A method and system for multi-physics decoupling of optical interferometry

Abstract

The application discloses a multi-physical field decoupling method and system for optical interference measurement, and belongs to the technical field of optical interference precision measurement. The pressure and temperature load in a deep sea environment can cause multi-physical field coupling, resulting in optical interference phase instability, and existing demodulation means is difficult to high-precision strip environmental error, and it is also not easy to extract a pure phase signal. The application establishes a differential optical path physical decomposition model of multi-physical field coupling, and calculates each error optical path in combination with real-time environmental parameters and pre-calibration material parameters. The absolute physical absorption peak of gas is introduced as a priori constraint to extract the total phase, and after the conversion of the phase and the optical path and the error stripping, the effective target phase is finally obtained. The supporting system is operated by multiple functional modules, and realizes the whole processing flow. The application completes error compensation based on the physical mechanism, and can obtain the phase signal in a complex noise environment, and can adapt to various optical interference measurement devices.

Description

Technical Field

[0001] This invention belongs to the field of optical interferometry precision measurement technology, specifically involving multi-physics field decoupling and error compensation technology in deep-sea in-situ optical interferometry. Background Technology

[0002] The extreme environment of the deep sea poses severe challenges to in-situ optical interferometry. Under strong thermo- and compressive loads, the multiphase heterogeneous interface of the optical interferometer exhibits complex physical responses, leading to severe instability in the interference phase. This instability stems from the dynamic coupling of multiple physical fields, including the elastic-optical effect of the material, elastic deformation, assembly hysteresis, and the dynamic thermal response during the three-phase conjugate heat transfer process. The background phase drift caused by these effects is often much larger than the measured signal itself, severely limiting the measurement accuracy of the optical interferometer in the deep-sea environment.

[0003] Existing demodulation methods are mostly based on simple empirical compensation models or black-box algorithms, lacking in-depth analysis and quantitative description of the thermo-optical coupling mechanism under extreme loads, making it difficult to achieve high-precision error stripping in dynamically changing extreme environments. Furthermore, traditional demodulation models fail to effectively address the nonlinearity caused by assembly hysteresis and the multiphase heterogeneity issues in elastic deformation processes. In the presence of strong background interference and environmental noise, high-fidelity intrinsic location extraction becomes a technical bottleneck limiting instrument performance. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-physics decoupling method and system for optical interferometry, which solves the problem that the interference phase is unstable due to multi-physics coupling in the extreme environment of deep sea, and that existing methods are unable to accurately remove background errors.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a multi-physics field decoupling method for optical interferometry, comprising the following steps: By analyzing the physical response of multiphase heterogeneous interfaces under extreme environments, a differential optical path decomposition model with multi-physics coupling is established. Using real-time acquired environmental parameters and pre-calibrated material parameters, the error terms are quantitatively calculated according to the differential optical path physical decomposition model to obtain the theoretical error optical path lengths of each term. Based on the prior constraint of the absolute physical absorption peak of the gas, the phase of the original interference light intensity signal is extracted to obtain the total phase. The total differential optical path is obtained by converting the total phase. The total differential optical path and the theoretical error optical path of each item are differentially processed to obtain the effective target optical path; The effective target phase is obtained by performing phase conversion based on the effective target optical path.

[0006] In one possible implementation, the step of establishing a multi-physics coupled differential optical path decomposition model by analyzing the physical response of a multiphase heterogeneous interface under extreme conditions includes: Combining the local non-uniform strain tensor and temperature field changes, based on the principle of load superposition and the theory of elasto-optic coefficient, the total differential optical path is decomposed into the sum of elasto-optic effect term, elastic deformation term, assembly hysteresis term, dynamic thermal hysteresis term and effective target term.

[0007] In one possible implementation, the step of using real-time acquired environmental parameters and pre-calibrated material parameters to quantitatively calculate the error terms according to the differential optical path physical decomposition model, and obtaining the theoretical error optical path lengths for each term, includes: By using real-time acquired temperature and pressure data, combined with pre-calibrated material mechanical parameters and elastic-optical coefficients, the error optical path length corresponding to the elastic-optical effect term and the error optical path length corresponding to the elastic deformation term are calculated. Based on the pressure change rate and temperature change rate, combined with the pre-calibrated assembly hysteresis experimental model and thermal hysteresis time constant, the error optical path corresponding to the assembly hysteresis term and the error optical path corresponding to the dynamic thermal hysteresis term are calculated.

