Laser self-mixing interference displacement reconstruction method and device based on unilateral time-frequency spectrum

Abstract

The invention discloses a laser self-mixing interference displacement reconstruction method and device based on a unilateral time-frequency spectrum, and the method comprises the following steps: S1, collecting a self-mixing interference signal of a target object, and carrying out the time-frequency transformation according to the self-mixing interference signal, thereby obtaining a bilateral time-frequency spectrogram; s2, selecting and retaining a unilateral time-frequency spectrum for analysis from the bilateral time-frequency spectrogram; s3, carrying out inverse transformation on the single-side time-frequency spectrum to obtain an analysis signal; s4, extracting a real part and an imaginary part of the analysis signal, and dividing the real part and the imaginary part to obtain a tangent signal; s5, performing arc tangent operation on the tangent signal to obtain a motion phase; and S6, calculating a relation between the phase and the distance according to the motion phase, and obtaining a displacement curve of the target object. According to the invention, complex optical elements do not need to be additionally introduced to obtain orthogonal signals, the composition of a measurement system is simplified, and a novel, efficient and economical solution is provided for the field of displacement measurement.

Description

Technical Field

[0001] The invention belongs to the technical field of optical measurement, and in particular relates to a laser self-mixing interference displacement reconstruction method and device based on a single-sided time-frequency spectrum. Background Art

[0002] Non-contact sensing technology plays a key role in fields such as biomedical monitoring and industrial manufacturing, and the need to accurately obtain information transmitted by vibrating targets in complex external environments is becoming increasingly urgent. Self-mixing interference technology uses the interference effect between the reflected light of the target and the original light of the laser in the cavity to achieve high-sensitivity, non-contact detection of target vibration information, and has therefore attracted widespread attention. In this process, the demodulation of the self-mixing signal is particularly important because it is directly related to the accurate extraction of vibration information.

[0003] To achieve this goal, researchers have developed a variety of reconstruction methods, including: fringe counting method, phase unwrapping method, orthogonal phase demodulation method, current modulation method, etc. Among them, the orthogonal phase demodulation method is regarded as a preferred solution due to its high efficiency and strong anti-interference ability, but the orthogonal phase demodulation method often requires the introduction of special optical elements in the measurement system, such as wedge prisms, wave plates, liquid crystal phase shifters, beam splitters, and electro-optic modulators, etc., to obtain two self-mixing signals with a phase difference of 90 degrees. Therefore, although this method effectively solves the problem of determining the direction of movement of the target object, it also brings about the problem of complicated optical path and increased difficulty in instrument debugging, and may introduce non-orthogonal phase errors. In addition, it also leads to an increase in the cost of vibration sensors.

[0004] Therefore, in the orthogonal detection method, a high-precision reconstruction scheme with a simple optical path structure and low cost is urgently needed to promote the wider application of laser self-mixing interferometry technology in precision measurement.

[0005] A Chinese patent with publication number CN116045815A discloses a wedge-shaped orthogonal laser self-mixing interference displacement detection device, the device comprising a wedge-shaped, an adjustable attenuation plate, a laser, a first light beam, a second light beam, a micro-motion platform, a signal acquisition module and a signal processing module; wherein the wedge-shaped, the adjustable attenuation plate, the laser and the first light beam are arranged in sequence in a straight line with the target to be measured to form a wedge-shaped orthogonal laser self-mixing interference optical path; the second light beam is carried on the micro-motion platform and is arranged on the reflection optical path of the wedge-shaped; the signal acquisition module is used to collect two self-mixing interference signals with phase difference emitted by the first light beam and the second light beam respectively during the detection process, and transmit them to the signal processing module; the signal processing module is used to provide a driving signal for the micro-motion platform to move the second light beam along the radial direction of the light spot; and is also used to obtain the displacement of the target to be measured from the self-mixing interference signal through a wedge-shaped orthogonal displacement detection algorithm. This invention adds a wedge tip to the external cavity of the laser self-mixing interference system to obtain two normalized self-mixing interference signals with a phase difference of 90°, which increases the complexity of the optical path and leads to an increase in the overall cost of the detection system. Summary of the invention

[0006] In order to solve the problems existing in the above-mentioned prior art, the present invention provides a laser self-mixing interference displacement reconstruction method and device based on single-sided time-frequency spectrum, which does not require the introduction of additional complex optical elements to obtain orthogonal signals, simplifies the composition of the measurement system, and provides a novel, efficient and economical solution for the field of displacement measurement.

