A square wave phase modulation and demodulation method and device for multi-wavelength interferometric displacement measurement

Abstract

The present invention discloses a square wave phase modulation and demodulation method and device for multi-wavelength interference displacement measurement. The method of the present invention includes using a square wave signal to modulate the phase of a multi-wavelength optical fiber sensor to generate an interference signal. Subsequently, the collected light intensity signal and the square wave modulation signal are filtered, normalized and normalized, and the signal is optimized through steps such as convolution operation, zero value elimination, and half-cycle compensation. The optimized signal is used to perform ellipse fitting to obtain parameters, and then the signal is numerically corrected. Finally, the interference phase information is obtained through inverse tangent operation, and combined with multi-wavelength composite calculation, accurate measurement of the displacement of the object under test is achieved. The present invention aims to realize a new scheme for phase modulation and demodulation of a multi-wavelength optical fiber interference displacement sensor using a square wave signal. The method is simple to operate and broadens the application of multi-wavelength optical fiber displacement interference measurement using phase carrier technology in phase modulation and demodulation methods.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber displacement sensors, and in particular to a square wave phase modulation and demodulation method and device for multi-wavelength interference displacement measurement. Background Art

[0002] Fiber optic displacement sensors use optical fibers as sensing elements to measure the displacement or vibration of an object. Multi-wavelength fiber optic sensors offer high accuracy, sensitivity, and interference immunity, enabling non-contact, high-precision, and high-resolution displacement measurement. They are widely used in applications requiring precise displacement measurement, such as precision machining and optical measurement.

[0003] Fiber optic displacement sensors operate based on the principle of optical interference, determining the displacement of an object by measuring changes in the phase or intensity of light in an optical fiber. Multi-wavelength fiber optic sensors use multiple wavelengths for measurement, effectively improving the measurement range and accuracy. Phase carrier technology is a demodulation technology widely used in fiber optic sensing technology, characterized by simple demodulation and low hardware requirements. This technology introduces a phase-modulated signal of a certain frequency into the fiber optic sensing system, modulating the signal to be measured onto this carrier signal, thereby achieving signal demodulation and processing. In phase carrier technology, using a sinusoidal signal for phase modulation is a traditional demodulation strategy. However, the demodulation calculations for this modulation method are relatively cumbersome, and when implementing this modulation, if nonlinear interference factors such as the carrier phase modulation depth deviates from its optimal state, is accompanied by amplitude modulation, or there is a delay in the carrier phase are encountered, the use of a sinusoidal signal demodulation method may encounter nonlinear distortion problems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is as follows: In response to the above-mentioned problems of the prior art, a square wave phase modulation and demodulation method and device for multi-wavelength interferometric displacement measurement are provided. The present invention aims to propose a new scheme for phase modulation and demodulation of optical fiber interferometric displacement sensors using square wave signals. The scheme is simple to operate and broadens the application of multi-wavelength optical fiber displacement interferometric measurement using phase carrier technology in phase modulation and demodulation methods.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement comprises the following steps:

[0007] S1, filtering and normalizing the collected light intensity interference signals of different wavelengths, and normalizing and normalizing the square wave modulation signal; the light intensity interference signal is a light intensity interference signal generated by modulating the phase of the multi-wavelength optical fiber displacement sensor using the square wave modulation signal to generate a phase-shifted mode;

[0008] S2, performing convolution operations on the processed light intensity interference signal and the square wave modulation signal respectively;

[0009] S3, performing zero-value elimination and half-cycle compensation on the signal after the convolution operation, and performing ellipse fitting on the signal after the zero-value elimination to obtain signal parameters;

[0010] S4, performing numerical correction on the signal after half-cycle compensation according to the signal parameters;

[0011] S5, performing an arc tangent operation on the numerically corrected signal to obtain the interference phase information of a single wavelength;

[0012] S6, performing multi-wavelength composite calculation on the interference phase information of the two single wavelengths to obtain the displacement of the object being measured.

[0013] Optionally, before step S1, the method further includes modulating the phase of the multi-wavelength optical fiber displacement sensor with a square wave modulation signal to generate a light intensity interference signal in a phase shift mode, and when the phase of the multi-wavelength optical fiber displacement sensor is modulated with a square wave modulation signal, the measured light beam includes multiple laser beams with similar wavelengths, and the wavelengths of the multiple laser beams are ,in Indicates the number of light sources in the system and their average wavelength The calculation function expression is:

[0014] ,

[0015] In the above formula, is the kth wavelength; the square wave modulation signal is a square wave signal with a duty cycle of 50% as shown in the following formula:

[0016] ,

[0017] In the above formula, T is the period, The square wave modulation signal acts on the phase modulator through the driver so that when the square wave modulation signal is high, the phase modulator adjusts the multi-beam composite light path in the system light path relative to the average wavelength. produce Phase shift.