[0008] In one possible implementation, the step of performing phase extraction processing on the original interference light intensity signal based on the prior constraint of the absolute physical absorption peak of the gas to obtain the total phase includes: The absolute physical absorption peak of the gas within the spectral range of the light source is introduced as a prior probability constraint to construct a physical constraint predistortion model for the dynamic nonlinear perturbation of the light source. The original interference light intensity signal is corrected using the physical constraint predistortion model to obtain the corrected interference light intensity signal. A generalized phase-locked harmonic model is constructed, and the corrected interference light intensity signal is orthogonally separated to obtain the total phase.

[0009] In one possible implementation, the step of constructing a generalized phase-locked harmonic model and performing orthogonal separation processing on the corrected interference intensity signal to obtain the total phase includes: Using iterative weighted least squares and Hilbert transform techniques, the multiplicative distortion, additive noise, and clean phase carrier in the corrected interference light intensity signal are orthogonally separated to obtain the total phase.

[0010] In one possible implementation, the step of calculating the total differential optical path based on the total phase includes: Using the basic equations of interferometry, combined with the center wavelength of the light source and the number of round trips of the beam, the total phase is converted into the total differential optical path.

[0011] In one possible implementation, the step of performing phase conversion based on the effective target optical path to obtain the effective target phase includes: Using the basic equations of interferometry, combined with the center wavelength of the light source and the number of round trips of the beam, the effective target optical path is converted into the effective target phase.

[0012] In one possible implementation, the real-time acquired environmental parameters include temperature and pressure data in the deep-sea in-situ environment.

[0013] In one possible implementation, the pre-calibrated material parameters include material mechanical parameters, elastic-optical coefficient, thermophysical parameters, assembly hysteresis experimental model parameters, and thermal hysteresis time constant.

[0014] Secondly, the present invention provides a multi-physics decoupling system for optical interferometry, comprising: The physical decomposition modeling module is used to establish a differential optical path physical decomposition model of multi-physics coupling by analyzing the physical response of multiphase heterogeneous interfaces under extreme conditions. The error term calculation module is used to quantitatively calculate the error terms based on the differential optical path physical decomposition model using real-time acquired environmental parameters and pre-calibrated material parameters, and to obtain the theoretical error optical path for each term. The high-fidelity phase extraction module is used to perform phase extraction processing on the original interference light intensity signal based on the prior constraint of the absolute physical absorption peak of the gas to obtain the total phase; The total optical path conversion module is used to perform optical path conversion based on the total phase to obtain the total differential optical path. An error optical path stripping module is used to perform differential processing on the total differential optical path and the theoretical error optical paths of each item to obtain the effective target optical path. The target phase generation module is used to perform phase conversion based on the effective target optical path to obtain the effective target phase.

[0015] Compared with existing technologies, the advantages of this invention are as follows: This invention establishes a differential optical path physical decomposition model with multi-physics coupling, and decomposes the total differential optical path into multiple independent physical mechanism terms based on the load superposition principle and the elastic-optical coefficient theory. Compared with the empirical compensation model or black-box algorithm used in existing technologies, it can quantitatively calculate the error optical path caused by elastic-optical effect, elastic deformation, assembly hysteresis, and dynamic thermal hysteresis, so that error compensation has a clear physical mechanism support, avoids the limitations of manual calibration, and improves the error stripping accuracy under extreme environments.

[0016] This invention introduces the absolute physical absorption peak of the gas as a priori constraint, constructs a generalized phase-locked harmonic model, and employs orthogonal separation technology to process the original interference light intensity signal. Compared with existing phase extraction methods, it can effectively suppress the interference of strong thermo-baric loads on the light source spectrum, achieve the separation of multiplicative distortion, additive noise, and pure phase carrier, extract a high-fidelity total phase signal under complex background noise, and avoid the weak test signal being submerged by background interference.

