An acoustic field time-grating linear displacement sensing system

Abstract

The present invention discloses a difference-frequency acoustic field-type time-grating linear displacement sensing system, comprising a laser light source, a movable ruler, a photoelectric receiver, and a signal control system; the movable ruler comprises a movable ruler acousto-optic crystal. The laser light source, movable ruler, and photoelectric receiver are arranged from top to bottom, and the movable ruler can move left and right relative to the photoelectric receiver. The signal control system comprises a signal generation and loading module and a signal processing module. The signal generation and loading module generates a DC excitation signal I0 to drive the laser light source, generates a reference signal with a frequency of |f1-f2| and inputs it into the signal processing module, generates an ultrasonic drive signal related to the frequency f1, and loads it to the movable ruler acousto-optic crystal via an ultrasonic transducer. The present invention can improve anti-interference performance while reducing dependence on manufacturing processes.

Description

Technical Field

[0001] The present invention belongs to the field of precision measurement, and particularly relates to an acoustic field type time grating linear displacement sensing system. Background Art

[0002] At present, the main methods for ultra-precision large-range displacement measurement are: laser interferometers and grating interferometers. Due to the different generation methods of the measurement reference, these two measurement methods have their own advantages and disadvantages in actual application processes; generally speaking, they are as follows: (1) Laser interferometers with the wavelength of light waves as the measurement reference have the advantages of no need for engraving of the reference, high precision, and large range, but due to the lack of physical protection for the measurement reference, they have high requirements for the environment and are difficult to integrate; (2) Grating interferometers with the grating pitch as the measurement reference have the advantages of high precision, strong anti-interference ability, and easy integration, but due to the mechanical engraving of the grating pitch, they have high requirements for processing, resulting in high manufacturing difficulty and cost. Summary of the Invention

[0003] The purpose of the present invention is to provide an acoustic field type time grating linear displacement sensing system to improve the anti-interference ability and reduce the dependence on the manufacturing process at the same time.

[0004] The acoustic field type time grating linear displacement sensing system described in the present invention includes a laser light source, a moving scale, a photoelectric receiver, and a signal control system. The moving scale has a moving scale acousto-optic crystal. The laser light source is located above the moving scale, and the photoelectric receiver is located below the moving scale. The laser light source and the photoelectric receiver are fixedly installed, and the moving scale can move left and right relative to the photoelectric receiver.

[0005] The signal control system includes a signal generation and loading module and a signal processing module. The signal generation and loading module is connected to the laser light source and the signal processing module. The signal generation and loading module is connected to the moving scale through an ultrasonic transducer. The photoelectric receiver is connected to the signal processing module; the signal generation and loading module generates an excitation signal i to drive the laser light source to output an optical signal with an alternating light intensity, generates a reference signal with a frequency of |f1 - f2| and inputs it to the signal processing module, and generates an ultrasonic drive signal related to the frequency f1 and loads it to the moving scale acousto-optic crystal through the ultrasonic transducer.

[0006] When the moving scale moves relative to the photoelectric receiver, the optical signal passes through the moving scale acousto-optic crystal and reaches the photoelectric receiver. The photoelectric receiver converts the received optical signal into an electrical signal and inputs it to the signal processing module. The signal processing module processes the electrical signal (i.e., the electrical signal converted from the optical signal received by the photoelectric receiver) and the reference signal to obtain the linear displacement value of the moving scale relative to the photoelectric receiver. Where, i = I0 + I m sin(f2t), 0 < |f1 - f2| < min(f1, f2), I0 represents the DC current component in the excitation signal i, and the current amplitude of the excitation signal i is I m, the current frequency is f2, min() means taking the smaller value, that is, min(f1,f2) means taking the smaller value of f1 and f2.

[0007] Preferably, there are two types of ultrasonic driving signals.

