A structured light-guided full-field OCT tomography measurement system and method

Abstract

The present invention discloses a structured light-guided full-field optical coherence tomography (OCT) measurement system and method. The method comprises: a computer controls a six-axis motion platform via a motion controller to move to above a measured object; a measurement optical path module projects sinusoidal stripe structured light onto the surface of the measured object; and structured light technology is used to reconstruct the complete measured object's surface 3D topography with a large field of view, thereby obtaining the measured object's 3D coordinate information in space. Based on the results of the structured light 3D reconstruction and in conjunction with a pre-calibrated system spatial coordinate transformation relationship, 3D scanning path planning is performed; the six-axis motion platform moves along the 3D scanning path and uses OCT technology to perform local tomographic measurements; and multiple OCT local tomographic measurement results are 3D-joined to obtain a large-field tomographic phase result, thereby obtaining a large-field tomographic measurement result. The present invention can realize large-field OCT tomographic measurements.

Description

Technical Field

[0001] The present invention relates to the technical field of full-field coherence tomography measurement, and in particular to a structured light-guided full-field OCT tomography measurement system and method. Background Art

[0002] OCT tomographic measurement technology, characterized by high sensitivity, high resolution, and non-contact performance, is widely used in biological and industrial material testing. However, existing OCT systems suffer from a limited field of view, resulting in inefficient tomographic detection. Furthermore, due to the limited imaging range, it is difficult to obtain the global strain field distribution when measuring deformation in large, complex tissue materials, hindering analysis of the material's mechanical properties.

[0003] Currently, there are two main methods for expanding the OCT measurement field of view. The first involves using a long coherence length light source to achieve large-field-of-view three-dimensional volume measurement. However, because this method expands the imaging range by changing the optical path design, it reduces the lateral resolution of the measurement system. The second method relies on multiple measurements and image stitching to achieve large-field-of-view measurement. However, existing technologies are limited to simple translation devices or even handheld scanning, which can lead to lens defocus and jitter errors during each OCT measurement.

[0004] In summary, expanding the imaging field of view without reducing the lateral resolution is a key issue that the current OCT tomography measurement system urgently needs to overcome. Summary of the Invention

[0005] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a structured light guided full-field OCT tomography measurement system to achieve large field of view and high resolution OCT measurement.

[0006] To achieve the above objectives, the technical solutions provided by the present invention are:

[0007] A structured light-guided full-field OCT tomography measurement system, comprising a six-axis motion platform, a motion controller, a measurement optical path module, an OCT probe, a material loading platform, a computer, and a display;

[0008] The six-axis motion platform is connected to the measuring optical path module and is used to drive the measuring optical path module to move;

[0009] The motion controller is connected to the six-axis motion platform and is used to control the movement trajectory of the six-axis motion platform;

[0010] The measurement optical path module is a structured light and OCT integrated optical path built with optical components;

[0011] The OCT probe is installed at the bottom of the measurement optical path module and is used for positioning of OCT scanning;

[0012] The material loading platform is located below the OCT probe;

[0013] The motion controller, the measuring optical path module and the display are all connected to the computer.

[0014] Furthermore, the measurement optical path module includes a DLP projection light source, an RGB industrial camera, a first polarizer, a second polarizer, an infrared laser light source, a collimating lens, a first reflector, a second reflector, a beam splitter, an infrared camera, a reference light wedge, and a double-sided reflector for separating the OCT beam and the structured light beam;

[0015] in,

[0016] The DLP projection light source emits structured light which is reflected by a double-sided reflector and then reaches the surface of the object to be measured;

[0017] The RGB industrial camera is used to collect structured light images of the material being tested;

[0018] The first polarizer and the second polarizer are placed in front of the DLP projection light source and in front of the RGB industrial camera respectively to eliminate highlight reflected light;

[0019] The collimating lens is located between the infrared laser light source and the first reflector, and is used to convert the infrared laser light source beam into parallel light. The first reflector then changes the angle and direction of the parallel light and irradiates the parallel light into the beam splitter prism located on one side of the first reflector.

[0020] The beam splitter prism splits the light into two beams with different paths, one beam is directly irradiated onto the object to be measured, and the other beam is irradiated onto the reference light wedge after passing through a double-sided reflector;

[0021] The infrared camera collects the interference image generated by the infrared laser light source through the second reflector, that is, the image obtained by the reflection and convergence of two beams of light.

