Anti-noise-interference high-precision optical coherent ranging frequency parameter estimation method

Abstract

The invention provides an anti-noise interference frequency parameter estimation method for high-precision optical coherence ranging, which comprises the following steps: acquiring a spectral interference signal of an optical low-coherence interference system and a reference light spectral signal output only by a reference arm, and converting the spectral interference signal into interference signals with wave number space arranged at equal intervals, carrying out spectral density amplitude normalization to obtain a standard interference signal so as to eliminate interference of light source spectrum fluctuation and non-uniform sampling on frequency estimation; hanning window modulation is applied to a standard interference signal, spectrum leakage is suppressed, spectrum analysis is performed on the modulated signal, a peak value and an adjacent secondary peak value of a spectrum main lobe are extracted, a frequency correction amount is calculated based on a peak value and secondary peak value amplitude ratio relation derived by a Hanning window spectrum mode function, and an accurate frequency of the interference signal is obtained; and calculating the displacement of the object to be measured according to the product of the accurate frequency and the spectral resolution of the optical low-coherence interference system in combination with the refractive index of the light in the measurement medium.

Description

Technical Field

[0001] This invention belongs to the field of optical measurement technology, and specifically relates to an optical low-coherence measurement device and signal processing for high-precision micro-nano displacement measurement, and more specifically to a frequency parameter estimation method for high-precision optical coherent ranging with noise resistance. Background Technology

[0002] Interferometric distance measurement achieves high-precision measurement by converting micro-nano displacements into macroscopic changes in interference fringes. Among these techniques, low-coherence interferometry, employing broadband light sources to encode displacement information as spectral interference fringes, possesses absolute displacement measurement capabilities and a high signal-to-noise ratio, making it a research hotspot in the field of precision measurement. Optical coherence theory indicates that displacement and the frequency of the spectral interference signal have a linear relationship; therefore, the accuracy of frequency estimation directly determines the system's measurement performance.

[0003] Traditional Fast Fourier Transform (FFT), a commonly used frequency analysis tool, is limited by the integer-cycle sampling assumption and can only identify frequencies that are integer multiples of each other. This results in the axial measurement accuracy of low-coherence systems typically remaining at the micrometer level, making it difficult to meet the requirements of nanometer-level precision measurements. Although super-resolution frequency extraction methods such as the energy centroid method and the ratio correction method have been proposed, these methods are mostly designed for ideal sine / cosine signals with equal-interval sampling and equal amplitude. However, the actual signals of low-coherence systems differ significantly: on the one hand, spectrometers use wavelength as the uniform sampling unit, while the frequency information of the interference signal depends on the uniformity of the wavenumber (the reciprocal of the wavelength), leading to non-uniform sampling bias in the acquired signal; on the other hand, the uneven spectral power distribution of broadband light sources causes the amplitude of the interference signal to vary with the wavelength, forming variable amplitude characteristics that deviate from the ideal model, making it difficult to guarantee the accuracy of traditional methods.

[0004] Furthermore, in real-world measurement scenarios, signals are often mixed with various types of noise, such as electromagnetic interference and shot noise. Existing methods lack robustness under noise interference and are prone to frequency estimation errors, further restricting the application of low-coherence interferometry in high-precision industrial measurements. Overcoming the technical bottlenecks caused by non-uniform sampling, variable amplitude characteristics, and noise interference to achieve super-resolution and noise-resistant estimation of interferometric signal frequencies is the core challenge for the current development of low-coherence interferometric ranging technology. Summary of the Invention

