Light path calibration method for household optical coherence tomography equipment

Abstract

The invention relates to the technical field of optical equipment calibration methods, in particular to an optical path calibration method for household optical coherence tomography equipment, which comprises the following steps: starting an optical path calibration mode in response to one or more calibration trigger conditions being met; controlling a scanning device of the sample arm, and positioning the light beam to a fixed calibration target integrated in the equipment; a reference arm is driven to perform optical path scanning, and interference signals from the calibration target are collected at the same time; processing the interference signal to determine the zero optical path difference position of the system, and calculating the interference contrast of the current state; determining the qualification of light path calibration according to the interference contrast, and starting a parameter optimization adjustment program under the condition that the light path calibration is unqualified; and under the condition that light path calibration is qualified, depth calibration verification is carried out, final system parameters are stored, and then the calibration mode is quitted. According to the invention, the long-term measurement precision and the operation convenience of the household OCT equipment in a non-professional environment are improved.

Description

Technical Field

[0001] This invention relates to the field of optical equipment calibration methods, and more particularly to an optical path calibration method for a home-use optical coherence tomography (OCT) device. Background Technology

[0002] Optical coherence tomography (OCT) is a non-invasive, high-resolution optical imaging technology widely used in the diagnosis and follow-up of diseases such as macular degeneration, glaucoma, and diabetic retinopathy. With the aging population and increasing demand for chronic disease management, extending OCT technology to home settings for daily disease monitoring and early warning has become a clear technological trend. Home-use OCT devices face challenges vastly different from professional equipment. The long-term stability of the optical path and the user's ability to self-calibrate are the core bottlenecks to achieving home-use functionality. In home use, devices are subject to handling, collisions, and changes in environmental temperature and humidity, which can easily cause slight shifts in the core optical path. These shifts can directly lead to signal attenuation, image blurring, or even failure to form an image. Therefore, there is a need for a fully automatic and rapid optical path calibration method that can be embedded within home-use OCT devices, enabling the device to automatically diagnose and calibrate the optical path status after power-on self-test or simple user triggering.

[0003] Chinese Patent Application Publication No. CN101915547A discloses a method for time-domain OCT measurement, comprising: controlling the illumination optical path of the sample arm of a time-domain optical coherence tomography (OCT) system to measure a sample preset in the time-domain OCT system; analyzing the measurement results of the sample to obtain the current detection depth value of the time-domain OCT system; and measuring the thickness value of the object under test based on the detection depth value.

[0004] However, the existing technology has the following problems: the lack of a fully automated optical path calibration method leads to complicated equipment operation and unreliable results. Summary of the Invention

[0005] Therefore, the present invention provides an optical path calibration method for a home-use optical coherence tomography (OCT) device, which overcomes the problem that the lack of a fully automatic optical path calibration method in existing home-use OCT devices leads to complex operation and unreliable results.

[0006] To achieve the above objectives, the present invention provides an optical path calibration method for a home-use optical coherence tomography (OCT) device, comprising: Step S1: In response to one or more calibration trigger conditions being met, the optical path calibration mode is started; Step S2: Control the scanning device of the sample arm to position the beam to the fixed calibration target integrated inside the device; Step S3: Drive the reference arm to perform optical path scanning, and simultaneously acquire interference signals from the calibration target; Step S4: Process the interference signal to determine the zero optical path difference position of the system and calculate the interference contrast of the current state; Step S5: Determine the passability of the optical path calibration based on the interference contrast. If the optical path calibration fails, start the parameter optimization and adjustment program. Step S6: Under the condition that the optical path calibration is qualified, perform depth calibration verification and save the final system parameters, and then exit the calibration mode.

[0007] Furthermore, the calibration triggering conditions include one or more of the following: The device's cumulative standby time is greater than or equal to the first preset time. The rate of temperature change inside the equipment is greater than or equal to the first preset rate of change. The impact acceleration of the equipment is greater than or equal to the first preset acceleration; The real-time signal-to-noise ratio is less than the first preset signal-to-noise ratio; The cumulative number of actual imaging scans performed by the device is greater than or equal to the first preset number.

[0008] Furthermore, in step S3, the process of determining the zero optical path difference position of the system includes: Envelope detection is performed on the acquired interference signal to identify the peak value of the signal envelope, and the reference arm position corresponding to the peak value is defined as the zero optical path difference position.

[0009] Further, step S4 includes: The acquired interference signal is bandpass filtered to improve the signal-to-noise ratio; Perform a Hilbert transform on the filtered interference signal to extract its signal envelope; Determine the global maximum point of the signal envelope, and define the reference arm position corresponding to this point as the zero optical path difference position; The interference contrast is calculated based on the global maximum value and the average value measured in the signal background region.