[0018] Optionally, in step S1, normalizing and normalizing the square wave modulated signal includes: normalizing the square wave modulated signal After normalization and standardization, the signal is obtained , according to the signal The positive and negative values ​​of the signal Decomposed into two complementary signals and ,Signal When the signal is high 1, otherwise the signal is 0; signal When the signal is low is 1, otherwise the signal is 0; in step S2, the function expression for performing convolution operation on the processed light intensity interference signal and the square wave modulation signal is:

[0019] ,

[0020] ,

[0021] ,

[0022] ;

[0023] In the above formula, 、 、 and is the signal after convolution operation, and is the light intensity interference signal of different wavelengths obtained after processing, Represents different wavelengths and Serial number.

[0024] Optionally, in step S3, performing zero-value elimination and half-cycle compensation on the signal after the convolution operation includes: performing zero-value elimination and half-cycle compensation on the signal after the convolution operation respectively. 、 、 and , identify and remove the periodic 0 values ​​in the original signal and use the least squares fitting interpolation method to compensate for the missing parts. The periodic 0 values ​​include the beginning 0 value, the middle 0 value and the ending 0 value. The beginning 0 value is interpolated from the first non-0 point forward, the middle 0 value is interpolated forward and backward respectively, and the ending 0 value is interpolated from the last non-0 point backward. Finally, the signal after half-period compensation is obtained , , and .

[0025] Optionally, the signal parameters obtained by ellipse fitting in step S3 include the signal after convolution operation 、 、 and A pair of convolution signals with the same wavelength and Perform the following processing:

[0026] S3.1, the signal Filter out all non-zero data points to form new data sets , the signal Filter out all non-zero data points to form new data sets ;

[0027] S3.2, from the dataset 、 Select data points, ;Will data points Construct the equation of the ellipse shown below:

[0028] ,

[0029] In the above formula, is the equation of the ellipse, are the ellipse parameters, is the kth data point, ; According to the least squares principle, according to the following formula:

[0030] ,

[0031] Solve for the ellipse parameters ;

[0032] S3.3, according to the ellipse parameters Calculate the DC and AC components:

[0033] ,

[0034] ,

[0035] ,

[0036] ,

[0037] In the above formula, and is the DC component, and is the AC component; thus the AC components of the signals corresponding to the two wavelengths are obtained 、 、 、 and DC component 、 、 、 .

[0038] Optionally, the function expression for performing numerical correction on the signal after half-cycle compensation according to the signal parameters in step S4 is:

[0039] ,

[0040] ,

[0041] ,

[0042] ,

[0043] In the above formula, , , and are the signals after half-cycle compensation, 、 、 、 is the AC component of the signal parameters obtained by ellipse fitting, 、 、 、 The DC component of the signal parameter is obtained by ellipse fitting; in step S5, the arc tangent operation is performed on the numerically corrected signal to obtain the function expression of the interference phase information of a single wavelength:

[0044] ,

[0045] ,

[0046] In the above formula, and Different wavelengths and phase information.

[0047] Optionally, in step S6, the interference phase information of a single wavelength is subjected to multi-wavelength composite calculation to obtain the functional expression of the displacement of the measured object:

[0048] ,

[0049] In the above formula, is the displacement of the object being measured, is the phase difference, is the composite wavelength, and:

[0050] ,

[0051] ,

[0052] In the above formula, and Different wavelengths and phase information.

[0053] In addition, the present invention also provides a square wave phase modulation and demodulation device for multi-wavelength interference displacement measurement, including a multi-wavelength narrow linewidth laser, an optical isolator, a wavelength division multiplexer, a spectrometer, a circulator, a focusing lens, a phase modulator, an optical attenuator, a coupler, a demultiplexer, a photodetector, a data acquisition module, a computer device and a driver module. In the working state, the multi-wavelength narrow linewidth laser generates multiple lasers of different wavelengths with similar wavelengths, which pass through the optical isolator to reach the wavelength division multiplexer, and are combined into a light beam containing multiple wavelengths in the wavelength division multiplexer. The light beam is divided into two beams by the spectrometer, one of which is focused on the surface of the object to be measured by the circulator and the focusing lens, and the reflected light beam formed on the surface of the object returns to the focusing lens. and coupled back to the circulator by a focusing lens; wherein another beam is phase-modulated by a phase modulator and then enters an optical attenuator; the light beam output from the optical attenuator and the light beam returned from the circulator enter the coupler together and are combined into one light beam, and then pass through a demultiplexer and are detected by multiple photodetectors for detecting different wavelengths, and then pass through a data acquisition module and are sent to a computer device, the computer device is connected to the control end of the driver module for use, the driver module is connected to the phase modulator for use in providing the square wave modulation signal required by the phase modulator, the computer device includes a microprocessor and a memory connected to each other, and the microprocessor is programmed or configured to execute the aforementioned square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement.

