Calibration method for optical coherence tomography, oct system and storage medium

Abstract

The application relates to the technical field of calibration of optical coherence tomography, and discloses a calibration method of optical coherence tomography, an OCT system and a storage medium.The method comprises the following steps: determining the relationship between the physical coordinates of an OCT imaging plane and camera pixel coordinates based on a camera correction model; determining a light vector model based on the scanning position of a reflected light beam on the imaging plane, and pre-correcting the scanning mechanism based on the light vector model; and determining the mapping relationship between the control quantity of the scanning mechanism and the physical coordinates of the OCT imaging plane based on the OCT image of the calibration board obtained by scanning the calibration board by the corrected scanning mechanism, the image obtained by photographing the same calibration board by an observation camera, the light vector model and the camera correction model. The application can calculate the relationship between the physical distance coordinates of the imaging plane and the control quantity of the scanning mechanism, so that the accurate calibration of optical coherence tomography is completed.

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] An OCT system is essentially a Michelson interferometer. Light from a light source enters two arms—a sample arm and a reference arm. The reflected / scattered light from the sample arm and the reflected light from the reference arm generate an interference signal. This interference signal is received by a photodetector and processed by a computer to produce an image of the sample.

[0004] A one-dimensional image of the sample's axial depth is called an A-scan. A scanning mechanism scans the sample arm's beam laterally, generating a series of A-scan images that can be combined into a vertical cross-sectional image (B-scan). If the scanning mechanism performs two-dimensional scanning, a three-dimensional volume scan image can be obtained. By intercepting the volume image at a specific axial depth, a horizontal cross-sectional image (enface) can be obtained.

[0005] OCT is widely used in medical imaging, and distortion correction is typically performed on OCT images. However, as OCT is used in precision-critical scenarios such as surgical assistance and industrial inspection, accurately measuring the physical dimensions of imaged objects and the true distances between them is becoming increasingly important.

[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. These orthogonal mirrors can cause pincushion distortion in OCT images during scanning. 2) dual-axis single-sided reflective mirrors, such as fast-reflection mirrors and microelectromechanical system (MEMS) scanning mirrors, offer advantages such as small size, high speed, and low cost. However, these mirrors can produce various distortions in the OCT image, such as trapezoidal and fan-shaped distortions.

[0009] However, current methods only perform distortion correction on OCT images or data extracted from them as a post-processing method. This inevitably increases measurement time and computing resource consumption. For severely distorted images, image correction can reduce the actual imaging range, making it difficult to measure large objects. Summary of the Invention

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

[0011] In a first aspect, a method for calibrating 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 calibration 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 above-mentioned optical coherence tomography calibration method are implemented.

[0017] The optical coherence tomography calibration method proposed in the present invention determines the relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates based on a camera calibration model. A light vector model is then determined based on a predetermined scanning position of a reflected light beam on the imaging plane. The scanning mechanism is pre-corrected based on the light vector model. The mapping relationship between the control variables of the scanning mechanism and the physical coordinates of the OCT imaging plane is then determined based on an OCT image of the calibration plate obtained by scanning the calibration plate with the corrected scanning mechanism, an image obtained by photographing the same calibration plate with an 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, directly pre-correcting the control variables of the scanning mechanism using the light vector model, thereby eliminating most of the distortion introduced by the scanning mechanism during the scanning process. For the same calibration plate, an image of the calibration plate captured by a calibrated auxiliary camera is used, along with an OCT image scanned by the OCT system after the scanning mechanism pre-calibration. Calibration point coordinates are extracted from each of the two images, and the mapping relationship between the control variables 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 quantity 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 following briefly introduces the drawings required for use in the embodiments or the description of the prior art. 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 any creative work.

[0019] in:

[0020] Figure 1 An OCT system according to an embodiment of a calibration method for optical coherence tomography;

[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 : A schematic diagram of the spatial vector of light passing through a reflector in an optical coherence tomography calibration method according to 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 one embodiment;

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

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

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

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

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall 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. The thin solid line in the figure 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 collimating lens 4 and a reflector 5. The sample arm 6 may include a collimating lens 7, a spectroscopic component 8, an observation camera 9, a beam scanning mechanism 10, a scanning controller 11, a scanning lens 12 and an object 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 object stage 13. The scanning controller 11 receives instructions from 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 transmits the light incident on the sample arm. For the light exiting the sample arm, the spectroscopic component 8 will reflect a portion of the light 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 is transmitted to the processor 15 for processing. The light returned from the reference arm 3 and the sample arm 6 is combined and interfered by 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 according to an embodiment of the present invention includes 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 by the observation camera is generally used. Because glass calibration plates are easily affected by interference between the upper and lower glass surfaces, non-transparent materials are preferred. Observation cameras can be calibrated using commonly used calibration methods, 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 camera's intrinsic and extrinsic parameters and distortion coefficients. The physical coordinates of the OCT imaging plane are obtained from the pixel coordinates of the image captured by the observation camera using a 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 internal 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 pre-correction of the scanning mechanism is achieved by presetting the scanning position (trajectory) of the reflected light beam on the imaging plane and calculating the control amount required by the reflector to reflect the light to that position using a light vector model. The scanning mechanism moves according to the calculated control amount to achieve the pre-correction effect.

