Evaluation method and system for axial resolution precision calculation based on swept-source OCT

Abstract

The application discloses an evaluation method and system for accurate calculation of axial resolution based on sweep frequency OCT, the method comprising: generating adjustable spectrum signals as analog interference signals by using a simulation light source model; and calculating simulation axial resolution based on the analog interference signals. An axial resolution measurement system is constructed, and the actual axial resolution is calculated based on a PSF method; the simulation axial resolution is compared with the actual axial resolution, if the difference is not more than a preset range, it is determined that the actual axial resolution is effective, if the difference exceeds the preset range, it is determined that the actual axial resolution is invalid, and the axial resolution measurement system is readjusted. The simulation method is consistent with the actual resolution calculation result, the evaluation method can be used to accurately evaluate the actual resolution calculation result by using the calculated simulation axial resolution, and is favorable for timely adjustment during actual OCT system measurement, and realization of accurate evaluation of the axial resolution of the OCT.

Description

Technical Field

[0001] This invention relates to the field of OCT imaging technology, and in particular to an evaluation method and system for accurate calculation of axial resolution based on swept-frequency OCT. Background Technology

[0002] OCT (Optical Coherence Tolerance) imaging is based on the principle of optical coherence, generating low-coherence signals through two backlight paths. One signal enters the reference arm, and the other enters the sample arm. Based on the imaging method and principle, OCT can be further divided into TD (Time-Domain) OCT and FD (Frequency-Domain) OCT. Time-Domain OCT uses a linear motor in the reference arm to move it back and forth, thus detecting information at different tissue depths. Frequency-Domain OCT is a more advanced technology than Time-Domain OCT, emitting light of different frequencies and wavelengths to penetrate tissues at different depths. Frequency-Domain OCT can be further divided into SD (Spectral-Domain) OCT and SS (Sweep-Frequency) OCT based on the imaging method. The advantage of OCT imaging in the endoscopic field lies in its ultra-high resolution. Therefore, accurate simulation calculation and detection resolution play a crucial role in system imaging. Current calculations of axial resolution for frequency-domain OCT imaging use standard formulas: Examples include patent (CN112057050A). However, this formula is actually derived for broadband Gaussian spectral images and is not entirely applicable to swept-frequency OCT. When using this formula to calculate the axial resolution of swept-frequency OCT, the measured axial resolution will differ significantly from the theoretical resolution. Therefore, a new simulation method for axial resolution is needed to accurately evaluate the actual axial resolution measurement using the simulation results. Summary of the Invention

[0003] Therefore, the purpose of this invention is to provide an evaluation method and system for accurate calculation of axial resolution based on swept frequency OCT, which can replace the traditional method of obtaining theoretical resolution based on spectral Gaussian, and obtain the axial resolution of OCT more accurately.

[0004] To achieve the above objectives, an evaluation method for accurate calculation of axial resolution based on swept-frequency OCT is characterized by the following steps:

[0005] S1. Construct a simulated light source model and generate simulated interference signals;

[0006] S2. Based on the simulated interference signal, roughly calculate the PSF function;

[0007] S3. Perform precise interpolation calculations for the PSF function using the results of the coarse calculations;

[0008] S4. Calculate the simulation axial resolution using the PSF function for accurate interpolation.

[0009] S5. Adjust the actual axial resolution measurement system and calculate the actual axial resolution of the actual interference signal based on PSF;

[0010] S7. Compare the simulated axial resolution with the actual axial resolution. If the difference does not exceed the preset range, the actual axial resolution is determined to be valid. If the difference exceeds the preset range, the actual axial resolution is determined to be invalid, and the axial resolution measurement system is readjusted.

[0011] More preferably, in S1, the construction of the simulated light source model and the generation of the simulated interference signal include the following methods:

[0012] Based on preset spectral parameters, a simulated spectrum is generated;

[0013] Construct bandwidth equal wavenumber distribution series and wavelength equal wavenumber distribution series, and use interpolation functions to generate envelopes;

[0014] The generated envelope is corrected using a cosine function to form a simulated interference signal.