[0005] To address the shortcomings and deficiencies of existing technologies, this invention provides a high-precision frequency parameter estimation method for optical coherent ranging with strong noise resistance. This invention addresses the limited frequency estimation accuracy caused by non-uniform signal sampling and spectral density fluctuations in low-coherence optical interferometry systems by proposing a complete signal processing scheme. First, the spectral interferometric signal is converted from wavelength space to wavenumber space, and resampling is used to ensure uniform distribution in the wavenumber domain, thus solving the non-uniform sampling problem. Second, a reference light spectral signal is introduced to normalize the amplitude of the interferometric signal, effectively eliminating the influence of light source spectral density fluctuations on the measurement results. Next, a Hanning window is innovatively used to modulate the preprocessed standard interferometric signal, fully utilizing the excellent sidelobe suppression characteristics of the Hanning window to significantly reduce spectral leakage and noise interference. Finally, based on the spectral characteristics of the Hanning window, the frequency correction is accurately calculated by analyzing the amplitude ratio between the main lobe peak and adjacent secondary peaks, achieving super-resolution estimation of the interferometric signal frequency. This method overcomes the limitation of traditional fast Fourier transform, which can only identify the whole-cycle frequency. It improves the displacement measurement accuracy of optical low-coherence ranging systems from the micrometer level to the nanometer level. At the same time, it exhibits excellent stability and reliability in noisy environments, greatly expanding the application potential of optical coherence ranging technology in the field of precision measurement.

[0006] The specific technical solution adopted by this invention to solve its technical problem is as follows:

[0007] A high-precision optical coherent ranging method with strong noise resistance for frequency parameter estimation includes:

[0008] The spectral interference signal of the optical low-coherence interferometer system and the reference light spectral signal output by only the reference arm are obtained. The spectral interference signal is converted into an interference signal with equal intervals in wavenumber space. The spectral density amplitude of the interference signal is normalized by the reference light spectral signal to obtain a standard interference signal with equal intervals in wavenumber space and constant amplitude, so as to eliminate the interference of light source spectral fluctuations and non-uniform sampling on frequency estimation.

[0009] Hanning window modulation is applied to the standard interference signal, and the sidelobe suppression characteristic of the Hanning window is used to suppress spectral leakage. Then, spectral analysis is performed on the modulated signal to extract the peak value of the main lobe and the adjacent second peak value. The frequency correction is calculated based on the ratio of the peak value to the second peak value derived from the Hanning window spectral modulus function, so as to obtain the accurate frequency of the interference signal.

[0010] The displacement of the object under test is calculated by multiplying the precise frequency by the spectral resolution of the low-coherence optical interference system and combining this with the refractive index of light in the measurement medium.

[0011] Further, converting the spectral interference signal into an interference signal arranged at equal intervals in wavenumber space specifically includes: converting the spectral interference signal uniformly arranged by wavelength into the corresponding original wavenumber sequence according to the inherent conversion relationship between wavelength and wavenumber; performing equal interval processing on the original wavenumber sequence to obtain an equal interval wavenumber sequence; and interpolating the spectral interference signal corresponding to the original wavenumber sequence using an interpolation algorithm so that the interpolated interference signal is uniformly arranged on the equal interval wavenumber sequence.

[0012] Furthermore, the specific method for acquiring the reference light spectrum signal output by only the reference arm is as follows: the sample arm of the optical low coherence interference system is blocked, only the optical path of the reference arm is kept open, and the light intensity signal output by the reference arm is acquired through an optical signal receiving device, corresponding to the reference light spectrum signal.

[0013] Furthermore, the window function of the Hanning window applied to the standard interference signal has a cosine-weighted form. By modulating the amplitude of the standard interference signal, the sidelobe signal in the subsequent spectrum analysis is suppressed.

[0014] Furthermore, the modulated signal is subjected to spectral analysis and peak and sub-peak values ​​are extracted. Specifically, this includes: processing the Hanning window modulated signal using spectral transformation to obtain the corresponding spectral sequence; the peak of the main lobe of the spectrum is the spectral line with the largest amplitude in the spectral sequence, and the adjacent sub-peak values ​​are the spectral lines on both sides of the peak whose amplitudes are closest to the peak. The specific position of the sub-peak value is determined by comparing the amplitudes of the spectral lines on both sides of the peak.

