Optimization Method for Dual-Source FSI Ranging System Based on Wavelet Synchronous Compression Transform

Abstract

This invention discloses an optimization method for a dual-source FSI ranging system based on wavelet synchronous compression transform, mainly addressing the problems of high system complexity and poor performance in existing dual-source FSI ranging systems when separating mixed interference signals. The solution includes: constructing a dual-source FSI ranging optical path to generate mixed interference signals; building a signal processing module based on the wavelet synchronous compression transform algorithm; sending the mixed interference signals to the signal processing module through a data acquisition device in the ranging optical path; using wavelet synchronous compression transform to separate the interference signals generated by the two lasers in the frequency domain; then achieving separation of the individual interference signals by reconstructing the frequency bands of the two interference signals; and finally using the separated two interference signals to calculate the distance and obtain the final ranging result. This invention can guarantee ranging accuracy without increasing the complexity and design cost of the dual-source FSI ranging system.

Description

Technical Field

[0001] This invention belongs to the field of optical precision measurement technology, and further relates to a dual-source FSI ranging system. Specifically, it is an optimization method for a dual-source FSI ranging system based on wavelet synchronous compression transform, which can be used to improve the separation quality of two interference signals in a dual-source FSI ranging system and reduce the impact of spectral cross-interference on the ranging results. Background Technology

[0002] With the development of science and technology, precision measurement technology has become increasingly popular in many fields. Whether it is space exploration represented by formation flying, basic space research represented by gravitational wave detection, or high-end equipment manufacturing represented by the assembly of components for aircraft, ships, and trains, all of these fields have shown an urgent technical demand for precision measurement.

[0003] In optical precision measurement, frequency scanning interferometry (FSI) ranging is a typical technology. As a large-scale, high-precision measurement technique, FSI ranging has been practically applied and developed in numerous scientific research programs and projects. However, under the FSI ranging mechanism, minute vibrations of the target can be amplified, thus affecting the ranging accuracy. Using two lasers with the same sweep frequency band to perform synchronous reverse scanning measurements on the same target can effectively suppress the impact of target vibration on ranging accuracy. The frequency-modulated light generated by the two lasers needs to pass through the same optical path and form interference at the same point. Therefore, what the detector detects is a mixed interference signal formed by the sweep frequency mechanisms of the two lasers. In the subsequent distance calculation process, it is necessary to effectively separate the mixed interference signal. Therefore, effective separation of the interference signal is a key step in distance calculation and vibration suppression.

[0004] For the separation of mixed interference signals, several common techniques exist: 1) using bandpass filters to separate the spectrum of mixed interference signals from two lasers; 2) using EMD signal processing to decompose the mixed interference signals in the time domain; and 3) using polarization optics systems to separate the interference signals from the two sources. However, the performance of digital bandpass filters is affected by filter parameter settings and laser sweep nonlinearity, resulting in spectrum broadening of the interference signals. This leads to a lack of clear spectral boundaries between the interference signals generated by the two lasers, resulting in cross-interference. Therefore, effective separation of the two interference signals cannot be achieved when using bandpass filters for filtering and separation. Furthermore, because the filter does not decay rapidly at the cutoff frequency, spectral information from other signals is also introduced into the filter's passband. The EMD algorithm itself suffers from mode aliasing, which severely affects the signal separation quality. Moreover, the decomposed components lack clear selection criteria, making them susceptible to human interference and lacking rigor. Polarization optics systems require the introduction of multiple polarization optical components, resulting in complex designs and increasing the overall complexity of the ranging system, which is not suitable for practical applications. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing an optimization method for dual-source FSI ranging systems based on wavelet synchronous compression transform. This method solves the problems of high system complexity and high design cost when separating mixed interference signals in dual-source FSI ranging systems. Furthermore, this method can further improve the separation effect of mixed interference signals. This invention utilizes wavelet synchronous compression transform to separate the interference signals generated by the two lasers in the frequency domain. Then, it achieves the separation of the individual interference signals by reconstructing the frequency bands of the two interference signals.