[0017] The technical solution of this invention has good versatility, and its core multi-physics decoupling and phase extraction mechanism can be applied to various deep-sea in-situ optical precision measurement instruments. Compared with compensation methods developed for single instruments, it can provide a unified error suppression scheme for different types of optical interferometry equipment, reducing the development difficulty of optical measurement systems in extreme environments. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is an overall flowchart of the multi-physics decoupling and error compensation method based on physical mechanisms according to an embodiment of the present invention; Figure 2 This is a block diagram illustrating the multi-physics field load action and signal decoupling logic principle of the optical interferometric measurement probe according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the module architecture of the optical interferometry measurement system according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the cross-sectional structure of a deep-sea exploration probe based on the Michelson interferometer architecture according to an embodiment of the present invention; Figure 5 This is a flowchart illustrating the multi-physics decoupling method for optical interferometry according to an embodiment of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] Example: It should be noted that the terms "comprising" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0022] See Figure 5 This embodiment provides a multi-physics decoupling method for optical interferometry, which includes the following steps: Step 101: By analyzing the physical response of multiphase heterogeneous interfaces under extreme conditions, a differential optical path decomposition model with multi-physics coupling is established.

[0023] Specifically, the extreme environment can be a deep-sea operating environment with high pressure and wide temperature variation; the multiphase heterogeneous interface can be the interface formed between the optical pressure-bearing window and the medium under test; the differential optical path physical decomposition model can be a mathematical model that splits the optical path of multiple physical fields coupled together. For example, the extreme environment is a deep-sea environment with pressure exceeding 100 MPa; the multiphase heterogeneous interface is the contact interface between the sapphire window and seawater.

[0024] The step of establishing a multi-physics coupled differential optical path decomposition model by analyzing the physical response of multiphase heterogeneous interfaces under extreme conditions includes: Combining the local non-uniform strain tensor and temperature field changes, based on the principle of load superposition and the theory of elasto-optic coefficient, the total differential optical path is decomposed into the sum of elasto-optic effect term, elastic deformation term, assembly hysteresis term, dynamic thermal hysteresis term and effective target term.

[0025] Specifically, the local non-uniform strain tensor can be the strain distribution parameter generated by the material under stress at the heterogeneous interface; the temperature field can be the overall temperature distribution state within the detection area; the load superposition principle can be the physical law that multiple external forces can be superimposed and calculated; the elastic-optical coefficient theory can be the relevant theory describing the change of the optical refractive index of the medium by stress; the elastic-optical effect term can be the optical path component corresponding to the change of the refractive index of the medium by high pressure; the elastic deformation term can be the optical path component corresponding to the change of the interface geometry; the assembly hysteresis term can be the optical path component caused by the gap in the structural assembly and the elastic nonlinearity; the dynamic thermal hysteresis term can be the optical path component generated by the heat transfer process; and the effective target term can be the target optical path component corresponding to the medium under test itself. For example, the local non-uniform strain tensor is calculated for the sapphire optical window; the temperature field covers the entire area around the optical probe; the elastic-optical coefficient is calibrated according to the sapphire material properties; and the five components of the total differential optical path correspond to different sources of physical interference.

[0026] Step 102: Using real-time acquired environmental parameters and pre-calibrated material parameters, the error terms are quantitatively calculated according to the differential optical path physical decomposition model to obtain the theoretical error optical path lengths of each term.

[0027] Specifically, environmental parameters can be temperature and pressure data monitored in real time on site; material parameters can be material physical performance parameters calibrated in advance; and theoretical error optical path can be the optical path deviation value corresponding to various interference factors.

[0028] The step of using real-time acquired environmental parameters and pre-calibrated material parameters to quantitatively calculate the error terms according to the differential optical path physical decomposition model, and obtaining the theoretical error optical path lengths, includes: By using real-time acquired temperature and pressure data, combined with pre-calibrated material mechanical parameters and elastic-optical coefficients, the error optical path length corresponding to the elastic-optical effect term and the error optical path length corresponding to the elastic deformation term are calculated. Based on the pressure change rate and temperature change rate, combined with the pre-calibrated assembly hysteresis experimental model and thermal hysteresis time constant, the error optical path corresponding to the assembly hysteresis term and the error optical path corresponding to the dynamic thermal hysteresis term are calculated.

[0029] Specifically, temperature data can be real-time temperature values ​​monitored around the probe; pressure data can be real-time pressure values ​​of the environment where the probe is located; material mechanical parameters can be physical indicators such as the material's elastic modulus and deformation parameters; the elastic-optical coefficient can be a characteristic parameter characterizing the effect of stress on the refractive index; the pressure change rate can be the change in ambient pressure per unit time; the temperature change rate can be the change in ambient temperature per unit time; the assembly hysteresis experimental model can be a pre-fitted assembly gap response model; and the thermal hysteresis time constant can be a characteristic value characterizing the heat transfer hysteresis properties. For example, the acquisition frequency of temperature and pressure data is set to 10Hz; the material mechanical parameters and elastic-optical coefficient are pre-calibrated under different temperature and pressure conditions; the assembly hysteresis experimental model is obtained based on pressure cycle tests; and the thermal hysteresis time constant is calibrated according to the heat transfer characteristics of the medium.