[0010] Furthermore, the pass / fail status of the optical path calibration is determined based on the interference contrast, among which, If the interference contrast is within the preset contrast range, the optical path calibration is deemed qualified, depth calibration verification is performed, and the final system parameters are saved. Then, the calibration mode is exited. If the interference contrast exceeds the acceptable threshold range, the optical path calibration is deemed unacceptable, and the parameter optimization and adjustment program is initiated.

[0011] Furthermore, the parameter optimization and adjustment procedure includes: The polarization controller driven by the motor iteratively adjusts the rotation angle of its internal waveplate, and after each adjustment, steps S3 and S4 are re-executed to calculate the new interference contrast. The polarization controller state that maximizes the interference contrast is searched through an optimization algorithm. If the interference contrast is still lower than the qualified threshold range after optimization, the position of the collimator or focusing lens in the sample arm in the X, Y, and Z directions is fine-tuned, and steps S3 and S4 are re-executed after each fine-tuning. The optimization algorithm searches for the lens position that makes the interference contrast approach the maximum. In any optimization step, if the interference contrast enters the qualified threshold range, the parameter optimization and adjustment program is immediately exited.

[0012] Furthermore, in step S6, the depth calibration and verification process includes: Position the beam to another built-in, known and stable optical thickness etalon target; Obtain the A-scan signal of the etalon and measure the pixel index difference of the reflection peaks on its front and rear surfaces in the signal; Based on the optical thickness of the standard etalon, verify whether the theoretical pixel index difference calculated according to the current depth scale factor and the measured pixel index difference are within the allowable error range; If the error exceeds the range, the system depth scale is determined to be inaccurate, and the system depth scale factor is recalculated and updated based on the known optical thickness of the etalon and the difference between the measured pixel index.

[0013] Furthermore, in the depth calibration and verification step, if it is found that the full width at half maximum (FWHM) of the two reflection peaks exceeds the preset FWHM, the dispersion compensation optimization program is automatically started.

[0014] Compared with existing technologies, the advantages of this invention lie in its ability to define multiple calibration trigger conditions closely related to actual usage scenarios, enabling the device to autonomously determine when calibration is needed. This overcomes the drawbacks of relying on user subjective experience or periodic inspections. The entire calibration process, from startup, signal acquisition, analysis to final decision-making and parameter saving, requires no manual intervention, achieving fully automated calibration. This allows non-professional users to easily and correctly maintain the optimal performance of their devices at home.

[0015] Furthermore, this invention uses advanced signal processing technology to determine the interference contrast and uses it as an objective and quantitative basis for judging whether the calibration is qualified. When the performance is not up to standard, the system can automatically start a structured parameter optimization program to perform multi-dimensional iterative optimization according to preset priorities, ensuring that the interferometer system can always be adjusted to a state close to the theoretical optimal state, thus laying a solid foundation for obtaining high-quality and highly reliable OCT images.

[0016] Furthermore, after completing the core optical path calibration, this invention introduces a depth calibration and verification step. This step utilizes a standard with known optical thickness to perform secondary verification and calibration of the system's depth measurement scale, and can further trigger dispersion compensation optimization, ensuring the accuracy of the dimensions of a single image. This guarantees the longitudinal and lateral comparability of data collected by the device throughout its entire lifespan and among different users, laying a solid technical foundation for accurate and reliable disease monitoring in home environments. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the optical path calibration method for a home-use optical coherence tomography (OCT) device according to an embodiment of the present invention. Figure 2 A flowchart for determining interference contrast in an embodiment of the present invention; Figure 3 This is a flowchart illustrating how the optical path calibration is determined based on interference contrast, according to an embodiment of the present invention. Figure 4 This is a flowchart of the depth calibration and verification process in an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0019] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0020] It should be noted that the data in this embodiment are all derived from a comprehensive analysis and evaluation of historical test data and corresponding historical test results from the three months prior to this test. Those skilled in the art will understand that the determination of the above-mentioned parameters for any single item in this invention can be achieved by selecting the value with the highest percentage based on the data distribution as the preset standard parameter, using weighted summation to obtain the value as the preset standard parameter, substituting each historical data point into a specific formula and using the value obtained from that formula as the preset standard parameter, or other selection methods, as long as the invention can clearly define different specific situations in the single-item judgment process through the obtained values.

[0021] Please see Figures 1 to 4 The flowcharts shown are respectively: a flowchart of the optical path calibration method for a home-use optical coherence tomography device according to an embodiment of the present invention; a flowchart of determining the interference contrast according to an embodiment of the present invention; a flowchart of determining the qualification of optical path calibration based on the interference contrast according to an embodiment of the present invention; and a flowchart of the depth calibration verification process according to an embodiment of the present invention.