[0015] Furthermore, the calculation of the frequency correction amount based on the peak-to-second peak amplitude ratio derived from the Hanning window spectral modulus function specifically includes: first, calculating the amplitude ratio of the main lobe peak to the adjacent second peak; then, converting the amplitude ratio into a corresponding frequency deviation compensation value according to the pre-established "amplitude ratio-frequency deviation" correlation of the Hanning window spectral modulus function; finally, determining the identifier bit based on the position of the second peak relative to the peak, and determining the compensation direction through the identifier bit, thereby obtaining the frequency correction amount; the precise frequency of the interference signal is obtained by superimposing the integer frequency of the coordinate position corresponding to the peak with the frequency correction amount.

[0016] Furthermore, the spectral resolution of the optical low-coherence interference system is determined in the following way: the spectral resolution is determined by the wavelength range of the broadband light source used by the system, and is calculated by the correlation between the starting operating wavelength and the cutoff operating wavelength of the light source. The starting operating wavelength and the cutoff operating wavelength are determined according to the wavelength range of the broadband light source used by the optical low-coherence interference system.

[0017] Furthermore, a high-precision optical coherent ranging frequency parameter estimation system resistant to noise interference includes:

[0018] The signal acquisition module is used to acquire the spectral interference signal of the optical low-coherence interferometer system and the reference light spectral signal output only by the reference arm;

[0019] The preprocessing module, connected to the signal acquisition module, is used to convert the spectral interference signal into an interference signal with equal intervals in wavenumber space, and to normalize the spectral density amplitude of the interference signal using the reference light spectral signal to obtain a standard interference signal with equal intervals in wavenumber space and constant amplitude, so as to eliminate the interference of light source spectral fluctuations and non-uniform sampling on frequency estimation.

[0020] The Hanning window modulation module, connected to the preprocessing module, is used to apply Hanning window modulation to the standard interference signal and suppress spectral leakage by utilizing the sidelobe suppression characteristics of the Hanning window.

[0021] The frequency estimation module, connected to the Hanning window modulation module, is used to perform spectral analysis on the modulated signal, extract the peak value of the main lobe of the spectrum and the adjacent second peak value, calculate the frequency correction amount based on the peak value to second peak value amplitude ratio derived from the Hanning window spectral modulus function, and obtain the accurate frequency of the interference signal.

[0022] The displacement calculation module, connected to the frequency estimation module, is used to calculate the displacement of the object under test based on the product of the precise frequency and the spectral resolution of the optical low-coherence interference system, combined with the refractive index of light in the measurement medium.

[0023] And a computer device including a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the method described above.

[0024] A non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, implements the method described above.

[0025] Compared with the prior art, the present invention and its preferred embodiments have at least the following beneficial effects:

[0026] First, this invention effectively solves the core technical defects of non-uniform sampling and amplitude variation of the original interference signal in existing low-coherence optical ranging systems through targeted signal preprocessing design. By performing wavelength-wavenumber spatial conversion and equal-interval processing, the non-uniform signal collected by wavelength is transformed into a signal uniformly arranged in the wavenumber domain. Then, the spectral density amplitude is normalized by combining the reference light spectrum signal, so that the signal meets the characteristics of a standard oscillating signal. This lays the foundation for subsequent high-precision frequency estimation and avoids the frequency estimation deviation caused by directly processing non-standard signals in existing methods.

[0027] Secondly, this invention uses a Hanning window to modulate the preprocessed signal. By leveraging the excellent sidelobe suppression characteristics of the Hanning window, the impact of noise interference and spectral leakage on frequency estimation is effectively reduced. Compared with traditional rectangular windows or other window function modulation methods, it can maintain more stable frequency estimation accuracy under the same noise environment. This solves the problem that the accuracy of existing frequency extraction methods is prone to decline in actual noise scenarios, and improves the anti-interference capability and environmental adaptability of the system.

[0028] Furthermore, this invention calculates the frequency correction based on the ratio of peak to subpeak amplitude derived from the Hanning window spectral modulus function. This breaks through the limitation of traditional fast Fourier transform, which can only identify integer frequency, and achieves high-precision frequency estimation of interference signals. Consequently, it improves the displacement measurement accuracy of optical low-coherence ranging systems from the traditional micrometer level to a higher precision level, meeting the current demand for micro-nano level displacement measurement in the field of precision measurement and filling the application gap of existing technologies in this precision range.