[0030] The environmental parameters collected in real time include temperature and pressure data in the deep-sea in-situ environment. Specifically, the deep-sea in-situ environment can be the actual deep-sea operating area where the detection equipment is deployed; the temperature data can be the real-time temperature value of the entire area around the detection probe; and the pressure data can be the deep-sea hydrostatic pressure value acting on the optical pressure window.

[0031] The pre-calibrated material parameters include material mechanical parameters, elastic-optical coefficients, thermophysical parameters, assembly hysteresis experimental model parameters, and thermal hysteresis time constant. Specifically, material mechanical parameters can be physical indices characterizing the mechanical properties of the component; elastic-optical coefficients can be characteristic parameters describing the change in refractive index of the medium due to stress; thermophysical parameters can be physical indices characterizing the heat transfer capacity of the material; assembly hysteresis experimental model parameters can be model coefficients obtained by fitting the nonlinear response of the assembly gap of the structure; and the thermal hysteresis time constant can be a characteristic value characterizing the three-phase conjugate heat transfer hysteresis characteristics.

[0032] Step 103: Based on the prior constraint of the absolute physical absorption peak of the gas, the phase of the original interference light intensity signal is extracted to obtain the total phase.

[0033] Specifically, the absolute physical absorption peak of a gas can be a fixed absorption characteristic position of a specific gas in the spectrum; the prior constraint can be a known physical condition introduced; the original interference intensity signal can be the initial interference waveform signal acquired by the instrument; and the total phase can be the overall interference phase after superimposing various interferences. For example, HF or HCN gases can be selected as the medium providing the absorption peak.

[0034] The step of performing phase extraction processing on the original interference light intensity signal to obtain the total phase based on the prior constraint of the absolute physical absorption peak of the gas includes: The absolute physical absorption peak of the gas within the spectral range of the light source is introduced as a prior probability constraint to construct a physical constraint predistortion model for the dynamic nonlinear perturbation of the light source. The original interference light intensity signal is corrected using the physical constraint predistortion model to obtain the corrected interference light intensity signal. A generalized phase-locked harmonic model is constructed, and the corrected interference light intensity signal is orthogonally separated to obtain the total phase.

[0035] Specifically, the absolute physical absorption peak of a gas can be a characteristic absorption signal formed by a specific gas at a fixed spectral position; the prior probability constraint can be a judgment condition established based on known physical characteristics; the physical constraint predistortion model can be a mathematical model used to compensate for spectral distortion of the light source; the original interference intensity signal can be an unprocessed interference waveform signal directly acquired by the equipment; the corrected interference intensity signal can be an interference waveform signal after eliminating light source disturbances; the generalized phase-locked harmonic model can be a harmonic analysis model for analyzing interference signals; and orthogonal separation processing can be a computational method for splitting different components of the signal. For example, HF or HCN gas can be selected to provide the absolute physical absorption peak; the spectral range of the light source covers the near-infrared band; and the physical constraint predistortion model is used to compensate for the spectral shift of the light source caused by deep-sea temperature and pressure loads.

[0036] Furthermore, the step of constructing a generalized phase-locked harmonic model and performing orthogonal separation processing on the corrected interference light intensity signal to obtain the total phase includes: Using iterative weighted least squares and Hilbert transform techniques, the multiplicative distortion, additive noise, and clean phase carrier in the corrected interference light intensity signal are orthogonally separated to obtain the total phase.

[0037] Specifically, iterative weighted least squares can be a numerical calculation method for signal fitting and error optimization; Hilbert transform can be a mathematical transformation method for analyzing signal phase characteristics; multiplicative distortion can be the signal amplitude interference component caused by light source fluctuations; additive noise can be the background interference component formed by environmental clutter; and clean phase carrier can be the basic signal component carrying phase information. For example, the number of iterations in iterative weighted least squares is set to 20; Hilbert transform is used to extract instantaneous phase characteristics of the signal; multiplicative distortion mainly comes from light source intensity fluctuations, and additive noise mainly comes from electromagnetic interference in the deep-sea environment.

