SPMI dynamic range expansion method and system based on in-phase component signal reconstruction

Abstract

The invention provides an SPMI dynamic range expansion method and system based on in-phase component signal reconstruction, and relates to the technical field of data processing, and the method comprises the steps: obtaining an interference optical signal; converting the interference optical signal into an electric signal through a photoelectric detector to obtain an interference signal; performing phase demodulation on the measurement interference signal through a PGC algorithm, and extracting an in-phase component and an orthogonal component; performing normalization processing on the in-phase component and the orthogonal component; through carrier phase delay compensation and carrier phase modulation depth control, extracting a non-loss quadrature component signal in the normalized quadrature component; reconstructing a distorted in-phase component signal according to the non-loss real quadrature component signal; carrying out normalization processing on the non-loss real quadrature component signal and the reconstructed in-phase component signal; and demodulating the vibration range of the measurement light path through a DCM algorithm according to the normalized real quadrature component signal and the reconstructed in-phase component signal.

Description

Technical Field

[0001] The present invention relates to the technical field of data processing, and in particular to a SPMI dynamic range expansion method and system based on in-phase component signal reconstruction. Background Art

[0002] In recent years, sinusoidal phase modulated laser interferometer (SPMI) has attracted wide attention in the fields of absolute distance measurement, precision vibration measurement and surface topography recovery due to its simple structure, high sensitivity and good noise characteristics. SPMI's high-precision measurement makes it increasingly important in scientific research and industrial applications. Phase generated carrier (PGC) technology plays an important role in SPMI phase demodulation due to its superior demodulation dynamic range and linearity, and is widely used in various high-precision measurement occasions.

[0003] There are existing methods for dynamic range expansion. One is to adjust the compensation phase on the carrier to synchronize the carrier with the measured interference signal, so that SPMI can achieve nanometer-level displacement measurement accuracy. The other is the PGC improved algorithm, which performs elliptical parameter fitting on non-ideal orthogonal signal pairs to eliminate the influence of nonlinear factors. Both existing methods can achieve dynamic range expansion.

[0004] However, existing dynamic range expansion methods often find it difficult to ensure the accuracy of demodulation results in the case of spectrum aliasing, resulting in low measurement stability. At the same time, the dynamic range of the system is usually restricted by the aliasing of the measured interference signal spectrum, making it difficult to achieve effective range expansion. Summary of the invention

[0005] In order to solve the technical problems that the existing dynamic range expansion methods are often difficult to ensure the accuracy of demodulation results in the case of spectrum aliasing, resulting in low measurement stability; at the same time, the dynamic range of the system is usually restricted by the aliasing of the spectrum of the measured interference signal, making it difficult to achieve effective range expansion, the present invention provides an SPMI dynamic range expansion method and system based on reconstruction of the in-phase component signal.

[0006] The technical solution provided by the embodiment of the present invention is as follows:

[0007] First aspect:

[0008] An embodiment of the present invention provides an SPMI dynamic range extension method based on in-phase component signal reconstruction, comprising:

[0009] S1: Obtain interference light signal;

[0010] S2: converting the interference light signal into an electrical signal through a photoelectric detector to obtain an interference signal, wherein the interference signal includes a measurement interference signal and a reference interference signal;

[0011] S3: performing phase demodulation on the measurement interference signal by using a PGC algorithm to extract an orthogonal signal pair of the measurement interference signal, wherein the orthogonal signal pair includes an in-phase component and an orthogonal component;

[0012] S4: performing normalization processing on the orthogonal signal pair by using an ellipse fitting algorithm;

[0013] S5: extracting the true-loss quadrature component signal from the normalized orthogonal signal pair by compensating for carrier phase delay and controlling carrier phase modulation depth;

[0014] S6: Calculate the ratio of the major and minor axes of the ellipse based on the reference interference signal, and reconstruct the distorted in-phase component signal in combination with the undistorted cross-component signal to obtain a reconstructed in-phase component signal;

[0015] S7: normalizing the undistorted quadrature component signal and the reconstructed in-phase component signal;

[0016] S8: According to the normalized non-lossy quadrature component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated through the DCM algorithm.

[0017] Second aspect:

[0018] An embodiment of the present invention provides an SPMI dynamic range extension system based on in-phase component signal reconstruction, comprising:

[0019] processor;

[0020] A memory having computer-readable instructions stored thereon, wherein when the computer-readable instructions are executed by the processor, the SPMI dynamic range extension method based on in-phase component signal reconstruction as described in the first aspect is implemented.

[0021] The third aspect:

[0022] An embodiment of the present invention provides a computer-readable storage medium on which a computer program is stored. When the program is executed by a processor, the SPMI dynamic range extension method based on in-phase component signal reconstruction as described in the first aspect is implemented.

