Optical coherence tomography calibration method, OCT system and storage medium

Abstract

The invention relates to the technical field of optical coherence tomography calibration, and discloses an optical coherence tomography calibration method, an OCT system and a storage medium, and the method comprises the steps: determining a relation between a physical coordinate of an OCT imaging plane and a camera pixel coordinate based on a camera correction model; determining a light vector model based on a preset scanning position of the reflected light beam on an imaging plane, and pre-correcting the scanning mechanism based on the light vector model; and based on the corrected calibration plate OCT image obtained by scanning the calibration plate by the scanning mechanism, observing the image obtained by shooting the same calibration plate by the camera, the light vector model and the camera correction model, and determining the mapping relation between the control quantity of the scanning mechanism and the physical coordinates of the OCT imaging plane. According to the invention, accurate calibration of optical coherence tomography can be completed by calculating the relationship between the physical distance coordinates of the imaging surface and the control quantity of the scanning mechanism.

Description

Technical Field

[0001] The present invention relates to the technical field of optical coherence tomography calibration, and in particular to an optical coherence tomography calibration method, an OCT system and a storage medium. Background Art

[0002] Optical Coherence Tomography (OCT) is a non-invasive, non-destructive imaging technique that uses low-coherence light to capture micrometer-resolution two- and three-dimensional images from within optically scattering media.

[0003] The OCT system is essentially a Michelson interferometer. The light emitted by the light source enters two arms, the sample arm and the reference arm. The reflected / scattered light from the sample arm and the reflected light from the reference arm generate interference signals. The interference signals are received by the photodetector and processed by the computer to finally obtain the imaging image of the sample.

[0004] The one-dimensional imaging of the axial depth of the sample is called A-scan. The scanning mechanism performs a transverse scan of the sample arm beam, and the obtained series of A-scan images can be combined into a vertical cross-sectional image (B-scan). If the scanning mechanism performs a two-dimensional scan, a three-dimensional volume scan image can be obtained, and the volume image can be intercepted at a certain axial depth to obtain a horizontal cross-sectional image (enface).

[0005] OCT is widely used in medical imaging, and the distortion of OCT images is generally corrected. However, as OCT is used in precision-oriented scenarios such as surgical assistance and industrial inspection, it becomes increasingly important to accurately measure the physical size of the imaged objects and the true distance between the imaged objects.

[0006] Therefore, to achieve accurate measurement, it is necessary not only to correct the distorted imaging but also to accurately calibrate the imaging.

[0007] The distortion of the image is caused by the mechanical distortion of the scanning components, the optical distortion of the optical components and the collimation of the system light path.

[0008] There are two main types of scanning mechanisms: 1) A pair of orthogonally oriented single-axis mirrors, such as galvanometer mirrors. Orthogonal dual mirrors will cause pincushion distortion in OCT images during scanning; 2) Dual-axis single-sided reflective mirrors, such as fast-reflecting mirrors and micro-electromechanical system (MEMS) scanning mirrors, which have the advantages of small size, high speed, and low cost, but the OCT images during scanning will show various distortions such as trapezoidal and fan-shaped.

[0009] However, currently, only distortion correction is performed on OCT images or data extracted from images as a post-processing method for acquired images, which will inevitably consume measurement time and increase the cost of computing resources for image processing. For images with severe distortion, image correction will reduce the actual imaging range, which is not conducive to the measurement of some large-area objects. Summary of the invention

[0010] Based on this, it is necessary to address the technical problem that the calibration effect of optical coherence tomography in the prior art is poor, and propose an optical coherence tomography calibration method, an OCT system and a storage medium.

[0011] In a first aspect, a calibration method for optical coherence tomography is provided, the method comprising:

[0012] Determine the relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates based on the camera calibration model;

[0013] Determining a light vector model based on a preset scanning position of the reflected light beam on the imaging plane, and pre-correcting the scanning mechanism based on the light vector model;

[0014] Based on the OCT image of the calibration plate obtained by scanning the calibration plate with the corrected scanning mechanism, the image obtained by photographing the same calibration plate with the observation camera, the light vector model, and the camera correction model, the mapping relationship between the control amount of the scanning mechanism and the physical coordinates of the OCT imaging plane is determined.