[0038] Step 104: Perform optical path conversion based on the total phase to obtain the total differential optical path.

[0039] Specifically, optical path conversion can be a numerical conversion operation between phase and optical path; total differential optical path can be the total optical path value obtained by the instrument.

[0040] The step of calculating the total differential optical path based on the total phase includes: Using the basic equations of interferometry, combined with the center wavelength of the light source and the number of round trips of the beam, the total phase is converted into the total differential optical path.

[0041] Specifically, the basic equation of interferometry can be a standard optical calculation formula for realizing the mutual conversion between phase and optical path; the center wavelength of the light source can be the characteristic operating wavelength of the interferometric light source; the number of round trips of the beam can be the number of times the light propagates back and forth inside the interference structure; the optical path conversion can be a numerical conversion operation between the phase parameter and the optical path parameter; the total differential optical path can be the overall optical path value that includes various interference components.

[0042] Step 105: Perform differential processing on the total differential optical path and the theoretical error optical path of each item to obtain the effective target optical path.

[0043] Specifically, the effective target optical path can be the optical path that reflects only the medium under test after eliminating interference.

[0044] Step 106: Perform phase conversion based on the effective target optical path to obtain the effective target phase.

[0045] Specifically, the effective target phase can be the pure interference phase that is ultimately used for analysis.

[0046] The step of performing phase conversion based on the effective target optical path to obtain the effective target phase includes: Using the basic equations of interferometry, combined with the center wavelength of the light source and the number of round trips of the beam, the effective target optical path is converted into the effective target phase.

[0047] Specifically, the basic equation of interferometry can be an optical calculation formula for realizing the mutual conversion between optical path and phase; the center wavelength of the light source can be the standard operating wavelength of the interferometric light source; the number of round trips of the beam can be the number of times the light propagates back and forth inside the interference structure; the effective target optical path can be the optical path that reflects only the medium under test after eliminating various interferences; and the effective target phase can be the pure interferometric phase that is finally used for the analysis of medium parameters.

[0048] See Figure 3 Based on the same inventive concept, this embodiment also provides a multi-physics decoupling system for optical interferometry, comprising: The physical decomposition modeling module is used to establish a differential optical path physical decomposition model of multi-physics coupling by analyzing the physical response of multiphase heterogeneous interfaces under extreme conditions. The error term calculation module is used to quantitatively calculate the error terms based on the differential optical path physical decomposition model using real-time acquired environmental parameters and pre-calibrated material parameters, and to obtain the theoretical error optical path for each term. The high-fidelity phase extraction module is used to perform phase extraction processing on the original interference light intensity signal based on the prior constraint of the absolute physical absorption peak of the gas to obtain the total phase; The total optical path conversion module is used to perform optical path conversion based on the total phase to obtain the total differential optical path. An error optical path stripping module is used to perform differential processing on the total differential optical path and the theoretical error optical paths of each item to obtain the effective target optical path. The target phase generation module is used to perform phase conversion based on the effective target optical path to obtain the effective target phase.

[0049] Since this device corresponds to the multi-physics field decoupling method of optical interferometry in this embodiment of the invention, and the principle of this device in solving the problem is similar to that of this method, the implementation of this device can refer to the implementation process of the above method embodiment, and repeated parts will not be described again.

[0050] This implementation method is applied to in-situ optical interferometry precision measurement in the deep sea. The overall process of this method is as follows: Figure 1 As shown, error compensation for optical interferometry under extreme environments is achieved through a process involving establishing a physical decomposition model, quantitatively calculating error terms, extracting high-fidelity positions, and decoupling multiple fields. The multi-physics field loading effect and signal decoupling logic principle of the optical interferometry probe are as follows: Figure 2 As shown, the optical pressure-bearing window of the measuring arm directly bears the external pressure and ambient temperature loads, resulting in aliasing of various background errors in the measurement signal.

[0051] First, the physical response of a multiphase heterogeneous interface under extreme conditions is analyzed, and a multi-physics coupled differential optical path decomposition model is established. For the multiphase heterogeneous interface under extreme conditions, combining the local non-uniform strain tensor and temperature field changes, based on the principle of load superposition and the theory of elastic-optical coefficients, the total differential optical path of the interferometer is decomposed into the sum of multiple independent physical mechanism terms. The expression for the total differential optical path is as follows:

[0052] In the formula, This is the elasto-optical effect term due to the change in the refractive index of the medium in the optical pressure-bearing window caused by high-pressure stress. This is the elastic deformation term resulting from the change in the geometric cavity length of the heterogeneous interface due to high pressure. This is the stress-strain assembly hysteresis term caused by the elastic nonlinearity of materials and the clearance of mechanical assembly fits. This is the dynamic thermal hysteresis term caused by three-phase conjugate heat transfer. The effective target items are those caused by changes in the physical parameters of the medium under test.

