A method and system for extending the dynamic range of SPMI based on in-phase component signal reconstruction

Abstract

This invention provides a method and system for extending the dynamic range of SPMI based on in-phase component signal reconstruction, relating to the field of data processing technology. The method includes: acquiring an interference optical signal; converting the interference optical signal into an electrical signal using a photodetector to obtain an interference signal; performing phase demodulation on the measured interference signal using a PGC algorithm to extract in-phase and quadrature components; normalizing the in-phase and quadrature components; extracting the non-distorted quadrature component signal from the normalized quadrature component by carrier phase delay compensation and controlling the carrier phase modulation depth; reconstructing the distorted in-phase component signal based on the non-distorted quadrature component signal; normalizing the non-distorted quadrature component signal and the reconstructed in-phase component signal; and demodulating the vibration range of the measurement optical path using a DCM algorithm based on the normalized non-distorted quadrature component signal and the reconstructed in-phase component signal.

Description

Technical Field

[0001] This invention relates to the field of data processing technology, and in particular to a method and system for extending the dynamic range of SPMI based on in-phase component signal reconstruction. Background Technology

[0002] In recent years, sinusoidal phase-modulated laser interferometers (SPMIs) have attracted widespread attention in fields such as absolute distance measurement, precision vibration measurement, and surface topography reconstruction due to their simple structure, high sensitivity, and good noise characteristics. The high precision of SPMIs makes them increasingly important in scientific research and industrial applications. Phase-generated carrier (PGC) technology, with its superior demodulation dynamic range and linearity, plays a crucial role in the phase demodulation of SPMIs and is widely used in various high-precision measurement applications.

[0003] Existing dynamic range extension methods include one that synchronizes the carrier with the measurement interference signal by adjusting the compensation phase on the carrier, ultimately enabling SPMI to achieve nanometer-level displacement measurement accuracy; and another that uses the PGC improved algorithm to perform elliptic parameter fitting on non-ideal orthogonal signal pairs to eliminate the influence of nonlinear factors. Both existing methods can achieve dynamic range extension.

[0004] However, existing dynamic range extension methods often fail to guarantee the accuracy of demodulation results in cases of spectral aliasing, resulting in low measurement stability. At the same time, the dynamic range of the system is usually constrained by the spectral aliasing of the measurement interference signal, making it difficult to achieve effective range extension. Summary of the Invention

[0005] To address the challenges of existing dynamic range extension methods that often fail to guarantee demodulation accuracy under spectral aliasing conditions, resulting in low measurement stability, and the fact that the dynamic range of the system is typically constrained by spectral aliasing of the measurement interference signal, making effective range extension difficult, this invention provides a SPMI dynamic range extension method and system based on in-phase component signal reconstruction.

[0006] The technical solutions provided by the embodiments of the present invention are as follows:

[0007] First aspect:

[0008] This invention provides a method for extending the dynamic range of SPMI based on in-phase component signal reconstruction, comprising:

[0009] S1: Acquire the interference light signal;

[0010] S2: The interference light signal is converted into an electrical signal by a photodetector to obtain an interference signal, which includes a measurement interference signal and a reference interference signal;

[0011] S3: The measurement interference signal is phase demodulated using the PGC algorithm to extract the orthogonal signal pairs of the measurement interference signal, wherein the orthogonal signal pairs include in-phase components and quadrature components;

[0012] S4: Normalize the orthogonal signal pairs using an ellipse fitting algorithm;

[0013] S5: Extract the non-distorted true quadrature component signal from the normalized orthogonal signal pair by carrier phase delay compensation 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 by combining it with the undistorted true intersecting component signal to obtain the reconstructed in-phase component signal;

[0015] S7: Normalize the non-loss true intersecting component signal and the reconstructed in-phase component signal;

[0016] S8: Based on the normalized, lossless true cross-component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated using the DCM algorithm.

[0017] The second aspect:

[0018] This invention provides an SPMI dynamic range extension system based on in-phase component signal reconstruction, comprising:

[0019] processor;

[0020] A memory storing computer-readable instructions, which, when executed by the processor, implement the SPMI dynamic range extension method based on in-phase component signal reconstruction as described in the first aspect.