[0015] In a second aspect, an OCT system is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned optical coherence tomography calibration method when executing the computer program.

[0016] In a third aspect, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the optical coherence tomography calibration method are implemented.

[0017] The calibration method of optical coherence tomography proposed in the present invention determines the relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates based on the camera calibration model, then determines the light vector model based on the scanning position of the pre-set reflected light beam on the imaging plane, and pre-corrects the scanning mechanism based on the light vector model, and then determines the mapping relationship between the control amount of the scanning mechanism and the physical coordinates of the OCT imaging plane based on the calibration plate OCT image obtained by scanning the calibration plate by the corrected scanning mechanism, the image obtained by photographing the same calibration plate by the observation camera, the light vector model, and the camera calibration model. The present invention uses a common camera calibration plate to calibrate the OCT system, and uses the light vector model to directly pre-correct the control amount of the scanning mechanism, so that the system eliminates most of the distortion caused by the scanning mechanism during the scanning process. For the same calibration plate, the calibration plate image obtained by photographing the calibration plate with a calibrated auxiliary camera is used, and the OCT image obtained by scanning the calibration plate by the OCT system after the scanning mechanism pre-correction is used. The calibration point coordinates are extracted from the two images respectively, and the mapping relationship between the control amount of the scanning mechanism and the camera image pixel coordinate system is calculated. Through this mapping relationship and the parameters of the camera correction model, the relationship between the physical distance coordinates of the imaging surface and the control amount of the scanning mechanism can be obtained, thereby completing accurate calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0019] in:

[0020] Figure 1 An OCT system of a calibration method for optical coherence tomography in one embodiment;

[0021] Figure 2 is a flow chart of a calibration method for optical coherence tomography in one embodiment;

[0022] Figure 3 The relationship between the control amount and the optical angle of the dual-axis single-sided reflector in the calibration method of optical coherence tomography in one embodiment;

[0023] Figure 4 : is a schematic diagram of the spatial vector of light passing through a reflector in a calibration method for optical coherence tomography in one embodiment;

[0024] Figure 5 : A calibration method for optical coherence tomography using a normal vector of a reflective mirror in one embodiment Calculate the control coordinates (x m ,y m );

[0025] Figure 6 : An OCT system calibration process of an optical coherence tomography calibration method in an embodiment;

[0026] Figure 7 : is a distorted OCT image under uniform control amount scanning of an optical coherence tomography calibration method in an embodiment;

[0027] Figure 8 : An OCT image scanned after pre-correction of an optical coherence tomography calibration method in an embodiment. DETAILED DESCRIPTION

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the present application; the terms used in the specification of the application herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "including" and "having" and any variations thereof in the specification and claims of the present application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of the present application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0029] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] refer to Figure 1 , Figure 1It is a structural schematic diagram of an OCT system. In the figure, the thin solid line represents the optical path, and the thick solid line represents the circuit. The equipment of the OCT system includes a light source 1, which provides incident light to the reference arm 3 and the sample arm 6 respectively through a coupler / beam splitter 2. The light source 1 can be any laser light source suitable for OCT imaging. Suitable light sources that can be used for SD-OCT include but are not limited to broadband light sources such as superluminescent laser diodes (SLDs), and can also be swept laser light sources for SS-OCT. The coupler / beam splitter 2 receives light from the light source 1 and sends the light to the reference arm 3 and the sample arm 6 respectively. The reference arm 3 includes a collimator 4 and a reflector 5. The sample arm 6 may include a collimator lens 7, a spectroscopic component 8, an observation camera 9, a beam scanning mechanism 10, a scanning controller 11, a scanning lens 12 and a stage 13. The beam scanning mechanism 10 is a single-sided reflector with two-dimensional scanning capability, which is used to guide the light beam to perform one-dimensional or two-dimensional scanning on the sample on the stage 13. The scanning controller 11 receives the instruction of the processor 15 and provides a specific current / voltage signal to drive the beam scanning mechanism 10 to perform the corresponding scanning action. The spectroscopic component 8 is transparent to the light incident on the sample arm direction, and the spectroscopic component 8 will reflect a part of the light emitted from the sample arm to the observation camera 9, providing the observation camera 9 with light for sample imaging. The observation camera 9 is used for sample observation and auxiliary calibration, and the acquired image will be transmitted to the processor 15 for processing. The light returned from the reference arm 3 and the sample arm 6 is merged and interfered through the coupler / beam splitter 2, and the interference light is transmitted to the detection system 14. The detection system 14 can be a spectrometer for SD-OCT, or a photodiode detector system based on SS-OCT. The detection system 14 converts the interference light signal into an electrical signal and sends it to the processor 15 for processing. The processor 15 is a computer device with sufficient signal acquisition, data processing and storage capabilities, and simultaneously performs signal output control and input processing for the observation camera 9, the scanning component controller 11 and the detection system 14.