[0053] Using real-time acquired environmental parameters and pre-calibrated material parameters, the error terms are quantitatively calculated based on the differential optical path decomposition model to obtain the theoretical optical path errors for each term. The real-time acquired environmental parameters include temperature and pressure data from the deep-sea in-situ environment. The pre-calibrated material parameters include material mechanical parameters, elastic-optical coefficients, thermophysical parameters, assembly hysteresis experimental model parameters, and thermal hysteresis time constant. Using the real-time acquired temperature and pressure data, combined with the pre-calibrated material mechanical parameters and elastic-optical coefficients, the error optical path corresponding to the elastic-optical effect term and the error optical path corresponding to the elastic deformation term are calculated. Based on the pressure change rate and temperature change rate, combined with the pre-calibrated assembly hysteresis experimental model and thermal hysteresis time constant, the error optical path corresponding to the assembly hysteresis term and the error optical path corresponding to the dynamic thermal hysteresis term are calculated.

[0054] Based on the prior constraint of the absolute physical absorption peak of the gas, the phase of the original interference light intensity signal is extracted to obtain the total phase. The absolute physical absorption peak of the gas within the spectral range of the light source is introduced as a prior probability constraint to construct a physical constraint predistortion model for the dynamic nonlinear perturbation of the light source. The original interference light intensity signal is corrected using the physical constraint predistortion model to obtain the corrected interference light intensity signal. A generalized phase-locked harmonic model is constructed, and the corrected interference light intensity signal is orthogonally separated to obtain the total phase. The expression of the generalized phase-locked harmonic model is as follows:

[0055] In the formula, This represents the original interference light intensity signal acquired at time t; Represents the multiplicative distortion component of the signal; This represents the total phase extracted at time t; This represents the additive noise component of the signal.

[0056] By using iterative weighted least squares and Hilbert transform techniques, multiplicative distortion, additive noise and clean phase carrier in the corrected interference light intensity signal are orthogonally separated to obtain the total phase.

[0057] The total differential optical path is obtained by converting the total phase. Using the fundamental equations of interferometry, combined with the center wavelength of the light source and the number of round trips of the beam, the total phase is converted into the total differential optical path. The conversion formula for the total differential optical path is as follows:

[0058] In the formula, This represents the total phase obtained from the extraction; Let m be the center wavelength, and m be the number of round trips of the beam in the Michelson structure, which is taken as m=2; This represents the total differential optical path after conversion.

[0059] The effective target optical path is obtained by differential processing of the total differential optical path and the sum of the calculated theoretical error optical paths. Then, the effective target optical path is obtained by subtracting the sum of the theoretical error optical paths from the converted total observed optical path and removing environmental interference. The formula for calculating the effective target optical path is as follows:

[0060] In the formula, This represents the effective target differential optical path after stripping errors.

[0061] The effective target phase is obtained by phase conversion based on the effective target optical path length. Using the fundamental equations of interferometry, combined with the center wavelength of the light source and the number of round trips of the beam, the effective target optical path length is converted into the effective target phase. The formula for calculating the effective target phase is as follows:

[0062] In the formula, This represents the effective target phase in the final solution.

[0063] The following section uses the multiphysics decoupling and error compensation of a deep-sea in-situ density meter as an example to describe this implementation method in detail. The cross-sectional structure of the deep-sea probe based on the Michelson interferometry architecture is shown below. Figure 4 As shown.

