam splitter prism NPBS.

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

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

6. The dynamic heterodyne laser interferometer dynamic interference light signal simulation apparatus based on an acousto-optic modulator according to claim 1, characterized in that, The first optical element can also be realized by a first convex lens, and the second optical element can also be realized 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 heterodyne laser interferometer dynamic interference light signal simulation apparatus based on an acousto-optic modulator according to claim 1, characterized in that, 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. The first mirror group and the second mirror group are both used for reducing the spot diameter of the incident linearly polarized light.

8. The dynamic heterodyne laser interferometer dynamic interference light signal simulation apparatus based on an acousto-optic modulator according to claim 1, characterized in that, The first mirror group and the second mirror group both include a convex lens and a concave lens. The convex lens is arranged in front of the concave lens, and the back focal point of the convex lens coincides with the back focal point of the concave lens.

9. A method of simulating dynamic interference optical signals of a heterodyne laser interferometer based on acousto-optic modulators, characterized in that, The method is implemented by the dynamic interference optical signal simulation device of the heterodyne laser interferometer based on the acousto-optic modulator according to any one of claims 1-8, and the simulation method is: S1, pre-measurement: adjusting the frequency, bias and amplitude of the two sinusoidal signals output by the driver control board card, respectively testing and recording the light power and AC / DC ratio of the measurement light signal and the reference light signal that can be simulated under different frequencies; S2, measurement initialization: adjusting the frequency, bias and amplitude of the two sinusoidal signals output by the driver control board card, respectively making the frequency, light power and AC / DC ratio of the measurement light signal and the reference light signal reach the preset value; S3, test point selection; S4, adjusting the frequency of the two sinusoidal signals output by the driver control board card, so that the measurement light signal and the reference light signal reach the test point, adjusting the bias and amplitude of the two sinusoidal signals output by the driver control board card to respectively adjust the light power and AC / DC ratio of the measurement light signal and the reference light signal, using a phase meter to real-time solve the phase difference between the simulated measurement light signal and the simulated reference light signal, and performing dynamic performance test and evaluation of the heterodyne laser interferometer.

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