OCT (optical coherence tomography) wide-spectrum nonlinear interference signal wave number calibration and depth reconstruction method

Abstract

The invention discloses an OCT (Optical Coherence Tomography) broadband spectrum nonlinear interference signal wave number calibration and depth reconstruction method, which comprises the following steps of: acquiring a nonlinear sampling broadband spectrum interference signal of a single-layer reflector by utilizing frequency domain OCT, removing a direct current item and noise, performing continuous wavelet transform on the signal by taking Morlet complex wavelet as a generating function, detecting and extracting a wavelet ridge line through a wavelet modulus maximum value, and reconstructing the depth of the nonlinear sampling broadband spectrum interference signal. Obtaining an instantaneous phase and converting the instantaneous phase into wave number information, and constructing a nonlinear Fourier transform matrix by using the wave number information; and testing a to-be-tested target by using the frequency domain OCT to obtain a broadband spectrum interference signal, carrying out direct current item removal and noise treatment, and then carrying out calculation by using the constructed nonlinear Fourier transform matrix to obtain reflectivity information of the to-be-tested target at different depths. According to the method, the problem of nonlinear sampling of the broadband spectrum interference signal in the frequency domain OCT is solved, and high-precision wave number calibration and accurate recovery of nonlinear sampling interference signal depth information are realized.

Description

TECHNICAL FIELD

[0001] The present application relates to an OCT wide spectrum nonlinear interference signal wave number calibration and depth reconstruction method, in particular to an OCT wide spectrum nonlinear interference signal wave number calibration and depth reconstruction method for realizing accurate restoration and wave number calibration of depth imaging of nonlinear interference signals, and belongs to the field of frequency domain OCT imaging. BACKGROUND

[0002] OCT, namely optical coherence tomography, is a non-invasive and high-resolution imaging technology, which has been widely used in clinical practice. Among them, the most successful application of OCT is ophthalmology, which has become a standard eye examination method.

[0003] In the OCT imaging system, the micron-level structure information of biological tissues is obtained by analyzing the interference signals of the reference light and the sample backscattered light. There are two technical bottlenecks in the traditional method. One is that the imaging spectrometer obtains nonlinear interference signals due to the existence of jitter motion; the other is that in the nonlinear sampling of the interference signals, it is very complex to obtain the wave number information, and the interference signals will be non-uniformly sampled due to mechanical push scanning nonlinearity or environmental disturbance.

[0004] Therefore, a new method with high robustness and high resolution is needed to realize accurate restoration and wave number calibration of depth imaging of nonlinear interference signals. SUMMARY

[0005] The problem to be solved by the present application is to provide an OCT wide spectrum nonlinear interference signal wave number calibration and depth reconstruction method, which has the characteristics of realizing accurate restoration and wave number calibration of depth imaging of nonlinear interference signals.

[0006] To solve the above technical problems, the technical scheme of the present application is as follows: an OCT wide spectrum nonlinear interference signal wave number calibration and depth reconstruction method, which has the following steps:

[0007] Step S1: obtaining nonlinear sampling wide spectrum interference signals of a single layer mirror by frequency domain OCT, removing the direct current term to generate a complex domain interference signal sequence, and performing noise reduction processing on the interference signals;

[0008] Step S2: using Morlet complex wavelet as a mother function to perform continuous wavelet transform on the processed interference signals to obtain wavelet coefficients in the scale-time domain;

[0009] Step S3: based on the wavelet modulus maximum detection algorithm, extracting wavelet ridge points in the scale-time plane, connecting to form a wavelet ridge line, extracting the instantaneous phase of the interference signals according to the wavelet ridge line, and converting it into wave number information through a phase formula;

[0010] Step S4: Using the wavenumber information obtained in step S3, construct the nonlinear Fourier transform matrix kernel;

[0011] Step S5: Use frequency domain OCT to acquire the nonlinear sampling broadband interference signal of the target under test, remove the DC term, generate the complex domain interference signal sequence of the target under test, and perform noise reduction processing on the interference signal of the target under test;

[0012] Step S6: Perform nonlinear Fourier matrix calculation on the nonlinear sampled broadband interferometric signal of the target to be measured and the nonlinear Fourier transform matrix kernel constructed in step S4 to obtain the depth information of the target to be measured.