[0064] from Figure 4As can be seen, the incident signal enters from the left side of the probe and enters the beam splitting coupling assembly. The beam splitting coupling assembly splits the incident signal into two paths, which are transmitted to the reference arm and the measuring arm respectively. The reference arm, along the optical path, sequentially includes an optical pressure-bearing window, a reference fluid, an optical path compensation cavity, and a reflector. The incident signal passes through the optical pressure-bearing window into the reference fluid, passes through the optical path compensation cavity, reaches the reflector, and is reflected back to the beam splitting coupling assembly along the original path. The reference arm employs a cascaded structure of the reference fluid and the optical path compensation cavity, enabling precise optical path matching and suppressing thermal drift. The measuring arm is arranged parallel to the reference arm, with an optical pressure-bearing window, a measuring fluid, and a reflector sequentially arranged along the optical path. The incident signal passes through the optical pressure-bearing window into the measuring fluid, is reflected by the reflector at the end of the measuring fluid, and is reflected back to the beam splitting coupling assembly along the original path. The optical pressure-bearing window of the measuring arm is in direct contact with the external measured medium, bearing the multi-physics cross-linking load caused by external water pressure and ambient temperature. An O-ring is installed between the stainless steel shell and the optical pressure-bearing window to achieve a sealed connection and prevent external media from entering the probe.

[0065] In terms of hardware design, the system probe consists of a reference arm and a measurement arm connected by a beam-splitting coupling assembly. The end of the measurement arm features an optical pressure-bearing window, allowing the internal optical path to contact the external sample and withstand the multi-physics cross-linking loads caused by external pressure and ambient temperature. The optical pressure-bearing window is made of sapphire material to withstand the high pressure of the deep sea, forming a heterogeneous interface between the sapphire window and the seawater being measured. The reference arm employs a cascaded design of a reference fluid and an optical path compensation cavity to achieve precise optical path matching and suppress thermal drift. A sealed structure is used between the stainless steel shell, the measurement fluid cavity, and the sapphire window. The signal processing unit in the back-end hardware utilizes a high-performance FPGA chip.

[0066] In terms of software processing, the elasto-optic coefficient and elastic modulus of sapphire material under different temperatures and pressures are pre-calibrated, as well as the assembly hysteresis experimental model and thermal hysteresis time constant of the assembly under pressure cycling. During deep-sea deployment, the signal processing unit collects data from the temperature sensor network, pressure sensor data, and the original interference signal contaminated by noise, which is acquired through FPGA driving. The software processing unit runs a pre-loaded multi-physics coupled differential optical path physical decomposition analytical model, inputs measured local temperature field and pressure data, and reconstructs the elasto-optic effect optical path and elastic deformation optical path caused by pure temperature and pressure loads. Based on the pre-calibrated experimental calibration model, combined with the pressure change rate and temperature change rate, the differential optical path caused by dynamic assembly hysteresis and dynamic thermal hysteresis is calculated. The phase extraction subroutine inside the FPGA uses the physical absorption peak of the reference gas to correct the harmonic model generated by the FPGA in real time, suppressing light source jitter, and then uses Hilbert transform and iterative weighted least squares operator to orthogonally separate noise and multiplicative distortion in the original signal to extract the total phase. The overall processing program converts the extracted total phase into the total differential optical path, and then, according to the physical decomposition equation, removes all error optical path terms, finally extracting the effective target phase with multi-physics decoupling and error compensation, thereby obtaining a high-fidelity effective phase residual that has removed temperature and pressure stress errors.

[0067] This method can be applied to various precision optical interferometers that face phase instability problems caused by high pressure and temperature variations, such as deep-sea density meters, deep-sea optical refractometers, and online monitoring of extreme high-pressure reactors.

[0068] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0069] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A multi-physics decoupling method for optical interferometry, characterized in that, Includes the following steps: By analyzing the physical response of multiphase heterogeneous interfaces under extreme conditions, a differential optical path physical decomposition model coupled with multiple physics fields is established. Specifically, it includes: combining the local non-uniform strain tensor and temperature field changes, and based on the load superposition principle and the elastic-optical coefficient theory, the total differential optical path is decomposed into the sum of elastic-optical effect term, elastic deformation term, assembly hysteresis term, dynamic thermal hysteresis term and effective target term. Using real-time acquired environmental parameters and pre-calibrated material parameters, the error terms are quantitatively calculated according to the differential optical path physical decomposition model to obtain the theoretical error optical path lengths for each term. Specifically, this includes: using real-time acquired temperature and pressure data, combined with pre-calibrated material mechanical parameters and elastic-optical coefficients, calculating the error optical path lengths corresponding to the elastic-optical effect term and the elastic deformation term; and using the pressure change rate and temperature change rate, combined with the pre-calibrated assembly hysteresis experimental model and thermal hysteresis time constant, calculating the error optical path lengths corresponding to the assembly hysteresis term and the dynamic thermal hysteresis term. Based on the prior constraint of the absolute physical absorption peak of the gas, the phase extraction processing of the original interference light intensity signal is performed to obtain the total phase. Specifically, this includes: introducing the absolute physical absorption peak of the gas within the spectral range of the light source as a prior probability constraint to construct a physical constraint predistortion model for the dynamic nonlinear perturbation of the light source; using the physical constraint predistortion model to correct the original interference light intensity signal to obtain the corrected interference light intensity signal; constructing a generalized phase-locked harmonic model to perform orthogonal separation processing on the corrected interference light intensity signal to obtain the total phase. Specifically, iterative weighted least squares and Hilbert transform techniques are used to orthogonally separate the multiplicative distortion, additive noise, and clean phase carrier in the corrected interference light intensity signal to obtain the total phase. The total differential optical path is obtained by converting the total phase. The total differential optical path and the theoretical error optical path of each item are differentially processed to obtain the effective target optical path; The effective target phase is obtained by performing phase conversion based on the effective target optical path.