[0022] To achieve the above objectives, the present invention further provides a structured light guided full-field OCT tomography measurement method.

[0023] include:

[0024] Calibration of the measurement system's spatial coordinate system;

[0025] The computer controls the six-axis motion platform to its initial position above the object under test through a motion controller. The DLP projection light source projects sinusoidal fringe structured light onto the surface of the object under test. The RGB industrial camera captures the structured light image sequence and performs large-field phase recovery and surface 3D topography reconstruction on the complete object under test, thereby obtaining 3D point cloud information of the object under test in space.

[0026] Based on the 3D point cloud information obtained by structured light measurement and the system calibration parameters, the spatial position coordinates of the OCT probe in each sub-area measurement are calculated to obtain the corresponding OCT 3D scanning path;

[0027] The motion controller controls the six-axis motion platform to move along the three-dimensional scanning path, allowing the OCT probe to accurately focus and acquire OCT tomographic images each time, and demodulates the tomographic signals to obtain local tomographic imaging data;

[0028] The rotation and translation vectors between the two fixed positions of the six-axis motion platform in the three-dimensional scanning path are used to three-dimensionally stitch the local tomographic imaging data of multiple OCT measurements to obtain large-field-of-view tomographic three-dimensional volume measurement results.

[0029] Furthermore, the measurement system space coordinate system calibration includes:

[0030] Phase-depth calibration for RGB industrial cameras and DLP projection light sources;

[0031] Perform stereo calibration on the RGB industrial camera and infrared camera to obtain the relative pose and coordinate transformation matrix between the two cameras;

[0032] Establish the conversion relationship between the motion platform coordinate system, the camera coordinate system and the measured object coordinate system.

[0033] Furthermore, phase-depth calibration of RGB industrial cameras and DLP projection light sources includes:

[0034] Place a tablet on a precision lift, and control the lift to move to more than 3 different heights in sequence. At each height position, the DLP projection light source projects structured light onto the tablet on the lift, and the camera collects the structured light image for phase extraction; more than 3 sets of phase The following nonlinear mapping model is established with the data of height H to obtain the phase-depth mapping parameters:

[0035]

[0036] Where (x, y) represents the image coordinates, and A(x, y), B(x, y), and C(x, y) are the phase-depth mapping parameters.

[0037] Furthermore, stereo calibration of RGB industrial cameras and infrared cameras includes:

[0038] The Zhang Zhengyou calibration method is used to obtain the intrinsic and intrinsic parameters of the two cameras. The intrinsic parameters are the focal length, center point and other intrinsic information of the camera lens, and the extrinsic parameters are the rotation matrix and translation vector of the camera relative to the world coordinate system. After obtaining the intrinsic and extrinsic parameters, the transformation relationship between the image coordinate system and the world coordinate system is established:

[0039]

[0040] Where s is the depth scaling factor, f x and f y is the focal length of the lens, (u0, v0) is the coordinate of the camera principal point; R is the rotation matrix, and T is the translation vector; let the rotation and translation vectors of the RGB industrial camera be represented by R1 and T1, and the rotation and translation vectors of the infrared camera be represented by R2 and T2, then the relative pose between the two cameras is as follows:

[0041]

[0042] Among them, R 12 and T 12 Represent the rotation and translation vectors between the two cameras respectively.

[0043] Furthermore, a large-field phase recovery and surface 3D topography reconstruction are performed on the complete object to obtain 3D point cloud information of the object in space, including:

[0044] The structured light image captured by the RGB industrial camera is a sinusoidal fringe image, which is expressed as

[0045]

[0046] Among them, a and b represent the background light intensity and modulation degree of the structured light image respectively. is the surface phase distribution of the object under test, N is the number of structured light images, i = 1, 2, ..., N;

[0047] Use the N-step phase shift method to solve the wrapped phase and perform phase unwrapping to obtain:

[0048]

[0049] Where K is the fringe level, which is used to assist the wrapping phase unwrapping;

[0050] Finally, the three-dimensional point cloud information of the object is obtained by combining the phase-depth calibration parameters.