[0032] See also Figure 2 As shown, Figure 2 A schematic flow chart of a calibration method for optical coherence tomography provided in one embodiment of the present invention comprises the following steps:

[0033] Step S101: determining the relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates based on the camera calibration model;

[0034] In this embodiment, a calibration plate with a checkerboard or dot grid pattern that can be clearly imaged in the observation camera is generally used. Since the calibration plate made of glass is easily affected by the interference of the upper and lower glass surfaces, the calibration plate can preferably be made of non-transparent material. The observation camera can be calibrated using a more commonly used calibration method, such as the Zhang Zhengyou calibration method.

[0035] In one embodiment, the observation camera is calibrated based on a preset calibration method to obtain the internal and external parameters and distortion coefficients of the camera, and the physical coordinates of the OCT imaging plane are obtained by the pixel coordinates of the image taken by the observation camera through the camera calibration model;

[0036] The camera calibration model is shown in the following formula (1):

[0037] (X w ,Y w )=F c (u c ,v c ,K,R,T,D) (1)

[0038] Among them, F c Represents the mapping relationship function, (u c ,v c ) is the pixel coordinate of the image, K, R, T, D are the camera intrinsic parameters, rotation matrix, translation matrix and distortion coefficient respectively, (X w ,Y w ) is the physical coordinate of the OCT imaging plane.

[0039] Step S102: determining a light vector model based on a preset scanning position of the reflected light beam on the imaging plane, and pre-correcting the scanning mechanism based on the light vector model;

[0040] It should be noted that the pre-correction of the scanning mechanism is to pre-set the scanning position (track) of the reflected light beam on the imaging plane, and calculate the control amount required for the reflector to reflect the light to that position through the light vector model. The scanning mechanism moves according to the calculated control amount to achieve the effect of pre-correction.

[0041] In one embodiment, the controller of the reflector drives two rotation axes of the reflector respectively by using current or voltage as a control variable, and the step of determining the light vector model based on a preset scanning position of the reflected light beam on the imaging plane includes:

[0042] Step S1021: define a Cartesian coordinate system (x m ,y m ), the control amount is associated with the rotation state of the reflector of the scanning mechanism, where the Cartesian coordinate system (x m ,y m ) is the maximum deflection angle θ in the optical angle through the reflector max The maximum positive deflection of the reflector along each axis corresponds to a value of +1, and the maximum negative deflection corresponds to a value of -1. The reflector is a dual-axis single-sided reflector, such as Figure 3 As shown, the deflection angle θ xThe analytical relationship between and along the coordinate value is shown in the following formula (2):

[0043]

[0044] The control amount of the two rotating axes of the reflector (c x ,c y ) is linearly related to the coordinates of the reflector as shown in the following formula (3):

[0045]

[0046] Among them, k is the linear coefficient set inside the control system;

[0047] Step S1022: Determine a light vector model based on a preset scanning position of the reflected light beam on the imaging plane, the formula (2) and the formula (3).