[0015] More preferably, the preset spectral parameters include: setting the number of simulated sampling points according to the acquisition rate of the acquisition card; adjusting the spectral shape through Gaussian filtering; and setting the wavelength bandwidth of the light source.

[0016] More preferably, the step of constructing the bandwidth isowavenumber distribution series and the wavelength isowavenumber distribution series, and generating the envelope using an interpolation function, includes the following steps:

[0017] The bandwidth isowavenumber distribution series and the wavelength isowavenumber distribution series are constructed using the following formulas:

[0018] λ=[λ1,λ1+Δλ,λ1+2*Δλ,…,λ n ]

[0019] k=[k1,k1+Δk,k1+2*Δk,…,k2]

[0020] Establish a mapping relationship between the bandwidth equal wavenumber distribution series and the wavelength equal wavenumber distribution series;

[0021] make

[0022] but

[0023] The envelope is generated using the following interpolation function:

[0024] envelope=f(λ n ,envelpoe1,λ)

[0025] Where λ1 is the starting wavelength within the bandwidth, λ nThe terminator wavelength is defined within the bandwidth range, Δλ represents the equally divided bandwidth, k1 is the wavenumber corresponding to the maximum wavelength, k2 is the wavenumber corresponding to the minimum wavelength, and N is the wavelength. p The number of simulated acquisition points is Δk, the wavenumber is the evenly divided wavenumber, envelope1 is the simulated spectrum, and envelope is the generated envelope.

[0026] More preferably, the step of correcting the generated envelope using a cosine function includes: simulating the envelope of the interference signal using the following cosine function;

[0027] spectrum = envelope * cos(2k * Z) 0_nm )

[0028] Where k is the wavelength equal wavenumber distribution series, Z 0_nm is the optical path difference, envelope is the generated envelope, and spectrum represents the simulated interference signal.

[0029] More preferably, in S2, the coarse calculation of the PSF function includes obtaining the power spectrum of the image using the following formula and drawing a rough outline of the PSF function using a piecewise linear form;

[0030] spectrum power =20*log10(abs(fft(spectrum*win)))

[0031] Where win is the window function, abs represents the absolute value modulus operation, fft represents the fast Fourier transform, and spectrum represents the analog interference signal.

[0032] More preferably, in S3, the precise interpolation calculation of the PSF function includes the following process:

[0033] Based on the roughly calculated PSF function, a quadratic polynomial function is fitted using neighborhood data of the peak position of the PSF function.

[0034] Calculate the peak decibel and the x-coordinate of the peak center of the fitted quadratic polynomial function;

[0035] The peak value of the fitted function is truncated to 3dB or 6dB, and the difference in the truncated abscissa is calculated as the axial resolution.

[0036] More preferably, in S5, when the actual axial resolution measurement system is adjusted to calculate the actual axial resolution of the actual interference signal based on the PSF, the following steps are included:

[0037] S501. Perform phase balance calibration and dispersion compensation on the envelope of the acquired actual interference signal and the acquisition clock.

[0038] S502. Perform a coarse calculation of the PSF function on the calibrated actual interference signal;

[0039] S503. Perform precise interpolation calculations for the PSF function using the results of the coarse calculations;

[0040] S504. Calculate the actual axial resolution using the PSF function for accurate interpolation.

[0041] More preferably, in S501, the phase near-far balance calibration includes the following method:

[0042] Hardware adjustment is achieved by adjusting the signal delay of the frequency sweep light source;

[0043] Software adjustments are made by adjusting the registration rules of the signal data points acquired by the signal and the clock.

[0044] After software adjustment, the degree of phase adjustment can be visually judged by plotting a phase comparison curve, thus eliminating intensity interference.

[0045] The present invention also provides an evaluation system for accurate calculation of axial resolution based on swept frequency OCT, used to implement the above-mentioned evaluation method for accurate calculation of axial resolution based on swept frequency OCT, characterized in that it includes a simulation light source module, a simulation axial resolution calculation module, an actual axial resolution test module, and a comparison module;

[0046] The simulation light source module is used to generate simulated interference signals using a simulation light source model;

[0047] The simulation axial resolution calculation module performs a coarse calculation of the PSF function based on the simulated interference signal; it then performs a precise interpolation calculation of the PSF function using the coarse calculation result; and finally, it uses the precise interpolation calculation result of the PSF function to obtain the simulation axial resolution.