[0023] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0024] (1) In the present invention, by compensating for carrier phase delay and controlling the carrier phase modulation depth, the lossless quadrature component signal in the normalized orthogonal component is extracted, the ratio of the major and minor axes of the ellipse is calculated based on the reference interference signal, and the distorted in-phase component signal is reconstructed in combination with the lossless quadrature component signal to obtain a reconstructed in-phase component signal. The accuracy of the demodulation result in the case of spectrum aliasing is improved, thereby improving the stability of the measurement.

[0025] (2) In the present invention, the ratio of the major and minor axes of the ellipse is calculated based on the reference interference signal, and the distorted in-phase component signal is reconstructed in combination with the true-loss quadrature component signal to obtain a reconstructed in-phase component signal, and the true-loss quadrature component signal and the reconstructed in-phase component signal are normalized. According to the normalized true-loss quadrature component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated through the DCM algorithm. The dynamic range of the system is reduced by the spectral aliasing of the measurement interference signal, and the dynamic range can be effectively expanded. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 A flow chart of a SPMI dynamic range extension method based on in-phase component signal reconstruction provided by an embodiment of the present invention;

[0028] Figure 2 A schematic structural diagram of an SPMI dynamic range extension system based on in-phase component signal reconstruction provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0030] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations or explanations. Any embodiment or design described as "example" in the present invention should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of the word "example" is intended to present the concept in a specific way. In addition, in the embodiments of the present invention, the meaning expressed by "and / or" can be both, or it can be either of the two.

[0031] In the embodiments of the present invention, "image" and "picture" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they intend to express are the same. "of", "corresponding, relevant" and "corresponding" can sometimes be used interchangeably. It should be noted that when the difference between them is not emphasized, the meanings they intend to express are the same.

[0032] In the embodiments of the present invention, sometimes a subscript such as W1 may be mistakenly written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are consistent.

[0033] In order to make the technical problems, technical solutions and advantages to be solved by the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0034] Reference Manual Attached Figure 1 , shows a flow chart of an SPMI dynamic range extension method based on in-phase component signal reconstruction provided by an embodiment of the present invention.

[0035] The embodiment of the present invention provides an SPMI dynamic range extension method based on in-phase component signal reconstruction, which can be implemented by an SPMI dynamic range extension device based on in-phase component signal reconstruction, and the SPMI dynamic range extension device based on in-phase component signal reconstruction can be a terminal or a server. The processing flow of the SPMI dynamic range extension method based on in-phase component signal reconstruction can include the following steps:

[0036] S1: Obtain interference light signal.

[0037] Specifically, the frequency-stabilized laser emitted by the helium-neon laser passes through a linear polarizer to obtain a beam of linearly polarized light, which is then divided into two beams, measurement light and reference light, through a beam splitter. The transmitted light is the measurement light, and the optical path where the measurement light is located is composed of a corner cube prism mounted on a vibration platform, wherein the corner cube prism is driven by the vibration platform to achieve vibrations of small amplitude; the reflected light is the reference light, and after phase modulation and reflection from the corner cube prism, the reference light interferes with the measurement light reflected from the corner cube prism at the beam splitter to form an interference light signal.

[0038] S2: Convert the interference light signal into an electrical signal through a photoelectric detector to obtain an interference signal, wherein the interference signal includes a measurement interference signal and a reference interference signal.

[0039] Among them, a photodetector is a device that converts light signals into electrical signals and is widely used in optical communications, optical measurement and imaging systems. It can detect the intensity of light and generate corresponding electrical signals for subsequent processing and analysis.

[0040] In a possible implementation manner, the expression for measuring the interference signal in S2 is specifically:

[0041]

[0042] Where S(t) represents the measured interference signal, I1 represents the DC bias of the measured interference signal, I0 represents the fringe contrast of the measured interference signal, C represents the carrier phase modulation depth, θ c represents the carrier phase delay, represents the phase to be demodulated, d(t) represents the vibration of the corner cube, λ represents the wavelength of the laser, represents the initial phase caused by the initial optical path difference between the measurement arm and the reference arm, ω c Indicates the carrier frequency of the phase modulation.

[0043] In the present invention, given the expression of the measured interference signal, the role of each parameter can be clarified. This helps to make precise adjustments during experimental design and data processing, and optimize system performance. At the same time, various filtering and noise suppression techniques can be applied in the processing of electrical signals, but it is difficult to process optical signals, especially when the signal is very weak. Therefore, the interference optical signal is converted into an electrical signal to facilitate subsequent processing.

[0044] S3: Phase demodulate the measurement interference signal through the PGC algorithm to extract an orthogonal signal pair of the measurement interference signal, where the orthogonal signal pair includes an in-phase component and an orthogonal component.

[0045] Among them, the PGC algorithm (Phase Gradient Compensation Algorithm) is an algorithm for phase demodulation, which is particularly suitable for processing phase information in optical interference signals. It is mainly used to extract useful phase information from interference signals with carriers. The PGC algorithm can effectively compensate and demodulate the phase information in the signal by processing the phase gradient.