[0013] Preferably, the method for removing the DC term in step S1 is to use the direct subtraction of the average value, and the method for noise reduction is to use Gaussian smoothing filtering;

[0014] The expression for the preprocessed interference signal is:

[0015]

[0016] In the formula, I(σ) represents the interference signal of a single-layer mirror, σ represents the wavenumber information, and Δ represents the optical path difference. The intensities of reflected light at different depths of the probe are represented by , where i represents a complex number and d represents the infinitesimal element of the integral variable.

[0017] Preferably, the Morlet complex wavelet used as the generating function in step S2 is represented as:

[0018]

[0019] In the formula, ψ(t) represents the Morlet complex wavelet, t represents the variable of the wavelet transform, and f b f represents the envelope width of the mother wavelet. C denoted by , i represents the wavelet center frequency, and i represents a complex number.

[0020] Preferably, in step S2, a continuous wavelet transform is performed on the processed interference signal to obtain the wavelet coefficients in the scale-time domain:

[0021]

[0022] In the formula, W f (a,b) represent the wavelet coefficients in the scale-time domain, f represents the acquired signal, and ψ a,b (t) represents a sub-wavelet sequence obtained by scaling and translating the mother wavelet ψ(t). <f,ψ a,b (t)> represents the inner product of the signal and the mother wavelet. express Complex conjugate, For ψa,b (t) is calculated by inner product and conjugate is obtained. x represents a continuous variable, the scaling factor a and the translation factor b also represent continuous variables, and t represents the variables of wavelet transform.

[0023] Preferably, in step S3, the wavelet ridge is extracted using the modulus maxima method, and the phase on the obtained ridge is:

[0024]

[0025] In the formula, Indicates the phase on the ridge line, ImW f (a,b) represents the imaginary part of the wavelet transform, ReW f (a,b) represents the real part of the wavelet transform, where a represents the scaling factor and b represents the translation factor. Both a and b are continuous variables.

[0026] Preferably, in step S3, the instantaneous phase of the interference signal is extracted based on the wavelet ridge, and the wave number information is calculated using the phase formula;

[0027] The phase formula is:

[0028]

[0029] In the formula, σ m Indicates wavenumber information, Δ0 represents the phase, and Δ0 represents the interference optical path difference corresponding to the mirror.

[0030] Preferably, in step S4, the nonlinear Fourier transform matrix kernel S is a van der Monte Carlo matrix, and its expression is:

[0031]

[0032] in,

[0033]

[0034] In the formula, S(σ) m ) represents the m-th wavenumber sampling point obtained through wavelet transform, σ m Let σ represent the wavenumber of the m-th wavenumber sampling point, where i represents a complex number. max This represents the maximum wavenumber, and the properties of this matrix are related to the wavenumber information of the sampling points.

[0035] Preferably, the method for removing the DC term in step S5 is to use the direct subtraction of the average value, and the method for noise reduction is to use Gaussian smoothing filtering;

[0036] The expression for the preprocessed interferometric signal of the target under test is as follows:

[0037]

[0038] In the formula, I1(σ) represents the interference signal of the target under test, σ represents the wavenumber information, and Δ represents the optical path difference. This represents the reflected light intensity information at different depths of the target, where i represents a complex number and d represents the infinitesimal symbol of the integral variable.

[0039] Preferably, the formula for the nonlinear Fourier transform matrix in step S6 is:

[0040]

[0041] In the formula, The spectral information representing the depth reconstruction of the target under test is given by S, which represents the nonlinear Fourier transform matrix kernel, and I represents the interference signal of the target under test after preprocessing.

[0042] The advantages of this invention are as follows: The OCT wide-spectrum nonlinear interferometric signal wavenumber calibration and depth reconstruction method of this invention utilizes frequency-domain OCT to acquire the nonlinear sampled wide-spectrum interferometric signal of a single-layer reflector, performs DC term removal and noise reduction, performs continuous wavelet transform on the signal using Morlet complex wavelet as the mother function, extracts wavelet ridges through wavelet modulus maxima detection, obtains the instantaneous phase and converts it into wavenumber information, and then constructs a nonlinear Fourier transform matrix using the wavenumber information; the target under test is tested using frequency-domain OCT to obtain the wide-spectrum interferometric signal, performs DC term removal and noise reduction, and then uses the constructed nonlinear Fourier transform matrix to calculate and obtain the reflectivity information of the target at different depths. This method solves the problem of nonlinear sampling of wide-spectrum interferometric signals in frequency-domain OCT, and achieves high-precision wavenumber calibration and accurate reconstruction of depth information of nonlinear sampled interferometric signals.