[0021] Third aspect:

[0022] The present invention provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the SPMI dynamic range extension method based on in-phase component signal reconstruction as described in the first aspect.

[0023] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0024] (1) In this invention, by carrier phase delay compensation and controlling the carrier phase modulation depth, the non-distortion true quadrature component signal in the normalized quadrature component is extracted. Based on the reference interference signal, the ratio of the major and minor axes of the ellipse is calculated, and combined with the non-distortion true quadrature component signal, the distorted in-phase component signal is reconstructed to obtain the reconstructed in-phase component signal. This improves the accuracy of demodulation results under spectral aliasing conditions, thereby enhancing the stability of the measurement.

[0025] (2) In this 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 by combining the non-distorted true cross-axis component signal to obtain the reconstructed in-phase component signal. The non-distorted true cross-axis component signal and the reconstructed in-phase component signal are normalized. Based on the normalized non-distorted true cross-axis component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated using the DCM algorithm. This reduces the dynamic range of the system from the spectral aliasing of the measurement interference signal, thus achieving an effective expansion of the dynamic range. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A flowchart illustrating a method for extending the dynamic range of SPMI based on in-phase component signal reconstruction, provided in an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of the structure of an SPMI dynamic range extension system based on in-phase component signal reconstruction, provided in an embodiment of the present invention. Detailed Implementation

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

[0030] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0031] In the embodiments of the present invention, the terms "image" and "picture" may be used interchangeably. It should be noted that, when the distinction between them is not emphasized, their intended meanings are the same. The terms "of," "corresponding," and "corresponding" may be used interchangeably. It should be noted that, when the distinction between them is not emphasized, their intended meanings are the same.

[0032] In this embodiment of the invention, sometimes a subscript such as W1 may be mistakenly written as a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0033] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0034] Reference manual attached Figure 1 The diagram shows a flowchart of a SPMI dynamic range extension method based on in-phase component signal reconstruction provided by an embodiment of the present invention.

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

[0036] S1: Acquire the interference light signal.

[0037] Specifically, the frequency-stabilized laser emitted by the helium-neon laser passes through a linear polarizer to obtain a linearly polarized beam, which is then split into two beams—a measurement beam and a reference beam—by a beam splitter. The transmitted beam is the measurement beam, which is composed of a cornerstone prism mounted on a vibration platform. The cornerstone prism is driven by the vibration platform to achieve small-amplitude vibrations. The reflected beam is the reference beam. After phase modulation and reflection by the cornerstone prism, the reference beam interferes with the measurement beam reflected back by the cornerstone prism at the beam splitter, forming an interference light signal.

[0038] S2: The interference light signal is converted into an electrical signal by a photodetector to obtain an interference signal, which includes a measurement interference signal and a reference interference signal.

[0039] A photodetector is a device that converts light signals into electrical signals and is widely used in optical communication, optical measurement, and imaging systems. It detects the intensity of light and generates corresponding electrical signals for subsequent processing and analysis.

[0040] In one possible implementation, the expression for measuring the interference signal in S2 is specifically as follows:

[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, and θ c Indicates carrier phase delay, Let represent the phase to be demodulated, d(t) represent the vibration of the cornerstone prism, and λ represent the wavelength of the laser. The initial phase, ω, represents the initial optical path difference between the measuring arm and the reference arm. c This indicates the carrier frequency for phase modulation.

[0043] In this invention, by providing an expression for the measured interference signal, the role of each parameter can be clearly defined. This facilitates precise adjustments during experimental design and data processing, optimizing system performance. Furthermore, while various filtering and noise suppression techniques can be applied in the processing of electrical signals, this is difficult in the processing of optical signals, especially when the signal is very weak. Therefore, converting the interference optical signal into an electrical signal facilitates subsequent processing.

[0044] S3: The phase demodulation of the measured interference signal is performed by the PGC algorithm to extract the orthogonal signal pairs of the measured interference signal. The orthogonal signal pairs include in-phase components and quadrature components.

[0045] The PGC (Phase Gradient Compensation Algorithm) is a phase demodulation algorithm, particularly suitable for processing phase information in optical interference signals. It is primarily used to extract useful phase information from interference signals with a carrier wave. By processing the phase gradient, the PGC algorithm can effectively compensate for and demodulate the phase information in the signal.