[0007] The technical solution of the present invention is as follows:

[0008] In one aspect, the present invention provides a laser self-mixing interference displacement reconstruction method based on a single-sided time-frequency spectrum, comprising the following steps:

[0009] S1: Collect the self-mixing interference signal of the target object, and perform time-frequency transformation on the self-mixing interference signal to obtain a bilateral time-frequency spectrum diagram.

[0010] S2: Selecting and retaining a single-sided time-frequency spectrum for analysis from the double-sided time-frequency spectrum diagram.

[0011] S3: Perform inverse transform on the single-sided time-frequency spectrum to obtain the analytical signal.

[0012] S4: extracting the real part and the imaginary part of the analytical signal, and dividing the two to obtain a tangent signal.

[0013] S5: Perform an inverse tangent operation on the tangent signal to obtain the motion phase.

[0014] S6: Calculate the relationship between the phase and the distance according to the motion phase to obtain the displacement curve of the target object.

[0015] Preferably, the time-frequency transformation in step S1 includes but is not limited to: short-time Fourier transform and Wigner quasi-probability distribution.

[0016] Preferably, the single-sided time-frequency spectrum selected and retained for analysis in step S2 is specifically:

[0017] The single-sided time-frequency spectrum for analysis is selected and retained according to the moving direction of the target: when the target is far away from the laser, the positive frequency part in the time-frequency matrix is ​​selected and retained; when the target is close to the laser, the negative frequency part in the time-frequency matrix is ​​selected and retained.

[0018] Preferably, obtaining the target object's direction of motion includes but is not limited to: representing the self-mixing interference signal as the phase portion of a complex exponential, and extracting the instantaneous frequency containing the target object's direction of motion information through time-frequency domain transformation processing; or calculating the target object's direction of motion using the tilt characteristics of the time domain signal.

[0019] Preferably, in step S3, the inverse transformation of the single-sided time-frequency spectrum to obtain the analytical signal is specifically:

[0020] After performing an inverse time-frequency transform on the single-sided time-frequency spectrum, an analytical signal with orthogonal real and imaginary parts is obtained: in is the signal phase in the presence of optical feedback interference.

[0021] Preferably, the calculation formula of the displacement curve of the target object is specifically:

[0022]

[0023] Where L(t) is the displacement curve of the target; t is time; λ is the central wavelength of the laser; The motion phase.

[0024] Preferably, the motion type of the target object measured by the self-mixing interference signal is simple harmonic motion or non-simple harmonic motion.

[0025] On the other hand, the present invention provides a laser self-mixing interference displacement reconstruction device based on single-sided time-frequency spectrum, including a time-frequency analysis and extraction module and a phase displacement recovery module.

[0026] The time-frequency analysis and extraction module is used to convert the self-mixing interference signal from the time domain to the time-frequency domain to generate a bilateral time-frequency spectrum, select and retain the unilateral time-frequency spectrum for analysis, and inversely transform the retained unilateral time-frequency spectrum to obtain the analytical signal.

[0027] The phase displacement recovery module is used to extract phase information from the analytical signal and obtain the displacement curve of the target object.

[0028] On the other hand, the present invention also provides an electronic device, comprising: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum as described in any embodiment of the present invention when executing the computer program.

[0029] On the other hand, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed by a processor, the laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum as described in any embodiment of the present invention is implemented.

[0030] Compared with the prior art, the present invention has the following technical effects:

[0031] The present invention particularly retains the required negative frequency components when processing the time-frequency spectrum, which can more comprehensively reveal the characteristics of the self-mixing interference signal and improve the accuracy and reliability of displacement measurement. At the same time, by avoiding the introduction of complex optical elements, the structure of the measurement system is simplified, the cost is reduced, and a novel and effective solution is provided for the field of displacement measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is an overall flow chart of the laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum described in the present invention;

[0033] Figure 2 This is a schematic diagram of the laser self-mixing interference displacement reconstruction method based on a single-sided time-frequency spectrum described in the present invention;

[0034] Figure 3 It is a simulation result diagram of the present invention for simple harmonic vibration displacement reconstruction;

[0035] Figure 4 This is a simulation result diagram of the present invention for the reconstruction of the simple harmonic vibration displacement of the signal affected by speckle;

[0036] Figure 5 This is a diagram of the experimental results of the present invention for non-harmonic vibration displacement reconstruction. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in combination with specific embodiments of the present application and with reference to the accompanying drawings.