[0043] The frequency domain OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method of the present invention combines the high time-frequency resolution of wavelet transform with the high-precision restoration capability of nonlinear Fourier kernel matrix, thereby completing the depth imaging restoration and wavenumber information acquisition of nonlinear sampled interferometric signals without the need for additional calibration equipment.

[0044] The OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method of the present invention is a novel method with both high robustness and high resolution, realizing accurate depth imaging reconstruction and wavenumber calibration of nonlinear interferometric signals. It is suitable for applications where depth imaging distortion and insufficient wavenumber information measurement accuracy are caused by nonlinear sampling of interferometric signals. Attached Figure Description

[0045] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0046] Figure 1 This is a flowchart illustrating a method for wavenumber calibration and depth reconstruction of OCT broadband nonlinear interferometric signals. Detailed Implementation

[0047] The frequency domain OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method of the present invention includes the following steps:

[0048] Step S1: Acquisition and preprocessing of interference signals from a single-layer mirror

[0049] The nonlinear sampling broadband interference signal of a single-layer mirror is obtained by frequency domain OCT, and the DC term is removed to generate a complex domain interference signal sequence. The interference signal is then subjected to noise reduction processing.

[0050] Step S2: Morlet complex wavelet transform and wavelet coefficient modulus distribution; Morlet complex wavelet is used as the mother function to perform continuous wavelet transform on the processed interference signal to obtain wavelet coefficients in the scale-time domain.

[0051] Step S3: Extraction of modulus maxima ridges and unwrapping of phases to obtain wavenumber information

[0052] Based on the wavelet modulus maxima detection algorithm, wavelet ridge points are extracted in the scale-time plane and connected to form wavelet ridge lines. The instantaneous phase of the interference signal is extracted based on the wavelet ridge lines and converted into wave number information using the phase formula.

[0053] Step S4: Construct the nonlinear Fourier transform matrix kernel

[0054] Using the wavenumber information obtained in step S3, a nonlinear Fourier transform matrix kernel is constructed;

[0055] Step S5: Interference signal of the target under test and preprocessing of the interference signal

[0056] The nonlinear sampling broadband interferometric signal of the target under test is obtained by frequency domain OCT, and the DC term is removed to generate a complex domain interferometric signal sequence of the target under test. The interferometric signal of the target under test is then subjected to noise reduction processing.

[0057] Step S6: Calculation of nonlinear Fourier transform matrix and depth reconstruction of the target.

[0058] The nonlinear sampling broadband interferometric signal of the target to be tested is obtained and the nonlinear Fourier transform matrix kernel constructed in step S4 is used to calculate the depth reconstruction information of the target to be tested.

[0059] The frequency domain OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method of the present invention combines the high time-frequency resolution of wavelet transform with the high-precision restoration capability of nonlinear Fourier kernel matrix, thereby completing the depth imaging restoration and wavenumber information acquisition of nonlinear sampled interferometric signals without the need for additional calibration equipment.

[0060] The OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method of the present invention is a novel method with both high robustness and high resolution, realizing accurate depth imaging reconstruction and wavenumber calibration of nonlinear interferometric signals. It is suitable for applications where depth imaging distortion and insufficient wavenumber information measurement accuracy are caused by nonlinear sampling of interferometric signals.

[0061] In step S1 above, the method for removing the DC term is to directly subtract the average value, and the method for noise reduction is to use Gaussian smoothing filter.

[0062] The expression for the preprocessed interference signal is as follows:

[0063]

[0064] In the formula, I(σ) represents the interference signal of a single-layer mirror, σ represents the wavenumber information, and Δ represents the optical path difference. The intensities of reflected light at different depths of the probe are represented by , where i represents a complex number and d represents the infinitesimal element of the integral variable.

[0065] The specific step S1 is as follows:

[0066] The original nonlinear sampling broadband interferometric signal of the single-layer mirror was obtained using frequency domain OCT.