[0029] Finally, the technical solution of the present invention does not require complex hardware modifications. It can achieve a dual improvement in measurement accuracy and noise resistance simply by optimizing the signal processing flow. This not only reduces the cost of system upgrades but also ensures compatibility with the hardware architecture of existing optical low coherence ranging systems. This significantly enhances the practical value of the technical solution and effectively expands the application potential of optical coherence ranging technology in the fields of micro-nano precision measurement, such as semiconductor manufacturing, microelectromechanical system testing, and precision calibration. Attached Figure Description

[0030] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0031] Figure 1 This is a diagram of an optical low-coherence displacement measurement system according to an embodiment of the present invention, wherein 1 is a superluminescent light source, 2 is a collimating lens, 3 is a filter, 4 is a grating, 5 is a focusing lens, 6 is a camera, 7 is a host computer, 8 is a signal generator, 9 is a PZT, 10 is a focusing objective lens, 11 is a reference mirror, 12 is a focusing lens, and 13 is a beam splitter.

[0032] Figure 2 This is a diagram illustrating the signal processing procedure according to an embodiment of the present invention;

[0033] Figure 3 The graph shows the spectral interference signal and the spectral density function of the light source in an embodiment of the present invention.

[0034] Figure 4 The graph shows the interference signal and spectral density function after wavenumber homogenization in an embodiment of the present invention.

[0035] Figure 5 This is an interference signal diagram after wavenumber homogenization and power normalization according to an embodiment of the present invention;

[0036] Figure 6 The fast Fourier transform results and main lobe detail images are shown in the embodiments of the present invention.

[0037] Figure 7 This is a comparison chart of frequency correction and no correction results in an embodiment of the present invention;

[0038] Figure 8 This is a comparison diagram of the Hanning window ratio correction method and the rectangular window ratio correction method according to an embodiment of the present invention;

[0039] Figure 9 This is a comparison chart of measurement errors between the Hanning window ratio correction method and the rectangular window ratio correction method in an embodiment of the present invention. Detailed Implementation

[0040] To make the features and advantages of the present invention more apparent and understandable, specific embodiments are described below in detail:

[0041] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0043] This invention employs a spectral ratio correction method based on Hanning window modulation to achieve high-precision estimation of the frequency of spectral interference signals. First, addressing the non-uniform sampling and spectral density fluctuations in low-coherence optical systems, a method is proposed to convert the interference spectral signal from wavelength space to wavenumber space and normalize the spectral density amplitude using a reference light signal, transforming the interference signal into a standard oscillation form with equal intervals and amplitudes. Subsequently, Hanning window modulation is applied and an FFT transform is performed. Utilizing the functional relationship between the ratio of the main lobe peak to the secondary peak of the interference signal spectrum and the deviation between the true frequency and peak position, combined with the established mathematical model and modulus function relationship, the frequency of the interference signal is accurately estimated. Compared to other window function modulation methods, Hanning window modulation can significantly improve the signal's noise immunity, enhance the accuracy and stability of practical optical coherent ranging systems, and greatly broaden the application potential of low-coherence ranging systems.

[0044] The implementation process of this embodiment is described in detail below:

[0045] The specific principle of Hanning window modulation ratio correction is as follows:

[0046] The definition of a Hanning window is:

[0047] (1)

[0048] Its spectral modulus function is:

[0049] (2)

[0050] in , This is the frequency correction factor. At this point, the ratio of the peak value to the sub-peak value of the frequency signal can be obtained as:

[0051] (3)

[0052] The frequency correction amount can be calculated from the above formula:

[0053] (4)

[0054] Therefore, the accurate frequency of the single-frequency signal can be obtained. The value is:

[0055] (5)

[0056] Because the Hanning window has excellent sidelobe suppression, the comparison correction method based on Hanning window modulation has higher frequency estimation accuracy and better noise immunity under the same noise interference.