[0038] Embodiment 1

[0039] When the target moves relative to the laser, the information of its movement direction is contained in the frequency characteristics of the self-mixing interference signal. In order to accurately extract this information, the present embodiment provides a laser self-mixing interference displacement reconstruction method based on a single-sided time-frequency spectrum, which selects and retains the spectral components directly related to the movement direction of the target, and then performs an inverse transformation on the selected single-sided time-frequency spectrum to obtain an analytical signal. Subsequently, the real and imaginary parts are extracted from the analytical signal, and the two are divided to obtain a tangent signal. Then, an inverse tangent operation is performed to obtain the motion phase, and finally the displacement curve of the target is derived based on the phase information. When processing the time-frequency spectrum, the method described in the present embodiment particularly retains the required negative frequency components, which can more comprehensively reveal the characteristics of the self-mixing interference signal and improve the accuracy and reliability of displacement measurement.

[0040] See also Figure 1 As shown, the following steps are included:

[0041] S1: Collect the self-mixing interference signal of the target object, and perform time-frequency transformation on the self-mixing interference signal to obtain a bilateral time-frequency spectrum diagram.

[0042] S2: Selecting and retaining a single-sided time-frequency spectrum for analysis from the double-sided time-frequency spectrum diagram.

[0043] S3: Perform inverse transform on the single-sided time-frequency spectrum to obtain the analytical signal.

[0044] S4: extracting the real part and the imaginary part of the analytical signal, and dividing the two to obtain a tangent signal.

[0045] S5: Perform an inverse tangent operation on the tangent signal to obtain the motion phase.

[0046] S6: Calculate the relationship between the phase and the distance according to the motion phase to obtain the displacement curve of the target object.

[0047] As a preferred implementation of this embodiment, the time-frequency transformation in step S1 includes but is not limited to: short-time Fourier transform and Wigner quasi-probability distribution. In practical applications, there is no restriction on the selection of time-frequency transformation methods. This embodiment preferably uses short-time Fourier transform as the time-frequency transformation method.

[0048] As a preferred implementation of this embodiment, when the target moves relative to the laser, the information of its movement direction is contained in the main frequency of the self-mixing interference signal, which reflects the instantaneous frequency change of the self-mixing interference signal and also provides us with important information about the movement direction of the target. Therefore, by analyzing the sign of the instantaneous frequency, the corresponding spectrum can be selected and retained. Therefore, the spectrum components directly related to the movement direction of the target can be selected and retained based on the above principle. The unilateral time-frequency spectrum selected and retained for analysis in step S2 is specifically:

[0049] The single-sided time-frequency spectrum for analysis is selected and retained according to the moving direction of the target: when the target is far away from the laser, the positive frequency part in the time-frequency matrix is ​​selected and retained; when the target is close to the laser, the negative frequency part in the time-frequency matrix is ​​selected and retained.

[0050] As a preferred implementation of this embodiment, obtaining the target object's moving direction includes but is not limited to: representing the self-mixing interference signal as the phase part of a complex exponential, and extracting the instantaneous frequency containing the target object's moving direction information through time-frequency domain transformation processing; or calculating the target object's moving direction using the tilt characteristics of the time domain signal. Among them, the specific method for obtaining the target object's moving direction can be selected according to actual needs. There is no fixed emphasis when selecting the moving direction obtaining method. At the same time, the selection has no direct correlation with the target object's moving type, and is not limited here.

[0051] The methods for obtaining the target object's motion direction can be roughly divided into two categories: time domain processing and frequency domain processing. This embodiment selects the complex exponential method as an example mainly based on the following two advantages: 1. The robustness of time-frequency domain processing: This method performs well in dealing with noise and interference, and can provide relatively accurate analysis results even in the case of poor signal quality. 2. It has good performance in processing weak light feedback signals: The self-mixing signal obtained under weak light feedback intensity has unclear stripe tilt characteristics and becomes difficult to analyze, but the complex exponential method can effectively extract and process the self-mixing signal obtained under weak light feedback intensity, thereby accurately obtaining the motion direction.