[0048] The axial resolution test module is used to adjust the actual axial resolution measurement system and calculate the actual axial resolution based on the PSF of the actual interference signal.

[0049] The comparison module is used to compare the simulated axial resolution with the actual axial resolution. If the difference does not exceed a preset range, the actual axial resolution is determined to be valid. If the difference exceeds the preset range, the actual axial resolution is determined to be invalid, and the axial resolution measurement system is readjusted.

[0050] More preferably, the axial resolution test module further includes a system dispersion calibration module. The system dispersion calibration module sets a dispersion coefficient cyclic adjustment range, judges the peak value of the PSF function within the adjustment range, and realizes dispersion calibration when the PSF intensity reaches the maximum value.

[0051] Further preferably, it also includes an actual resolution testing device, which comprises a rear reflector, an attenuator, an SC / FC-APC flange, and jumpers connected in sequence.

[0052] The evaluation method and system for accurate axial resolution calculation based on swept-frequency OCT disclosed in this application have at least the following advantages compared with the prior art:

[0053] In this application, a simulated light source model is set up to generate a simulated interference signal. The resolution is calculated by performing coarse and precise calculations of the PSF function on the acquired signal. The resolution calculated by this method is more accurate than the traditional method of obtaining the theoretical resolution based on the spectral Gaussian. In the simulation calculation process, the phase comparison method can more intuitively judge the balance situation, which is easier to implement and easier to eliminate intensity interference. Attached Figure Description

[0054] Figure 1 This is a flowchart illustrating the evaluation method for accurate calculation of axial resolution based on swept-frequency OCT according to the present invention.

[0055] Figure 2 This is a spectral shape diagram from a swept-frequency OCT simulation.

[0056] Figure 3 This is for simulating the interference envelope diagram.

[0057] Figure 4 This is a comparison of the phase difference between the far and near position signals without phase balance.

[0058] Figure 5 To compare the phase difference between the far and near position signals for phase balance.

[0059] Figure 6 The image shows the PSF function calculated using the simulated envelope.

[0060] Figure 7 for Figure 6 A magnified view of a portion of the image.

[0061] Figure 8 This is a magnified view of the PSF function after fitting and interpolation.

[0062] Figure 9 This is a schematic diagram of the resolution tooling structure.

[0063] Figure 10 This is the PSF function for the real signal.

[0064] Figure 11 This is a flowchart illustrating the evaluation method and actual verification process for accurate axial resolution calculation based on swept-frequency OCT of the present invention. Detailed Implementation

[0065] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0066] like Figure 1 As shown, an evaluation method for accurate calculation of axial resolution based on swept-frequency OCT provided by one embodiment of the present invention includes the following steps:

[0067] S1. Construct a simulated light source model and generate simulated interference signals;

[0068] S2. Based on the simulated interference signal, roughly calculate the PSF function;

[0069] S3. Perform precise interpolation calculations for the PSF function using the results of the coarse calculations;

[0070] S4. Calculate the simulation axial resolution using the PSF function for accurate interpolation.

[0071] S5. Adjust the actual axial resolution measurement system and calculate the actual axial resolution of the actual interference signal based on PSF;

[0072] S7. Compare the simulated axial resolution with the actual axial resolution. If the difference does not exceed the preset range, the actual axial resolution is determined to be valid. If the difference exceeds the preset range, the actual axial resolution is determined to be invalid, and the axial resolution measurement system is readjusted.

[0073] In practice, the simulation system includes a simulation light source module, a simulation axial resolution calculation module, an actual axial resolution testing module, and a comparison module.

[0074] The simulation light source module is used to generate simulated interference signals using a simulation light source model;

[0075] The simulation axial resolution calculation module performs a coarse calculation of the PSF function based on the simulated interference signal; it then performs a precise interpolation calculation of the PSF function using the coarse calculation result; and finally, it uses the precise interpolation calculation result of the PSF function to obtain the simulation axial resolution.