[0048] It should be noted that if Figure 4 As shown, the normal vector of the center point M of the reflector is Rotate around the center of rotation and reflect a point P i and the unit vector The incident beam is specified. Assume that the reflected beam is reflected from the center of the mirror and has a unit vector Finally, the reflected light beam reaches point P on the target plane. t , the distance between the target plane and the center of the reflector is D.

[0049] There are two coordinate systems involved here. One is the mirror plane with the mirror at zero position (not deflected) as the xy plane, and the center of the mirror as the origin O m The other is the coordinate system I with the target plane as the xy plane and the intersection point O of the vertical line passing through the center of the reflector and the xy plane. t The coordinate system T is the origin. The representation of the same vector in two coordinate systems can be transformed by the orthogonal transformation matrix:

[0050] A IT =A TI -1 =A TI T (4)

[0051] Among them, A IT is the orthogonal transformation matrix from coordinate system I to coordinate system T, A TI is the orthogonal transformation matrix from coordinate system T to coordinate system I.

[0052] When the reflector is at zero position, the angle between the incident light beam and the normal of the mirror plane is α, and the unit vector of the incident light beam is

[0053]

[0054] The distance from the center of the reflector to the target plane is D. The reflected beam vector in the mirror coordinate system can be calculated

[0055]

[0056] in, is O in coordinate system I m P t Vector, A TI T is the orthogonal transformation matrix, is O in coordinate system T m P t Vector, you can use Indicates that x t and t is the coordinate on the target plane, and D is the distance from the center of the mirror to the target plane.

[0057] Unit vector of the reflected beam:

[0058]

[0059] According to the law of reflection, the normal vector of the reflecting surface of the reflector is:

[0060]

[0061] Then, as long as the incident direction of the light beam is constant, it can be obtained from any point (x t ,y t ) calculates the corresponding mirror normal vector If we change the target plane to the control coordinate system xy plane, using the mirror normal vector obtained above Similarly, using the law of light reflection and vector analysis, we can convert (x t ,y t ) and (x m ,y m ) are associated.

[0062] In one embodiment, the step of determining the light vector model based on the preset scanning position of the reflected light beam on the imaging plane, the formula (2) and the formula (3) includes:

[0063] When the reflector is at zero position, it is parallel to the xy plane of the control coordinate system. i and the unit vector The specified incident light beam is incident from the vertical control coordinate system xy plane to the center of the reflector. The normal vector of the center point M of the reflector is Rotate around the center of rotation and reflect from point P i and the unit vector The incident beam is specified, where the reflected beam is reflected from the center of the mirror and is a unit vector The reflected light beam reaches point P in the control coordinate system. t ; The distance between the target plane and the center of the reflector is d; The reflector is in the xy plane with the zero mirror plane as the xy plane and the center of the reflector as the origin O m The control coordinate system T is the intersection point O of the vertical line passing through the center of the reflector and the target plane. t As the origin, the target plane is the control coordinate system T of the xy plane. The target plane is parallel to the reflector when it is at zero position.

[0064] Incident beam The unit vector of :

[0065]

[0066] The unit vector of the reflected beam is expressed as follows:

[0067]

[0068]

[0069] in, is the unit vector of the reflected beam, is the unit vector of the incident beam, is the normal unit vector to the mirror plane, is the incident beam O m P i The vector of is the reflected beam vector Length;

[0070] When the optical angle of the reflector is the largest, the corresponding control quantity coordinate is ±1, so:

[0071]

[0072] Based on formulas (1), (2), (10) and (11), the light vector model is obtained. The light vector model is expressed as follows:

[0073]

[0074] Based on the light vector model and the physical position coordinates of the imaging plane, the control amount required by the scanning mechanism is calculated, wherein the control amount required by the scanning mechanism is calculated as follows:

[0075] (c x ,c y)=F s (x t ,y t ,A IT ,D,α,θ max ) (14)

[0076] Among them, F s is the mapping function, (x t ,y t ) is the scanning position of the imaging surface set according to the measurement object, A IT is the orthogonal transformation matrix between the reflector coordinate system and the imaging surface coordinate system, D is the vertical distance from the center of the reflector to the imaging surface, α is the incident angle relative to the normal of the reflector surface, θ max It is the maximum optical angle that the reflective mechanism can deflect.