[0054] In addition, the present invention also provides a computer-readable storage device, which stores a computer program or instruction, and the computer program or instruction is programmed or configured to execute the square wave phase modulation and demodulation method of multi-wavelength interferometric displacement measurement through a processor.

[0055] In addition, the present invention also provides a computer program product, including a computer program or instructions, which are programmed or configured to execute the square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement through a processor.

[0056] Compared with the prior art, the present invention mainly has the following advantages:

[0057] 1. The present invention realizes a new scheme of phase modulation and demodulation of optical fiber interferometric displacement sensor using square wave signal, broadens the phase modulation and demodulation methods of multi-wavelength optical fiber displacement interferometry, and proposes a new scheme that can still achieve the displacement measurement effect.

[0058] 2. Compared with traditional sinusoidal signal phase modulation and demodulation, the modulation and demodulation method of the present invention only performs calculations in the time domain, has a simple calculation process, a concise optical path, and high robustness. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 Schematic diagram of the basic principle of phase demodulation according to the embodiment of the present invention.

[0060] Figure 2 Schematic diagram of the signal processing principle of phase demodulation in an embodiment of the present invention.

[0061] Figure 3 Graph showing displacement measurement results in an embodiment of the present invention.

[0062] Figure 4 Schematic diagram of the principle structure of the device in an embodiment of the present invention.

[0063] Legend: 1. Multi-wavelength narrow-linewidth laser; 2. Optical isolator; 3. Wavelength division multiplexer; 4. Optical splitter; 5. Circulator; 6. Focusing lens; 7. Object surface; 8. Phase modulator; 9. Optical attenuator; 10. Coupler; 11. Demultiplexer; 12. Photodetector; 13. Data acquisition module; 14. Computer equipment; 15. Driver module. DETAILED DESCRIPTION

[0064] The basic principle of the square wave phase modulation and demodulation method and device for multi-wavelength interferometric displacement measurement of the present invention is to use a square wave signal to modulate the phase of the measurement light in the multi-wavelength optical fiber displacement sensor and at the same time use a demodulation algorithm to demodulate the phase information of different wavelengths in the system light intensity signal to complete the demodulation of the displacement measurement. The demodulated signal is obtained from the multi-wavelength displacement interferometric measurement system. The square wave phase modulation and demodulation method and device for multi-wavelength interferometric displacement measurement of the present invention will be further described in detail below with reference to examples. Figure 1 As shown, the square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement in this embodiment has the following steps:

[0065] S1, filtering and normalizing the collected light intensity interference signals of different wavelengths, and normalizing and normalizing the square wave modulation signal; the light intensity interference signal is a light intensity interference signal generated by modulating the phase of the multi-wavelength optical fiber displacement sensor using the square wave modulation signal to generate a phase-shifted mode;

[0066] S2, performing convolution operations on the processed light intensity interference signal and the square wave modulation signal respectively;

[0067] S3, performing zero-value elimination and half-cycle compensation on the signal after the convolution operation, and performing ellipse fitting on the signal after the zero-value elimination to obtain signal parameters;

[0068] S4, performing numerical correction on the signal after half-cycle compensation according to the signal parameters;

[0069] S5, performing an arc tangent operation on the numerically corrected signal to obtain the interference phase information of a single wavelength;

[0070] S6, performing multi-wavelength composite calculation on the interference phase information of the two single wavelengths to obtain the displacement of the object being measured.

[0071] Fiber optic displacement sensors work based on the principle of optical interference and determine the displacement of an object by measuring the phase or intensity change of light in the optical fiber. When phase modulation is performed using phase carrier technology, the light intensity signal can be expressed as the coherent superposition of the reference beam and the measurement beam. The single laser light intensity of the system is:

[0072] ,

[0073] In the above formula, The light intensity signal collected by the photodetector, is the reference beam intensity of the interferometer, is the intensity of the interference beam reflected from the surface of the object, To measure the displacement of an object, is the intrinsic distance between the reference surface of the interferometer and the object surface, To measure the wavelength of the light beam, The interferometer measures the phase change of the optical path caused by the modulated signal.