[0006] The basic idea behind this invention is as follows: A dual-source FSI ranging optical path is constructed to generate a mixed interference signal. The generated mixed interference signal is a dual-frequency signal. This signal is sent to a signal processing module built into the system via a data acquisition device within the ranging optical path. This module uses a wavelet synchronous compression transform algorithm to separate the signals. The two separated interference signals are then used by a distance calculation module to obtain the final ranging result. The dual-source FSI ranging system optimized by this invention can further improve ranging accuracy and achieve superior performance without increasing system complexity or design cost.

[0007] The specific steps of this invention to achieve the above objectives are as follows:

[0008] (1) A dual-source FSI ranging optical path is constructed using two tunable external cavity semiconductor lasers (ECDL), collimators, beam splitters, Fabry-Perot FP etalons, mirrors, Michelson interference optical path and a photodetector placed in the Michelson interference optical path, and a data acquisition device is equipped in the ranging optical path.

[0009] (2) The first tuned light source S and the second tuned light source S′ with frequency varying with time t are generated by two tunable external cavity semiconductor lasers ECDL in the dual-source FSI ranging optical path, and are output to the collimator respectively.

[0010] (3) The collimator collimates the first tuned light source S and the second tuned light source S′ respectively. Then, different optical prisms are used to split the collimated first tuned light source S and the second tuned light source S′. Part of the processed light enters the Fabry-Perot FP etalon to generate the FP signal, and the other part continues to propagate forward to form the mixed light S″.

[0011] (4) The mixed light S″ propagates forward into the Michelson interference path. Before entering the Michelson interference path, it is split into two beams by a beam splitter, namely the reference light S1″ and the measurement light S2″. S1″ and S2″ are reflected by a reflecting prism and then converged and interfered by the beam splitter to obtain the final mixed light S. z ”;

[0012] (5) The final mixed light S is detected by a photodetector placed in the Michelson interferometer optical path. z "Probes were performed to obtain mixed interference signals;"

[0013] (6) Use a data acquisition device to synchronously acquire the mixed interference signal in step (5) and the FP signal generated by the Fabry-Perot FP etalon in step (3) to obtain the final mixed interference signal I(t);

[0014] (7) Construct a signal processing module for signal separation in the ranging system, and input the final mixed interference signal I(t) obtained in step (6) into the module;

[0015] (8) The signal processing module uses wavelet synchronous compression transform to separate the final mixed interference signal obtained from the acquisition, resulting in two interference signals, namely the first interference signal I1(t) and the second interference signal I2(t). The implementation steps are as follows:

[0016] (8.1) Perform wavelet transform on the final hybrid interference signal I(t) under the continuous wavelet function ψ(t) to transform it from the time domain form to the frequency domain form W. I (a,t), where a is the scale factor and t is the time factor;

[0017] (8.2) The instantaneous frequency ω of the mixed interference signal is obtained according to the following formula. I (a,t):

[0018]

[0019] Where i represents the imaginary part, This represents the derivative, and π represents pi (the mathematical constant).

[0020] (8.3) Using synchronous compression, the frequency domain form W of the final mixed interference signal is obtained. I (a,t) is converted to the compressed form T I (ξ,t), that is, its scale factor a is transformed into the frequency component ξ:

[0021]

[0022] (8.4) Two time-frequency curves are obtained on the time-frequency surface, showing the frequency change with time factor t. These are the first time-frequency curve T. I (ξ1,t) and the second time-frequency curve T I (ξ2,t), where ξ1 and ξ2 are the frequency components of the two interference signals corresponding to the two time-frequency curves, respectively;

[0023] (8.5) Using the time-frequency curve T obtained in step (8.4) I (ξ1,t) and T I Two interference signals, I1(t) and I2(t), are reconstructed from (ξ2,t):

[0024]

[0025] Where Re(·) denotes taking the real part of the complex number, Let d denote the Fourier transform of the wavelet function ψ(t), and d denote the differential sign;

[0026] (9) Construct a distance calculation module in the ranging system to calculate the distance. Use this module to obtain the final ranging result based on the reconstructed two interference signals I1(t) and I2(t).

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] First, this invention uses wavelet synchronous compression as a high-resolution time-frequency analysis method. In response to the situation where the spectrum of the two interference signals cross-interference due to the broadening of the interference signal spectrum, the resolution of the interference signal is improved by using time-frequency rearrangement technology through wavelet synchronous compression, which overcomes the spectrum cross-interference and enables the two interference signals to be effectively separated.