[0046] In a possible implementation, S3 specifically includes:

[0047] S301: Expand the expression of the measured interference signal using the first kind of Bessel identity combined with the trigonometric function formula:

[0048]

[0049] Where J0 represents the zero-order first-kind Bessel function, J 2k represents an even-order Bessel function of the first kind, J 2k+1 represents an odd-order Bessel function of the first kind.

[0050] Among them, Bessel's First Kind Identities are mathematical equations involving Bessel functions, which are a special type of functions often used to solve problems with circular symmetry.

[0051] S302: Mix the measurement interference signal with the first harmonic and the second harmonic of the carrier.

[0052] In the present invention, the measurement interference signal is mixed with the first harmonic and the second harmonic of the carrier, so that the high-frequency components in the signal spectrum can be moved to the low-frequency range, which makes it easier to extract and analyze the signal phase information.

[0053] S303: Filter the mixed measurement interference signal through a low-pass filter to extract the in-phase component and the orthogonal component of the orthogonal signal pair:

[0054]

[0055] Wherein, I(t) represents the in-phase component of the orthogonal signal pair, Q(t) represents the orthogonal component of the orthogonal signal pair, a1 represents the amplitude of the first harmonic of the demodulated carrier, and a2 represents the amplitude of the second harmonic of the demodulated carrier.

[0056] Among them, a low-pass filter (LPF) is an electronic filter that allows low-frequency signals to pass through while suppressing high-frequency signals. It is widely used in signal processing, communication systems, audio processing, and image processing. The main function of a low-pass filter is to remove high-frequency noise or interference from a signal while retaining low-frequency components.

[0057] In the present invention, the PGC algorithm can effectively extract useful phase information from the measurement interference signal containing the carrier, thereby improving the accuracy of phase measurement. At the same time, by using the first-class Bessel identity combined with the trigonometric function formula to expand the measurement interference signal, the signal can be represented as a combination of Bessel functions of different orders. This expansion method helps to decompose the measurement interference signal into simpler components, which is convenient for subsequent mixing and filtering processing.

[0058] S4: normalize the orthogonal signal pair by using an ellipse fitting algorithm.

[0059] Among them, the elliptical fitting algorithm is used to fit an ellipse from given data points. This algorithm is widely used in image processing, computer vision, data analysis and other fields. The goal of elliptical fitting is to find an elliptical shape that best fits the data points so as to model and analyze the data.

[0060] It should be noted that in order to compensate for the influence of the coefficient term, normalization processing is required.

[0061] In a possible implementation manner, S4 is specifically:

[0062] According to the following formula, the in-phase component and the orthogonal component are normalized by the ellipse fitting algorithm:

[0063]

[0064] a=-α2I1J2(C)cos(2θ c )

[0065] b=-α1I1J1(C)cos(θ c )

[0066] Among them, I N (t) represents the normalized in-phase component, Q N (t) represents the normalized orthogonal component, I(t) represents the in-phase component of the orthogonal signal pair, Q(t) represents the orthogonal component of the orthogonal signal pair, a represents the major semi-axis of the fitted ellipse, b represents the minor semi-axis of the fitted ellipse, I1 represents the DC bias of the measured interference signal, a1 represents the amplitude of the first harmonic of the demodulated carrier, a2 represents the amplitude of the second harmonic of the demodulated carrier, J1() represents the odd-order first-kind Bessel function, and J2() represents the even-order first-kind Bessel function.

[0067] In the present invention, the normalization process can effectively compensate for the system error or deviation introduced by factors such as DC bias, carrier harmonic amplitude and Bessel function. This compensation makes the final in-phase component and orthogonal component unaffected by these additional coefficient terms and more accurately reflects the true characteristics of the signal. At the same time, normalization through the ellipse fitting algorithm can adjust the in-phase component and the orthogonal component to a unified scale, which helps to simplify the subsequent processing steps.

[0068] S5: extracting the true-loss orthogonal component signal from the normalized orthogonal signal pair by compensating for carrier phase delay and controlling carrier phase modulation depth.

[0069] Among them, Carrier Phase Delay Compensation is a technology used in signal processing to correct or compensate for signal distortion caused by carrier phase delay. This technology is widely used in communication systems, radar systems and interferometric measurement systems to improve system accuracy and performance.

[0070] Among them, Carrier Phase Modulation Depth refers to the amplitude of the phase change of the carrier signal in the phase modulation (PM) system. Phase modulation is a modulation technique that transmits information by changing the phase of the carrier signal. The modulation depth describes the amplitude or strength of this phase change.