[0008] The first ultrasonic driving signal is a modulated signal obtained by the signal generation and loading module using the sinusoidal modulation signal U1 to modulate the ultrasonic excitation signal U'. The ultrasonic driving signal is expressed as: A1sin(f1t)[A0sin(f0t)+U m ] Among them, the ultrasonic excitation signal U' and the sinusoidal modulation signal U1 are generated by the signal generation and loading module, U1 = A1sin(f1t), U' = A0sin(f0t)+U m ,f1<f0,f2<f0,U m It represents the DC voltage component in the ultrasonic excitation signal U′. The voltage amplitude of the ultrasonic excitation signal U′ is A0 and the voltage frequency is f0. The voltage amplitude of the sinusoidal modulation signal U1 is A1 and the voltage frequency is f1.

[0009] The second ultrasonic driving signal is the ultrasonic excitation signal U′1 generated by the signal generation and loading module. Wherein, U′1=A1sin(f1t)+U m1 , U m1 It represents the DC voltage component in the ultrasonic excitation signal U′1. The voltage amplitude of the ultrasonic excitation signal U′1 is A1 and the voltage frequency is f1.

[0010] Preferably, the photoelectric receiver receives two types of optical signals.

[0011] The first optical signal received by the photoelectric receiver is the +1st order moving scale diffraction light emitted by the moving scale acousto-optic crystal. The +1st order moving scale diffraction light is generated by the light signal with alternating light intensity output by the laser light source being incident on the moving scale acousto-optic crystal and being diffracted by the moving scale acousto-optic crystal.

[0012] The second optical signal received by the photoelectric receiver is the -1st order moving ruler diffraction light emitted by the moving ruler acousto-optic crystal. The -1st order moving ruler diffraction light is generated by the light signal with alternating light intensity output by the laser light source being incident on the moving ruler acousto-optic crystal and being diffracted by the moving ruler acousto-optic crystal.

[0013] Preferably, the signal processing module processes the electrical signal and the reference signal to obtain the linear displacement value of the movable ruler relative to the photoelectric receiver by performing bandpass filtering on the electrical signal to obtain an electrical traveling wave signal, then performing zero-crossing comparison on the electrical traveling wave signal to obtain a square wave signal corresponding to the electrical signal and having a frequency of |f1-f2|. This square wave signal is then compared with the reference signal, with the phase difference represented by the number of interpolated high-frequency clock pulses, and then converted to obtain the linear displacement value of the movable ruler relative to the photoelectric receiver; wherein the reference signal is a square wave signal.

[0014] Preferably, the frequencies f1 and f2 satisfy the following relationship: |f1-f2|≤0.1min(f1, f2). The smaller the value of |f1-f2|, the higher the resolution of the displacement measurement. |f1-f2|≤0.1min(f1, f2) is a reasonable limit for improving measurement resolution.

[0015] This invention uses an ultrasonic traveling wave (corresponding to an ultrasonic drive signal) propagating within an acousto-optic crystal as the measurement medium. It utilizes the physical principles of acousto-optic diffraction and acousto-optic communication to detect the ultrasonic traveling wave signal, thereby achieving displacement measurement based on ultrasonic wave length. Drawing on the principle of controlling diffracted light intensity through ultrasonic power modulation in acousto-optic communication, combined with the spatial motion of the ultrasonic traveling wave (corresponding to the movement of a moving ruler), the diffracted light intensity shifts back and forth in time as the ruler moves to different positions, thereby synthesizing a new ultrasonic traveling wave signal that can be directly detected using the diffracted light intensity signal.

[0016] The laser light source outputs continuous laser light in a continuous excitation mode, which is irradiated onto the photoelectric receiver through the moving ruler acousto-optic crystal. When the moving ruler moves, the ultrasonic traveling wave undergoes periodic changes in the moving ruler acousto-optic crystal. Through the acousto-optic effect, a diffraction light intensity signal reflecting the movement of the moving ruler and the motion of the ultrasonic traveling wave is obtained. After photoelectric conversion and bandpass filtering, an electrical traveling wave signal is obtained. The electrical traveling wave signal shows a temporal sequence change with the change of spatial position, thereby realizing the measurement of spatial displacement by time.

[0017] The present invention uses traveling waves within entities as a motion reference system to convert spatial measurements into temporal measurements. Guided by the concept of time-grating measurement, this invention uses traveling waves within entities as a measurement carrier and integrates the advantages of multiple sensing measurement methods.