[0077] Step S103: Based on the OCT image of the calibration plate obtained by scanning the calibration plate by the calibrated scanning mechanism, the image obtained by photographing the same calibration plate by the observation camera, the light vector model, and the camera calibration model, determine the mapping relationship between the control amount of the scanning mechanism and the physical coordinates of the OCT imaging plane.

[0078] Due to the influence of factors such as the collimation of the optical path assembly and the optical distortion of the scanning lens, the light beam reflected by the scanning mechanism may not be able to accurately reach the preset image plane position. The above pre-correction can only improve the distortion caused by the scanning mechanism to a large extent. Therefore, it is necessary to introduce a calibrated observation camera to calibrate the OCT system.

[0079] In one embodiment, the step of determining the mapping relationship between the control amount of the scanning mechanism and the actual physical coordinates of the imaging plane based on the OCT image of the calibration plate obtained by scanning the calibration plate by the scanning mechanism, the image obtained by photographing the calibration plate by the observation camera, and the light vector model includes:

[0080] Because each pixel of the OCT image corresponds to the control value one by one, the position coordinates of the calibration point are extracted from the OCT image of the calibration plate obtained by scanning the calibration plate by the scanning mechanism, and the precise mapping relationship between the pixel and the control value is obtained by interpolation. o , mapping relationship F o It is expressed as follows:

[0081] (c x ,c y )=F o (u o ,v o ) (15)

[0082] Among them, (u o ,v o ) are the pixel coordinates of the OCT image;

[0083] When the scanning angle of the scanning mechanism is 0, the observation camera is used to shoot the calibration plate in the same posture. After the calibration points of the obtained image are extracted, the calibration points of the observation camera are matched with the calibration points of the OCT image to obtain the mapping model F m , the matching method can use feature matching, optimization method or machine learning method, mapping model F m It is expressed as follows:

[0084] (u c ,v c )=F m (u o ,v o ) (16)

[0085] Among them, F m is the mapping model, (u c ,v c ) is the image coordinate obtained by observing the camera shooting the calibration plate;

[0086] Based on formulas (1)(14)(15)(16), the mapping relationship between the control amount of the scanning mechanism and the actual physical coordinates of the imaging plane is obtained, which is expressed as follows:

[0087]

[0088] refer to Figure 6 , Figure 7 as well as Figure 8 , Figure 6 Calibration process for OCT system, Figure 7 This is the distorted OCT image under uniform control volume scanning. Figure 8 This is the OCT image scanned after pre-correction.

[0089] The calibration method of optical coherence tomography proposed in this embodiment determines the relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates based on the camera calibration model, then determines the light vector model based on the preset scanning position of the reflected light beam on the imaging plane, and pre-corrects the scanning mechanism based on the light vector model, and finally determines the mapping relationship between the control amount of the scanning mechanism and the physical coordinates of the OCT imaging plane based on the OCT image of the calibration plate obtained by scanning the calibration plate by the corrected scanning mechanism, the image obtained by photographing the same calibration plate by the observation camera, the light vector model, and the camera calibration model. The present invention uses a common camera calibration plate to calibrate the OCT system, and uses the light vector model to directly pre-correct the control amount of the scanning mechanism, so that the system eliminates most of the distortion caused by the scanning mechanism during the scanning process. For the same calibration plate, the calibration plate image obtained by photographing the calibration plate with the calibrated auxiliary camera is used, and the OCT image obtained by scanning the calibration plate by the OCT system after the scanning mechanism pre-corrects is used. The calibration point coordinates are extracted from the two images respectively, and the mapping relationship between the control amount of the scanning mechanism and the camera image pixel coordinate system is calculated. Through this mapping relationship and the parameters of the camera correction model, the relationship between the physical distance coordinates of the imaging surface and the control amount of the scanning mechanism can be obtained, thereby completing accurate calibration.