[0057] The ratio correction principle described above is applied to oscillating signals with equal sampling intervals and equal amplitudes. However, signals obtained from low-coherence light sources are oscillating signals with non-equal sampling intervals and non-equal amplitudes, and cannot be directly processed using the above method. Therefore, this invention proposes preprocessing low-coherence interference signals to make them meet the characteristics of equal sampling intervals and equal amplitudes.

[0058] Preprocessing 1: Wavelength-Wavenumber Spatial Homogenization Resampling. Low-coherence systems typically use a spectrometer as the signal receiver, obtaining data that is light intensity uniformly arranged according to wavelength. However, the principle of low-coherence optical interference signals indicates that the interference signal is uniformly arranged according to wavenumber (the reciprocal of wavelength). Therefore, it is necessary to resample the spectral interference data using wavenumber spatial homogenization. The specific process is as follows:

[0059] Obtain the initial sequence of wavelength and light intensity { }, where wavelength sequence for Through the relationship between wavenumber and wavelength Obtain the corresponding wavenumber sequence for For wavenumber sequences The operation transforms it into a new wavenumber sequence with equal intervals. for The process is as follows:

[0060] (6)

[0061] Then it can be based on the original wavenumber sequence and new wavenumber sequence and the original interference signal sequence Interference signals uniformly arranged in wavenumber space are obtained using algorithms such as cubic spline interpolation. The example process is as follows:

[0062] (7)

[0063] Interp2 is Matlab's spline interpolation algorithm; those skilled in the art can choose different implementation methods according to actual needs. Through the above operations, the wavenumber spatial uniformity of the low-coherence optical interference signal is achieved.

[0064] Preprocessing 2: Optical Power Normalization. Due to the limitations of the light emission mechanism, the light energy radiated by all light sources varies with wavelength. Therefore, in low-coherence systems, the optical interference signal is modulated by the spectral density function of the light source, exhibiting non-constant amplitude characteristics. Optical power normalization of the spectral interference data is necessary. The specific process is as follows:

[0065] The sample arm is blocked, and only the spectral signal of the reference arm is collected as a spectral density function. Preprocessing operation 1 is performed to make it a spectral density function uniformly arranged according to wavenumber. Then the spectral interference signal Divide by Obtain equally spaced and equal amplitude interference signals ,Right now:

[0066] (8)

[0067] Subsequently, a Hanning window is applied to the signal as follows:

[0068] (9)

[0069] After the above preprocessing, the frequency calculation result can be corrected by the ratio correction method to obtain a high-precision displacement measurement result. The specific process is as follows: Figure 2 As shown:

[0070] Step S1: Modulate the signal using the Hanning window Perform a Fast Fourier Transform to obtain its spectral sequence The transformation formula is as follows:

[0071] (10)

[0072] Step S2: Process the spectral sequence Find its peak and second peak and obtain the corresponding coordinates. , and judgment flag (Used to indicate the position of the secondary peak relative to the peak), the specific method is as follows:

[0073] (11)

[0074] (12)

[0075] (13)

[0076] (14)

[0077] Step S3: Precise frequency of the equal-amplitude single-frequency interference fringe signal From the integer part and decimal part The result is obtained by adding the ingredients together, and the calculation formula is as follows:

[0078] (15)

[0079] (16)

[0080] Step S4: Results of optical low-coherence displacement measurement Spectral resolution of low coherence systems With the precise frequency of the interference fringes and the refractive index of light in air Multiplying them together, their relationship is as follows:

[0081] (17)

[0082] (18)

[0083] in, , These are the start wavelength and cutoff wavelength of the low-coherence system, respectively; The refractive index of the working wavelength in air can be obtained by looking up environmental parameters in a table. In scenarios without extremely high requirements, it can be directly taken as 1.

[0084] Compared to existing technologies, the solutions provided in the embodiments of the present invention above are as follows:

[0085] 1. Addressing the variable-interval and variable-amplitude characteristics of optical coherent interference signals, this study employs equally spaced resampling and power normalization to ensure the signal conforms to the characteristics of a standard oscillating signal. Subsequently, the frequency correction function is derived from the Hanning window's spectral density function. High-precision frequency identification of the interference signal is achieved using the measured ratio of peak to subpeak values ​​in the spectrum. This improves the measurement accuracy of the optical coherent displacement measurement system from the micrometer level to the nanometer level, significantly enhancing system performance and expanding its application potential in precision measurement.