2. The multi-physics decoupling method for optical interferometry according to claim 1, characterized in that, The step of calculating the total differential optical path based on the total phase includes: Using the basic equations of interferometry, combined with the center wavelength of the light source and the number of round trips of the beam, the total phase is converted into the total differential optical path.

3. The multi-physics decoupling method for optical interferometry according to claim 1, characterized in that, The step of performing phase conversion based on the effective target optical path to obtain the effective target phase includes: Using the basic equations of interferometry, combined with the center wavelength of the light source and the number of round trips of the beam, the effective target optical path is converted into the effective target phase.

4. The multi-physics decoupling method for optical interferometry according to claim 1, characterized in that, The real-time collected environmental parameters include temperature and pressure data in the deep-sea in-situ environment.

5. The multi-physics decoupling method for optical interferometry according to claim 1, characterized in that, The pre-calibrated material parameters include material mechanical parameters, elastic coefficient, thermophysical parameters, assembly hysteresis experimental model parameters, and thermal hysteresis time constant.

6. A multi-physics decoupling system for optical interferometry, characterized in that, include: The physical decomposition modeling module is used to establish a multi-physics field coupled differential optical path physical decomposition model by analyzing the physical response of multiphase heterogeneous interfaces under extreme environments. Specifically, it includes: combining the local non-uniform strain tensor and temperature field changes, and based on the load superposition principle and the elastic-optical coefficient theory, decomposing the total differential optical path into the sum of elastic-optical effect term, elastic deformation term, assembly hysteresis term, dynamic thermal hysteresis term and effective target term. The error term calculation module is used to quantitatively calculate the error terms based on the differential optical path physical decomposition model using real-time acquired environmental parameters and pre-calibrated material parameters, to obtain the theoretical error optical path lengths for each term. Specifically, it includes: using real-time acquired temperature and pressure data, combined with pre-calibrated material mechanical parameters and elastic-optical coefficients, to calculate the error optical path lengths corresponding to the elastic-optical effect term and the elastic deformation term; and using the pressure change rate and temperature change rate, combined with the pre-calibrated assembly hysteresis experimental model and thermal hysteresis time constant, to calculate the error optical path lengths corresponding to the assembly hysteresis term and the dynamic thermal hysteresis term. The high-fidelity phase extraction module is used to perform phase extraction processing on the original interference light intensity signal based on the prior constraint of the absolute physical absorption peak of the gas to obtain the total phase. Specifically, it includes: introducing the absolute physical absorption peak of the gas in the spectral range of the light source as a prior probability constraint to construct a physical constraint predistortion model of the dynamic nonlinear perturbation of the light source; using the physical constraint predistortion model to correct the original interference light intensity signal to obtain the corrected interference light intensity signal; constructing a generalized phase-locked harmonic model to perform orthogonal separation processing on the corrected interference light intensity signal to obtain the total phase. Among them, iterative weighted least squares technique and Hilbert transform technique are used to orthogonally separate the multiplicative distortion, additive noise and pure phase carrier in the corrected interference light intensity signal to obtain the total phase. The total optical path conversion module is used to perform optical path conversion based on the total phase to obtain the total differential optical path. An error optical path stripping module is used to perform differential processing on the total differential optical path and the theoretical error optical paths of each item to obtain the effective target optical path. The target phase generation module is used to perform phase conversion based on the effective target optical path to obtain the effective target phase.

Images