[0090] In one embodiment, an OCT system is provided. The OCT system includes a processor, a memory, a network interface, and a database connected via a system bus. The processor of the OCT system is used to provide computing and control capabilities. The memory of the OCT system includes a non-volatile and / or volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the OCT system is used to communicate with an external client via a network connection. When the computer program is executed by the processor, the functions or steps of an optical coherence tomography calibration method are implemented.

[0091] In one embodiment, an OCT system is provided, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the following steps are implemented:

[0092] Based on the camera correction model, the relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates is determined. Then, based on the preset scanning position of the reflected light beam on the imaging plane, the light vector model is determined, and the scanning mechanism is pre-corrected based on the light vector model. Then, based on the OCT image of the calibration plate obtained by scanning the calibration plate with the corrected scanning mechanism, the image obtained by photographing the same calibration plate with the observation camera, the light vector model, and the camera correction model, the mapping relationship between the control amount of the scanning mechanism and the physical coordinates of the OCT imaging plane is determined.

[0093] In one embodiment, a computer-readable storage medium is provided, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the following steps are implemented:

[0094] Based on the camera correction model, the relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates is determined. Then, based on the preset scanning position of the reflected light beam on the imaging plane, the light vector model is determined, and the scanning mechanism is pre-corrected based on the light vector model. Then, based on the OCT image of the calibration plate obtained by scanning the calibration plate with the corrected scanning mechanism, the image obtained by photographing the same calibration plate with the observation camera, the light vector model, and the camera correction model, the mapping relationship between the control amount of the scanning mechanism and the physical coordinates of the OCT imaging plane is determined.

[0095] It should be noted that the functions or steps that can be implemented by the computer-readable storage medium or the OCT system can be found in the relevant descriptions of the server side and the client side in the aforementioned method embodiment. To avoid repetition, they will not be described one by one here.

[0096] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be completed by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application can include non-volatile and / or volatile memory. Non-volatile memory can include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory can include random access memory (RAM) or external cache memory. As an illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).

[0097] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0098] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A calibration method for optical coherence tomography, characterized in that: Applied to an OCT system, the OCT system includes an observation camera and a scanning mechanism, the scanning mechanism uses a dual-axis single-sided reflector, and the optical coherence tomography calibration method includes: Determine the relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates based on the camera calibration model; Determining a light vector model based on a preset scanning position of the reflected light beam on the imaging plane, and pre-correcting the scanning mechanism based on the light vector model; Based on the OCT image of the calibration plate obtained by scanning the calibration plate with the corrected scanning mechanism, the image obtained by photographing the same calibration plate with the observation camera, the light vector model, and the camera correction model, the mapping relationship between the control amount of the scanning mechanism and the physical coordinates of the OCT imaging plane is determined.

2. The optical coherence tomography calibration method according to claim 1, characterized in that: The step of determining the relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates based on the camera calibration model comprises: The observation camera is calibrated based on the preset calibration method to obtain the internal and external parameters and distortion coefficients of the camera. The relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates is obtained by the pixel coordinates of the image taken by the observation camera through the camera calibration model; The camera calibration model is shown in the following formula (1): (X w ,Y w )=F c (u c ,v c ,K,R,T,D) (1) Among them, F c Represents the mapping relationship function, (u c , v c ) is the pixel coordinate of the image, K, R, T, D are the camera intrinsic parameters, rotation matrix, translation matrix and distortion coefficient respectively, (X w , Y w ) is the physical coordinate of the OCT imaging plane.

3. The optical coherence tomography calibration method according to claim 2, characterized in that: The step of determining the light vector model based on the preset scanning position of the reflected light beam on the imaging plane includes: Define a Cartesian coordinate system (x m ,y m ), the control amount is associated with the rotation state of the reflector of the scanning mechanism, where the Cartesian coordinate system (x m ,y m ) is the maximum deflection angle θ in the optical angle through the reflector max The maximum positive deflection of the mirror along each axis corresponds to a value of +1, the maximum negative deflection corresponds to a value of -1, and the deflection angle θ x The analytical relationship between and along the coordinate value is shown in the following formula (2): The control amount of the two rotating axes of the reflector (c x , c y ) is linearly related to the coordinates of the reflector as shown in the following formula (3): Among them, k is the linear coefficient set inside the control system; The light vector model is determined based on the preset scanning position of the reflected light beam on the imaging plane, the formula (2) and the formula (3).