[0086] 2. The proposed Hanning window ratio correction method has excellent noise resistance. Compared with the traditional rectangular window modulation ratio correction method, the Hanning window modulation-based comparison correction method has higher frequency estimation accuracy and better measurement accuracy even under noisy conditions, making the optical coherent displacement measurement system more practical.

[0087] The following further demonstrates and introduces the specific implementation and testing process of the above-mentioned solutions of the present invention:

[0088] like Figure 1 As shown, this embodiment includes a reflector (as the sample to be tested) attached to the PZT (9), a collimating lens (2), a beam splitter (13), a superluminescent light source (1), a spectral analysis assembly (including a filter (3), a grating (4), a focusing lens (5) and a camera (6)), a host computer (7), a reference reflector (11) and a signal generator (8).

[0089] The specific working principle is as follows: The wide-bandwidth light emitted by the superluminescent light source (1) is split into two paths by the beam splitter (13) according to the set beam splitting ratio: reference light and probe light. The reference light is transmitted to the reference arm, reflected by the reference mirror (11), and returns to the beam splitter (13) along the same path; the probe light is focused by the collimating lens (2) onto the surface of the mirror attached to the PZT (9), and also returns to the beam splitter (13) after reflection. The two light signals meet and interfere in the beam splitter (13). The interference signal is received by the spectral analysis component (first, stray light is filtered out by the filter (3), then dispersed by the grating (4), and then the spectrum is focused onto the camera (6) by the focusing lens (5), converted into an electrical signal, and transmitted to the host computer (7) for further processing. The signal generator (8) is used to generate an electrical signal to drive the PZT (9) and control the precise displacement of the sample under test.

[0090] By combining this optical low-coherence displacement measurement system with the Hanning window modulation spectral ratio correction method, displacement measurement with nanometer-level precision can be achieved, effectively resisting noise interference and improving the stability and accuracy of the system measurement.

[0091] The above interference signals are received by the spectrometer and converted into electrical signals, which are then transmitted to the host computer for further processing. Figure 3 The original interferometric signal acquired by the spectrometer and the spectral density function of the light source acquired only by the reference light are shown. The signal is then converted to the wavenumber domain and subjected to homogenization interpolation to obtain... Figure 4 The wavenumber domain uniformly arranged interference signal and light source spectral density function are shown; further, the signal is power normalized and multiplied by a Hanning window to obtain... Figure 5 The Hanning window modulated standard cosine interference signal is shown. Subsequently, a Fast Fourier Transform is performed on this signal to extract the peak and subpeak values, as shown below. Figure 6 As shown (signal-to-noise ratio approximately 60dB), the frequency deviation is calculated using the peak-to-peak relationship derived from the spectral modulus function of the Hanning window, thereby determining the precise number of periods of the interference signal. The product of this number of periods and the system resolution is the current position of the sample relative to the reference mirror. By comparing the position data at different times with the initial time, the distance the sample has moved can be obtained.

[0092] To verify the effectiveness of the present invention, a signal generator was used to drive the piezoelectric ceramic to generate a frequency of 3.2 Hz and an amplitude of 6.6 Hz. The vibration signal was collected, and the interference signal sequence was acquired simultaneously. The ratio correction method and the peak method were used for processing, respectively. The results show that the peak method, due to spectral leakage, cannot accurately calculate the number of periods of the interference signal, resulting in insufficient system resolution and a stepped distribution of the measurement results. The Hanning window ratio correction method effectively overcomes this problem, improving the system resolution to the nanometer level. The measurement results are in high agreement with the set amplitude, as shown in the results... Figure 7 As shown. To further verify the high-precision performance of the proposed Hanning window ratio correction method, the interference signal was subjected to both the Hanning window ratio correction method and the rectangular window ratio correction method. The calculation results are shown below. Figure 8 As shown in the figure, the results of the Hanning window ratio correction method are in better agreement with the ideal error-free result, while the rectangular window ratio correction method, although generally consistent, exhibits noticeable errors in certain areas. Subtracting the ideal error-free result from the measurement results of the rectangular window ratio correction method and the Hanning window ratio correction method yields the measurement errors of the different methods, as shown in the figure. Figure 9 As shown, it is evident that the rectangular window ratio correction method has an error of approximately 10 nm, while the Hanning window ratio correction method has a measurement error of less than 1 nm. These measurement results demonstrate that the Hanning window ratio correction method has higher measurement accuracy and is more suitable for applications requiring nanometer-level precision.