[0029] Secondly, since this invention utilizes a signal time-frequency processing method to post-process the acquired hybrid interference, there is no need to introduce additional auxiliary devices, which greatly simplifies the structure of the ranging system.

[0030] Third, by using a synchronous compressed signal separation algorithm, this invention effectively avoids the introduction of additional optical components and reduces system construction costs compared to other existing related technologies.

[0031] Fourth, because the present invention performs wavelet synchronous compression on the hybrid interference signal, the noise attached to the hybrid interference signal is also suppressed or even eliminated as the signal is compressed and transformed, thereby further improving the ranging accuracy. Attached image description:

[0032] Figure 1 This is a flowchart illustrating the implementation of the present invention;

[0033] Figure 2 This is a schematic diagram of a dual-laser-based FSI ranging system;

[0034] Figure 3 The time-domain distribution of the FP signal and the mixed interferometric signal in a dual-laser FSI ranging system is shown.

[0035] Figure 4 The figure shows the simulation results of wavelet synchronous compression transform for the separation and reconstruction of noisy mixed interference signals. Among them, (a) is the simulated mixed interference signal with superimposed noise; (b) is a comparison between simulated interference signal 1 and reconstructed interference signal 1; and (c) is a comparison between simulated interference signal 2 and reconstructed interference signal 2. Detailed Implementation

[0036] The present invention will now be further described with reference to the accompanying drawings.

[0037] Example 1:

[0038] See attached document Figure 1 The present invention proposes a method for separating hybrid interferometric signals based on wavelet synchronous compression transform, which specifically includes the following steps:

[0039] Step 1: Construct a dual-source FSI ranging optical path using two tunable external cavity semiconductor lasers (ECDL), collimators, beam splitters, Fabry-Perot FP etalons, mirrors, Michelson interference optical path, and a photodetector placed in the Michelson interference optical path, and equip the ranging optical path with a data acquisition device.

[0040] Step 2: The two tunable external cavity semiconductor lasers (ECDLs) in the dual-source FSI ranging optical path generate a first tunable source S and a second tunable source S′ whose frequencies vary with time t, and output them to the collimator respectively.

[0041] Step 3: The collimator collimates the first tuned light source S and the second tuned light source S′ respectively. Then, different optical prisms are used to split the collimated first tuned light source S and the second tuned light source S′. Part of the processed light enters the Fabry-Perot FP etalon to generate the FP signal, and the other part continues to propagate forward to form the mixed light S″.

[0042] Step 4: The mixed light S″ propagates forward into the Michelson interference path. Before entering the Michelson interference path, it is split into two beams by a beam splitter, namely the reference beam S1″ and the measurement beam S2″. S1″ and S2″ are reflected by a reflecting prism and then converged and interfered by the beam splitter to obtain the final mixed light S. z ”;

[0043] Step 5: The final mixed light S is detected by a photodetector placed in the Michelson interferometer optical path. z "Probes were performed to obtain mixed interference signals;"

[0044] Step 6: Use a data acquisition device to synchronously acquire the mixed interference signal from Step 5 and the FP signal generated by the Fabry-Perot FP etalon from Step 3 to obtain the final mixed interference signal I(t); Figure 3 As shown.

[0045] Step 7: Construct a signal processing module in the ranging system to separate the signals, and input the final mixed interference signal I(t) obtained in step 6 into the module;

[0046] Step 8: The signal processing module uses the wavelet synchronous compression transform algorithm to separate the acquired final mixed interference signal, obtaining two interference signals, namely the first interference signal I1(t) and the second interference signal I2(t). The implementation steps are as follows:

[0047] (8.1) Perform wavelet transform on the final hybrid interference signal I(t) under the continuous wavelet function ψ(t) to transform it from the time domain form to the frequency domain form W. I (a,t), where a is the scale factor and t is the time factor; its specific expression is as follows:

[0048]

[0049] in, For the frequency domain representation of the mixed interference signal, Let ψ(t) be the frequency domain representation of the continuous wavelet function, and e be the base of the exponential function.