[0051] Furthermore, obtaining an OCT three-dimensional scanning path includes:

[0052] The large field of view 3D point cloud reconstruction result P{X, Y, Z} obtained by structured light measurement is divided into n sub-areas according to the size of the OCT measurement field of view. The coordinates of the OCT probe focus point are determined for each sub-area in turn. The edges of two adjacent sub-areas need to be set to overlap to facilitate subsequent data splicing. Specifically, the point p with the largest depth coordinate z is determined in the i-th sub-area. ci (x ci ,y ci ,zci ), and then calculate the normal vector corresponding to the point, and the direction of the normal vector is used as the image acquisition direction of the OCT probe in the sub-area; the six-axis motion platform moves the OCT probe at the bottom of the measurement optical path module to the direction of the normal vector and stays at the spatial coordinate p ci (x ci -Δx,y ci -Δy,z ci +Δf), where Δx and Δy are the set coordinate offsets to ensure that the edges of adjacent sub-areas coincide; Δf is the focal length of the infrared camera lens; at this time, through system calibration, the distance between the motion platform and p is calculated. ci The posture relationship between them:

[0053]

[0054] in, and are the rotation matrix and translation vector of the motion platform corresponding to the i-th sub-region respectively; by performing the above operations on n sub-regions, the OCT probe spatial coordinate sequence p is obtained c ={p c1 ,p c2 ,...,p cn The spatial coordinate sequence is input into the motion platform controller, which controls the six-axis motion platform to move according to the coordinate sequence, which is the three-dimensional scanning path of the OCT probe.

[0055] Furthermore, local tomographic imaging data is obtained, including:

[0056] The OCT interference image collected by the infrared camera is expressed as:

[0057]

[0058] Where t=1,2,...,T represents the image index captured by the camera; M is the number of tomographic measurement layers of the object being measured; k(t) represents the wave number; y p and y q Represents the dielectric layer S from the material p and S q The reflected light intensity; pq and Respectively represent S p and S q The optical path difference and initial phase are obtained by Fourier transforming the tomographic interference signal y:

[0059]

[0060] Where W[k(t)] is the window function, f represents the frequency in the Fourier domain, and is a continuous spectrum. The frequency signal corresponding to each dielectric layer is extracted, and the phase distribution information of a dielectric layer in a single scan is obtained using the following formula:

[0061]

[0062] Among them, Im[·] and Re[·] represent the imaginary and real parts of the Fourier transform respectively; the phase distribution of all dielectric layers is expressed as a tensor: The local tomographic phase result of OCT can be obtained.

[0063] Furthermore, the local tomographic imaging data of multiple OCT measurements are 3D stitched together to obtain large-field tomographic 3D volume measurement results, including:

[0064] The OCT tomographic phase results of two adjacent sub-regions obtained by three-dimensional path planning are spliced; since adjacent sub-regions have overlapping parts, the three-dimensional coordinates of the tomographic phase obtained by the same phase point in the overlapping part in the i-th scan and the i+1-th scan are respectively:

[0065]

[0066]

[0067] Φ sub i and Φ sub i+1 The conversion relationship between them is solved using the i+1th motion platform rotation matrix R in the three-dimensional path planning. bo and the translation vector T bo It is expressed as follows:

[0068]

[0069] Through the above conversion, the spatial pose of the i+1th scanning result is converted to the same as the i-th scanning result, realizing the three-dimensional stitching of the tomographic phases of adjacent sub-regions; the above operation is repeated until all n scanning results are converted to the same pose, and a large-field-of-view tomographic phase stitching result is obtained.

[0070] Compared with the existing technology, the principles and advantages of this solution are as follows:

[0071] Integrating the structured light measurement optical path into the OCT measurement optical path creates a completely new measurement system. Leveraging the advantages of structured light technology for large-field 3D reconstruction, global 3D prior information is provided for OCT local tomographic scans, enabling planning of the 3D scanning path and ensuring precise focus for each OCT local tomographic scan. Furthermore, by splicing 3D tomographic data, large-field, high-resolution tomographic 3D volumetric imaging results can be obtained. Compared to conventional OCT, the measurement system of the present invention achieves large-field OCT tomographic measurements without compromising lateral resolution. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the services required for use in the embodiments or the prior art descriptions 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 any creative work.