[0093] Based on the same inventive concept, this invention also provides a computer device, comprising: one or more processors, and a memory for storing one or more computer programs; the programs include program instructions, and the processor executes the program instructions stored in the memory. The processor may be a Central Processing Unit (CPU), or 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. It is the computing and control core of the terminal, used to implement one or more instructions, specifically for loading and executing one or more instructions stored in a computer storage medium to implement the above-described method.

[0094] It should be further explained that, based on the same inventive concept, the present invention also provides a computer storage medium storing a computer program, which, when executed by a processor, performs the above-described method. This storage medium can be any combination of one or more computer-readable media. A computer-readable medium can be a computer-readable signal medium or a computer-readable storage medium. A computer-readable storage medium can be, for example, but not limited to, an electrical, magnetic, optical, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of computer-readable storage media (a non-exhaustive list) include: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), optical fiber, portable compact disk read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In the present invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device.

[0095] It should be noted that, unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0096] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

[0097] This invention is not limited to the preferred embodiment described above. Anyone inspired by this invention can derive other forms of frequency parameter estimation methods for high-precision optical coherent ranging that are resistant to noise interference. All equivalent variations and modifications made within the scope of the claims of this invention shall fall within the scope of this invention.

Claims

1. A frequency parameter estimation method for anti-noise interference high-precision optical coherent ranging, characterized in that, The method comprises the following steps: obtaining a spectral interference signal of an optical low-coherence interference system and a reference light spectral signal output by a reference arm only, converting the spectral interference signal into an interference signal arranged at equal intervals in wave number space, and normalizing the interference signal in spectral density amplitude by using the reference light spectral signal to obtain a standard interference signal arranged at equal intervals in wave number space and having constant amplitude, so as to eliminate the interference of spectral fluctuation of a light source and non-uniform sampling on frequency estimation; applying a Hanning window modulation to the standard interference signal, suppressing spectral leakage by using the sidelobe suppression characteristic of the Hanning window, performing spectral analysis on the modulated signal, extracting a peak value and an adjacent secondary peak value of a spectral main lobe, calculating a frequency correction amount based on a peak value to secondary peak value amplitude ratio relationship derived from a Hanning window spectral modulus function, and obtaining an accurate frequency of the interference signal; calculating a displacement amount of a measured object according to a product of the accurate frequency and a spectral resolution of the optical low-coherence interference system, and combining a refractive index of light in a measurement medium.

2. The frequency parameter estimation method of anti-noise interference high-precision optical coherent ranging according to claim 1, characterized in that: The conversion of the spectral interference signal into an interference signal arranged at equal intervals in wave number space specifically comprises the following steps: converting the spectral interference signal arranged uniformly in wavelength into a corresponding original wave number sequence according to an inherent conversion relationship between wavelength and wave number; performing equal interval processing on the original wave number sequence to obtain an equal interval wave number sequence; and performing interpolation on the spectral interference signal corresponding to the original wave number sequence by using an interpolation algorithm, so that the interference signal after interpolation is arranged uniformly on the equal interval wave number sequence.

3. The frequency parameter estimation method of anti-noise interference high-precision optical coherent ranging according to claim 1, characterized in that: The specific manner of collecting the reference light spectral signal output by the reference arm only is as follows: shielding a sample arm of the optical low-coherence interference system, leaving only the reference arm light path on, and collecting an optical intensity signal output by the reference arm by using an optical signal receiving device, so as to obtain the corresponding reference light spectral signal.