[0052] Furthermore, this embodiment takes the self-mixing interference signal as the phase part of the complex exponential, and extracts the instantaneous frequency containing the target object's motion direction information through time-frequency domain transformation as an example, specifically:

[0053] The self-mixing interference signal P(t) is expressed as:

[0054]

[0055] Where P(t) is the self-mixing interference signal power measured in actual measurement; t is time; is the signal phase with optical feedback interference, and also represents the motion phase of the target object; P o (t) is the power without light feedback.

[0056] The obtained self-mixing interference signal P(t) is expressed as the phase part of the complex exponential e i*P(t) .

[0057] For i*P(t) Perform time-frequency domain transformation to obtain a bilateral time-frequency spectrum. The time-domain features of the signal are converted into time-frequency domain features to reflect the changes of the signal spectrum over time at different moments.

[0058] The corresponding frequency value at which the frequency amplitude of the signal reaches the maximum at each moment is extracted to obtain the instantaneous frequency. The instantaneous frequency obtained at this time not only contains the numerical information of the frequency, but also implies the positive and negative signs of the frequency.

[0059] The instantaneous frequency extracted above is converted into a symbolic representation. In this conversion process, the following principle is followed: if the frequency value is positive, it is assigned a positive sign; if the frequency value is negative, it is assigned a negative sign.

[0060] Specifically, the symbol representation is not limited in practical applications, and may include but is not limited to the form of a square wave signal or a rectangular wave signal.

[0061] Furthermore, this embodiment selects a square wave signal as a symbol representation, performs a time-frequency domain transform on the original self-mixing interference signal to obtain a bilateral time-frequency spectrum, and then performs spectrum selection based on the square wave signal: if the square wave signal is positive, the positive frequency portion of the time-frequency spectrum is retained; if the square wave signal is negative, the negative frequency portion of the time-frequency spectrum is retained.

[0062] As a preferred implementation of this embodiment, an inverse transformation is performed based on the obtained single-sided time-frequency spectrum containing positive and negative frequency components, and the time-frequency domain features are converted to the time-domain features. The inverse transformation of the single-sided time-frequency spectrum in step S3 to obtain the analytical signal is specifically:

[0063] After performing an inverse time-frequency transform on the single-sided time-frequency spectrum, an analytical signal with orthogonal real and imaginary parts is obtained: in is the signal phase in the presence of optical feedback interference.

[0064] Furthermore, the real part of the analytical signal is extracted Imaginary part Dividing these two gives the tangent signal

[0065] For tangent signal Perform an inverse tangent operation to obtain the motion phase

[0066] The displacement curve of the target object is calculated according to the displacement curve formula of the target object.

[0067] As a preferred implementation of this embodiment, the displacement curve calculation formula of the target object is specifically:

[0068]

[0069] Where L(t) is the displacement curve of the target; t is time; λ is the central wavelength of the laser; The motion phase.

[0070] As a preferred implementation manner of this embodiment, the target object motion type measured by the self-mixing interference signal is simple harmonic motion or non-simple harmonic motion.

[0071] In order to verify the effectiveness and superiority of the method provided in this embodiment, some specific cases are provided below:

[0072] Application example 1:

[0073] See also Figure 2 As shown, the target object's motion direction is obtained by taking "taking the self-mixing interference signal as the phase part of the complex exponential and processing it in the time-frequency domain to extract the instantaneous frequency containing the target object's motion direction information" as an example, converting the instantaneous frequency into a square wave signal, retaining the corresponding time-frequency spectrum frequency component according to the square wave signal, and obtaining an analytical signal with a real part and an imaginary part phase difference of 90 degrees after inverse transformation, and then obtaining the target displacement curve. The simple harmonic vibration is tested using MATLAB software, and the simulation parameters are set as shown in Table 1.

[0074] Table 1 Parameter setting table

[0075] symbol meaning value C Optical Feedback Factor 0.1 α Linewidth broadening factor 4 N Number of sampling points 6k <![CDATA[f s ]]> Sampling frequency 200kHz f Target vibration frequency 100Hz A Target vibration amplitude 3.25μm λ Laser wavelength 650nm

[0076] The self-mixing interference signal obtained by simulation is as follows Figure 3 As shown in (a), the obtained self-mixing signal P(t) is multiplied by the imaginary number i as the phase term of the e index: e i*P(t) .

[0077] For the above signal e i*P(t) Perform short-time Fourier transform to obtain the bilateral time-frequency spectrum of the signal changing with time, such as Figure 3 (b) as shown.