[0073] Figure 1 This is a schematic structural diagram of a structured light-guided full-field OCT tomography measurement system of the present invention;

[0074] Figure 2 This is a schematic diagram of the structure of a six-axis motion platform in a structured light-guided full-field OCT tomography measurement system of the present invention;

[0075] Figure 3 This is a schematic structural diagram of a measurement optical path module in a structured light-guided full-field OCT tomography measurement system of the present invention.

[0076] Reference numerals

[0077] 1-Display; 2-Computer; 3-Motion controller; 4-Six-axis motion platform; 5-Measurement optical path module; 6-OCT probe; 7-Material loading platform; 8-Measured object; 4-1-Motion axis; 4-2-Motion platform; 4-3-Support base; 5-1-Infrared laser light source; 5-2-Collimating lens; 5-3-First reflector; 5-4-Beam splitter; 5-5-Infrared camera; 5-6-Reference wedge; 5-7-Double-sided reflector; 5-8-DLP projection light source; 5-9-RGB industrial camera; 5-10-First polarizer; 5-11-Second reflector; 5-12-Second polarizer. DETAILED DESCRIPTION

[0078] The present invention will be further described below in conjunction with specific embodiments:

[0079] like Figure 1As shown, the structured light-guided full-field OCT tomography measurement system described in this embodiment includes a six-axis motion platform 4, a motion controller 3, a measurement optical path module 5, an OCT probe 6, a material loading platform 7, a computer 2, and a display 1.

[0080] Among them, the six-axis motion platform 4 is connected to the measurement optical path module 5, which is used to drive the measurement optical path module 5 to move; the motion controller 3 is connected to the six-axis motion platform 4, which is used to control the movement trajectory of the six-axis motion platform 4; the measurement optical path module 5 is a structured light and OCT integrated optical path built with optical components; the OCT probe 6 is installed at the bottom of the measurement optical path module 5 for positioning the OCT scan; the material loading platform 7 is located below the OCT probe 6 for placing the object to be measured 8; the motion controller 3, the measurement optical path module 5, and the display 1 are all connected to the computer 2; the computer 2 is used to control the operation of the full-field OCT tomography measurement system and to process and analyze the collected image data; the display 1 is used for visual display of measurement signals and measurement results.

[0081] Specifically, if Figure 2 As shown, the six-axis motion platform 4 includes motion axes 4-1, a motion platform 4-2, and a support base 4-3. The motion platform 4-2 and the support base 4-3 are connected by six motion axes 4-1. By moving the motion axes 4-1 at different angles, the motion platform 4-2 can be driven to achieve a six-degree-of-freedom spatial posture.

[0082] Specifically, if Figure 3As shown, the measurement optical path module 5 includes a DLP projection light source 5-8, an RGB industrial camera 5-9, a first polarizer 5-10, a second polarizer 5-12, an infrared laser light source 5-1, a collimating lens 5-2, a first reflector 5-3, a second reflector 5-11, a beam splitter 5-4, an infrared camera 5-5, a reference light wedge 5-6, and a double-sided reflector 5-7 for separating the OCT beam and the structured light beam; wherein, the DLP projection light source 5-8 emits structured light which is reflected by the double-sided reflector 5-7 to the surface of the object to be measured 8; the RGB industrial camera 5-9 is used to collect the structured light image of the material to be measured; the first polarizer 5-10 and the second polarizer 5-12 are respectively placed on the DLP projection light source 5-8 In front of the infrared laser light source 5-1 and in front of the RGB industrial camera 5-9, it is used to eliminate high-brightness reflected light; the collimating lens 5-2 is located between the infrared laser light source 5-1 and the first reflector 5-3, and is used to convert the light beam of the infrared laser light source 5-1 into parallel light, and then the first reflector 5-3 changes the angle and direction of the parallel light, and irradiates the parallel light into the dichroic prism 5-4 located on one side of the first reflector 5-3; the dichroic prism 5-4 is divided into two light beams with different paths, one beam is directly irradiated onto the object to be measured 8, and the other beam passes through the double-sided reflector 5-7 and irradiates the reference light wedge 5-6; the infrared camera 5-5 collects the interference image generated by the infrared laser light source 5-1 through the second reflector 5-11, that is, the image obtained by the reflection and convergence of the two light beams.