[0076] The axial resolution test module is used to adjust the actual axial resolution measurement system and calculate the actual axial resolution based on the PSF of the actual interference signal.

[0077] The comparison module is used to compare the simulated axial resolution with the actual axial resolution. If the difference does not exceed a preset range, the actual axial resolution is determined to be valid. If the difference exceeds the preset range, the actual axial resolution is determined to be invalid, and the axial resolution measurement system is readjusted.

[0078] In S1, the construction of the simulated light source model and the generation of the simulated interference signal include the following methods:

[0079] S101. Generate a simulated spectrum based on preset spectral parameters; further, the preset spectral parameters include: setting the number of simulated sampling points according to the acquisition rate of the acquisition card; adjusting the spectral shape through Gaussian filtering; and setting the wavelength bandwidth of the light source.

[0080] A simulated spectrum is generated based on preset spectral parameters; the spectral shape of the simulated light source is set, which is achieved through Gaussian filtering and parameter adjustment. The center wavelength (CWL) of the light source is set, and this center wavelength can be adjusted according to the specific light source parameters, such as... Figure 2 In this embodiment, 1310nm is selected, and the wavelength bandwidth is SR, which is the range covered from the minimum wavelength to the maximum wavelength. The bandwidth SR can be set from tens to hundreds of nanometers; in this embodiment, it is set to 108nm. The number of simulated sampling points is set, which is determined by the acquisition card's acquisition rate and can range from tens of MHz to several GHz as needed. In this embodiment, the number of sampling points is set to 2048. Then, the interference signal model is calculated, and the simulated spectrum is obtained. The formula for calculating the simulated spectrum is as follows:

[0081]

[0082] Where α is the parameter for adjusting the spectral shape, and the range of α is between 0 and 1, so that the simulated spectrum and the spectral shape of the real light source are basically consistent.

[0083] S102. Construct bandwidth equal wavenumber distribution series and wavelength equal wavenumber distribution series, and use interpolation functions to generate envelopes;

[0084] Construct a sequence with an equal bandwidth wavenumber distribution:

[0085] λ=[λ1,λ1+Δλ,λ1+2*Δλ,…,λ n ]

[0086] λ1 is the starting wavelength within the bandwidth, λ n The termination wavelength is within the bandwidth range.

[0087] make

[0088] k1 is the wavenumber corresponding to the maximum wavelength, and k2 is the wavenumber corresponding to the minimum wavelength.

[0089]

[0090] N p The number of sampling points is used to simulate the wave number, where Δk is the wave number that is equally divided.

[0091] Construct a sequence with an equal wavenumber distribution across wavelengths:

[0092] k=[k1,k1+Δk,k1+2*Δk,…,k2]

[0093] The corresponding wavelength sequence distribution is then:

[0094]

[0095] Generate an envelope using an interpolation function:

[0096] envelope=f(λ n ,envelpoe1,λ)

[0097] S103. Correct the generated envelope using a cosine function to form a simulated interference signal; simulate the envelope of the interference signal using a cosine function: the result is as follows. Figure 3 As shown.

[0098] spectrum = envelope * cos(2k * Z) 0_nm )

[0099] Z 0_nm This is the optical path difference.

[0100] In S2, the PSF function is coarsely calculated based on the simulated interference signal;

[0101] Rough numerical calculation of PSF. PSF plotting is achieved by directly obtaining the power spectrum of the image, such as... Figure 6 As shown.

[0102] The calculation formula is as follows:

[0103] spectrum power =20*log10(abs(fft(spectrum.*win)))

[0104] `win` is a window function, which can be either a hanning window or a hanming window; `abs` represents the absolute value modulus operation; `fft` represents the Fast Fourier Transform; and `spectrum` represents the simulated interference signal or the calibrated interferometer signal.

[0105] The plot uses a polyline format, which can directly draw the general outline of the PSF function, such as... Figure 7 As shown.