[0041] In one embodiment, a controller of the reflector drives two rotation axes of the reflector respectively using current or voltage as a control variable. The step of determining the light vector model based on a predetermined 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, wherein 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 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 is 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, It is O in coordinate system I m P t Vector, A TI T is the orthogonal transformation matrix, It is O in coordinate system T m P t Vector, you can use Indicates that x t and y 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 detected from any point (x t ,y t ) calculate 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 get (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, and the normal vector of the reflector center point M 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 unit vector normal to the mirror plane, is the incident beam O m P i vector, 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, which 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. The control amount required by the scanning mechanism is expressed 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 plane coordinate system, D is the vertical distance from the center of the reflector to the imaging plane, α is the incident angle relative to the normal of the reflector, 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 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 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 factors such as the optical path assembly's collimation and the optical distortion of the scanning lens, the light beam reflected by the scanning mechanism may not reach the preset image plane position accurately. The aforementioned pre-correction can only largely improve the distortion introduced by the scanning mechanism. Therefore, it is necessary to calibrate the OCT system using a calibrated observation camera.

[0079] In one embodiment, the step of determining a mapping relationship between a control variable of the scanning mechanism and an actual physical coordinate of the imaging plane based on an OCT image of the calibration plate obtained by scanning the calibration plate by the scanning mechanism, an image of the calibration plate captured 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 the scanning mechanism, and the accurate 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 calibration plate by the camera;

[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 as follows:

[0087]

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

[0089] The optical coherence tomography calibration method proposed in this embodiment determines the relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates based on a camera calibration model. Then, based on a predetermined scanning position of the reflected light beam on the imaging plane, a light vector model is determined, and the scanning mechanism is pre-corrected based on the light vector model. Finally, based on the corrected OCT image of the calibration plate obtained by scanning the calibration plate with the scanning mechanism, an image obtained by photographing the same calibration plate with the observation camera, the light vector model, and the camera calibration model, the mapping relationship between the control variable of the scanning mechanism and the physical coordinates of the OCT imaging plane is determined. The present invention uses a common camera calibration plate to calibrate the OCT system, directly pre-correcting the control variable of the scanning mechanism using the light vector model, so that the system eliminates most of the distortion caused by the scanning mechanism during the scanning process. For the same calibration plate, an image of the calibration plate obtained by photographing the calibration plate with a calibrated auxiliary camera is used, and an OCT image obtained by scanning the calibration plate with the OCT system after the scanning mechanism pre-calibration is used. The coordinates of the calibration points are extracted from each of the two images, and the mapping relationship between the control variable 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 quantity 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 non-volatile and / or volatile storage media 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 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, it implements the functions or steps of an optical coherence tomography calibration method.

[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 calibration 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 calibration 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 calibration 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 calibration 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 referred to in the corresponding 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 will appreciate that all or part of the processes in the above-mentioned embodiments can be implemented by instructing the relevant hardware through a computer program. 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. By way of illustration and not limitation, RAM is available in various 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 will clearly understand that for the sake of convenience and brevity 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 they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection 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; Determine 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 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 calibration model; 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 , the control quantity is associated with the rotation state of the reflector of the scanning mechanism, wherein the Cartesian coordinate system is the maximum deflection angle in optical angle through the reflector 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 The analytical relationship between and along the coordinate value is shown in the following formula (2): Control amount of the two rotating axes of the reflector The linear relationship with the coordinates of the reflector is shown in the following formula (3): in, It is the linear coefficient set inside the control system; Determine a light vector model based on a predetermined scanning position of the reflected light beam on the imaging plane, the formula (2) and the formula (3); 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: When the reflector is at zero position, it is in the control coordinate system plane parallel, a point and the unit vector The incident beam is specified from the vertical control coordinate system The plane is incident on the center of the reflector, and the center point of the reflector Normal vector Rotate around the center of rotation and reflect the 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 the point on the control coordinate system. ; The distance between the target plane and the center of the reflector is d; the reflector is at the mirror plane with the zero position as Plane, with the center of the mirror as the origin Coordinate system ;Control coordinate system is the intersection of a vertical line through the center of the reflector and the target plane As the origin, the target plane is the control coordinate system of the xy plane , the target plane is parallel to the reflector 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 unit vector normal to the mirror plane, is the incident beam vector, 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 the camera calibration model, formulas (2), (10) and (11), the light vector model is obtained. The light vector model is expressed as follows: 。 2. The optical coherence tomography calibration method according to claim 1, wherein: 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 includes: The observation camera is calibrated based on a preset calibration method to obtain the camera's internal and external parameters and distortion coefficients. The relationship between the physical coordinates of the OCT imaging plane and the camera pixel coordinates is obtained using the camera calibration model based on the image pixel coordinates captured by the observation camera. The camera calibration model is shown in the following formula (1): in, Represents the mapping relationship function, are the pixel coordinates of the image, They are camera intrinsic parameters, rotation matrix, translation matrix and distortion coefficient, is the physical coordinate of the OCT imaging plane.

3. The optical coherence tomography calibration method according to claim 2, wherein: 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) further includes: 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: in, is a mapping function, It is the scanning position of the imaging surface set according to the measurement object. is the orthogonal transformation matrix between the mirror coordinate system and the imaging surface coordinate system, is the vertical distance from the center of the reflector to the imaging surface, is the angle of incidence relative to the normal of the reflector surface, It is the maximum optical angle that the reflective mechanism can deflect.

4. The optical coherence tomography calibration method according to claim 3, wherein: 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 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 includes: 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. , mapping relationship It is expressed as follows: in, is the pixel coordinate of the calibration plate OCT image; When the scanning angle of the scanning mechanism is 0, the calibration plate of the same posture is photographed with an observation camera. 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 calibration plate OCT image to obtain the mapping model. , mapping model It is expressed as follows: in, For the mapping model, It is the image coordinate obtained by observing the camera shooting the calibration plate; Based on formula (1)(14)(15) , 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:

5. An OCT system 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 steps of the optical coherence tomography calibration method according to any one of claims 1 to 4 are implemented.

6. 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 4 are implemented.

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