[0083] The working principle of the full-field OCT tomography measurement system is as follows:

[0084] S1. Calibration of the measurement system spatial coordinate system, including:

[0085] S1-1, perform phase-depth calibration on the RGB industrial camera 5-9 and the DLP projection light source 5-8;

[0086] Place a flat panel on a precision lift, and control the lift to move to more than three different heights in sequence. At each height, DLP projection light sources 5-8 project structured light onto the flat panel on the lift, and the camera collects the structured light image for phase extraction. More than three phases are obtained. The following nonlinear mapping model is established with the data of height H to obtain the phase-depth mapping parameters:

[0087]

[0088] Where (x, y) represents the image coordinates, and A(x, y), B(x, y), and C(x, y) are the phase-depth mapping parameters.

[0089] S1-2. Stereo calibration is performed on the RGB industrial camera 5-9 and the infrared camera 5-5 to obtain the relative pose and coordinate transformation matrix between the two cameras. The process specifically includes:

[0090] The Zhang Zhengyou calibration method is used to obtain the intrinsic and intrinsic parameters of the two cameras. The intrinsic parameters are the focal length, center point and other intrinsic information of the camera lens, and the extrinsic parameters are the rotation matrix and translation vector of the camera relative to the world coordinate system. After obtaining the intrinsic and extrinsic parameters, the transformation relationship between the image coordinate system and the world coordinate system is established:

[0091]

[0092] Where s is the depth scaling factor, f x and f y is the focal length of the lens, (u0, v0) is the coordinate of the camera principal point; R is the rotation matrix, and T is the translation vector; let the rotation and translation vectors of the RGB industrial camera 5-9 be represented by R1 and T1, and the rotation and translation vectors of the infrared camera 5-5 be represented by R2 and T2, then the relative position between the two cameras is as follows:

[0093]

[0094] Among them, R 12 and T 12 Represent the rotation and translation vectors between the two cameras respectively.

[0095] S1-3. Establish the motion platform coordinate system H b , camera coordinate system H c With the measured object 8 coordinate system H o The conversion relationship between them; wherein the coordinate system conversion between the motion platform 4-2 and the object under test 8 is expressed as [R bo ,T bo ], the coordinate system transformation between the motion platform 4-2 and the camera is expressed as [R bc ,T bc ], the coordinate system transformation between the camera and the object 8 is expressed as [R co ,T co ], the three coordinate systems satisfy the following relationship:

[0096] [R bo ,T bo ]=[R bc ,T bc ][R co ,T co ]

[0097] Among them, [R bc ,T bc ] can be obtained by controlling the six-axis motion platform 4, [R co ,T co ] can be obtained by the above Zhang Zhengyou calibration method, so [R bo ,T bo ].

[0098] S2, 3D reconstruction using structured light technology;

[0099] S2-1: Computer 2 controls six-axis motion platform 4 to an initial position above object 8 via motion controller 3, and DLP projection light source 5-8 projects sinusoidal stripe structured light onto the surface of object 8;

[0100] S2-2: The RGB industrial camera 5-9 collects a structured light image sequence, performs large-field phase recovery and surface three-dimensional topography reconstruction on the complete object 8, thereby obtaining three-dimensional point cloud information of the object 8 in space;

[0101] The structured light image captured by the RGB industrial camera 5-9 is a sinusoidal fringe image, which can be expressed as

[0102]

[0103] Among them, a and b represent the background light intensity and modulation degree of the structured light image respectively. is the surface phase distribution of the object 8, N is the number of structured light images, i = 1, 2, ..., N;

[0104] Using the N-step phase shift method to solve the wrapped phase and perform phase unwrapping, we can obtain:

[0105]

[0106] Where K is the fringe level, which is used to assist the wrapping phase unwrapping;

[0107] S2-3: Finally, the phase-depth calibration parameters in step S1 are used to obtain the three-dimensional point cloud information of the measured object.

[0108] S3, planning a three-dimensional scanning path;

[0109] S3-1: Divide the large-field-of-view 3D point cloud reconstruction result P{X, Y, Z} obtained by structured light measurement into n sub-regions according to the size of the OCT measurement field of view. For each sub-region, determine the coordinates of the OCT probe's six focus points for subsequent OCT local scanning. The edges of two adjacent sub-regions need to overlap to facilitate subsequent data stitching.