[0106] S3. Use the results of the coarse calculation to perform precise interpolation calculations for the PSF function;

[0107] After completing the PSF calculation in the previous step, directly using the width value at the 3dB or 6dB drop point of the PSF as the axial resolution of OCT is not accurate enough. This is because the PSF here is directly connected by polyline points, which cannot fully and accurately reflect the true PSF situation. Therefore, a fitting algorithm is introduced here to accurately plot the PSF function, making the calculated axial resolution more accurate. Based on the neighborhood data of the peak position of the PSF function, a quadratic polynomial function is fitted, such as... Figure 8 The image shown is a magnified view of the PSF function after fitting and interpolation.

[0108] pf(psf mm ,psf dB ,2)

[0109] Rewritten as a quadratic polynomial:

[0110] P = a²x 2 +a1x+a0

[0111] PSF peak decibels:

[0112]

[0113] The x-coordinate of the peak center is:

[0114]

[0115] S4. Calculate the simulation axial resolution using the PSF function for accurate interpolation.

[0116] To determine the simulated axial resolution, we need to find the width at the point where the PSF fitting function drops by 3dB or 6dB. This width can be converted from pixel values ​​to physical length units.

[0117] Resolution:

[0118]

[0119] Where intensitydrop_dB is the number of decibels that decrease from the peak value. intensitydrop_dB can be set to 3dB or 6dB as needed. In this embodiment, 3dB is selected.

[0120] Based on the PSF peak decibels, the x-coordinate of the peak center, and the resolution, plot a PSF resolution map, as follows: Figure 8 As shown.

[0121] To verify whether the resolution calculated by the above method matches the resolution calculated in the actual environment: Specifically, a real axial resolution measurement system is constructed, and the axial resolution of the real interference signal is calculated based on the PSF calculation method;

[0122] S501. Perform phase balance calibration and dispersion compensation on the envelope of the acquired actual interference signal and the acquisition clock.

[0123] S502. Perform a coarse calculation of the PSF function on the calibrated actual interference signal;

[0124] S503. Perform precise interpolation calculations for the PSF function using the results of the coarse calculations;

[0125] S504. Calculate the actual axial resolution using the PSF function for accurate interpolation.

[0126] The actual axial resolution measurement system also includes a swept-frequency optical engine and an actual resolution testing device. The actual resolution testing device comprises a rear-facing mirror 1, an attenuator 2, an SC / FC-APC flange 3, and a jumper 4 connected in sequence; the attenuator's attenuation value should be greater than 20 dB. The cumulative bidirectional insertion loss of the actual resolution testing device should be greater than 50 dB. The actual resolution testing device is as follows: Figure 9 As shown.

[0127] Point interference signals were acquired using an actual resolution testing device and an OCT scanning system.

[0128] In S501, the envelope of the interference signal is phase-balanced with the acquisition clock, including the following methods:

[0129] The mismatch in line length within the system leads to a phase mismatch between the signal envelope and the acquisition clock. This causes resolution variations near and far from the signal zero point, the root cause of which is a phase imbalance at the near and far points. To achieve phase balance, the system needs adjustment, which can be achieved through two methods: hardware adjustment and software adjustment. Hardware adjustment involves adjusting the signal delay of the sweep frequency light source, while software adjustment involves adjusting the registration rules of the interference signal and the clock acquisition signal data points. Determining the appropriate adjustment level requires observing the PSF (Power Sequence Filter) to confirm completion. However, the PSF shape is sensitive to both phase mismatch and optical path interference intensity, making PSF observation sometimes subjective and difficult to assess.

[0130] In this application, hardware adjustment is achieved by adjusting the clock signal delay of the frequency sweep light source, and software adjustment is achieved by adjusting the registration rules of the signal data points acquired by the interference signal and the clock. Based on the above, this application also proposes a new method for judging whether the phase adjustment is complete - the phase comparison method: that is, for the PSF function after software adjustment, the degree of phase adjustment is intuitively judged by drawing a phase comparison curve, and intensity interference is eliminated.