[0074] In this embodiment, the light intensity interference signal is a light intensity interference signal generated by modulating the phase of the multi-wavelength optical fiber displacement sensor with a square wave modulation signal to generate a phase-shifted light intensity interference signal. Before step S1, the light intensity interference signal is generated by modulating the phase of the multi-wavelength optical fiber displacement sensor with a square wave modulation signal, and when the phase of the multi-wavelength optical fiber displacement sensor is modulated with a square wave modulation signal, the measured light beam includes multiple laser beams with similar wavelengths, and the wavelengths of the multiple laser beams are ,in Indicates the number of light sources in the system and their average wavelength The calculation function expression is:

[0075] ,

[0076] In the above formula, is the kth wavelength; the square wave modulation signal is a square wave signal with a duty cycle of 50% as shown in the following formula:

[0077] ,

[0078] In the above formula, T is the period, The square wave modulation signal acts on the phase modulator through the driver so that when the square wave modulation signal is high, the phase modulator adjusts the multi-beam composite light path in the system light path relative to the average wavelength. produce Phase shift. The multiple laser beams with similar wavelengths refer to multiple laser beams with similar wavelengths that are sorted in order of size, with the difference between adjacent wavelengths not exceeding a preset threshold. As an optional implementation, the wavelength range in this embodiment covers 1525nm to 1575nm.

[0079] The multi-wavelength displacement measurement square wave signal demodulation method of this embodiment processes the various signals obtained by digital acquisition. Figure 2 As shown, the wavelength of the light is The light intensity interference signal and the wavelength of light is The light intensity interference signal And a square wave modulation signal with a duty cycle of 50% , Indicates the nth data point collected. The signal collection method is as follows: after starting the measurement, the first rising edge of the square wave modulation signal is used as the trigger collection condition. The collected light intensity signal is filtered and normalized after eliminating the signal noise. The purpose of normalization is to eliminate the DC component generated by the background light intensity in the interference signal and retain the interference light intensity change caused by the optical path phase change caused by the displacement of the object. After normalization, the signal is obtained. and In step S1 of this embodiment, the collected light intensity signals of different wavelengths are filtered and normalized to obtain and , The numbers represent different wavelengths. It should be noted that the phase demodulation method in this embodiment is explained using only two wavelengths. In actual use, when the system contains more than two wavelengths, similar methods are used to process the interference signals of light intensity at other wavelengths. The displacement reproduction results for the two selected wavelengths can be averaged to improve the accuracy of the measurement system.

[0080] like Figure 2 As shown, in step S1 of this embodiment, the square wave modulation signal is normalized and normalized, including: After normalization and standardization, the signal is obtained , which can be expressed as:

[0081] ,

[0082] In the above formula, N represents the number of acquired digital signals in one cycle;

[0083] The signal is simplified into two parts within one cycle: The high and medium level parts are mapped to 1, The low and medium level parts are mapped to -1, according to the signal The positive and negative values ​​of the signal Decomposed into two complementary signals and ,Signal When the signal is high 1, otherwise the signal is 0; signal When the signal is low is 1, otherwise the signal is 0, which can be expressed as:

[0084] ,

[0085] .

[0086] like Figure 2 As shown, the function expression for performing convolution operation on the processed light intensity interference signal and the square wave modulation signal in step S2 of this embodiment is:

[0087] ,

[0088] ,

[0089] ,

[0090] ;

[0091] In the above formula, 、 、 and is the signal after convolution operation, and is the light intensity interference signal of different wavelengths obtained after processing, Represents different wavelengths and Serial number.