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

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

[0048]

[0049] Where J0 represents the zeroth-order Bessel function of the first kind, J 2k J represents the even-order Bessel function of the first kind. 2k+1 This represents the 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 class of functions frequently used to solve problems with circular symmetry.

[0051] S302: Mix the measured interference signal with the first and second harmonics of the carrier wave.

[0052] In this invention, mixing the measured interference signal with the first and second harmonics of the carrier wave can shift the high-frequency components in the signal spectrum to the low-frequency range, which makes it easier to extract and analyze the signal phase information.

[0053] S303: The mixed measurement interference signal is filtered by a low-pass filter to extract the in-phase and quadrature components of the quadrature signal pairs.

[0054]

[0055] Where I(t) represents the in-phase component of the quadrature signal pair, Q(t) represents the quadrature component of the quadrature 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] A low-pass filter (LPF) is an electronic filter used to allow 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 preserving low-frequency components.

[0057] In this invention, the PGC algorithm effectively extracts useful phase information from the measurement interferometric signal containing the carrier wave, improving the accuracy of phase measurement. Simultaneously, by expanding the measurement interferometric signal using the first-kind Bessel identity combined with trigonometric function formulas, the signal can be represented as a combination of Bessel functions of different orders. This expansion method helps decompose the measurement interferometric signal into simpler components, facilitating subsequent mixing and filtering processes.

[0058] S4: Normalize the orthogonal signal pairs using an ellipse fitting algorithm.

[0059] The elliptical fitting algorithm is used to fit an ellipse to a given set of data points. This algorithm has wide applications in image processing, computer vision, and data analysis. The goal of elliptical fitting is to find the most suitable ellipse shape for the data points, enabling data modeling and analysis.

[0060] It should be noted that normalization is required to compensate for the influence of the coefficient terms.

[0061] In one possible implementation, S4 specifically refers to:

[0062] Based on the following formula, the in-phase and orthogonal components are normalized using an 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 in-phase component after normalization, Q N (t) represents the normalized quadrature component, I(t) represents the in-phase component of the quadrature signal pair, Q(t) represents the quadrature component of the quadrature 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 Bessel function of the first kind, and J2() represents the even-order Bessel function of the first kind.

[0067] In this invention, normalization processing can effectively compensate for system errors or deviations introduced by factors such as DC bias, carrier harmonic amplitude, and Bessel function. This compensation ensures that the final in-phase and quadrature components are unaffected by these additional coefficient terms, thus more accurately reflecting the true characteristics of the signal. Simultaneously, normalization using an elliptic fitting algorithm can adjust the in-phase and quadrature components to a uniform scale, simplifying subsequent processing steps.

[0068] S5: Extract the lossless true quadrature component signal from the normalized orthogonal signal pair by carrier phase delay compensation and controlling the carrier phase modulation depth.

[0069] Carrier phase delay compensation is a technique used in signal processing to correct or compensate for signal distortion caused by carrier phase delay. This technique is widely used in communication systems, radar systems, and interferometric systems to improve system accuracy and performance.

[0070] In a phase modulation (PM) system, the carrier phase modulation depth refers to the magnitude of the phase change of the carrier signal. Phase modulation is a modulation technique that transmits information by altering the phase of the carrier signal. The modulation depth describes the magnitude or intensity of this phase change.

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

[0072] S501: Determine the MQ(t) measurement interference signal after mixing the measurement interference signal with the first harmonic of the carrier wave as:

[0073] MQ(t) = α1S(t)cos(ω) c t)

[0074] Where MQ(t) represents the signal after mixing the measured interference signal with the first harmonic of the carrier wave, a1 represents the amplitude of the first harmonic of the demodulated carrier wave, S(t) represents the measured interference signal, and ω c This indicates the carrier frequency for phase modulation.

[0075] S502: Expanding the baseband signal MQ0(t) and the first harmonic band signal MQ1(t) of MQ(t) yields the expansions of the baseband signal and the first harmonic 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, and θ c Indicates carrier phase delay, J0 represents the initial phase caused by the initial optical path difference between the measuring arm and the reference arm, and J represents the zeroth-order Bessel function of the first kind. 2k J represents the even-order Bessel function of the first kind. 2k+1 Let ω represent the odd-order Bessel function of the first kind. d It means that A d λ 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 expanding the baseband signal MQ0(t) and the first harmonic band signal MQ1(t) of MQ(t) to obtain the expansion of the baseband signal and the first harmonic band signal MQ1(t) requires combining the formula of the phase to be demodulated, the expansion of the expression of the measured interference signal, and the formula of MQ(t).