[0022] The optical path calibration method for a home-use optical coherence tomography (OCT) device according to an embodiment of the present invention includes: Step S1: In response to one or more calibration trigger conditions being met, the optical path calibration mode is started; Step S2: Control the scanning device of the sample arm to position the beam to the fixed calibration target integrated inside the device; Step S3: Drive the reference arm to perform optical path scanning, and simultaneously acquire interference signals from the calibration target; Step S4: Process the interference signal to determine the zero optical path difference position of the system and calculate the interference contrast of the current state; Step S5: Determine the passability of the optical path calibration based on the interference contrast. If the optical path calibration fails, start the parameter optimization and adjustment program. Step S6: Under the condition that the optical path calibration is qualified, perform depth calibration verification and save the final system parameters, and then exit the calibration mode.

[0023] Specifically, calibration triggering conditions include one or more of the following: The device's cumulative standby time is greater than or equal to the first preset time. The rate of temperature change inside the equipment is greater than or equal to the first preset rate of change. The impact acceleration of the equipment is greater than or equal to the first preset acceleration; The real-time signal-to-noise ratio is less than the first preset signal-to-noise ratio; The cumulative number of actual imaging scans performed by the device is greater than or equal to the first preset number.

[0024] In this embodiment of the invention, the first preset duration is 24h, the first preset rate of change is 0.5 ℃ / min, the first preset acceleration is 5g, the first preset signal-to-noise ratio is 20dB, and the first preset number of times is 100 times. However, the above values ​​are not limited to these, and those skilled in the art can adjust the above values ​​according to actual needs.

[0025] Specifically, in step S3, the process of determining the zero optical path difference position of the system includes: Envelope detection is performed on the acquired interference signal to identify the peak value of the signal envelope, and the reference arm position corresponding to the peak value is defined as the zero optical path difference position.

[0026] Specifically, step S4 includes: The acquired interference signal is bandpass filtered to improve the signal-to-noise ratio; Perform a Hilbert transform on the filtered interference signal to extract its signal envelope; Determine the global maximum point of the signal envelope, and define the reference arm position corresponding to this point as the zero optical path difference position; The interference contrast is calculated based on the global maximum value and the average value measured in the signal background region.

[0027] Specifically, the pass / fail status of the optical path calibration is determined based on the interference contrast, whereby... If the interference contrast is within the preset contrast range, the optical path calibration is deemed qualified, depth calibration verification is performed, and the final system parameters are saved. Then, the calibration mode is exited. If the interference contrast exceeds the acceptable threshold range, the optical path calibration is deemed unacceptable, and the parameter optimization and adjustment program is initiated.

[0028] In this embodiment of the invention, the preset contrast range is 70% to 95%, but this value is not limited to this. Those skilled in the art can adjust this value according to actual needs.

[0029] Specifically, in step S5, the parameter optimization and adjustment procedure includes: The polarization controller driven by the motor iteratively adjusts the rotation angle of its internal waveplate, and after each adjustment, steps S3 and S4 are re-executed to calculate the new interference contrast. The polarization controller state that maximizes the interference contrast is searched through an optimization algorithm. If the interference contrast is still lower than the qualified threshold range after optimization, the position of the collimator or focusing lens in the sample arm in the X, Y, and Z directions is fine-tuned, and steps S3 and S4 are re-executed after each fine-tuning. The optimization algorithm searches for the lens position that makes the interference contrast approach the maximum. In any optimization step, if the interference contrast enters the qualified threshold range, the parameter optimization and adjustment program is immediately exited.

[0030] Specifically, in step S6, the depth calibration and verification process includes: Position the beam to another built-in, known and stable optical thickness etalon target; Obtain the A-scan signal of the etalon and measure the pixel index difference of the reflection peaks on its front and rear surfaces in the signal; Based on the optical thickness of the standard etalon, verify whether the theoretical pixel index difference calculated according to the current depth scale factor and the measured pixel index difference are within the allowable error range; If the error exceeds the range, the system depth scale is determined to be inaccurate, and the system depth scale factor is recalculated and updated based on the known optical thickness of the etalon and the difference between the measured pixel index.

[0031] Specifically, in the depth calibration and verification step, if it is found that the full width at half maximum (FWHM) of the two reflection peaks exceeds the preset FWHM, the dispersion compensation optimization program is automatically started.

[0032] Specifically, the dispersion compensation optimization program aims to automatically correct group velocity dispersion caused by the dispersion characteristics of internal optical components (such as lenses and beam splitters). This dispersion causes the interference signal to broaden and attenuate rapidly with increasing depth, severely reducing the axial resolution of the system. The program's execution process includes: when the system detects that the full width at half maximum (FWHM) of the etalon reflection peak exceeds a preset threshold during depth calibration verification, the dispersion compensation optimization program is automatically initiated. The program first evaluates the broadening and asymmetry of the current interference signal to quantify the dispersion amount; subsequently, the system iteratively adjusts the state of the dynamic dispersion compensation elements integrated within the reference arm (such as grating pair spacing or liquid crystal phase diagram), and re-acquires the signal after each adjustment, performing feedback control with the goal of minimizing the FWHM of the reflection peak and optimizing waveform symmetry; when the above indicators are optimized to within the acceptable range, the program determines that dispersion compensation is complete, saves the optimal compensator parameters at this time, and then exits the optimization process.