[0078] The time-frequency ridge is extracted from the bilateral time-frequency spectrum. The time-frequency ridge is as follows: Figure 3 The instantaneous frequency information contained in the time-frequency ridge is converted into a square wave signal, as shown in the red line of (b). Figure 3 (c) is shown by the red line.

[0079] Perform a short-time Fourier transform on the original self-mixing interference signal P(t), and retain the corresponding spectrum part according to the square wave signal. The result is as follows: Figure 3 (c) as shown.

[0080] Perform short-time inverse Fourier transform on the retained single-sided time-frequency spectrum to obtain the analytical signal. Select the real and imaginary parts of the analytical signal respectively. The results are as follows: Figure 3 As shown in the red and black lines in (d), the red line is the real signal The black line is the imaginary signal

[0081] Divide the two to get the tangent signal Using the inverse tangent function The motion phase is obtained by calculation And calculate the displacement curve. Among them, the reconstruction result is as follows Figure 3 As shown in (e), the blue curve is the reconstructed vibration displacement, and the red curve is the reference displacement.

[0082] The absolute error of reconstruction is Figure 3 As shown in (f), the root mean square error (red line) is 5.94nm.

[0083] The results show that the displacement reconstruction method proposed in the present invention exhibits high reconstruction accuracy. At the same time, the method does not require complex calculations and additional optical elements, providing a novel, efficient and economical solution for the field of displacement measurement.

[0084] Application Example 2

[0085] In order to verify the effect of the laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum proposed in this application under different line width broadening factors α and optical feedback factors C, simulations were performed for different parameter conditions of α and C.

[0086] The root mean square error of the reconstruction is shown in Table 2.

[0087] Table 2 Comparison of RMS error under different line width broadening factors α and optical feedback factors C

[0088] C / α 3 4 5 6 0.1 5.95nm 5.94nm 5.94nm 5.94nm 0.3 11.9nm 11.8nm 11.8nm 11.8nm 0.5 19.0nm 18.9nm 18.9nm 18.9nm 0.7 26.7nm 26.6nm 26.5nm 26.5nm 0.9 30.9nm 30.8nm 30.8nm 30.8nm

[0089] The results show that the laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum proposed in this embodiment has a small root mean square error under different linewidth broadening factors α and optical feedback factors C, and the method is robust to the linewidth broadening factor α and the optical feedback factor C.

[0090] Application Example 3

[0091] Consider whether the speckle effect caused by the uneven surface of the vibrating target will affect the reconstruction of the signal during the actual detection process. The SMI signal with speckle effect simulating the actual situation is as follows: Figure 4 (b) as shown.

[0092] The absolute error of reconstruction is obtained as Figure 4 As shown in (g), the root mean square error (red line) is 9.14nm.

[0093] The results show that the laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum proposed in this embodiment is well adapted to the SMI signal amplitude attenuation change caused by the speckle effect and has strong robustness.

[0094] Application Example 4

[0095] In order to verify the effect of the laser self-mixing interference displacement reconstruction method based on the single-sided time-frequency spectrum described in this embodiment in the experiment, the laser self-mixing interference signal obtained in the experiment is experimentally processed.

[0096] The experimental results of non-harmonic motion displacement reconstruction are as follows Figure 5 As shown in (f), the root mean square error of the reconstruction is 60 nm. The results show that the laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum proposed in this embodiment can effectively process the experimental signal.

[0097] Embodiment 2

[0098] Accordingly, the present embodiment provides a laser self-mixing interference displacement reconstruction device based on a single-sided time-frequency spectrum, including a time-frequency analysis and extraction module and a phase displacement recovery module.

[0099] The time-frequency analysis and extraction module is used to convert the self-mixing interference signal from the time domain to the time-frequency domain to generate a bilateral time-frequency spectrum, select and retain the unilateral time-frequency spectrum for analysis, and inversely transform the retained unilateral time-frequency spectrum to obtain an analysis signal. This module is used to implement the functions of steps S1, S2, and S3 in Example 1, which will not be repeated here.

[0100] The phase displacement recovery module is used to extract phase information from the analytical signal to obtain the displacement curve of the target object. This module is used to implement the functions of steps S4, S5, and S6 in the first embodiment, which will not be described in detail here.

[0101] Embodiment 3

[0102] This embodiment provides an electronic device, which includes: a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum as described in any embodiment of the present invention is implemented.