[0092] like Figure 2 As shown, in step S3 of this embodiment, the signal after the convolution operation is subjected to 0 value removal and half-cycle compensation, including: respectively performing the following operations on the signal after the convolution operation: 、 、 and , identify and remove the periodic 0 values ​​in the original signal and use the least squares fitting interpolation method to compensate for the missing parts to ensure the continuity and integrity of the data. The periodic 0 values ​​include the beginning 0 value, the middle 0 value and the ending 0 value. The specific processing method of the periodic 0 data varies according to the position of the 0 data (beginning, middle, end). The beginning 0 value is interpolated from the first non-0 point forward, the middle 0 value is interpolated forward and backward respectively, and the ending 0 value is interpolated from the last non-0 point backward to finally obtain the signal after half-period compensation. , , and . The method of this embodiment adopts the least square fitting interpolation method as the data compensation strategy. According to the position of the 0 data in the data sample (beginning, middle, end), it is specifically divided into the following three processing methods: (1) Processing of the beginning 0 data: When the 0 data is located at the beginning of the data sample, the first starting point of the continuous non-zero data segment immediately following it is selected, and the data in the second half cycle is used as a reference to perform least square fitting. Subsequently, this fitting result is applied to the original 0 data position for interpolation to replace the original 0 data. (2) Processing of the middle 0 data: If the 0 data appears in the middle position of the data sample, two parts of data are referenced at the same time: one is the subsequent half-cycle data starting from the first data point of the continuous non-zero data segment before the 0 data; the other is the first half-cycle data ending at the last data point of the continuous non-zero data segment after the 0 data. Least square fitting is performed on these two parts of data, and interpolation fitting is performed at the original 0 data position to update the original 0 data. (3) Ending 0 data processing: For the 0 data at the end of the data sample, only the first half cycle data with the last data point as the last digit is referenced in the continuous non-zero data segment immediately before it, and the least squares fitting is performed. After that, interpolation is performed at the original 0 data position to replace the original 0 data, and finally the signal after half cycle compensation is obtained. , , and , these data have eliminated the impact of periodic zero values ​​and restored continuity.

[0093] like Figure 2 As shown, the signal parameters obtained by ellipse fitting in step S3 of this embodiment include the signal after convolution operation 、 、 and A pair of convolution signals with the same wavelength and Perform the following processing:

[0094] S3.1, the signal Filter out all non-zero data points to form new data sets , the signal Filter out all non-zero data points to form new data sets ;

[0095] S3.2, from the dataset 、 Select data points, ;Will data points Construct the equation of the ellipse shown below:

[0096] ,

[0097] In the above formula, is the equation of the ellipse, are the ellipse parameters, is the kth data point, ; According to the least squares principle, according to the following formula:

[0098] ,

[0099] Solve for the ellipse parameters ;

[0100] S3.3, according to the ellipse parameters Calculate the DC and AC components:

[0101] ,

[0102] ,

[0103] ,

[0104] ,

[0105] In the above formula, and is the DC component, and is the AC component; thus the AC components of the signals corresponding to the two wavelengths are obtained 、 、 、 and DC component 、 、 、 .

[0106] In step S4 of this embodiment, the function expression for performing numerical correction on the signal after half-cycle compensation according to the signal parameters is:

[0107] ,

[0108] ,

[0109] ,

[0110] ,

[0111] In the above formula, , , and are the signals after half-cycle compensation, 、 、 、 is the AC component of the signal parameters obtained by ellipse fitting, 、 、 、 The DC component of the signal parameters obtained by ellipse fitting.

[0112] like Figure 2 As shown, in step S5 of this embodiment, the function expression for obtaining the single wavelength interference phase information by performing an arc tangent operation on the value-corrected signal is:

[0113] ,

[0114] ,

[0115] In the above formula, and Different wavelengths and phase information.

[0116] like Figure 2 As shown, in step S6 of this embodiment, the function expression for obtaining the displacement of the object under test by performing multi-wavelength composite calculation on the interference phase information of the two single wavelengths is:

[0117] ,

[0118] In the above formula, is the displacement of the object being measured, is the phase difference, is an intermediate variable, and there are:

[0119] ,

[0120] ,

[0121] In the above formula, and Different wavelengths and phase information.

[0122] In order to illustrate the feasibility of the square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement in this embodiment, a simulation is performed based on the Matlab platform. The simulation parameters are as follows: wavelength : 1530.33nm, wavelength :1560.61nm, displacement trajectory of the object being measured , simulation time , inherent distance d between reference surface and reflecting surface: 0.1m, sampling rate: 250kHz, intensity ratio of reference light and measurement light , modulation signal modulation frequency: =5kHz. Figure 3 is the simulation result, Figure 3 The original displacement in (a) is Figure 3 The demodulated displacement results in (b) are consistent, demonstrating the feasibility of the square wave phase modulation demodulation method for multi-wavelength interferometric displacement measurement in this embodiment. It should be noted that this embodiment only illustrates the demodulation method for two wavelengths. In actual use, when the system contains more than two wavelength laser light sources, a similar method is used to process signals at other wavelengths. The displacement reproduction results for two different wavelengths can be averaged to improve the measurement system's accuracy.