[0067]

[0068] In the formula, I(σ) represents the interference signal of a single-layer mirror, σ represents the wavenumber information, and Δ represents the optical path difference. This represents the detected spectral signal. The DC term, which lacks spectral information, is removed by directly subtracting the average value, and the spectral duality is extended to the complex domain, satisfying... Substituting into the formula, we get

[0069]

[0070] The acquired raw interference signal is then subjected to Gaussian smoothing filtering to reduce noise and minimize the impact of environmental noise and system errors. In practical processing, the interference signal is a discrete sequence; therefore, discrete Fourier transform is typically used to recover the spectral information.

[0071]

[0072] In the formula, I DFT (Δ n ) represents discrete spectral information, I(mδσ) represents discrete interference fringes, N represents the number of interference fringe points, δσ represents the fringe spacing, i represents a complex number, and σ represents wavenumber information. When the interference signal is sampled nonlinearly, I is used. DFT (Δn The formula can lead to distortion; nonlinear Fourier transform can be used to recover the spectral information.

[0073]

[0074] In the formula, This indicates that discrete spectral information has been obtained, σ m σ represents the wave value. max I(σ) represents the maximum wave value. m ) represents the directly obtained nonlinear interference fringes.

[0075] In step S2, the continuous wavelet transform is a linear transform form whose core idea is the inner product of the signal and the wavelet mother function at different scales and translation positions. The Morlet complex wavelet is used as the mother function; the Morlet complex wavelet is...

[0076]

[0077] In the formula, ψ(t) represents the Morlet complex wavelet, t represents the variable of the wavelet transform, and f b f represents the envelope width of the mother wavelet. C denoted by , i represents the wavelet center frequency, and i represents a complex number.

[0078] In step S2, a continuous wavelet transform is performed on the processed interference signal to obtain the wavelet coefficients in the scale-time domain.

[0079]

[0080] In the formula, W f (a,b) represent the wavelet coefficients in the scale-time domain, f represents the acquired signal, and ψ a,b (t) represents a sub-wavelet sequence obtained by scaling and translating the mother wavelet ψ(t). <f,ψ a,b (t)> represents the inner product of the signal and the mother wavelet. express Complex conjugate, For ψ a,b (t) The conjugate is obtained by inner product calculation, and the inner product calculation is related to ψ. a,b (t) takes the conjugate to ensure that the transformation result is a complex number. Its function is to extract local phase information. x represents a continuous variable, the scaling factor a and the translation factor b also represent continuous variables, and t represents the variables of the wavelet transform.

[0081] The definition of the continuous wavelet transform of a one-dimensional function f(t) describes the inner product relationship between the function and the wavelet sequence, reflecting the degree of similarity between the two. Amplitude a r(b) and the phase φ(b) of the wavelet transform together reflect the similarity between the one-dimensional function f(t) and the wavelet sequence. When the local frequency of the function is the same as or close to the oscillation frequency of the wavelet function at the corresponding scale, the wavelet transform coefficients, i.e., the amplitude, are relatively large; conversely, the amplitude is relatively small. The line connecting the positions of the maximum amplitude of the wavelet transform is the ridge of the wavelet transform. The wavelet scale a satisfies the following condition:

[0082]

[0083] In the formula, a represents the wavelet scale, a r (b) represents the amplitude, f c φ(b) represents the envelope width of the mother wavelet, and φ(b) represents the phase of the wavelet transform.

[0084] In step S3, the wavelet coefficient modulus reaches a local maximum, corresponding to the point [b, a]. r (b)] is called a wavelet ridge point. Connecting the corresponding ridge points on the time-scale plane forms the wavelet ridge line. The 'a' corresponding to the wavelet ridge line is the optimal scale. The wavelet ridge is extracted using the modulus maxima method, and the phase on the obtained ridge line is:

[0085]

[0086] In the formula, Indicates the phase on the ridge line, ImW f (a,b) represents the imaginary part of the wavelet transform, ReW f (a,b) represents the real part of the wavelet transform.

[0087] In step S3, the instantaneous phase of the interference signal is extracted based on the wavelet ridge, and the wave number information is calculated using the phase formula.

[0088] The phase formula is:

[0089]

[0090] In the formula, σ m Indicates wavenumber information, Δ0 represents the phase, and Δ0 represents the interference optical path difference corresponding to the mirror.