[0018] The present invention has the following advantages:

[0019] (1) The wavelength of the traveling wave in the physical object (dynamic ruler acousto-optic crystal) is used as the measurement reference. The physical ruler protects the measurement reference from interference from the external environment, improves the anti-interference performance, and reduces the dependence of traditional physical sensors on the manufacturing process of equidistant grid lines. At the same time, the stability and accuracy of the traveling wave wavelength are combined to improve the measurement accuracy.

[0020] (2) A measurement model is established with the traveling wave in the object as the motion reference system, and the displacement of the object to be measured is converted into a time measurement. The measurement resolution is improved by taking advantage of the high resolution characteristics of the clock frequency.

[0021] (3) The light signal with alternating light intensity is diffracted by the moving ruler acousto-optic crystal driven by the ultrasonic driving signal to obtain the acousto-optic diffraction light intensity signal. After photoelectric conversion and bandpass filtering, the difference frequency (i.e., the frequency of |f1-f2|) electric traveling wave signal is obtained. Since the values ​​of frequency f1 and frequency f2 are relatively close, the number of pulses of high-frequency clock interpolation is increased, which greatly improves the resolution of displacement measurement.

[0022] (4) Compared with the traditional time-grating linear displacement sensing system, the fixed length is eliminated and the structure is simpler. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a structural principle diagram of the acoustic field time-grating linear displacement sensing system in Example 1.

[0024] Figure 2 This is a block diagram of the measurement principle of the acoustic field time-grating linear displacement sensing system in Example 1.

[0025] Figure 3 This is a structural principle diagram of the acoustic field time-grating linear displacement sensing system in Example 2.

[0026] Figure 4 This is a block diagram of the measurement principle of the acoustic field time-grating linear displacement sensing system in Example 2.

[0027] Figure 5 This is a graph showing the relationship between ultrasonic power and (acousto-optic) diffraction efficiency. DETAILED DESCRIPTION

[0028] Example 1: Figure 1 、 Figure 2 As shown, the acoustic field time-grating linear displacement sensing system in this embodiment includes a laser light source 1, a movable ruler 2, a photoelectric receiver 3, and a signal control system 4. The laser light source 1 is a He-Ne laser with a wavelength of 633 nm, and the photoelectric receiver 3 is an avalanche photodetector. The movable ruler 2 has a movable ruler acousto-optic crystal 21. The laser light source 1 is located above the movable ruler 2, with a 5 mm gap between the laser light source 1 and the movable ruler 2. The photoelectric receiver 3 is located below the movable ruler 2, with a 5 mm gap between the photoelectric receiver 3 and the movable ruler 2. The laser light source 1 and the photoelectric receiver 3 are fixedly mounted, and the movable ruler 2 can move left and right relative to the laser light source 1 and the photoelectric receiver 3.

[0029] The signal control system 4 includes a signal generation and loading module 41 and a signal processing module 42. The signal generation and loading module 41 integrates a signal generator and a multiplier. The signal generation and loading module 41 is connected to the laser light source 1 and the signal processing module 42. The signal generation and loading module 41 is connected to the movable ruler 2 via an ultrasonic transducer (not shown in the figure), and the photoelectric receiver 3 is connected to the signal processing module 42.

[0030] The signal generator in the signal generation and loading module 41 generates an excitation signal i, an ultrasonic excitation signal U′ and a sinusoidal modulation signal U1. The multiplier in the signal generation and loading module 41 modulates the ultrasonic excitation signal U′ by adding the sinusoidal modulation signal U1 to obtain an ultrasonic driving signal. The ultrasonic driving signal is expressed as: A1sin(f1t)[A0sin(f0t)+U m ](i.e. U1*U′). Where i=I0+I m sin(f2t),U1=A1sin(f1t),U′=A0sin(f0t)+U m , f2<f1<f0, I0 represents the DC current component in the excitation signal i, and the current amplitude of the excitation signal i is I m , the current frequency is f2, U m represents the DC voltage component in the ultrasonic excitation signal U'. The voltage amplitude of the ultrasonic excitation signal U' is A0, and the voltage frequency is f0. The voltage amplitude of the sinusoidal modulation signal U1 is A1, and the voltage frequency is f1. In this embodiment, f0 = 80 MHz, f1 = 10.1 MHz, and f2 = 10 MHz. The difference frequency |f1 - f2| = 10.1 - 10 = 0.1 MHz, which is 0.01 min (f1, f2) = 0.01 * 10.