[0079] S503: Compensates for carrier phase delay, rewriting the expansion of the first harmonic frequency band signal as follows:

[0080]

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

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

[0083] S504: The carrier phase modulation depth is controlled to a preset value, and the expansion of the final first harmonic frequency band signal is determined as follows:

[0084] MQ1(t)=α1I0cos(ω c t)+Δ

[0085] Where 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 default value is 1.8412 rad.

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

[0088] S505: The processed MQ(t) is filtered by a low-pass filter to extract the true cross-component signal without loss.

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

[0090] In summary, by applying carrier phase delay compensation and controlling the carrier phase modulation depth in measurement interferometric signal processing, the accuracy, reliability, and signal-to-noise ratio of signal processing can be significantly improved. The use of a low-pass filter further optimizes signal quality, extracting distortion-free intersecting components, thereby enhancing the overall system performance and the accuracy of 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 by combining it with the undistorted true intersecting component signal to obtain the reconstructed in-phase component signal.

[0092] It should be noted that when the carrier phase modulation depth is 1.8412 rad, although the quadrature component signal can be extracted without distortion, the in-phase component signal is severely distorted due to spectral aliasing, so it is necessary to reconstruct the in-phase component signal.

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

[0094] S601: Based on the reference interference signal, calculate the ratio of the major and minor axes of the ellipse using an ellipse fitting algorithm;

[0095] S602: Calculate the absolute value of the in-phase component signal based on the ratio of the major and minor axes of the ellipse.

[0096] In one possible implementation, the formula for calculating 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 non-losswise cross-axis component signal, and Q(t) represents the non-losswise cross-axis component signal.

[0099] In one possible implementation, the formula for calculating the ratio of the major and minor axes of the ellipse is:

[0100]

[0101] Where Re represents 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 its orthogonal signal pairs can easily lead to unsolvable or singular solutions in elliptic fitting. However, since the reference and measurement signals have the same carrier generation optical path, the Re values ​​obtained from their elliptic fitting are basically the same. Therefore, the Re value obtained by fitting the orthogonal signal pairs of the reference interference signal can be used to reconstruct the in-phase component signal of the measurement interference signal.

[0103] In this invention, the ellipse fitting algorithm can provide the ratio of the major and minor axes of the in-phase component signal. This ratio can be used to normalize the in-phase component signal. This helps to eliminate the influence caused by changes in signal amplitude, making the reconstruction process more stable and reliable.

[0104] S603: Determine the extreme points in the quadrature component signal. The extreme points of the quadrature component signal include PP point and PD point, where PP point is the point where the polarity of the in-phase component signal changes, and 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 are 90° apart. Therefore, the location where the polarity of the in-phase component signal changes is also the location where the quadrature component signal reaches a local extremum.

[0106] In one possible implementation, S603 specifically includes:

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

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

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

[0110] Determining the derivative of Q(t) requires taking the derivative of Q(t) based on the in-phase component, the quadrature component formula, and the demodulated phase formula of the measured interference signal.

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

[0112] Specifically, there are two cases where an extreme point is reached: one is cos(ω) d t) = mπ / 2 (m = ±1, ±2, ...), the corresponding extreme point is point PP; the second is ω d t = mπ (m = ±1, ±2, ...), which corresponds to the point where the direction of vibration of the measured vibration changes, and is denoted as PD point;

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

[0114] S604: Based on the characteristic analysis of PD points, PD points in the extreme points of the orthogonal component signals are screened out, and PP points in the extreme points are selected.