[0091] The change in wavenumber can be calculated as follows:

[0092]

[0093] In step S4, the nonlinear Fourier transform matrix kernel S is a van der Monte Carlo matrix, and its expression is:

[0094]

[0095] in

[0096]

[0097] In the formula, S(σ) m ) represents the m-th wavenumber sampling point obtained through wavelet transform, σ m Let σ represent the wavenumber of the m-th wavenumber sampling point, where i represents a complex number. max This represents the maximum wavenumber, and the properties of this matrix are related to the wavenumber information of the sampling points.

[0098] Matrix S is a nonlinear Fourier transform kernel, belonging to the van der Monte Carlo matrix. The properties of this matrix are only related to the wavenumber information of the sampling points. The wavenumber information obtained in step S2 is substituted into S to construct the nonlinear Fourier transform matrix kernel.

[0099] In step S5, the method for removing the DC term is to directly subtract the average value, and the method for noise reduction is to use Gaussian smoothing filter.

[0100] The expression for the preprocessed interferometric signal of the target under test is as follows:

[0101]

[0102] In the formula, I1(σ) represents the interference signal of the target under test, σ represents the wavenumber information, and Δ represents the optical path difference. This represents the reflected light intensity information at different depths of the target, where i represents a complex number and d represents the infinitesimal symbol of the integral variable.

[0103] Step S5 is the same as step S1. The original nonlinear sampling broadband interferometric signal of the target under test is obtained by frequency domain OCT. The DC term without spectral information is removed by directly subtracting the average value. Then, the original interferometric signal is denoised by Gaussian smoothing filter to obtain the preprocessed original nonlinear sampling broadband interferometric signal I1(σ) of the target under test.

[0104] The formula for the nonlinear Fourier transform matrix in step S6 is:

[0105]

[0106] in,

[0107]

[0108] In the formula, The spectral information representing the depth reconstruction of the target under test is given by S, where S represents the nonlinear Fourier transform matrix kernel, and I represents the preprocessed interference signal of the target under test. The original nonlinear sampled broadband interference signal I1(σ) of the target under test obtained in step S5 is substituted into the equation... The depth reconstruction information of the target under test is obtained by performing nonlinear Fourier matrix transformation calculation.

[0109] The present invention discloses a method for wavenumber calibration and depth reconstruction of a broadband nonlinear interferometric signal using OCT. This method utilizes frequency-domain OCT to acquire a nonlinearly sampled broadband interferometric signal from a single-layer mirror. DC terms and noise are removed. A continuous wavelet transform is performed on the signal using Morlet complex wavelets as the mother function. Wavelet ridges are extracted through wavelet modulus maxima detection, and the instantaneous phase is obtained and converted into wavenumber information. A nonlinear Fourier transform matrix is ​​then constructed using this wavenumber information. The target under test is then tested using frequency-domain OCT to obtain a broadband interferometric signal. DC terms and noise are removed, and the constructed nonlinear Fourier transform matrix is ​​used to calculate the reflectivity information of the target at different depths. This method solves the problem of nonlinear sampling of broadband interferometric signals in frequency-domain OCT, achieving high-precision wavenumber calibration and accurate reconstruction of depth information from the nonlinearly sampled interferometric signal.

[0110] It should be understood that the above description is for illustrative purposes and not for limitation. Many embodiments and applications beyond the provided examples will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of this teaching should not be determined by reference to the above description, but rather by reference to the appended claims and the full scope of their equivalents. For purposes of completeness, all articles and references, including patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein in the preceding claims is not intended as a waiver of that subject matter, nor should it be construed as an indication that the inventors have not considered it part of the disclosed inventive subject matter.