[0103] Embodiment 4

[0104] This embodiment provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the laser self-mixing interference displacement reconstruction method based on a single-sided time-frequency spectrum as described in any embodiment of the present invention is implemented.

[0105] In the embodiments of the present application, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent the existence of A alone, the existence of A and B at the same time, and the existence of B alone. Among them, A and B can be singular or plural. The character " / " generally indicates that the previous and next associated objects are in an "or" relationship. "At least one of the following" and similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b and c can be represented by: a, b, c, a and b, a and c, b and c, or a and b and c, where a, b, c can be single or multiple.

[0106] Those of ordinary skill in the art will appreciate that the various units and algorithm steps described in the embodiments disclosed herein can be implemented in a combination of electronic hardware, computer software, and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0107] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0108] In several embodiments provided in the present application, if any function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (Read-Only Memory; hereinafter referred to as: ROM), random access memory (Random Access Memory; hereinafter referred to as: RAM), disk or optical disk, and other media that can store program codes.

[0109] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum, characterized in that: The following steps are involved: S1: Collect the self-mixing interference signal of the target object, and perform time-frequency transformation on the self-mixing interference signal to obtain a bilateral time-frequency spectrum; S2: Selecting and retaining a unilateral time-frequency spectrum for analysis from the bilateral time-frequency spectrum diagram; S3: Perform inverse transformation on the single-sided time-frequency spectrum to obtain the analytical signal; S4: extracting the real part and the imaginary part of the analytical signal, and dividing the two to obtain a tangent signal; S5: Performing an inverse tangent operation on the tangent signal to obtain the motion phase; S6: Calculate the relationship between the phase and the distance according to the motion phase to obtain the displacement curve of the target object.

2. The laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum according to claim 1 is characterized in that: The time-frequency transformation in step S1 includes, but is not limited to: short-time Fourier transform and Wigner quasi-probability distribution.

3. The laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum according to claim 1 is characterized in that: The single-sided time-frequency spectrum selected and retained for analysis in step S2 is specifically: The single-sided time-frequency spectrum for analysis is selected and retained according to the moving direction of the target: when the target is far away from the laser, the positive frequency part in the time-frequency matrix is ​​selected and retained; when the target is close to the laser, the negative frequency part in the time-frequency matrix is ​​selected and retained.

4. The laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum according to claim 3 is characterized in that: Obtaining the target object's direction of motion includes but is not limited to: representing the self-mixing interference signal as the phase part of a complex exponential, and extracting the instantaneous frequency containing the target object's direction of motion information through time-frequency domain transformation processing; or calculating the target object's direction of motion using the tilt characteristics of the time domain signal.

5. The laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum according to claim 1, characterized in that: In step S3, the inverse transformation of the single-sided time-frequency spectrum is performed to obtain the analytical signal: After performing an inverse time-frequency transform on the single-sided time-frequency spectrum, an analytical signal with orthogonal real and imaginary parts is obtained: in is the signal phase with optical feedback interference, that is, the motion phase of the target object.

6. The laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum according to claim 1, characterized in that: The calculation formula of the displacement curve of the target object is specifically: Where, L(t) is the displacement curve of the target; t is time; λ is the central wavelength of the laser; The motion phase.

7. The laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum according to claim 1 is characterized in that: The target object motion type measured by the self-mixing interference signal is simple harmonic motion or non-simple harmonic motion.

8. A laser self-mixing interference displacement reconstruction device based on a single-sided time-frequency spectrum, characterized in that: The device is used to implement the laser self-mixing interference displacement reconstruction method based on the single-sided time-frequency spectrum as described in any one of claims 1 to 7, including a time-frequency analysis extraction module and a phase displacement recovery module; A time-frequency analysis and extraction module is used to convert the self-mixing interference signal from the time domain to the time-frequency domain to generate a bilateral time-frequency spectrum, select and retain a unilateral time-frequency spectrum for analysis, and inversely transform the retained unilateral time-frequency spectrum to obtain an analytical signal; The phase displacement recovery module is used to extract phase information from the analytical signal and obtain the displacement curve of the target object.

9. An electronic device, comprising: A memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum as described in any one of claims 1 to 7 when executing the computer program.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the laser self-mixing interference displacement reconstruction method based on single-sided time-frequency spectrum as described in any one of claims 1 to 7 is implemented.

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