4. The frequency parameter estimation method of anti-noise interference high-precision optical coherent ranging according to claim 1, characterized in that: The window function of the Hanning window applied to the standard interference signal has a cosine weighting form, and the sidelobe signal in subsequent spectral analysis is suppressed by amplitude modulation of the standard interference signal.

5. The frequency parameter estimation method of anti-noise interference high-precision optical coherent ranging according to claim 1, characterized in that: The spectral analysis on the modulated signal and the extraction of the peak value and the secondary peak value specifically comprise the following steps: processing the signal modulated by the Hanning window by using a spectral transformation method to obtain a corresponding spectral sequence; the peak value of the spectral main lobe is a spectral line with the maximum amplitude in the spectral sequence, and the adjacent secondary peak value is a spectral line with an amplitude closest to the peak value on both sides of the peak value, and the specific position of the secondary peak value is determined by comparing the amplitudes of the spectral lines on both sides of the peak value.

6. The frequency parameter estimation method of anti-noise interference high-precision optical coherent ranging according to claim 1, characterized in that: The calculation of the frequency correction amount based on the peak value to secondary peak value amplitude ratio relationship derived from the Hanning window spectral modulus function specifically comprises the following steps: first, calculating the amplitude ratio of the peak value of the spectral main lobe to the adjacent secondary peak value; then, converting the amplitude ratio into a corresponding frequency deviation compensation value according to a pre-established "amplitude ratio-frequency deviation” correlation relationship of the Hanning window spectral modulus function; finally, determining an identification bit by combining the position of the secondary peak value relative to the peak value, determining a compensation direction by using the identification bit, and then obtaining the frequency correction amount; and the accurate frequency of the interference signal is obtained by superimposing an integer frequency of a coordinate position corresponding to the peak value and the frequency correction amount.

7. The frequency parameter estimation method of anti-noise interference high-precision optical coherent ranging according to claim 1, characterized in that: The spectral resolution of the optical low-coherence interferometry system is determined by the wavelength range of the broadband light source used by the system, and is calculated by the correlation of the start wavelength and the cutoff wavelength of the light source, which are determined according to the wavelength range of the broadband light source used by the optical low-coherence interferometry system.

8. A frequency parameter estimation system for anti-noise interference high precision optical coherent ranging, characterized in that, The method comprises the following steps: a signal acquisition module is configured to acquire a spectral interference signal of an optical low-coherence interferometry system and a reference light spectral signal output by a reference arm only; a preprocessing module is connected to the signal acquisition module and is configured to convert the spectral interference signal into an interference signal arranged at equal intervals in a wave number space, and normalize the spectral density amplitude of the interference signal by using the reference light spectral signal to obtain a standard interference signal with equal intervals in the wave number space and constant amplitude, so as to eliminate the interference of spectral fluctuations and non-uniform sampling of the light source on frequency estimation; a Hann window modulation module is connected to the preprocessing module and is configured to apply Hann window modulation to the standard interference signal, and suppress spectral leakage by using the sidelobe suppression characteristic of the Hann window; a frequency estimation module is connected to the Hann window modulation module and is configured to perform spectral analysis on the modulated signal, extract the peak value and the adjacent secondary peak value of the spectral main lobe, calculate a frequency correction amount based on the peak value and the secondary peak value amplitude ratio relationship derived by the Hann window spectral modulation function, and obtain an accurate frequency of the interference signal; a displacement calculation module is connected to the frequency estimation module and is configured to calculate the displacement amount of the measured object according to the product of the accurate frequency and the spectral resolution of the optical low-coherence interferometry system, and in combination with the refractive index of light in the measurement medium.

9. A computer device, comprising: The storage medium stores a computer program, and the processor executes the computer program to implement the method of any one of claims 1-7.

10. A non-transitory computer-readable storage medium, comprising: The storage medium stores a computer program, and the processor executes the computer program to implement the method of any one of claims 1-7.

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