[0071] In a possible implementation, S5 specifically includes:

[0072] S501: Determine that the MQ(t) measurement interference signal after the measurement interference signal is mixed with the first harmonic of the carrier is:

[0073] MQ(t)=α1S(t)cos(ω c t)

[0074] Wherein, MQ(t) represents the signal after the measured interference signal is mixed with the first harmonic of the carrier, a1 represents the amplitude of the first harmonic of the demodulated carrier, S(t) represents the measured interference signal, ω c Indicates the carrier frequency of the phase modulation.

[0075] S502: Expand the baseband signal MQ0(t) and the first harmonic frequency band signal MQ1(t) of MQ(t) to obtain the expansion formula of the baseband signal and the first harmonic frequency band signal:

[0076]

[0077] Where MQ0(t) represents the baseband signal of MQ(t), I1 represents the DC bias of the measured interference signal, a1 represents the amplitude of the first harmonic of the demodulated carrier, C represents the carrier phase modulation depth, θ c represents the carrier phase delay, represents the initial phase caused by the initial optical path difference between the measurement arm and the reference arm, J0 represents the zero-order first-kind Bessel function, and J 2k represents an even-order Bessel function of the first kind, J 2k+1 represents the odd-order Bessel function of the first kind, ω d Indicates that A d It represents the amplitude of the vibration of the target being measured, and λ represents the wavelength of the laser.

[0078] It should be noted that the baseband signal MQ0(t) and the first harmonic frequency band signal MQ1(t) of MQ(t) are expanded to obtain the expanded expressions of the baseband signal and the first harmonic frequency band signal MQ1(t). It is necessary to combine the phase formula to be demodulated, the expanded expression of the measured interference signal and the formula of MQ(t).

[0079] S503: Compensate for the carrier phase delay and rewrite the expansion of the first harmonic frequency band signal as follows:

[0080]

[0081] In the present invention, carrier phase delay compensation can correct the phase offset caused by system nonlinearity, transmission delay or other factors, thereby restoring the original phase characteristics of the signal. This is crucial for high-precision measurement and can significantly improve the accuracy and consistency of the signal.

[0082] It should be noted that, when the PMD value C is controlled near 1.8412rad, J0(C) is approximately equal to J2(C).

[0083] S504: Control the carrier phase modulation depth to a preset value, and determine the expansion of the final first harmonic frequency band signal as:

[0084] MQ1(t)=α1I0cos(ω c t)+Δ

[0085] Among them, MQ1(t) represents the first harmonic frequency band signal after controlling the carrier phase modulation depth, α1I0cos(ω c t) represents the first harmonic center band signal caused by the DC bias of the measured interference signal, and Δ represents the residual first harmonic sideband signal.

[0086] Optionally, the preset value is 1.8412 rad.

[0087] In the present invention, by adjusting the carrier phase modulation depth (PMD), the modulation effect can be optimized and the distortion in the signal can be reduced, which helps to obtain a clearer and more stable measurement interference signal and improve the overall performance of the system.

[0088] S505: Filter the processed MQ(t) through a low-pass filter to extract the lossless quadrature component signal.

[0089] In the present invention, after processing the signal after phase delay compensation and modulation depth control, filtering through a low-pass filter can remove high-frequency noise and interference, further improving the signal-to-noise ratio of the signal. This is because the low-pass filter can effectively reduce high-frequency noise while retaining the low-frequency information of the signal, that is, the effective in-phase component and orthogonal component.

[0090] In summary, by applying carrier phase delay compensation and controlling carrier phase modulation depth in the measurement interference signal processing, the accuracy, reliability and signal-to-noise ratio of signal processing can be significantly improved. The use of low-pass filters further optimizes the signal quality and extracts undistorted cross-component signals, thereby improving the overall performance of the system and the accuracy of the measurement results.

[0091] S6: Calculate the ratio of the major and minor axes of the ellipse based on the reference interference signal, and reconstruct the distorted in-phase component signal in combination with the undistorted cross-component signal to obtain a reconstructed in-phase component signal.

[0092] It should be noted that when the carrier phase modulation depth is 1.8412 rad, although the orthogonal component signal can be extracted without distortion, the in-phase component signal has been severely distorted due to spectrum aliasing, so the in-phase component signal needs to be reconstructed.

[0093] In a possible implementation, S6 specifically includes:

[0094] S601: Calculating the ratio of the major axis to the minor axis of the ellipse by an ellipse fitting algorithm based on the reference interference signal;

[0095] S602: Calculate the absolute value of the in-phase component signal according to the ratio of the major axis to the minor axis of the ellipse.

[0096] In a possible implementation manner, the calculation formula for the absolute value of the in-phase component signal is:

[0097]

[0098] Among them, |I r (t)| represents the absolute value of the in-phase component signal, Re represents the ratio of the major and minor axes of the ellipse, Qa represents the amplitude of the true quadrature component signal without loss of true phase, and Q(t) represents the true quadrature component signal without loss of true phase.