[0050] (8.2) The instantaneous frequency ω of the mixed interference signal is obtained according to the following formula. I (a,t):

[0051]

[0052] Where i represents the imaginary part, represents the derivative, t represents the time factor, and π represents pi;

[0053] (8.3) Using synchronous compression, the frequency domain form W of the final mixed interference signal is obtained. I (a,t) is converted to the compressed form T I (ξ,t), that is, its scale factor a is transformed into the frequency component ξ:

[0054]

[0055] (8.4) Two time-frequency curves are obtained on the time-frequency surface, showing the frequency change with time factor t. These are the first time-frequency curve T. I (ξ1,t) and the second time-frequency curve T I (ξ2,t), where ξ1 and ξ2 are the frequency components of the two interference signals corresponding to the two time-frequency curves, respectively;

[0056] (8.5) Using the time-frequency curve T obtained in step (8.4) I (ξ1,t) and T I Two interference signals, I1(t) and I2(t), are reconstructed from (ξ2,t):

[0057]

[0058] Where Re(·) denotes taking the real part of the complex number, Let d denote the Fourier transform of the wavelet function ψ(t), and d denote the differential sign;

[0059] Step 9: Construct a distance calculation module in the ranging system to calculate the distance. This module calculates the final ranging result based on the reconstructed two interference signals I1(t) and I2(t). The specific implementation is as follows:

[0060] (9.1) Place the FP signal 1 and the first interference signal I1(t) under the same time reference, obtain the first optical frequency variation range Δυ1 of a tunable external cavity semiconductor laser ECDL from the FP signal 1, and extract the phase of the first interference signal from I1(t). By placing the FP signal 2 and the second interference signal I2(t) under the same time reference, the second optical frequency variation range Δυ2 of the other tunable external cavity semiconductor laser ECDL is obtained from the FP signal 2, and the phase difference of the second interference signal is obtained by phase extraction of I2(t).

[0061] (9.2) Δυ1 and Δυ2 and Substituting these values ​​into the FSI ranging formula, we obtain the measured distance values ​​for the two interference signals:

[0062]

[0063] Where L1 and L2 are the measured distance values ​​corresponding to the first interference signal I1(t) and the second interference signal I2(t), respectively, c is the speed of light, and n is the air refractive index;

[0064] (9.3) Average L1 and L2 to obtain the final distance L, which is the final distance measurement result.

[0065] Example 2: Refer to Appendix Figure 2 The overall implementation steps of the method of the present invention are the same as those in Embodiment 1. Now, the construction of the dual-source FSI ranging optical path in the present invention will be described in further detail.

[0066] The dual-source FSI ranging optical path, constructed using two tunable external cavity semiconductor lasers (ECDL), collimators, beam splitters, Fabry-Perot FP etalons, mirrors, a Michelson interferometer optical path, and a photodetector placed within the Michelson interferometer optical path, comprises:

[0067] The beam splitter is provided in four parts: the first beam splitter BS1, the second beam splitter BS2, the third beam splitter BS3, and the fourth beam splitter BS4.

[0068] The Fabry-Perot FP etalon is provided in two parts, namely the first FP etalon and the second FP etalon;

[0069] The reflector includes a pyramidal reflecting prism RR1 and a second pyramidal reflecting prism RR2;

[0070] The collimator collimates the first tuned light source S and the second tuned light source S′ respectively. Then, the first beam splitter BS1 divides the collimated first tuned light source S into two parts, S1 and S2. Similarly, the second beam splitter BS2 divides the second tuned light source S′ into two parts, S1′ and S2′. S1 and S1′ enter the first and second FP etalons respectively, generating FP signal 1 and FP signal 2. S2 and S2′ continue to propagate forward.

[0071] After reflection, S2′ mixes with S2 at the third beam prism BS3 to form mixed light S″.

[0072] Example 3: The overall implementation steps of the method of the present invention are the same as those of Example 1. The principle of separation of mixed interference signals and the principle of wavelet synchronous compression transformation used in the present invention will be further explained in detail below.