[0123] In summary, the square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement in this embodiment includes a square wave phase modulation method and a corresponding demodulation method for multi-wavelength fiber-optic displacement interferometric measurement. A square wave signal is used to modulate the phase of a multi-wavelength fiber-optic displacement sensor to generate a specific phase shift pattern. During signal demodulation, the modulated signal is first normalized and normalized. Simultaneously, the collected light intensity signal is filtered and normalized. Next, a convolution operation is performed on the normalized modulated signal and the normalized interference signal. Zero values ​​are removed from the convolved signal, and half-cycle compensation is performed using the least squares method. Using the non-zero data in the convolved signal, the DC and AC components of the corresponding signal are extracted using an ellipse fitting method. With reference to these components, numerical correction is performed on the half-cycle compensated signal. Finally, an inverse tangent phase calculation is performed on the corrected signal based on wavelength classification to obtain phase information for a single wavelength. Using this multi-wavelength phase information, the precise displacement of the measured object is inversely resolved through composite calculation. The square wave phase modulation and demodulation method for multi-wavelength interference displacement measurement of the present embodiment broadens the phase modulation and demodulation methods in the field of multi-wavelength fiber optic displacement interference measurement, introduces a new scheme that can also effectively achieve high-precision displacement measurement effects, and can overcome the problem of nonlinear distortion that may be encountered when using sinusoidal signal demodulation. The square wave phase modulation and demodulation method for multi-wavelength interference displacement measurement of the present embodiment performs phase modulation on the multi-wavelength fiber optic interference displacement sensor by using a specific square wave signal. At the same time, the displacement information of the object to be measured can be reproduced by the above-mentioned demodulation algorithm. The method of the present embodiment only explains the demodulation method of two wavelengths in the phase demodulation method. When the system contains more than two wavelength laser light sources in actual use, similar methods are used for processing other wavelength signals. The square wave phase modulation and demodulation method for multi-wavelength interference displacement measurement of the present embodiment can adopt the method of averaging multiple reproduction results for the result of displacement reproduction of two different selected wavelengths to improve the accuracy of the measurement system.

[0124] like Figure 4 As shown, this embodiment also provides a square wave phase modulation and demodulation device for multi-wavelength interferometric displacement measurement, comprising a multi-wavelength narrow linewidth laser 1, an optical isolator 2, a wavelength division multiplexer 3, a beam splitter 4, a circulator 5, a focusing lens 6, a phase modulator 8, an optical attenuator 9, a coupler 10, a demultiplexer 11, a photodetector 12, a data acquisition module 13, a computer device 14 and a driver module 15. In the working state, the multi-wavelength narrow linewidth laser 1 (including a laser unit 1 generating lasers with similar wavelengths) a ~1 n ) generates multiple lasers of different wavelengths through optical isolator 2 (2 a ~2 n) reaches the wavelength division multiplexer 3, where it is combined into a beam of light containing multiple wavelengths. The beam is divided into two beams by the beam splitter 4, one of which passes through the circulator 5 and the focusing lens 6 and is focused onto the surface 7 of the object to be measured. The reflected beam formed on the surface 7 returns to the focusing lens 6 and is coupled back to the circulator 5 by the focusing lens 6; the other beam passes through the phase modulator 8 for phase modulation and then enters the optical attenuator 9. The beam output from the optical attenuator 9 and the beam returned from the circulator 5 enter the coupler 10 together and are combined into one beam, which then passes through the demultiplexer 11 and is detected by multiple photodetectors 12 (12 a ~12 n ) detection and then sent to the computer device 14 after passing through the data acquisition module 13. The computer device 14 is connected to the control end of the driver module 15 for use. The driver module 15 is connected to the phase modulator 8 for providing the square wave modulation signal required by the phase modulator 8. The computer device 14 includes a microprocessor and a memory connected to each other. The microprocessor is programmed or configured to execute the square wave phase modulation and demodulation method for the multi-wavelength interferometric displacement measurement described above. In the light source part of this embodiment, the multi-wavelength narrow linewidth laser 1 generates multiple lasers of different wavelengths, with a wavelength range covering 1525nm to 1575nm, respectively marked as . After these laser outputs, they pass through the optical isolator 2 and reach the wavelength division multiplexer 3. In the wavelength division multiplexer 3, multiple beams of laser light are merged into a beam of laser light containing multiple wavelengths. This integrated light beam is then split by the optical splitter 4. A part of the light beam split by the optical splitter 4 will first pass through the circulator 5, and then be focused onto the object surface 7 by the focusing lens 6. After forming a reflected light beam on the object surface 7, this part of the light beam will return to the focusing lens 6 again, and be coupled into the optical fiber by the focusing lens 6, and finally return to the circulator 5. Another part of the light beam split by the optical splitter 4 will pass through the phase modulator 8 for phase modulation, and then enter the optical attenuator 9. The light beam output from the optical attenuator 9 and the light beam returned from the circulator 5 enter the coupler 10 together and are merged into one light beam. The merged light beam passes through the demultiplexer 11, is accurately distinguished according to the wavelength, and then passes through the photodetector 12 respectively. The photodetector 12 converts it into a corresponding analog signal according to the light intensity of each light beam. The analog signal is collected by the data acquisition module 13 and transmitted to the computer 14. The computer demodulates the collected signals according to the signal processing method of the present invention, thereby determining the object's displacement. Furthermore, the computer is connected to the driver module 15. The square wave modulated signal generated by the computer passes through the driver module 15 and acts on the phase modulator 8, causing it to perform phase modulation according to the generated signal.