[0115] Specifically, the first type of PD points is determined by the polarity of their adjacent extreme points. At least one of the adjacent extreme points of a PP point has the opposite polarity to that of the PP point. Therefore, the polarity of the product of an extreme point and its two adjacent extreme points can be used as a criterion; if the product is positive, the extreme point is definitely a PD point. The second type of PD points shares the same polarity characteristics as ordinary PP points, but PD points correspond to the location where the oscillation direction of the d(t) signal changes. Firstly, the adjacent extreme points of a PD point are symmetrical about the PD point. Therefore, from the time domain perspective 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. Secondly, the change in d(t) is slowest near the PD point. Therefore, from the time domain perspective of the Q(t) signal, the time-domain interval between the PD point and its adjacent extreme points will be significantly larger than the average of the time-domain intervals between the PD point and the extreme points themselves. PD points are obtained by filtering out the extreme points.

[0116] In this invention, the polarity change points (PP points) of in-phase component signals can be accurately determined through feature analysis of extreme points. Accurate identification of these points is crucial for signal reconstruction because polarity change points represent key features in the signal, helping to avoid erroneous signal points during the reconstruction process.

[0117] S605: Based on the absolute value of the in-phase component signal and the in-phase component signal with distortion at point PP, the reconstructed in-phase component signal is obtained.

[0118] In this invention, the problem of spectral aliasing can be effectively solved by reconstructing the distorted in-phase component signal using the ratio of the major and minor axes of the ellipse and the non-distorted true cross component signal, thereby improving the accuracy of signal reconstruction.

[0119] S7: Normalize the non-lossy true cross component signal and the reconstructed in-phase component signal.

[0120] In this invention, normalizing the lossless intersecting component signal and the reconstructed in-phase component signal can improve the consistency of data processing, reduce the impact of amplitude changes, and enhance the accuracy of signal comparison and demodulation.

[0121] S8: Based on the normalized, lossless true cross-component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated using the DCM algorithm.

[0122] The DCM algorithm (Direct Current Measurement Algorithm) is a signal processing algorithm primarily used to extract the direct current (DC) component from a signal. This algorithm is widely used in various measurement systems, and is particularly useful when processing periodic signals or signals with DC bias.

[0123] In this invention, by removing the DC bias from the signal during vibration measurement of the optical path, the actual vibration range of the optical path can be accurately extracted. This helps improve the accuracy and reliability of the measurement. Simultaneously, the DCM algorithm helps remove the DC component from the signal, thereby improving signal quality. This reduces errors caused by bias or noise, making the measurement results more reliable.

[0124] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0125] (1) In this invention, by carrier phase delay compensation and controlling the carrier phase modulation depth, the non-distortion true quadrature component signal in the normalized quadrature component is extracted. Based on the reference interference signal, the ratio of the major and minor axes of the ellipse is calculated, and combined with the non-distortion true quadrature component signal, the distorted in-phase component signal is reconstructed to obtain the reconstructed in-phase component signal. This improves the accuracy of demodulation results under spectral aliasing conditions, thereby enhancing the stability of the measurement.

[0126] (2) In this 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 by combining the non-distorted true cross-axis component signal to obtain the reconstructed in-phase component signal. The non-distorted true cross-axis component signal and the reconstructed in-phase component signal are normalized. Based on the normalized non-distorted true cross-axis component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated using the DCM algorithm. This reduces the dynamic range of the system from the spectral aliasing of the measurement interference signal, thus achieving an effective expansion of the dynamic range.

[0127] Reference manual attached Figure 2 The diagram shows a schematic of the structure of an SPMI dynamic range extension system based on in-phase component signal reconstruction provided by the present invention.

[0128] The present invention also provides an SPMI dynamic range extension system 20 based on in-phase component signal reconstruction, 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, which, when executed by the processor 201, implement the SPMI dynamic range extension method based on in-phase component signal reconstruction as described in the method embodiment.

[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 elaborate further.

[0132] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0133] (1) In this invention, by carrier phase delay compensation and controlling the carrier phase modulation depth, the non-distortion true quadrature component signal in the normalized quadrature component is extracted. Based on the reference interference signal, the ratio of the major and minor axes of the ellipse is calculated, and combined with the non-distortion true quadrature component signal, the distorted in-phase component signal is reconstructed to obtain the reconstructed in-phase component signal. This improves the accuracy of demodulation results under spectral aliasing conditions, thereby enhancing the stability of the measurement.

[0134] (2) In this 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 by combining the non-distorted true cross-axis component signal to obtain the reconstructed in-phase component signal. The non-distorted true cross-axis component signal and the reconstructed in-phase component signal are normalized. Based on the normalized non-distorted true cross-axis component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated using the DCM algorithm. This reduces the dynamic range of the system from the spectral aliasing of the measurement interference signal, thus achieving an effective expansion of the dynamic range.