4. The optical coherence tomography calibration method according to claim 3, characterized in that: The step of determining the light vector model based on the preset scanning position of the reflected light beam on the imaging plane, the formula (2) and the formula (3) comprises: When the reflector is at zero position, it is parallel to the xy plane of the control coordinate system. i and the unit vector The specified incident light beam is incident from the vertical control coordinate system xy plane to the center of the reflector. The normal vector of the center point M of the reflector is Rotate around the center of rotation and reflect from point P i and the unit vector The incident beam is specified, where the reflected beam is reflected from the center of the mirror and is a unit vector The reflected light beam reaches point P in the control coordinate system. t ; The distance between the target plane and the center of the reflector is d; The reflector is in the xy plane with the zero mirror plane as the xy plane and the center of the reflector as the origin O m The control coordinate system T is the intersection point O of the vertical line passing through the center of the reflector and the target plane. t As the origin, the target plane is the control coordinate system T of the xy plane. The target plane is parallel to the reflector when it is at zero position. Incident beam The unit vector of : The unit vector of the reflected beam is expressed as follows: in, is the unit vector of the reflected beam, is the unit vector of the incident beam, is the normal unit vector to the mirror plane, is the incident beam O m P i The vector of is the reflected beam vector Length; When the optical angle of the reflector is the largest, the corresponding control quantity coordinate is ±1, so: Based on formulas (1), (2), (10) and (11), the light vector model is obtained. The light vector model is expressed as follows: Based on the light vector model and the physical position coordinates of the imaging plane, the control amount required by the scanning mechanism is calculated, wherein the control amount required by the scanning mechanism is expressed as follows: (c x ,c y )=F s (x t ,y t ,A IT ,D,α,θ max ) (14) Among them, F s is the mapping function, (x t ,y t ) is the scanning position of the imaging surface set according to the measurement object, A IT is the orthogonal transformation matrix between the reflector coordinate system and the imaging surface coordinate system, D is the vertical distance from the center of the reflector to the imaging surface, α is the incident angle relative to the normal of the reflector surface, and θ max It is the maximum optical angle that the reflective mechanism can deflect.

5. The optical coherence tomography calibration method according to claim 4, characterized in that: The step of determining the mapping relationship between the control amount of the scanning mechanism and the physical coordinates of the OCT imaging plane based on the calibration plate OCT image obtained by scanning the calibration plate by the rectified scanning mechanism, the image obtained by photographing the same calibration plate by the observation camera, the light vector model, and the camera calibration model comprises: The position coordinates of the calibration points are extracted from the OCT image of the calibration plate obtained by scanning the calibration plate by the scanning mechanism, and the mapping relationship between the pixel coordinates of the OCT image of the calibration plate and the control amount is obtained by interpolation method. o , mapping relationship F o It is expressed as follows: (c x ,c y )=F o (u o ,v o ) (15) Among them, (u o , v o ) is the pixel coordinate of the calibration plate OCT image; When the scanning angle of the scanning mechanism is 0, the observation camera is used to shoot the calibration plate in the same posture. After the calibration points of the obtained image are extracted, the calibration points of the observation camera are matched with the calibration points of the OCT image of the calibration plate to obtain the mapping model F m , mapping model F m It is expressed as follows: (u c ,v c )=F m (u o ,v o ) (16) Among them, F m is the mapping model, (u c , v c ) is the image coordinate obtained by observing the camera shooting the calibration plate; Based on formulas (1)(14)(15)(16), the mapping relationship between the control amount of the scanning mechanism and the physical coordinates of the OCT imaging plane is obtained, which is expressed as follows:

6. An OCT system comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the optical coherence tomography calibration method according to any one of claims 1 to 5 are implemented.

7. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the optical coherence tomography calibration method according to any one of claims 1 to 5 are implemented.

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