[0125] In addition, this embodiment also provides a computer-readable storage device, which stores a computer program or instruction. The computer program or instruction is programmed or configured to execute the square wave phase modulation and demodulation method of multi-wavelength interferometric displacement measurement through a processor.

[0126] In addition, this embodiment also provides a computer program product, including a computer program or instructions, which are programmed or configured to execute the square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement through a processor.

[0127] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present application may take the form of a computer program product implemented on one or more computer-readable storage devices (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code. The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of processes and / or boxes in the flowchart and / or block diagram, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the functions described in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 These computer program instructions can also be stored in a computer-readable memory that can guide a computer or other programmable data processing device to work in a specific way, so that the instructions stored in the computer-readable memory produce a product including the instruction device, which implements the function specified in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 These computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operation steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process in the process. Figure 1 a process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0128] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiment. All technical solutions based on the concept of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement, characterized in that: The steps include: S1, filtering and normalizing the collected light intensity interference signals of different wavelengths, and normalizing and normalizing the square wave modulation signal; S2, performing convolution operations on the processed light intensity interference signal and the square wave modulation signal respectively; S3, performing zero-value elimination and half-cycle compensation on the signal after the convolution operation, and performing ellipse fitting on the signal after the zero-value elimination to obtain signal parameters; S4, performing numerical correction on the signal after half-cycle compensation according to the signal parameters; S5, performing an arc tangent operation on the numerically corrected signal to obtain the interference phase information of a single wavelength; S6, performing multi-wavelength composite calculation on the interference phase information of the two single wavelengths to obtain the displacement of the object being measured.

2. The square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement according to claim 1, characterized in that: Before step S1, the method further includes modulating the phase of the multi-wavelength optical fiber displacement sensor with a square wave modulation signal to generate a light intensity interference signal in a phase shift mode, and when the phase of the multi-wavelength optical fiber displacement sensor is modulated with a square wave modulation signal, the measured light beam includes multiple laser beams with similar wavelengths, and the wavelengths of the multiple laser beams are ,in Indicates the number of light sources in the system and their average wavelength The calculation function expression is: ， In the above formula, is the kth wavelength; the square wave modulation signal is a square wave signal with a duty cycle of 50% as shown in the following formula: ， In the above formula, T is the period, The square wave modulation signal acts on the phase modulator through the driver so that when the square wave modulation signal is high, the phase modulator adjusts the multi-beam composite light path in the system light path relative to the average wavelength. produce Phase shift.

3. The square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement according to claim 1, characterized in that: In step S1, the square wave modulation signal is normalized and normalized, including: After normalization and standardization, the signal is obtained , according to the signal The positive and negative values ​​of the signal Decomposed into two complementary signals and ,Signal When the signal is high 1, otherwise the signal is 0; signal When the signal is low is 1, otherwise the signal is 0; in step S2, the function expression for performing convolution operation on the processed light intensity interference signal and the square wave modulation signal is: ， ， ， ； In the above formula, 、 、 and is the signal after convolution operation, and is the light intensity interference signal of different wavelengths obtained after processing, Represents different wavelengths and Serial number.