[0031] The signal generator in the signal generation and loading module 41 generates a reference signal with a frequency of f1-f2 (ie, 0.1 MHz) and a phase of 0, which is input to the signal processing module 42. The reference signal is a square wave signal.

[0032] The signal generation and loading module 41 uses the excitation signal i to drive the laser light source 1 to emit a light signal with alternating light intensities. The signal generation and loading module 41 loads the ultrasonic driving signal to the moving ruler acousto-optic crystal 21 through the ultrasonic transducer.

[0033] When the movable ruler 2 moves relative to the photoelectric receiver 3, the laser light source 1 emits a light signal of alternating intensity that passes through the movable ruler acousto-optic crystal 21. By adjusting the angle of the incident light to minimize the intensity of the 0th-order light, diffracted +1st-order movable ruler diffracted light 22 is generated. The +1st-order movable ruler diffracted light 22 is received by the photoelectric receiver 3. The photoelectric receiver 3 converts the received +1st-order movable ruler diffracted light 22 into an electrical signal and inputs it into the signal processing module 42. The signal processing module 42 performs bandpass filtering on the electrical signal to obtain an electrical traveling wave signal with a frequency of 0.1 MHz. This electrical traveling wave signal is then subjected to zero-crossing comparison to obtain a corresponding square wave signal with a frequency of 0.1 MHz. This square wave signal with a frequency of 0.1 MHz and a phase of 0 is compared with a reference signal with a frequency of 0.1 MHz and a phase of 0. The phase difference is represented by the number of interpolated high-frequency clock pulses. This phase difference is then converted to obtain the linear displacement of the movable ruler 2 relative to the photoelectric receiver 3.

[0034] In addition, the optical signal received by the photoelectric receiver 3 and converted into an electrical signal in this embodiment can also be a light signal with alternating light intensity output by a laser light source that is incident on the moving ruler acousto-optic crystal 21 and diffracted by the moving ruler acousto-optic crystal 21 to generate the -1 order moving ruler diffraction light 23.

[0035] The theoretical analysis of the 0.1 MHz electric traveling wave signal obtained by diffraction and conversion in Example 1 is as follows:

[0036] The ultrasonic power signal is obtained by applying the ultrasonic field converted by the ultrasonic transducer to the acousto-optic crystal, which makes the laser beam passing through the acousto-optic crystal diffract under the action of sound and light, and the intensity of the diffracted light is determined by the power of the ultrasonic driving signal. s and (acousto-optic) diffraction efficiency η s The relationship curve is as follows Figure 5 As shown, when the ultrasonic power P s In the linear region (i.e. P a <P s <P b ), the diffraction efficiency varies linearly with the ultrasonic power. During ultrasonic drive signal operation, to ensure diffraction efficiency, the ultrasonic drive signal power is typically set at the rated power, meaning that the ultrasonic power converted by the ultrasonic transducer is a constant value. When the ultrasonic excitation signal is loaded with a modulation signal, modulating its output power into the linear region, the ultrasonic power varies with the applied sinusoidal AC voltage.

[0037] The signal processing module 42 performs bandpass filtering on the +1-order moving ruler diffraction light 22 received by the photoelectric receiver 3 to remove high-frequency and DC components, and obtains an electric traveling wave signal reflecting the movement of the moving ruler 2 relative to the photoelectric receiver 3: Among them, H1 and P1 are constant values ​​obtained based on the parameters of the moving ruler. Represents the phase of the diffracted light intensity passing through the moving-rule acousto-optic crystal.

[0038] Due to the movement of the moving ruler and the movement of the ultrasonic traveling wave of the moving ruler, the diffraction light intensity signal of the moving ruler when the moving ruler moves to different positions corresponds to different times, that is, It will change with the movement of the ruler. The change in is used to reflect the change in the linear displacement of the movable ruler 2 relative to the photoelectric receiver 3.