[0033] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for calibrating the optical path of a home-use optical coherence tomography (OCT) device, characterized in that, include: Step S1: In response to one or more calibration trigger conditions being met, the optical path calibration mode is started; Step S2: Control the scanning device of the sample arm to position the beam to the fixed calibration target integrated inside the device; Step S3: Drive the reference arm to perform optical path scanning, and simultaneously acquire interference signals from the calibration target; Step S4: Process the interference signal to determine the zero optical path difference position of the system and calculate the interference contrast of the current state; Step S5: Determine the passability of the optical path calibration based on the interference contrast. If the optical path calibration fails, start the parameter optimization and adjustment program. Step S6: Under the condition that the optical path calibration is qualified, perform depth calibration verification and save the final system parameters, and then exit the calibration mode.

2. The optical path calibration method for a home-use optical coherence tomography device according to claim 1, characterized in that, Calibration trigger conditions include one or more of the following: The device's cumulative standby time is greater than or equal to the first preset time. The rate of temperature change inside the equipment is greater than or equal to the first preset rate of change. The impact acceleration of the equipment is greater than or equal to the first preset acceleration; The real-time signal-to-noise ratio is less than the first preset signal-to-noise ratio; The cumulative number of actual imaging scans performed by the device is greater than or equal to the first preset number.

3. The optical path calibration method for a home-use optical coherence tomography (OCT) device according to claim 2, characterized in that, In step S3, the process of determining the zero optical path difference position of the system includes: Envelope detection is performed on the acquired interference signal to identify the peak value of the signal envelope, and the reference arm position corresponding to the peak value is defined as the zero optical path difference position.

4. The optical path calibration method for a home-use optical coherence tomography (OCT) device according to claim 3, characterized in that, Step S4 includes: The acquired interference signal is bandpass filtered to improve the signal-to-noise ratio; Perform a Hilbert transform on the filtered interference signal to extract its signal envelope; Determine the global maximum point of the signal envelope, and define the reference arm position corresponding to this point as the zero optical path difference position; The interference contrast is calculated based on the global maximum value and the average value measured in the signal background region.

5. The optical path calibration method for a home-use optical coherence tomography device according to claim 4, characterized in that, The pass / fail status of the optical path calibration is determined based on the interference contrast. If the interference contrast is within the preset contrast range, the optical path calibration is deemed qualified, depth calibration verification is performed, and the final system parameters are saved. Then, the calibration mode is exited. If the interference contrast exceeds the acceptable threshold range, the optical path calibration is deemed unacceptable, and the parameter optimization and adjustment program is initiated.

6. The optical path calibration method for a home-use optical coherence tomography device according to claim 5, characterized in that, In step S5, the parameter optimization and adjustment procedure includes: The polarization controller driven by the motor iteratively adjusts the rotation angle of its internal waveplate, and after each adjustment, steps S3 and S4 are re-executed to calculate the new interference contrast. The polarization controller state that maximizes the interference contrast is searched through an optimization algorithm. If the interference contrast is still lower than the qualified threshold range after optimization, the position of the collimator or focusing lens in the sample arm in the X, Y, and Z directions is fine-tuned, and steps S3 and S4 are re-executed after each fine-tuning. The optimization algorithm searches for the lens position that makes the interference contrast approach the maximum. In any optimization step, if the interference contrast enters the qualified threshold range, the parameter optimization and adjustment program is immediately exited.

7. The optical path calibration method for a home-use optical coherence tomography (OCT) device according to claim 6, characterized in that, In step S6, the depth calibration and verification process includes: Position the beam to another built-in, known and stable optical thickness etalon target; Obtain the A-scan signal of the etalon and measure the pixel index difference of the reflection peaks on its front and rear surfaces in the signal; Based on the optical thickness of the standard etalon, verify whether the theoretical pixel index difference calculated according to the current depth scale factor and the measured pixel index difference are within the allowable error range; If the error exceeds the range, the system depth scale is determined to be inaccurate, and the system depth scale factor is recalculated and updated based on the known optical thickness of the etalon and the difference between the measured pixel index.

8. The optical path calibration method for a home-use optical coherence tomography device according to claim 7, characterized in that, In the depth calibration and verification step, if the full width at half maximum (FWHM) of the two reflection peaks is found to exceed the preset FWHM, the dispersion compensation optimization program is automatically started.

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