4. The square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement according to claim 2, characterized in that: In step S3, the signal after the convolution operation is subjected to 0 value elimination and half-cycle compensation, which includes: 、 、 and , identify and remove the periodic 0 values ​​in the original signal and use the least squares fitting interpolation method to compensate for the missing parts. The periodic 0 values ​​include the beginning 0 value, the middle 0 value and the ending 0 value. The beginning 0 value is interpolated from the first non-0 point forward, the middle 0 value is interpolated forward and backward respectively, and the ending 0 value is interpolated from the last non-0 point backward. Finally, the signal after half-period compensation is obtained , , and .

5. The square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement according to claim 4, characterized in that: In step S3, the signal parameters obtained by performing ellipse fitting on the signal after the 0 value is eliminated include the signal parameters after the convolution operation. 、 、 and A pair of convolution signals with the same wavelength and Perform the following processing: S3.1, the signal Filter out all non-zero data points to form new data sets , the signal Filter out all non-zero data points to form new data sets ; S3.2, from the dataset 、 Select data points, ;Will data points Construct the equation of the ellipse shown below: ， In the above formula, is the equation of the ellipse, are the ellipse parameters, is the kth data point, ; According to the least squares principle, according to the following formula: ， Solve for the ellipse parameters ; S3.3, according to the ellipse parameters Calculate the DC and AC components: ， ， ， ， In the above formula, and is the DC component, and is the AC component; thus the AC components of the signals corresponding to the two wavelengths are obtained 、 、 、 and DC component 、 、 、 .

6. The square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement according to claim 5, characterized in that: The function expression for numerically correcting the signal after half-cycle compensation according to the signal parameters in step S4 is: ， ， ， ， In the above formula, , , and are the signals after half-cycle compensation, 、 、 、 is the AC component of the signal parameters obtained by ellipse fitting, 、 、 、 The DC component of the signal parameter is obtained by ellipse fitting; in step S5, the arc tangent operation is performed on the numerically corrected signal to obtain the function expression of the interference phase information of a single wavelength: ， ， In the above formula, and Different wavelengths and phase information.

7. The square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement according to claim 6, characterized in that: In step S6, the function expression for the displacement of the object to be measured is obtained by performing multi-wavelength composite calculation on the single wavelength interference phase information: ， In the above formula, is the displacement of the object being measured, is the phase difference, is the composite wavelength, and: ， ， In the above formula, and Different wavelengths and phase information.

8. A square wave phase modulation and demodulation device for multi-wavelength interferometric displacement measurement, characterized in that: The invention comprises a multi-wavelength narrow linewidth laser (1), an optical isolator (2), a wavelength division multiplexer (3), a beam splitter (4), a circulator (5), a focusing lens (6), a phase modulator (8), an optical attenuator (9), a coupler (10), a demultiplexer (11), a photodetector (12), a data acquisition module (13), a computer device (14) and a driver module (15). In a working state, the multi-wavelength narrow linewidth laser (1) generates a plurality of laser beams of different wavelengths with similar wavelengths, which pass through the optical isolator (2) and reach the wavelength division multiplexer (3). In the wavelength division multiplexer (3), the laser beams are combined into a beam containing multiple wavelengths. The beams are divided into two beams through the beam splitter (4), one of which passes through the circulator (5) and the focusing lens (6) and is focused onto the object surface (7) of the object to be measured. The reflected beam formed on the object surface (7) returns to the focusing lens (6) and is coupled back by the focusing lens (6). A circulator (5); wherein another beam is phase-modulated by a phase modulator (8) and then enters an optical attenuator (9); the light beam output from the optical attenuator (9) and the light beam returned from the circulator (5) enter a coupler (10) together and are combined into one light beam, which is then detected by a plurality of photodetectors (12) for detecting different wavelengths after passing through a demultiplexer (11) and then sent to a computer device (14) after passing through a data acquisition module (13); the computer device (14) is connected to a control end of a driver module (15) for use, the driver module (15) is connected to a phase modulator (8) for use in providing a square wave modulation signal required by the phase modulator (8), the computer device (14) comprises a microprocessor and a memory connected to each other, the microprocessor being programmed or configured to execute the square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement according to any one of claims 1 to 7.

9. A computer-readable storage device having a computer program or instruction stored therein, characterized in that: The computer program or instruction is programmed or configured to execute the square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement according to any one of claims 1 to 7 through a processor.

10. A computer program product comprising a computer program or instructions, characterized in that The computer program or instruction is programmed or configured to execute the square wave phase modulation and demodulation method for multi-wavelength interferometric displacement measurement according to any one of claims 1 to 7 through a processor.

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