[0099] In a possible implementation, the calculation formula for the ratio of the major axis to the minor axis of an ellipse is:

[0100]

[0101] Where Re is the ratio of the major and minor axes of the ellipse.

[0102] It should be noted that, considering the large uncertainty of the measurement signal, directly normalizing and fitting the orthogonal signal pair will easily lead to no solution or singular solution in the ellipse fitting. The reference and measurement signals have the same carrier generation optical path, which means that the Re obtained by the ellipse fitting of the two is basically the same. Therefore, the Re obtained by fitting the orthogonal signal pair of the reference interference signal can be used to reconstruct the in-phase component signal of the measurement interference signal.

[0103] In the present invention, the ellipse fitting algorithm can provide the ratio of the major axis to the minor axis of the in-phase component signal, through which the in-phase component signal can be normalized, which helps to eliminate the influence caused by the change of signal amplitude and makes the reconstruction process more stable and reliable.

[0104] S603: Determine the extreme points in the orthogonal component signal, wherein the extreme points of the orthogonal component signal include PP point and PD point, wherein the PP point is the point where the polarity of the in-phase component signal changes, and the PD point is the point where the vibration direction of the measured target changes.

[0105] It should be noted that the phases of the in-phase and quadrature component signals differ by 90°, so the position where the polarity of the in-phase component signal changes is also the position where the quadrature component signal takes a local extreme value.

[0106] In a possible implementation manner, S603 specifically includes:

[0107] S6031: Determine the derivative of Q(t):

[0108] Q′(t)=-sin(ω d t)cos(cos(ω d t))

[0109] Where Q′(t) represents the derivative of Q(t), ω d Indicates the frequency of the vibration being measured.

[0110] To determine the derivative of Q(t), it is necessary to derive Q(t) according to the in-phase component of the measured interference signal, the orthogonal component formula, and the phase formula to be demodulated.

[0111] S6032: Calculate the extreme point of Q(t).

[0112] Specifically, there are two situations in which the extreme point is obtained: one is cos(ω d t)=mπ / 2(m=±1,±2,…), the corresponding extreme point is PP point; secondly, ω d t=mπ(m=±1,±2,…), which corresponds to the point where the vibration direction of the measured vibration changes, recorded as PD point;

[0113] It should be noted that in order to eliminate the PD points mixed in the extreme points, the characteristics of the PD points are further analyzed to screen out the PP points in the extreme points.

[0114] S604: According to the characteristic analysis of the PD points, the PD points among the extreme value points of the orthogonal component signal are screened out, and the PP points among the extreme value points are screened out.

[0115] Specifically, the first type of PD point is judged by the polarity of the left and right adjacent extreme points. At least one of the adjacent extreme points of the PP point has the opposite polarity to the PP point. Therefore, the polarity of the multiplication result of an extreme point and its two adjacent extreme points can be used as a criterion. If the multiplication result is positive, the extreme point must be a PD point. The second type of PD point has the same characteristics as the ordinary PP point in polarity, but the PD point corresponds to the position where the vibration direction of the d(t) signal changes. First, the adjacent extreme points of the PD point are symmetrical about the PD point. Therefore, from the time domain of the Q(t) signal, the standard deviation of the time domain interval between the PD point and its adjacent extreme points is very small; second, the d(t) change near the PD point is the slowest. Therefore, from the time domain of the Q(t) signal, the time domain interval between the PD point and its adjacent extreme points will be significantly larger than the time domain interval between the extreme points nearby and the average value of the time domain interval between the extreme points. The PP point can be obtained by filtering out the PD points in the extreme points.

[0116] In the present invention, the polarity change points (PP points) of the in-phase component signal can be accurately determined through the characteristic analysis of extreme points. The accurate identification of these points is crucial to signal reconstruction, because the polarity change points represent the key features in the signal and help avoid erroneous signal points during the reconstruction process.

[0117] S605: Reconstruct the distorted in-phase component signal according to the absolute value of the in-phase component signal and the PP point to obtain a reconstructed in-phase component signal.

[0118] In the present invention, the distorted in-phase component signal is reconstructed by using the ratio of the major and minor axes of the ellipse and the undistorted cross-component signal, which can effectively solve the problem caused by spectrum aliasing and improve the accuracy of signal reconstruction.

[0119] S7: normalize the true-loss quadrature component signal and the reconstructed in-phase component signal.

[0120] In the present invention, the lossless quadrature component signal and the reconstructed in-phase component signal are normalized, which can improve the consistency of data processing, reduce the influence of amplitude variation, and enhance the accuracy of signal comparison and demodulation.

[0121] S8: According to the normalized non-lossy quadrature component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated through the DCM algorithm.

[0122] Among them, the DCM algorithm (Direct Current Measurement Algorithm) is an algorithm used for signal processing, mainly used to extract the DC component from the signal. This algorithm is widely used in various measurement systems, especially when processing periodic signals or signals with DC bias.