[0131] The phase comparison method is implemented as follows: Take the point spread function of the nearest point and calculate its phase; take the point spread function of the farthest point and calculate its phase; subtract the two phases and plot the subtraction curve. For example... Figure 4 and Figure 5 As shown. Figure 4 This is a comparison of the phase difference between the far and near points, where the phase has not been balanced and calibrated. Figure 5 To perform a phase comparison between the far and near points after phase balance. This can be achieved through... Figure 5 It is clear that after phase balance calibration, the difference between near and far points becomes smaller.

[0132] It also includes performing dispersion calibration on the system. Dispersion calibration of the system is calculated according to the following dispersion calibration formula. A cyclic judgment range is designed, with a = -0.0002: 0.0002 and b = -0.0002: 0.0002. The system is cyclically checked within this range, and the dispersion calibration is achieved by judging the PSF peak value.

[0133] Φ(ω)≈a(ω(t0)-ω0) 2 +b(ω(t0)-ω0) 3

[0134] S502. Perform a coarse calculation of the PSF function on the calibrated actual interference signal;

[0135] S503. Perform precise interpolation calculations for the PSF function using the results of the coarse calculations;

[0136] S504. Calculate the actual axial resolution using the PSF function for accurate interpolation.

[0137] It should be noted that the process of calculating the actual axial resolution, S502 to S504, is the same as the process of calculating the simulated axial resolution, S2 to S4, and will not be repeated here.

[0138] Then, for the actual calculated value (such as...) Figure 10 The measured axial resolution in air after a 3dB drop (as shown in the figure) is 12.21μm, while the measured axial resolution in air after a 3dB drop is 12.31μm. It can be seen that the measured resolution and the theoretical resolution are basically consistent.

[0139] When actually measuring the axial resolution of the system, given the system's hardware parameters, the simulation method proposed in this application can be used to pre-evaluate the theoretical axial resolution level of the system, for example, a resolution value of δx. Then, the actual system resolution is measured, for example, δx1. An evaluation criterion of 10% is set. If (δx1-δx) / δx > 10%, it is recommended to readjust the system. If it is less than 10%, the actual system resolution is considered to meet the requirements.

[0140] The simulation and actual calculation process of the system described above is as follows: Figure 11 As shown, the simulation process is as follows: spectral parameters are set, a simulated spectrum is generated, the interference spectrum is obtained, the simulated PSF is obtained, the PSF center and peak are calculated, and the simulated axial resolution is obtained; the actual testing process is as follows: the actual OCT system is used, the system is combined with the actual resolution testing device, and the actual axial resolution is calculated based on the PSF; the resolutions are then compared.

[0141] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An evaluation method for accurate calculation of axial resolution based on swept-frequency OCT, characterized in that, Includes the following steps: S1. Construct a simulated light source model and generate simulated interference signals; S2. Based on the simulated interference signal, roughly calculate the PSF function; S3. Perform precise interpolation calculation of the PSF function using the results of the coarse calculation; the precise interpolation calculation of the PSF function includes the following process: Based on the roughly calculated PSF function, a quadratic polynomial function is fitted using neighborhood data of the peak position of the PSF function. Calculate the peak decibel and the x-coordinate of the peak center of the fitted quadratic polynomial function; The peak value of the fitted function is truncated at 3dB or 6dB, and the difference in the truncated abscissa is calculated as the axial resolution. S4. Calculate the simulation axial resolution using the PSF function for accurate interpolation. S5. Adjust the actual axial resolution measurement system and calculate the actual axial resolution of the actual interference signal based on PSF; S6. Compare the simulated axial resolution with the actual axial resolution. If the difference does not exceed the preset range, the actual axial resolution is determined to be valid. If the difference exceeds the preset range, the actual axial resolution is determined to be invalid, and the axial resolution measurement system is readjusted.

2. The evaluation method for accurate calculation of axial resolution based on swept-frequency OCT according to claim 1, characterized in that, In S1, the construction of the simulated light source model and the generation of the simulated interference signal include the following methods: Based on preset spectral parameters, a simulated spectrum is generated; Construct bandwidth equal wavenumber distribution series and wavelength equal wavenumber distribution series, and use interpolation functions to generate envelopes; The generated envelope is corrected using a cosine function to form a simulated interference signal.