[0110] S3-2: Determine the point p with the maximum depth coordinate z in the i-th sub-region ci (x ci ,y ci ,z ci ), then calculate the normal vector corresponding to the point, and use the normal vector direction as the image acquisition direction of the OCT probe 6 in the sub-area;

[0111] S3-3: The six-axis motion platform 4 moves the OCT probe 6 at the bottom of the measurement optical path module 5 to the direction of the normal vector and stops at the spatial coordinate p ci (x ci -Δx,y ci -Δy,z ci +Δf), where Δx and Δy are the set coordinate offsets to ensure that the edges of adjacent sub-areas coincide; Δf is the focal length of the infrared camera 5-5 lens; at this time, through the system calibration in step S1 above, the distance between the motion platform 4-2 and p can be calculated. ci The posture relationship between them:

[0112]

[0113] in, and are the rotation matrix and translation vector of the motion platform corresponding to the i-th sub-region respectively; by performing the above operations on n sub-regions, the spatial coordinate sequence p of the OCT probe 6 is obtained c ={p c1 ,p c2 ,...,p cn The spatial coordinate sequence is input into the motion controller 3, and the six-axis motion platform 4 is controlled to move according to the coordinate sequence, which is the three-dimensional scanning path of the OCT probe 6.

[0114] S4, OCT for local tomographic measurement;

[0115] S4-1: The motion controller 3 controls the six-axis motion platform 4 to move along the three-dimensional scanning path, so that the OCT probe 6 can accurately focus and capture OCT tomographic images each time. The OCT interference image captured by the infrared camera 5-5 is represented as:

[0116]

[0117] Where t = 1, 2, ..., T represents the image index captured by the camera; M is the number of layers of the object to be measured; k(t) represents the wave number; y p and y q Represents the dielectric layer S from the material p and S q The reflected light intensity; pq and Respectively represent S p and S q The optical path difference and initial phase;

[0118] S4-2: Perform Fourier transform on the tomographic interference signal y to obtain:

[0119]

[0120] Where W[k(t)] is the window function, f represents the frequency in the Fourier domain, and is a continuous spectrum. The frequency signal corresponding to each dielectric layer is extracted, and the phase distribution information of a dielectric layer in a single scan is obtained using the following formula:

[0121]

[0122] Among them, Im[·] and Re[·] represent the imaginary and real parts of the Fourier transform respectively; the phase distribution of all dielectric layers is expressed as a tensor: The local tomographic phase result of OCT can be obtained.

[0123] S5, 3D stitching of OCT tomographic data; stitching the OCT tomographic phase results of two adjacent sub-regions obtained by 3D path planning in step S3; since adjacent sub-regions have overlapping parts, the 3D coordinates of the tomographic phase obtained for the same phase point in the overlapping part in the i-th scan and the i+1-th scan are:

[0124]

[0125]

[0126] Φ sub i and Φ sub i+1 The conversion relationship between them is solved using the i+1th motion platform rotation matrix R in the three-dimensional path planning. bo and the translation vector T bo It is expressed as follows:

[0127]

[0128] Through the above conversion, the spatial pose of the i+1th scanning result is converted to the same as the i-th scanning result, realizing the three-dimensional stitching of the tomographic phases of adjacent sub-regions; the above operation is repeated until all n scanning results are converted to the same pose, and a large-field-of-view tomographic phase stitching result is obtained.

[0129] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, any changes made based on the shape and principle of the present invention should be included in the scope of protection of the present invention.