[0135] It should be understood that the processor in the embodiments of the present invention can be a central processing unit (CPU), or it can be other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose processor can be a microprocessor or any conventional processor.

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

[0137] The above embodiments can be implemented in whole or in part through software, hardware (such as circuits), firmware, or any other combination. When implemented using 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 program are loaded or executed on a computer, the processes or functions described in accordance with the embodiments of the present invention are 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. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired method (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 a collection of one or more available media. The available medium can be a magnetic medium (such as a floppy disk, hard disk, or magnetic tape), an optical medium (such as a DVD), or a semiconductor medium. The semiconductor medium can be a solid-state drive.

[0138] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0139] In this disclosure, "at least one" means one or more, and "plurality" 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 mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or plural.

[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. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0142] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the devices, apparatuses, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0143] In the several embodiments provided by this invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

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

[0145] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can 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, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. 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, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment 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] This invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the SPMI dynamic range extension method based on in-phase component signal reconstruction as described in the method embodiment.

[0148] The present invention provides a computer-readable storage medium that can implement the steps and effects of the SPMI dynamic range extension method based on in-phase component signal reconstruction in the above-described method embodiments. To avoid repetition, the present invention will not elaborate further.

[0149] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following:

[0150] (1) In this invention, by carrier phase delay compensation and controlling the carrier phase modulation depth, the non-distortion true quadrature component signal in the normalized quadrature component is extracted. Based on the reference interference signal, the ratio of the major and minor axes of the ellipse is calculated, and combined with the non-distortion true quadrature component signal, the distorted in-phase component signal is reconstructed to obtain the reconstructed in-phase component signal. This improves the accuracy of demodulation results under spectral aliasing conditions, thereby enhancing the stability of the measurement.

[0151] (2) In this invention, the ratio of the major and minor axes of the ellipse is calculated based on the reference interference signal, and combined with the non-distorted true cross-axis component signal, the distorted in-phase component signal is reconstructed to obtain the reconstructed in-phase component signal. The non-distorted true cross-axis component signal and the reconstructed in-phase component signal are normalized. Based on the normalized non-distorted true cross-axis component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated using the DCM algorithm. This reduces the dynamic range of the system from the spectral aliasing of the measurement interference signal, and effectively expands the dynamic range.

[0152] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

[0153] The following points need to be explained:

[0154] (1) The accompanying drawings of the embodiments of the present invention only involve the structures involved in the embodiments of the present invention. Other structures can refer to the general design.

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

[0156] (3) Where there is no conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other to obtain new embodiments.

[0157] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. The scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for extending the dynamic range of SPMI based on in-phase component signal reconstruction, characterized in that, include: S1: Acquire the interference light signal; S2: The interference light signal is converted into an electrical signal by a photodetector to obtain an interference signal, which includes a measurement interference signal and a reference interference signal; S3: The measurement interference signal is phase demodulated using the PGC algorithm to extract the orthogonal signal pairs of the measurement interference signal, wherein the orthogonal signal pairs include in-phase components and quadrature components; S4: Normalize the orthogonal signal pairs using an ellipse fitting algorithm; S5: Extract the non-distorted true quadrature component signal from the normalized orthogonal signal pair by carrier phase delay compensation 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 by combining it with the undistorted true intersecting component signal to obtain the reconstructed in-phase component signal; S7: Normalize the non-loss true intersecting component signal and the reconstructed in-phase component signal; S8: Based on the normalized, lossless true cross-component signal and the reconstructed in-phase component signal, the vibration range of the measurement optical path is demodulated using 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 as follows: 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, and θ c Indicates carrier phase delay, Let represent the phase to be demodulated, d(t) represent the vibration of the cornerstone prism, and λ represent the wavelength of the laser. The initial phase, ω, represents the initial optical path difference between the measuring arm and the reference arm. c This indicates the carrier frequency for phase modulation.

3. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 2, characterized in that, S3 specifically includes: S301: Expand the expression for the measured interference signal using the first kind of Bessel identity combined with trigonometric function formulas: Where J0 represents the zeroth-order Bessel function of the first kind, J 2k J represents the even-order Bessel function of the first kind. 2k+1 Represents odd-order Bessel functions of the first kind; S302: Mix the measured interference signal with the first and second harmonics of the carrier wave; S303: The mixed measurement interference signal is filtered by a low-pass filter to extract the in-phase component and quadrature component of the orthogonal signal pair: Where I(t) represents the in-phase component of the quadrature signal pair, Q(t) represents the quadrature component of the quadrature 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, Specifically, S4 is: According to the following formula, the in-phase components and orthogonal components are normalized using an ellipse fitting algorithm: a=-α2I1J2(C)cos(2θ c ) b=-α1I1J1(C)cos(θ c ) Among them, I N (t) represents the in-phase component after normalization, Q N (t) represents the normalized quadrature component, I(t) represents the in-phase component of the quadrature signal pair, Q(t) represents the quadrature component of the quadrature 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 Bessel function of the first kind, and J2() represents the even-order Bessel function of the first kind.

5. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 1, characterized in that, S5 specifically includes: S501: The signal after mixing the measured interference signal with the first harmonic of the carrier wave is determined to be: MQ(t)=α1S(t)cos(ω c t) Where MQ(t) represents the signal after mixing the measured interference signal with the first harmonic of the carrier wave, a1 represents the amplitude of the first harmonic of the demodulated carrier wave, S(t) represents the measured interference signal, and ω c Indicates the carrier frequency of phase modulation; S502: Expanding the baseband signal MQ0(t) and the first harmonic band signal MQ1(t) of MQ(t) yields the expansions of the baseband signal and the first harmonic band signal: Where MQ0(t) represents the baseband signal of MQ(t), MQ1(t) represents the first harmonic 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, and θ c Indicates carrier phase delay, J0 represents the initial phase caused by the initial optical path difference between the measuring arm and the reference arm, and J represents the zeroth-order Bessel function of the first kind. 2k J represents the even-order Bessel function of the first kind. 2k+1 Let ω represent the odd-order Bessel function of the first kind. c ω represents the carrier frequency of phase modulation. d A represents the frequency of the vibration of the target being measured. d λ represents the amplitude of the vibration of the target being measured, and λ represents the wavelength of the laser. S503: Compensates for carrier phase delay, rewriting the expansion of the first harmonic frequency band signal as follows: S504: The carrier phase modulation depth is controlled to a preset value, and the expansion of the final first harmonic frequency band signal is determined as follows: MQ1(t)=α1I0cos(ω c t)+D Where MQ1(t) represents the first harmonic frequency band signal after 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: The processed MQ(t) is filtered by a low-pass filter to extract the true cross-component signal without loss.

6. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 1, characterized in that, S6 specifically includes: S601: Based on the reference interference signal, calculate the ratio of the major and minor axes of the ellipse using an ellipse fitting algorithm; S602: Calculate the absolute value of the in-phase component signal based on the ratio of the major and minor axes of the ellipse; S603: Determine the extreme points in the quadrature component signal, wherein the extreme points of the quadrature component signal include PP point and PD point, wherein PP point is the point where the polarity of the in-phase component signal changes, and PD point is the point where the vibration direction of the measured target changes. S604: Based on the characteristic analysis of PD points, PD points in the extreme points of the orthogonal component signals are screened out, and PP points in the extreme points are selected. S605: Based on the absolute value of the in-phase component signal and the in-phase component signal with reconstruction distortion at point PP, the reconstructed in-phase component signal is obtained.

7. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 6, characterized in that, The formula for calculating the absolute value of the in-phase component signal is: Where |Ir(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 non-losswise cross-axis component signal, and Q(t) represents the non-losswise cross-axis component signal.

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

9. The SPMI dynamic range extension method based on in-phase component signal reconstruction according to claim 1, characterized in that, Specifically, S603 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 , which represents the frequency of the measured vibration; S6032: Calculate the extreme points of Q(t).

10. A SPMI dynamic range extension system based on in-phase component signal reconstruction, characterized in that, include: processor; A memory storing computer-readable instructions, which, when executed by the processor, implement the SPMI dynamic range extension method based on in-phase component signal reconstruction as described in any one of claims 1 to 9.

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