[0073] (I) Principle of Separating Hybrid Interference Signals:

[0074] The instantaneous frequency ξ(t) of the interference signal can be obtained from the instantaneous phase expression of the interference signal:

[0075]

[0076] When the optical frequency change rate β of the laser is different, the instantaneous frequency of the obtained interference signal is also different at each moment; to facilitate the separation of the two interference signals, the modulation rates of the two lasers are set to be different, and the instantaneous optical frequencies of the two interference signals are as follows:

[0077]

[0078]

[0079] Therefore, it can be seen that the mixed interference signal is formed by the superposition and mixing of interference signals with frequencies ξ1(t) and ξ2(t). Thus, the mixed interference signal can be separated by frequency domain separation.

[0080] However, the interference signal is affected by nonlinear frequency modulation of the laser and noise, causing spectral broadening and cross-interference between the two interference signals in the frequency domain. Using filtering methods such as bandpass filters cannot effectively separate the two interference signals. To address this challenge, this invention proposes a signal processing module based on a wavelet synchronous compression transform algorithm to separate the mixed interference signals in a dual-source FSI ranging system. This method overcomes the effects of spectral broadening and noise, obtains a high-resolution time-frequency image through compression transform, and achieves separation of the two interference signals through frequency domain reconstruction.

[0081] (II) Principle of Wavelet Synchronous Compression Transform:

[0082] Since the mixed interference signal is formed by the combination of two interference signals, the mixed interference signal can be represented as:

[0083]

[0084] Where I(t) is a linear combination of two single-frequency interference signal components, A i For amplitude function, For phase function, It is the instantaneous frequency function.

[0085] When using synchronous compression to analyze and process hybrid interferometric signals, the amplitude function A is first... i (t) and phase function Apply the following constraints:

[0086]

[0087] In the above equation, 0 < ε ≤ 1, and 0 < ε < c1 < c2 < ∞, which must hold for all t ∈ R. Furthermore, if we want the components of a multi-component non-stationary signal to be separable, the following condition must be satisfied:

[0088]

[0089] This expression holds for all t∈R and 0<d<1.

[0090] This invention is based on wavelet transform and performs compression and allocation of the time-frequency information of the wavelet-transformed signal. For a given hybrid interference signal I(t), a continuous wavelet transform (CWT) is performed under the continuous wavelet function ψ(t), transforming it from the time domain form to the frequency domain form W. I (a,t):

[0091]

[0092] Where a is the scale factor, t is the time factor, and ξ is the frequency of the mixed interference signal. For the frequency domain representation of the mixed interference signal, Let ψ(t) be the frequency domain representation of the continuous wavelet function, and e be the base of the exponential function.

[0093] The instantaneous frequency of the mixed interference signal I(t) is ω I (a,t) can be obtained using the following formula:

[0094]

[0095] On the time-frequency plane, using T I (ξ,t) denotes the Continuous Wavelet Synchronous Compression Transform (WSST), which is defined as:

[0096]

[0097] When the single-frequency interference signal is an analytic signal, the formula for reconstructing the single-frequency interference signal from the frequency domain to the time domain can be expressed as:

[0098]

[0099] In the above formula, C ψ satisfy

[0100] When the single-frequency interference signal is a real signal, the formula for reconstructing the single-frequency interference signal from the frequency domain to the time domain can be expressed as:

[0101]

[0102] Since the hybrid interference signal is a multi-frequency component signal, the time-frequency rearrangement can be performed using the wavelet synchronous compression algorithm for each component. For each component, the frequency domain after wavelet synchronous compression transformation can be reconstructed to the time domain. The reconstruction process is as follows:

[0103]

[0104] The effects of the present invention will be further explained below with reference to simulation experiments.

[0105] 1. Simulation conditions:

[0106] The simulation experiments of this invention were conducted in a hardware environment with a CPU clock speed of 3.1GHz, 16G of memory, an Intel(R) UHD Graphics 630 graphics card, and Windows 10, and a software environment of Matlab 2021a.