[0123] In the present invention, in the vibration measurement of the optical path, by removing the DC bias in the signal, the actual vibration range of the optical path can be accurately extracted. This helps to improve the accuracy and reliability of the measurement. At the same time, the DCM algorithm helps to remove the DC component in the signal, thereby improving the quality of the signal. This can reduce the error caused by bias or noise, making the measurement result more reliable.

[0124] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0125] (1) In the present invention, by compensating for carrier phase delay and controlling the carrier phase modulation depth, the lossless quadrature component signal in the normalized orthogonal component is extracted, the ratio of the major and minor axes of the ellipse is calculated based on the reference interference signal, and the distorted in-phase component signal is reconstructed in combination with the lossless quadrature component signal to obtain a reconstructed in-phase component signal. The accuracy of the demodulation result in the case of spectrum aliasing is improved, thereby improving the stability of the measurement.

[0126] (2) In the present invention, the ratio of the major and minor axes of the ellipse is calculated based on the reference interference signal, and the distorted in-phase component signal is reconstructed in combination with the true-loss quadrature component signal to obtain a reconstructed in-phase component signal, and the true-loss quadrature component signal and the reconstructed in-phase component signal are normalized. According to the normalized true-loss quadrature component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated through the DCM algorithm. The dynamic range of the system is reduced by the spectral aliasing of the measurement interference signal, and the dynamic range can be effectively expanded.

[0127] Reference Manual Attached Figure 2 , showing a structural schematic diagram of an SPMI dynamic range extension system based on in-phase component signal reconstruction provided by the present invention.

[0128] The present invention further provides an SPMI dynamic range extension system 20 based on in-phase component signal reconstruction, which is applied to the above-mentioned SPMI dynamic range extension method based on in-phase component signal reconstruction, comprising:

[0129] Processor 201;

[0130] The memory 202 stores computer-readable instructions, and when the computer-readable instructions are executed by the processor 201, the SPMI dynamic range extension method based on in-phase component signal reconstruction as described in the method embodiment is implemented.

[0131] The SPMI dynamic range extension system 20 based on in-phase component signal reconstruction provided by the present invention can execute the above-mentioned SPMI dynamic range extension method based on in-phase component signal reconstruction and achieve the same or similar technical effects. To avoid repetition, the present invention will not go into details.

[0132] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0133] (1) In the present invention, by compensating for carrier phase delay and controlling the carrier phase modulation depth, the lossless quadrature component signal in the normalized orthogonal component is extracted, the ratio of the major and minor axes of the ellipse is calculated based on the reference interference signal, and the distorted in-phase component signal is reconstructed in combination with the lossless quadrature component signal to obtain a reconstructed in-phase component signal. The accuracy of the demodulation result in the case of spectrum aliasing is improved, thereby improving the stability of the measurement.

[0134] (2) In the present invention, the ratio of the major and minor axes of the ellipse is calculated based on the reference interference signal, and the distorted in-phase component signal is reconstructed in combination with the true-loss quadrature component signal to obtain a reconstructed in-phase component signal, and the true-loss quadrature component signal and the reconstructed in-phase component signal are normalized. According to the normalized true-loss quadrature component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated through the DCM algorithm. The dynamic range of the system is reduced by the spectral aliasing of the measurement interference signal, and the dynamic range can be effectively expanded.

[0135] It should be understood that the processor in the embodiment of the present invention may be a central processing unit (CPU), and the processor may also be other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor may be a microprocessor or the processor may also be any conventional processor, etc.

[0136] It should also be understood that the memory in the embodiments of the present invention may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memories. Among them, the non-volatile memory may be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory may be a random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of random access memory (RAM) are available, such as static RAM (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), double data rate synchronous dynamic random access memory (DDR SDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link DRAM (SLDRAM), and direct rambus RAM (DR RAM).

[0137] The above embodiments can be implemented in whole or in part by software, hardware (such as circuits), firmware or any other combination. When implemented by software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions or computer programs. When the computer instructions or computer programs are loaded or executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center by wired (such as infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device such as a server or data center that contains one or more available media sets. The available medium can be a magnetic medium (for example, a floppy disk, a hard disk, a tape), an optical medium (for example, a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state hard disk.

[0138] It should be understood that the term "and / or" in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship, but it may also indicate an "and / or" relationship. Please refer to the context for specific understanding.

[0139] In the present invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can be represented by: a, b, c, ab, ac, bc, or abc, where a, b, c can be single or multiple.