[0039] After zero comparison, the above electric traveling wave signal is compared with the reference signal with a frequency of f1-f2 and a phase of 0, and the displacement of the moving ruler 2 relative to the photoelectric receiver 3 is obtained by conversion:

[0040]

[0041] Among them, x j represents the jth displacement value, λ1 is the wavelength of the ultrasonic traveling wave in the moving ruler acousto-optic crystal 21, V is the velocity of ultrasonic traveling waves in the moving-scale acousto-optic crystal 21 (a known constant), is the phase difference of the electrical traveling wave signal relative to the reference signal, Therefore, during the measurement process, the initial value x0 is set to 0, and then the displacement value of the measured object relative to the initial position (i.e. the linear displacement value x of the moving ruler relative to the photoelectric receiver) can be calculated according to the above formula. j ) to achieve measurement.

[0042] In Example 1, a light signal with alternating light intensity is used to illuminate the acousto-optic crystal of the moving ruler, and the ultrasonic traveling wave signal in the moving ruler is used as a measurement reference to obtain a difference frequency electric traveling wave signal. At the same time, the wavelength of the difference frequency electric traveling wave signal depends on the sinusoidal modulation signal. The advantage of this is that the difference frequency signal is used to increase the number of pulses for clock interpolation, while the spatially varying wavelength remains unchanged, which can proportionally improve the resolution of displacement measurement. For example, in this embodiment, a sinusoidal modulation signal U1 with a frequency of f1 is used for modulation, and the corresponding wavelength is After diffraction, photoelectric conversion, and bandpass filtering, an electric traveling wave signal with a frequency of f1-f2 can be obtained, so it can be proportional (the ratio is ) increases the number of clock pulses within the wavelength λ1, and thus the resolution of the displacement measurement is increased proportionally.

[0043] Example 2: Figure 3 、 Figure 4As shown, most of the structures of the acoustic field time-grating linear displacement sensor system in this embodiment are the same as those in embodiment 1, except that: the signal generation and loading module 41 does not integrate a multiplier, and the ultrasonic driving signal is the ultrasonic excitation signal U′1 generated by the signal generator in the signal generation and loading module 41. Wherein, U′1=A1sin(f1t)+U m1 , U m1 The voltage amplitude of the ultrasonic excitation signal U'1 is A1, and the voltage frequency is f1. In this embodiment, f1 = 81 MHz, f2 = 80 MHz, and the difference frequency |f1-f2| = 1 MHz.

[0044] The signal generator in the signal generation and loading module 41 generates a reference signal with a frequency of f1-f2 (ie, 1 MHz) and a phase of 0, and inputs the reference signal to the signal processing module 42. The reference signal is a square wave signal.

[0045] The signal generation and loading module 41 uses the excitation signal i to drive the laser light source 1 to emit a light signal with alternating light intensities. The signal generation and loading module 41 loads the ultrasonic driving signal to the moving ruler acousto-optic crystal 21 through the ultrasonic transducer.

[0046] When the movable ruler 2 moves relative to the photoelectric receiver 3, the laser light source 1 emits a light signal of alternating intensity that passes through the movable ruler acousto-optic crystal 21. By adjusting the angle of the incident light to minimize the intensity of the 0th-order light, diffracted +1st-order movable ruler diffracted light 22 is generated. The +1st-order movable ruler diffracted light 22 is received by the photoelectric receiver 3. The photoelectric receiver 3 converts the received +1st-order movable ruler diffracted light 22 into an electrical signal and inputs it into the signal processing module 42. The signal processing module 42 performs bandpass filtering on the electrical signal to obtain a 1MHz traveling wave signal. This traveling wave signal is then compared with a zero-crossing signal to obtain a corresponding 1MHz square wave signal. This 1MHz square wave signal is compared with a 1MHz reference signal. The phase difference is represented by the number of interpolated high-frequency clock pulses. This phase difference is then converted to obtain the linear displacement of the movable ruler 2 relative to the photoelectric receiver 3.