Claims

1. A structured light guided full-field OCT tomography measurement system, characterized in that: Includes six-axis motion platform, motion controller, measurement optical path module, OCT probe, material loading platform, computer, and display; The six-axis motion platform is connected to the measuring optical path module and is used to drive the measuring optical path module to move; The motion controller is connected to the six-axis motion platform and is used to control the movement trajectory of the six-axis motion platform; The measurement optical path module is a structured light and OCT integrated optical path built with optical components; The OCT probe is installed at the bottom of the measurement optical path module and is used for positioning of OCT scanning; The material loading platform is located below the OCT probe; The motion controller, the measuring optical path module and the display are all connected to the computer; The measurement optical path module includes a DLP projection light source, an RGB industrial camera, a first polarizer, a second polarizer, an infrared laser light source, a collimating lens, a first reflector, a second reflector, a beam splitter, an infrared camera, a reference light wedge, and a double-sided reflector for separating the OCT beam and the structured light beam; in, The DLP projection light source emits structured light which is reflected by a double-sided reflector and then reaches the surface of the object to be measured; The RGB industrial camera is used to collect structured light images of the material being tested; The first polarizer and the second polarizer are placed in front of the DLP projection light source and in front of the RGB industrial camera respectively to eliminate highlight reflected light; The collimating lens is located between the infrared laser light source and the first reflector, and is used to convert the infrared laser light source beam into parallel light. The first reflector then changes the angle and direction of the parallel light and irradiates the parallel light into the beam splitter prism located on one side of the first reflector. The beam splitter prism splits the light into two beams with different paths, one beam is directly irradiated onto the object to be measured, and the other beam is irradiated onto the reference light wedge after passing through a double-sided reflector; The infrared camera collects the interference image generated by the infrared laser light source through the second reflector, that is, the image obtained by the reflection and convergence of two beams of light.

2. A structured light guided full-field OCT tomography measurement method implemented by the system of claim 1, characterized in that: include: Calibration of the measurement system's spatial coordinate system; The computer controls the six-axis motion platform to its initial position above the object under test through a motion controller. The DLP projection light source projects sinusoidal fringe structured light onto the surface of the object under test. The RGB industrial camera captures the structured light image sequence and performs large-field phase recovery and surface 3D topography reconstruction on the complete object under test, thereby obtaining 3D point cloud information of the object under test in space. Based on the 3D point cloud information obtained by structured light measurement and the system calibration parameters, the spatial position coordinates of the OCT probe in each sub-area measurement are calculated to obtain the corresponding OCT 3D scanning path; The motion controller controls the six-axis motion platform to move along the three-dimensional scanning path, allowing the OCT probe to accurately focus and acquire OCT tomographic images each time, and demodulates the tomographic signals to obtain local tomographic imaging data; The rotation and translation vectors between the two fixed positions of the six-axis motion platform in the three-dimensional scanning path are used to three-dimensionally stitch the local tomographic imaging data of multiple OCT measurements to obtain large-field-of-view tomographic three-dimensional volume measurement results.

3. The structured light guided full-field OCT tomography measurement method according to claim 2, characterized in that: The calibration of the measurement system space coordinate system includes: Phase-depth calibration for RGB industrial cameras and DLP projection light sources; Perform stereo calibration on the RGB industrial camera and infrared camera to obtain the relative pose and coordinate transformation matrix between the two cameras; Establish the conversion relationship between the motion platform coordinate system, the camera coordinate system and the measured object coordinate system.

4. The structured light guided full-field OCT tomography measurement method according to claim 3, characterized in that: Phase-depth calibration for RGB industrial cameras and DLP projector light sources includes: Place a tablet on a precision lift, and control the lift to move to more than 3 different heights in sequence. At each height position, the DLP projection light source projects structured light onto the tablet on the lift, and the camera collects the structured light image for phase extraction; more than 3 sets of phase The following nonlinear mapping model is established with the data of height H to obtain the phase-depth mapping parameters: Where (x, y) represents the image coordinates, and A(x, y), B(x, y), and C(x, y) are the phase-depth mapping parameters.

5. The structured light guided full-field OCT tomography measurement method according to claim 3, characterized in that: Stereo calibration of RGB industrial cameras and infrared cameras includes: The Zhang Zhengyou calibration method is used to obtain the intrinsic and extrinsic parameters of the two cameras. The intrinsic parameters are the focal length of the camera lens and the intrinsic information of the center point. The extrinsic parameters are the rotation matrix and translation vector of the camera relative to the world coordinate system. After obtaining the intrinsic and extrinsic parameters, the transformation relationship between the image coordinate system and the world coordinate system is established: Where s is the depth scaling factor, f x and f y is the focal length of the lens, (u0, v0) is the coordinate of the camera principal point; R is the rotation matrix, and T is the translation vector; let the rotation and translation vectors of the RGB industrial camera be represented by R1 and T1, and the rotation and translation vectors of the infrared camera be represented by R2 and T2, then the relative pose between the two cameras is as follows: Among them, R 12 and T 12 Represent the rotation and translation vectors between the two cameras respectively.