[0140] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0141] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0142] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described equipment, devices and units can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0143] In the several embodiments provided by the present invention, it should be understood that the disclosed devices, apparatuses and methods can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0144] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0145] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0146] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention can be essentially or partly embodied in the form of a software product that contributes to the prior art. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage medium includes: various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0147] An embodiment of the present invention provides a computer-readable storage medium having a computer program stored thereon. When the program is executed by a processor, the SPMI dynamic range extension method based on in-phase component signal reconstruction as described in the method embodiment is implemented.

[0148] A computer-readable storage medium provided by the present invention can implement the steps and effects of the SPMI dynamic range extension method based on in-phase component signal reconstruction of the above method embodiment. To avoid repetition, the present invention will not go into details.

[0149] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least:

[0150] (1) In the present invention, by compensating for carrier phase delay and controlling the carrier phase modulation depth, the lossless quadrature component signal in the normalized orthogonal component is extracted, the ratio of the major and minor axes of the ellipse is calculated based on the reference interference signal, and the distorted in-phase component signal is reconstructed in combination with the lossless quadrature component signal to obtain a reconstructed in-phase component signal. The accuracy of the demodulation result in the case of spectrum aliasing is improved, thereby improving the stability of the measurement.

[0151] (2) In the present invention, the ratio of the major and minor axes of the ellipse is calculated based on the reference interference signal, and the distorted in-phase component signal is reconstructed in combination with the true-undistorted quadrature component signal to obtain a reconstructed in-phase component signal, and the true-undistorted quadrature component signal and the reconstructed in-phase component signal are normalized. According to the normalized true-undistorted quadrature component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated through the DCM algorithm. The dynamic range of the system is reduced by the spectral aliasing of the measurement interference signal, and the dynamic range can be effectively expanded.

[0152] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0153] There are a few points to note:

[0154] (1) The drawings of the embodiments of the present invention only relate to the structures related to the embodiments of the present invention, and other structures may refer to the general design.

[0155] (2) For the sake of clarity, in the drawings used to describe the embodiments of the present invention, the thickness of the layers or regions is exaggerated or reduced, that is, these drawings are not drawn according to the actual scale. It is understood that when an element such as a layer, film, region or substrate is referred to as being "on" or "under" another element, the element may be "directly" "on" or "under" the other element or there may be intermediate elements.

[0156] (3) In the absence of conflict, the embodiments of the present invention and the features therein may be combined with each other to obtain new embodiments.

[0157] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. The protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A SPMI dynamic range extension method based on in-phase component signal reconstruction, characterized in that: include: S1: Obtain interference light signal; S2: converting the interference light signal into an electrical signal through a photoelectric detector to obtain an interference signal, wherein the interference signal includes a measurement interference signal and a reference interference signal; S3: performing phase demodulation on the measurement interference signal by using a PGC algorithm to extract an orthogonal signal pair of the measurement interference signal, wherein the orthogonal signal pair includes an in-phase component and an orthogonal component; S4: performing normalization processing on the orthogonal signal pair by using an ellipse fitting algorithm; S5: extracting the true-loss quadrature component signal from the normalized orthogonal signal pair by compensating for carrier phase delay and controlling carrier phase modulation depth; S6: Calculate the ratio of the major and minor axes of the ellipse based on the reference interference signal, and reconstruct the distorted in-phase component signal in combination with the undistorted cross-component signal to obtain a reconstructed in-phase component signal; S7: normalizing the undistorted quadrature component signal and the reconstructed in-phase component signal; S8: According to the normalized non-lossy quadrature component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated through the DCM algorithm.

2. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 1, characterized in that: The expression for measuring the interference signal in S2 is specifically: Where S(t) represents the measured interference signal, I1 represents the DC bias of the measured interference signal, I0 represents the fringe contrast of the measured interference signal, C represents the carrier phase modulation depth, θ c represents the carrier phase delay, represents the phase to be demodulated, d(t) represents the vibration of the corner cube, λ represents the wavelength of the laser, represents the initial phase caused by the initial optical path difference between the measurement arm and the reference arm, ω c Indicates the carrier frequency of the phase modulation.

3. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 2, characterized in that: The S3 specifically includes: S301: Expand the expression of the measured interference signal using the first kind Bessel identity combined with the trigonometric function formula: Where J0 represents the zero-order first-kind Bessel function, J 2k represents an even-order Bessel function of the first kind, J 2k+1 represents the odd-order Bessel function of the first kind; S302: Mixing the measurement interference signal with the first harmonic and the second harmonic of the carrier; S303: Filter the mixed measurement interference signal through a low-pass filter to extract the in-phase component and the orthogonal component of the orthogonal signal pair: Wherein, I(t) represents the in-phase component of the orthogonal signal pair, Q(t) represents the orthogonal component of the orthogonal signal pair, a1 represents the amplitude of the first harmonic of the demodulated carrier, and a2 represents the amplitude of the second harmonic of the demodulated carrier.

4. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 1, characterized in that: The S4 is specifically: The in-phase component and the orthogonal component are normalized by an ellipse fitting algorithm according to the following formula: a=-α2I1J2(C)cos(2θ c ) b=-α1I1J1(C)cos(θ c ) Among them, I N (t) represents the normalized in-phase component, Q N (t) represents the normalized orthogonal component, I(t) represents the in-phase component of the orthogonal signal pair, Q(t) represents the orthogonal component of the orthogonal signal pair, a represents the major semi-axis of the fitted ellipse, b represents the minor semi-axis of the fitted ellipse, I1 represents the DC bias of the measured interference signal, a1 represents the amplitude of the first harmonic of the demodulated carrier, a2 represents the amplitude of the second harmonic of the demodulated carrier, J1() represents the odd-order first-kind Bessel function, and J2() represents the even-order first-kind Bessel function.

5. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 1, characterized in that: The S5 specifically includes: S501: Determine that the signal after the measurement interference signal is mixed with the first harmonic of the carrier is: MQ(t)=α1S(t)cos(ω c t) Wherein, MQ(t) represents the signal after the measured interference signal is mixed with the first harmonic of the carrier, a1 represents the amplitude of the first harmonic of the demodulated carrier, S(t) represents the measured interference signal, ω c represents the carrier frequency of phase modulation; S502: Expand the baseband signal MQ0(t) and the first harmonic frequency band signal MQ1(t) of MQ(t) to obtain the expansion formula of the baseband signal and the first harmonic frequency band signal: Wherein, MQ0(t) represents the baseband signal of MQ(t), MQ1(t) represents the first harmonic frequency band signal of MQ(t), I0 represents the DC bias of the measured interference signal, I1 represents the fringe contrast of the measured interference signal, a1 represents the amplitude of the first harmonic of the demodulated carrier, C represents the carrier phase modulation depth, θ c represents the carrier phase delay, represents the initial phase caused by the initial optical path difference between the measurement arm and the reference arm, J0 represents the zero-order first-kind Bessel function, and J 2k represents an even-order Bessel function of the first kind, J 2k+1 represents the odd-order Bessel function of the first kind, ω c represents the carrier frequency of phase modulation, ω d Indicates the frequency of the vibration of the measured target, A d represents the amplitude of the vibration of the target being measured, and λ represents the wavelength of the laser; S503: Compensate for the carrier phase delay and rewrite the expansion of the first harmonic frequency band signal as follows: S504: Control the carrier phase modulation depth to a preset value, and determine the expansion of the final first harmonic frequency band signal as: MQ1(t)=α1I0cos(ω c t)+D Among them, MQ1(t) represents the first harmonic frequency band signal after the carrier phase modulation depth control, α1I0cos(ω c t) represents the first harmonic center band signal caused by the DC bias of the measured interference signal, and Δ represents the residual first harmonic sideband signal; S505: Filter the processed MQ(t) through a low-pass filter to extract the lossless quadrature component signal.

6. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 1, characterized in that: The S6 specifically includes: S601: Calculating the ratio of the major axis to the minor axis of the ellipse by an ellipse fitting algorithm based on the reference interference signal; S602: Calculate the absolute value of the in-phase component signal according to the ratio of the major axis to the minor axis of the ellipse; S603: Determine extreme points in the orthogonal component signal, wherein the extreme points of the orthogonal component signal include PP point and PD point, wherein the PP point is a point where the polarity of the in-phase component signal changes, and the PD point is a point where the vibration direction of the measured target changes; S604: According to the characteristic analysis of the PD points, the PD points among the extreme value points of the orthogonal component signal are screened out, and the PP points among the extreme value points are screened out; S605: Obtain a reconstructed in-phase component signal according to the absolute value of the in-phase component signal and the PP point reconstructed distorted in-phase component signal.

7. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 6, characterized in that: The calculation formula of the absolute value of the in-phase component signal is: Wherein, |Ir(t)| represents the absolute value of the in-phase component signal, Re represents the ratio of the major axis to the minor axis of the ellipse, Qa represents the amplitude of the true-loss quadrature component signal, and Q(t) represents the true-loss quadrature component signal.

8. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 7, characterized in that: The calculation formula of the ratio of the major and minor axes of the ellipse is: Where Re is the ratio of the major and minor axes of the ellipse.

9. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 1, characterized in that: The S603 specifically includes: S6031 determines the derivative of Q(t) as: Q′(t)=-sin(ω d t)cos(cos(ω d t)) Where Q′(t) represents the derivative of Q(t), ω d , represents the frequency of the measured vibration; S6032: Calculate the extreme point of Q(t).

10. An SPMI dynamic range extension system based on in-phase component signal reconstruction, characterized in that: include: processor; A memory having computer-readable instructions stored thereon, wherein when the computer-readable instructions are executed by the processor, the SPMI dynamic range extension method based on in-phase component signal reconstruction as described in any one of claims 1 to 9 is implemented.

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