[0107] 2. Simulation content:

[0108] The simulated interference signal 1 is set as a sinusoidal signal with an amplitude of ±2, a frequency of 3000Hz, and a sampling rate of 10MHz; the simulated interference signal 2 is set as a sinusoidal signal with an amplitude of ±2, a frequency of 5000Hz, and a sampling rate of 10MHz; the signal duration is 0.1s; interference signal 1 and interference signal 2 are linearly superimposed to simulate a mixed interference signal, and Gaussian white noise with a signal-to-noise ratio of 10dB is added; the simulated mixed interference signal with superimposed noise is used as the input of wavelet synchronous compression transform, which performs frequency domain separation on the mixed interference signal and reconstructs simulated interference signal 1 and simulated interference signal 2.

[0109] 3. Simulation results:

[0110] The simulation results of wavelet synchronous compression transform for the separation and reconstruction of noisy mixed interference signals in this invention are as follows: Figure 4 As shown, (a) is the simulated mixed interference signal with superimposed noise, (b) the solid line is the simulated interference signal 1 and the dashed line is the reconstructed interference signal 1 obtained by wavelet synchronous compression transform, and (c) the solid line is the simulated interference signal 2 and the dashed line is the reconstructed interference signal 2 obtained by wavelet synchronous compression transform. The results show that wavelet synchronous compression transform can effectively separate the two interference signals of different frequencies in the mixed interference signal, and at the same time, it can suppress the influence of noise on the separation of the mixed interference signal.

[0111] The above simulation analysis proves the correctness and effectiveness of the method proposed in this invention.

[0112] In dual-source FSI ranging systems, the separation of mixed interferometric signals is a crucial step, directly impacting distance measurement accuracy. Existing technologies for mixed interferometric signal separation suffer from high design costs, high complexity, and poor separation results. To address these issues, this invention applies a wavelet synchronous compression algorithm to dual-source FSI ranging systems. As a time-frequency processing method, wavelet synchronous compression can effectively separate signals containing multiple frequency components in the frequency domain. In the constructed dual-source FSI ranging optical path, the generated mixed interferometric signal is a dual-frequency signal. Therefore, after wavelet synchronous compression transformation, the frequency components contained in the mixed interferometric signal are effectively separated in the frequency domain. Effective separation of the individual interferometric signals is achieved by reconstructing the frequency bands of the two interferometric signals. This method utilizes time-frequency processing, eliminating the need for hardware auxiliary equipment, effectively controlling the complexity and design cost of the dual-source FSI ranging system. Furthermore, the wavelet synchronous compression algorithm possesses excellent time-frequency resolution performance, effectively overcoming the influence of the measurement environment and noise on the separation of mixed interferometric signals.