[0047] In addition, the optical signal received by the photoelectric receiver 3 and converted into an electrical signal in this embodiment can also be a light signal with alternating light intensity output by a laser light source that is incident on the moving ruler acousto-optic crystal 21 and diffracted by the moving ruler acousto-optic crystal 21 to generate the -1 order moving ruler diffraction light 23.

[0048] The theoretical analysis of the 1 MHz electric traveling wave signal obtained by diffraction and conversion in Example 2 is as follows:

[0049] The ultrasonic power signal is obtained by applying the ultrasonic field converted by the ultrasonic transducer to the acousto-optic crystal, which makes the laser beam passing through the acousto-optic crystal diffract under the action of sound and light, and the intensity of the diffracted light is determined by the power of the ultrasonic driving signal. s and (acousto-optic) diffraction efficiency η s The relationship curve is as follows Figure 5 As shown, when the ultrasonic power is in the linear region (i.e. P a <P s <P b ), the diffraction efficiency will change linearly with the ultrasonic power. In this embodiment, the ultrasonic power of the ultrasonic drive signal is in a linear region that is proportional to the diffraction efficiency.

[0050] The signal processing module 42 performs bandpass filtering on the +1-order moving ruler diffraction light 22 received by the photoelectric receiver 3 to remove high-frequency and DC components, and obtains an electric traveling wave signal reflecting the movement of the moving ruler 2 relative to the photoelectric receiver 3: Among them, P1 is a constant value obtained based on the parameters of the moving ruler, Represents the phase of the diffracted light intensity passing through the moving-rule acousto-optic crystal.

[0051] Due to the movement of the moving ruler and the movement of the ultrasonic traveling wave of the moving ruler, the diffraction light intensity signal of the moving ruler when the moving ruler moves to different positions corresponds to different times, that is, It will change with the movement of the ruler. The change in is used to reflect the change in the linear displacement of the movable ruler 2 relative to the photoelectric receiver 3.

[0052] After zero comparison, the above electric traveling wave signal is compared with the reference signal with a frequency of f1-f2 and a phase of 0, and the displacement of the moving ruler 2 relative to the photoelectric receiver 3 is obtained by conversion:

[0053]

[0054] Among them, x j represents the jth displacement value, λ1 is the wavelength of the ultrasonic traveling wave in the moving ruler acousto-optic crystal 21, V is the velocity of ultrasonic traveling waves in the moving-scale acousto-optic crystal 21 (a known constant), is the phase difference of the electrical traveling wave signal relative to the reference signal, Therefore, during the measurement process, the initial value x0 is set to 0, and then the displacement value of the measured object relative to the initial position (i.e. the linear displacement value x of the moving ruler relative to the photoelectric receiver) can be calculated according to the above formula. j ) to achieve measurement.

[0055] In Example 2, a light signal with alternating light intensity is used to illuminate the moving ruler acousto-optic crystal, and the ultrasonic traveling wave signal in the moving ruler is used as a measurement reference to obtain a difference frequency electric traveling wave signal. At the same time, the spatial period of the difference frequency electric traveling wave signal is the wavelength of the ultrasonic excitation signal. The advantage of this is that the difference frequency signal is used to increase the number of pulses of clock interpolation, while the spatially varying wavelength remains unchanged, which can proportionally improve the resolution of displacement measurement. For example, in this embodiment, an ultrasonic excitation signal U′1 with a frequency of f1 is used to drive the moving ruler acousto-optic crystal, and the corresponding wavelength is After diffraction, photoelectric conversion, and bandpass filtering, an electric traveling wave signal with a frequency of f1-f2 can be obtained, so it can be proportional (the ratio is ) increases the number of clock pulses within the wavelength λ1, and thus the resolution of the displacement measurement is increased proportionally.