Claims

1. A method for wavenumber calibration and depth reconstruction of OCT broadband nonlinear interferometric signals, characterized in that... Includes the following steps: Step S1: Use frequency domain OCT to acquire the nonlinear sampling broadband interference signal of the single-layer mirror, remove the DC term, generate a complex domain interference signal sequence, and perform noise reduction processing on the interference signal; Step S2: Using Morlet complex wavelet as the mother function, perform continuous wavelet transform on the processed interference signal to obtain wavelet coefficients in the scale-time domain; Step S3: Based on the wavelet modulus maxima detection algorithm, extract wavelet ridge points in the scale-time plane and connect them to form wavelet ridge lines. Extract the instantaneous phase of the interference signal based on the wavelet ridge lines and convert it into wavenumber information using the phase formula. Step S4: Using the wavenumber information obtained in step S3, construct the nonlinear Fourier transform matrix kernel; Step S5: Use frequency domain OCT to acquire the nonlinear sampling broadband interference signal of the target under test, remove the DC term, generate the complex domain interference signal sequence of the target under test, and perform noise reduction processing on the interference signal of the target under test; Step S6: Perform nonlinear Fourier matrix calculation on the nonlinear sampled broadband interferometric signal of the target to be measured and the nonlinear Fourier transform matrix kernel constructed in step S4 to obtain the depth information of the target to be measured.

2. The OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method as described in claim 1, characterized in that: The method for removing the DC term in step S1 is to directly subtract the average value, and the method for noise reduction is to use Gaussian smoothing filter. The expression for the preprocessed interference signal is: In the formula, I(σ) represents the interference signal of a single-layer mirror, σ represents the wavenumber information, and Δ represents the optical path difference. The intensities of reflected light at different depths of the probe are represented by , where i represents a complex number and d represents the infinitesimal element of the integral variable.

3. The OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method as described in claim 1, characterized in that: The Morlet complex wavelet, which serves as the generating function in step S2, is represented as follows: In the formula, ψ(t) represents the Morlet complex wavelet, t represents the variable of the wavelet transform, and f b f represents the envelope width of the mother wavelet. C denoted by , i represents the wavelet center frequency, and i represents a complex number.

4. The OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method as described in claim 1, characterized in that: In step S2, a continuous wavelet transform is performed on the processed interference signal to obtain the wavelet coefficients in the scale-time domain: In the formula, W f (a,b) represent the wavelet coefficients in the scale-time domain, f represents the acquired signal, and ψ a,b (t) represents a sub-wavelet sequence obtained by scaling and translating the mother wavelet ψ(t). <f,ψ a,b (t)> represents the inner product of the signal and the mother wavelet. express Complex conjugate, For ψ a,b (t) is calculated by inner product and conjugate is obtained. x represents a continuous variable, the scaling factor a and the translation factor b also represent continuous variables, and t represents the variables of wavelet transform.

5. The OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method as described in claim 1, characterized in that: In step S3, the wavelet ridge is extracted using the modulus maxima method, and the phase on the obtained ridge is: In the formula, Indicates the phase on the ridge line, ImW f (a,b) represents the imaginary part of the wavelet transform, ReW f (a,b) represents the real part of the wavelet transform, where a represents the scaling factor and b represents the translation factor. Both a and b are continuous variables.

6. The OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method as described in claim 1, characterized in that: In step S3, the instantaneous phase of the interference signal is extracted based on the wavelet ridge, and the wave number information is calculated using the phase formula. The phase formula is: In the formula, σ m Indicates wavenumber information, Δ0 represents the phase, and Δ0 represents the interference optical path difference corresponding to the mirror.

7. The OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method as described in claim 1, characterized in that: In step S4, the nonlinear Fourier transform matrix kernel S is a van der Monte Carlo matrix, and its expression is: in, In the formula, S(σ) m ) represents the m-th wavenumber sampling point obtained through wavelet transform, σ m Let σ represent the wavenumber of the m-th wavenumber sampling point, where i represents a complex number. max This represents the maximum wavenumber, and the properties of this matrix are related to the wavenumber information of the sampling points.

8. The OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method as described in claim 1, characterized in that: In step S5, the method for removing the DC term is to directly subtract the average value, and the method for noise reduction is to use Gaussian smoothing filter. The expression for the preprocessed interferometric signal of the target under test is as follows: In the formula, I1(σ) represents the interference signal of the target under test, σ represents the wavenumber information, and Δ represents the optical path difference. This represents the reflected light intensity information at different depths of the target, where i represents a complex number and d represents the infinitesimal symbol of the integral variable.

9. The OCT broadband nonlinear interferometric signal wavenumber calibration and depth reconstruction method as described in claim 1, characterized in that: The formula for the nonlinear Fourier transform matrix in step S6 is: In the formula, The spectral information representing the depth reconstruction of the target under test is given by S, which represents the nonlinear Fourier transform matrix kernel, and I represents the interference signal of the target under test after preprocessing.

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