[0113] The parts of this invention not described in detail are common knowledge to those skilled in the art.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Obviously, those skilled in the art, after understanding the content and principle of the present invention, may make various modifications and changes in form and detail without departing from the principle and structure of the present invention. However, these modifications and changes based on the concept of the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. An optimization method for a dual-source FSI ranging system based on wavelet synchronous compression transform, characterized in that, Includes the following steps: (1) A dual-source FSI ranging optical path is constructed using two tunable external cavity semiconductor lasers (ECDL), collimators, beam splitters, Fabry-Perot FP etalons, mirrors, Michelson interference optical path and a photodetector placed in the Michelson interference optical path, and a data acquisition device is equipped in the ranging optical path. (2) The first tuned light source S and the second tuned light source S′ with frequency varying with time t are generated by two tunable external cavity semiconductor lasers ECDL in the dual-source FSI ranging optical path, and are output to the collimator respectively. (3) The collimator collimates the first tuned light source S and the second tuned light source S′ respectively. Then, different optical prisms are used to split the collimated first tuned light source S and the second tuned light source S′. Part of the processed light enters the Fabry-Perot FP etalon to generate the FP signal, and the other part continues to propagate forward to form the mixed light S″. (4) The mixed light S″ propagates forward into the Michelson interference path. Before entering the Michelson interference path, it is split into two beams by a beam splitter, namely the reference light S1″ and the measurement light S2″. S1″ and S2″ are reflected by a reflecting prism and then converged and interfered by the beam splitter to obtain the final mixed light S. z ”; (5) The final mixed light S is detected by a photodetector placed in the Michelson interferometer optical path. z "Probes were performed to obtain mixed interference signals;" (6) Use a data acquisition device to synchronously acquire the mixed interference signal in step (5) and the FP signal generated by the Fabry-Perot FP etalon in step (3) to obtain the final mixed interference signal I(t); (7) Construct a signal processing module for signal separation in the ranging system, and input the final mixed interference signal I(t) obtained in step (6) into the module; (8) The signal processing module uses wavelet synchronous compression transform to separate the final mixed interference signal obtained from the acquisition, resulting in two interference signals, namely the first interference signal I1(t) and the second interference signal I2(t). The implementation steps are as follows: (8.1) Perform wavelet transform on the final hybrid interference signal I(t) under the continuous wavelet function ψ(t) to transform it from the time domain form to the frequency domain form W. I (a,t), where a is the scale factor and t is the translation factor; (8.2) The instantaneous frequency ω of the mixed interference signal is obtained according to the following formula. I (a,t): Where i represents the imaginary part, represents the derivative, t represents the time factor, and π represents pi; (8.3) Using synchronous compression, the frequency domain form W of the final mixed interference signal is obtained. I (a,t) is converted to the compressed form T I (ξ,t), that is, its scale factor a is transformed into the frequency component ξ: (8.4) Two time-frequency curves are obtained on the time-frequency surface, showing the frequency change with time factor t. These are the first time-frequency curve T. I (ξ1,t) and the second time-frequency curve T I (ξ2,t), where ξ1 and ξ2 are the frequency components of the two interference signals corresponding to the two time-frequency curves, respectively; (8.5) Using the time-frequency curve T obtained in step (8.4) I (ξ1,t) and T I Two interference signals, I1(t) and I2(t), are reconstructed from (ξ2,t): Where Re(·) denotes taking the real part of the complex number, Let d denote the Fourier transform of the wavelet function ψ(t), and d denote the differential sign; (9) Construct a distance calculation module in the ranging system to calculate the distance. Use this module to obtain the final ranging result based on the reconstructed two interference signals I1(t) and I2(t).

2. The method according to claim 1, characterized in that: In step (1), a dual-source FSI ranging optical path is constructed, wherein there are four beam splitters, namely the first beam splitter BS1, the second beam splitter BS2, the third beam splitter BS3 and the fourth beam splitter BS4; there are two Fabry-Perot FP etalons, namely the first FP etalon and the second FP etalon; the reflectors include the corner bevel prism RR1 and the second corner bevel prism RR2.

3. The method according to claim 2, characterized in that: In step (3), the collimator collimates the first tuned light source S and the second tuned light source S′ respectively. Then, the collimated first tuned light source S is divided into two parts, S1 and S2, by the first beam splitter BS1. The second tuned light source S′ is divided into two parts, S1′ and S2′, by the second beam splitter BS2. S1 and S1′ enter the first FP etalon and the second FP etalon respectively, generating FP signal 1 and FP signal 2. S2 and S2′ continue to propagate forward. After reflection, S2′ mixes with S2 at the third beam splitter BS3 to form mixed light S″.

4. The method according to claim 3, characterized in that: The final ranging result described in step (9) is obtained according to the following steps: (9.1) Place the FP signal 1 and the first interference signal I1(t) under the same time reference, obtain the first optical frequency variation range Δυ1 of a tunable external cavity semiconductor laser ECDL from the FP signal 1, and extract the phase of the first interference signal from I1(t). By placing the FP signal 2 and the second interference signal I2(t) under the same time reference, the second optical frequency variation range Δυ2 of the other tunable external cavity semiconductor laser ECDL is obtained from the FP signal 2, and the phase difference of the second interference signal is obtained by phase extraction of I2(t). (9.2) Δυ1 and Δυ2 and Substituting these values ​​into the FSI ranging formula, we obtain the measured distance values ​​for the two interference signals: Where L1 and L2 are the measured distance values ​​corresponding to the first interference signal I1(t) and the second interference signal I2(t), respectively, c is the speed of light, and n is the air refractive index; (9.3) Average L1 and L2 to obtain the final distance L, which is the final distance measurement result.

5. The method according to claim 1, characterized in that: The frequency domain form W described in step (8.1) I (a,t), its specific form is as follows: in, For the frequency domain representation of the mixed interference signal, Let ψ(t) be the frequency domain representation of the continuous wavelet function, and e be the base of the exponential function.

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