Claims

1. An acoustic field time-grating linear displacement sensing system, comprising a laser light source (1), a moving ruler (2), a photoelectric receiver (3) and a signal control system (4), characterized in that: The moving ruler (2) has a moving ruler acousto-optic crystal (21); The laser light source (1) is located above the movable ruler (2), and the photoelectric receiver (3) is located below the movable ruler (2). The laser light source (1) and the photoelectric receiver (3) are fixedly installed, and the movable ruler (2) can move left and right relative to the photoelectric receiver (3); The signal control system (4) includes a signal generating and loading module (41) and a signal processing module (42), wherein the signal generating and loading module (41) is connected to the laser light source (1) and the signal processing module (42), the signal generating and loading module (41) is connected to the movable ruler (2) via an ultrasonic transducer, and the photoelectric receiver (3) is connected to the signal processing module (42); the signal generating and loading module (41) generates an excitation signal i to drive the laser light source (1) to output an optical signal with alternating light intensity, generates a reference signal with a frequency of |f1-f2| and inputs it into the signal processing module (42), generates an ultrasonic driving signal related to the frequency f1 and loads it to the movable ruler acousto-optic crystal (21) via the ultrasonic transducer; When the movable ruler moves relative to the photoelectric receiver (3), the optical signal passes through the movable ruler acousto-optic crystal and reaches the photoelectric receiver (3). The photoelectric receiver (3) converts the received optical signal into an electrical signal and inputs it into a signal processing module (42). The signal processing module (42) processes the electrical signal and the reference signal to obtain a linear displacement value of the movable ruler (2). The optical signal received by the photoelectric receiver (3) is the +1st order movable ruler diffraction light (22) or -1st order movable ruler diffraction light (23) emitted by the movable ruler acousto-optic crystal (21). The +1st order movable ruler diffraction light (22) or -1st order movable ruler diffraction light (23) is generated by the optical signal with alternating light intensity output by the laser light source (1) and incident on the movable ruler acousto-optic crystal, and diffracted by the movable ruler acousto-optic crystal. i=I0+I m sin(f2t), 0<|f1-f2|<min(f1,f2), I0 represents the DC current component in the excitation signal i, and the current amplitude of the excitation signal i is I m , the current frequency is f2, t represents time, and min( ) represents the smaller operation.

2. The acoustic field time-grating linear displacement sensing system according to claim 1, characterized in that: The ultrasonic driving signal is a modulated signal obtained by the signal generation and loading module (41) modulating the ultrasonic excitation signal U' using the sinusoidal modulation signal U1; Among them, the ultrasonic excitation signal U' and the sinusoidal modulation signal U1 are both generated by the signal generation and loading module (41), U1=A1sin(f1t), U'=A0sin(f0t)+ U m ,f1<f0,f2<f0,U m It represents the DC voltage component in the ultrasonic excitation signal U'. The voltage amplitude of the ultrasonic excitation signal U' is A0, the voltage frequency is f0, and the voltage amplitude of the sinusoidal modulation signal U1 is A1.

3. The acoustic field time-grating linear displacement sensing system according to claim 2, characterized in that: The ultrasonic driving signal is: A1sin(f1t)[ A0sin(f0t)+ U m ].

4. The acoustic field time-grating linear displacement sensing system according to claim 1, characterized in that: The ultrasonic driving signal is an ultrasonic excitation signal U'1 generated by the signal generation and loading module (41); wherein U'1=A1sin(f1t)+U m1 , U m1 It represents the DC voltage component in the ultrasonic excitation signal U'1. The voltage amplitude of the ultrasonic excitation signal U'1 is A1.

5. The acoustic field time-grating linear displacement sensing system according to any one of claims 1 to 4, characterized in that: The signal processing module (42) processes the electrical signal and the reference signal to obtain the linear displacement value of the movable ruler (2) in the following manner: The signal processing module (42) performs bandpass filtering on the electrical signal to obtain an electrical traveling wave signal, and then performs zero-crossing comparison on the electrical traveling wave signal to obtain a square wave signal with a frequency of |f1-f2| corresponding to the electrical signal; The square wave signal is compared with the reference signal, and the phase difference is represented by the number of interpolated high-frequency clock pulses, and then converted to obtain the linear displacement value of the moving ruler (2); wherein the reference signal is a square wave signal.

6. The acoustic field time-grating linear displacement sensing system according to any one of claims 1 to 4, characterized in that: The frequencies f1 and f2 satisfy: |f1-f2|≤0.1min(f1,f2).

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