3. The evaluation method for accurate calculation of axial resolution based on swept-frequency OCT according to claim 2, characterized in that, The preset spectral parameters include: setting the number of simulated sampling points according to the acquisition rate of the acquisition card; adjusting the spectral shape through Gaussian filtering; and setting the wavelength bandwidth of the light source.

4. The evaluation method for accurate calculation of axial resolution based on swept-frequency OCT according to claim 2, characterized in that, The process of constructing the bandwidth equal wavenumber distribution series and the wavelength equal wavenumber distribution series, and generating the envelope using an interpolation function, includes the following steps: The bandwidth isowavenumber distribution series is constructed using the following formula. Wavenumber distribution series with wavelength : Establish a mapping relationship between the bandwidth equal wavenumber distribution series and the wavelength equal wavenumber distribution series; make , = but , The envelope is generated using the following interpolation function: in, The starting wavelength within the bandwidth range, The termination wavelength within the bandwidth range, The bandwidth is divided equally, k1 is the wavenumber corresponding to the maximum wavelength, and k2 is the wavenumber corresponding to the minimum wavelength. To simulate the number of data collection points, For equally divided wavenumbers, For simulating the spectrum, This is the generated envelope.

5. The simulation evaluation method for accurate calculation of axial resolution based on swept-frequency OCT according to claim 4, characterized in that, The step of correcting the generated envelope using a cosine function includes: simulating the envelope of the interference signal using the following cosine function; Where k is a wavelength equal wavenumber distribution series, For optical path difference, For the generated envelope, This represents a simulated interference signal.

6. The evaluation method for accurate calculation of axial resolution based on swept-frequency OCT according to claim 1, characterized in that, In S2, the coarse calculation of the PSF function includes obtaining the power spectrum of the image using the following formula and drawing a rough outline of the PSF function using a piecewise linear form; Where win is the window function. This represents the modulo operation of absolute value; Represents the Fast Fourier Transform. This represents a simulated interference signal.

7. The evaluation method for accurate calculation of axial resolution based on swept-frequency OCT according to claim 1, characterized in that, In S5, when the actual axial resolution measurement system is adjusted to calculate the actual axial resolution of the actual interference signal based on the PSF, the following steps are included: S501. Perform phase balance calibration and dispersion compensation on the envelope of the acquired actual interference signal and the acquisition clock. S502. Perform a coarse calculation of the PSF function on the calibrated actual interference signal; S503. Perform precise interpolation calculations for the PSF function using the results of the coarse calculations; S504. Calculate the actual axial resolution using the PSF function for accurate interpolation.

8. The evaluation method for accurate calculation of axial resolution based on swept-frequency OCT according to claim 7, characterized in that, In S501, the phase near-far balance calibration includes the following methods: Hardware adjustment is achieved by adjusting the signal delay of the frequency sweep light source; Software adjustments are made by adjusting the registration rules of the signal data points acquired by the signal and the clock. After software adjustment, the degree of phase adjustment is determined by plotting a phase comparison curve, thus eliminating intensity interference.

9. An evaluation system for accurate axial resolution calculation based on swept-frequency OCT, used to implement the evaluation method for accurate axial resolution calculation based on swept-frequency OCT as described in any one of claims 1-8, characterized in that, It includes a simulation light source module, a simulation axial resolution calculation module, an actual axial resolution testing module, and a comparison module; The simulation light source module is used to generate simulated interference signals using a simulation light source model; The simulation axial resolution calculation module performs a coarse calculation of the PSF function based on the simulated interference signal; it then performs a precise interpolation calculation of the PSF function using the coarse calculation result; and finally, it uses the precise interpolation calculation result of the PSF function to obtain the simulation axial resolution. The axial resolution test module is used to adjust the actual axial resolution measurement system and calculate the actual axial resolution based on the PSF of the actual interference signal. The comparison module is used to compare the simulated axial resolution with the actual axial resolution. If the difference does not exceed a preset range, the actual axial resolution is determined to be valid. If the difference exceeds the preset range, the actual axial resolution is determined to be invalid, and the axial resolution measurement system is readjusted.

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