6. The structured light guided full-field OCT tomography measurement method according to claim 2, characterized in that: Perform large-field phase recovery and surface 3D topography reconstruction on the complete object to obtain 3D point cloud information of the object in space, including: The structured light image captured by the RGB industrial camera is a sinusoidal fringe image, which is expressed as: Among them, a and b represent the background light intensity and modulation degree of the structured light image respectively. is the surface phase distribution of the object under test, N is the number of structured light images, i = 1, 2, ..., N; Use the N-step phase shift method to solve the wrapped phase and perform phase unwrapping to obtain: Where K is the fringe level, which is used to assist the wrapping phase unwrapping; Finally, the three-dimensional point cloud information of the object is obtained by combining the phase-depth calibration parameters.

7. The structured light guided full-field OCT tomography measurement method according to claim 2, characterized in that: Obtain OCT 3D scanning path, including: The large field of view 3D point cloud reconstruction result P{X, Y, Z} obtained by structured light measurement is divided into n sub-areas according to the size of the OCT measurement field of view. The coordinates of the OCT probe focus point are determined for each sub-area in turn. The edges of two adjacent sub-areas need to be set to overlap to facilitate subsequent data splicing. Specifically, the point p with the largest depth coordinate z is determined in the i-th sub-area. ci (x ci ,y ci ,z ci ), and then calculate the normal vector corresponding to the point, and the direction of the normal vector is used as the image acquisition direction of the OCT probe in the sub-area; the six-axis motion platform moves the OCT probe at the bottom of the measurement optical path module to the direction of the normal vector and stays at the spatial coordinate p ci (x ci -Δx,y ci -Δy,z ci +Δf), where Δx and Δy are the set coordinate offsets to ensure that the edges of adjacent sub-areas coincide; Δf is the focal length of the infrared camera lens; at this time, through system calibration, the distance between the motion platform and p is calculated. ci The posture relationship between them: in, and T i bo are the rotation matrix and translation vector of the motion platform corresponding to the i-th sub-region respectively; by performing the above operations on n sub-regions, the OCT probe spatial coordinate sequence p is obtained c ={p c1 ,p c2 ,...,p cn The spatial coordinate sequence is input into the motion platform controller, which controls the six-axis motion platform to move according to the coordinate sequence, which is the three-dimensional scanning path of the OCT probe.

8. The structured light guided full-field OCT tomography measurement method according to claim 2, characterized in that: Acquire local tomographic data, including: The OCT interference image collected by the infrared camera is expressed as: Where t=1,2,...,T represents the image index captured by the camera; M is the number of tomographic measurement layers of the object being measured; k(t) represents the wave number; y p and y q Represents the dielectric layer S from the material p and S q The reflected light intensity; pq and Respectively represent S p and S q The optical path difference and initial phase; Perform Fourier transform on the tomographic interference signal y and obtain: Where W[k(t)] is the window function, f represents the frequency in the Fourier domain, and is a continuous spectrum. The frequency signal corresponding to each dielectric layer is extracted, and the phase distribution information of a dielectric layer in a single scan is obtained using the following formula: Among them, Im[·] and Re[·] represent the imaginary and real parts of the Fourier transform respectively; the phase distribution of all dielectric layers is expressed as a tensor: The local tomographic phase result of OCT can be obtained.

9. The structured light guided full-field OCT tomography measurement method according to claim 2, characterized in that: The local tomographic imaging data of multiple OCT measurements are stitched together in 3D to obtain large-field tomographic 3D volume measurement results, including: The OCT tomographic phase results of two adjacent sub-regions obtained by three-dimensional path planning are spliced; since adjacent sub-regions have overlapping parts, the three-dimensional coordinates of the tomographic phase obtained by the same phase point in the overlapping part in the i-th scan and the i+1-th scan are respectively: Φ sub i and Φ sub i+1 The conversion relationship between them is solved using the i+1th motion platform rotation matrix R in the three-dimensional path planning. bo and the translation vector T bo It is expressed as follows: Through the above conversion, the spatial pose of the i+1th scanning result is converted to the same as the i-th scanning result, realizing the three-dimensional stitching of the tomographic phases of adjacent sub-regions; the above operation is repeated until all n scanning results are converted to the same pose, and a large-field-of-view tomographic phase stitching result is obtained.

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