Multi-angle composite optical coherence tomography system and method

Abstract

The invention relates to a multi-angle composite optical coherence tomography imaging system and method, the imaging system comprises an OCT system, a sample arm of the OCT system comprises a multi-angle scanning part and a Bscan scanning part, the OCT system emits parallel light beams to the sample arm, the multi-angle scanning part realizes multi-angle scanning of a sample, and the Bscan scanning part realizes Bscan scanning of the sample. According to the high-resolution image reconstruction algorithm, a plane wave delay accumulation beam forming algorithm is taken as a core, and signals after beam forming of echo data under plane wave emission of different angles are coherently compounded and processed into an image. According to the invention, a multi-angle scanning mode is realized on the system, a sample is kept immobile in a detection process, the system can be applied to the field of clinical diagnosis more favorably, and a coherent composite imaging method ensures that a high-resolution OCT image can be reconstructed under a limited scanning angle.

Description

Technical Field

[0001] The present invention relates to the technical field of optical coherence tomography, and in particular to a multi-angle composite optical coherence tomography system and method. Background Art

[0002] Optical coherence tomography (OCT) is a non-contact, non-invasive, high-resolution tomographic imaging technology. It is based on the principle of coherent light interferometry and obtains two-dimensional or three-dimensional structural images by collecting back-reflected or scattered signals returned from biological tissues. Currently, OCT has become a relatively mature technology and is widely used in medical fields such as ophthalmology, dermatology, and dentistry. However, this imaging technology has always had problems with unbalanced depth of field and lateral resolution, making it difficult to perform routine imaging of cells, affecting its further development in the biomedical field.

[0003] Frequency domain OCT has two clear resolutions, namely the axial resolution in the depth direction and the lateral resolution in the lateral image plane. The lateral resolution is mainly determined by the light diffraction limit, specifically by the numerical aperture (NA) of the system. A high NA will make the focused spot finer, thereby improving the lateral resolution, but at the expense of depth of field. A low NA will provide a large depth of field, but the focused spot will become coarser, resulting in a loss of lateral resolution. Traditional OCT systems usually design the lateral resolution to be more than 10 microns to achieve an imaging depth of several hundred microns to several millimeters for the measurement of human tissue. From the perspective of resolution and imaging depth, it can be found that there is always a trade-off between the two parameters. Therefore, how to break through the diffraction limit and achieve a large depth of field and high lateral resolution at the same time has always been an important direction for the development of frequency domain OCT. In order to solve this problem, previous studies have also made different attempts. (1) An improved system specifically designed to improve resolution is the optical coherence microscope (OCM). OCM uses a larger NA than traditional OCT to achieve high resolution. Typically, the lateral resolution can reach 1μm and the longitudinal resolution is about 2-4μm. Combined with the coherence gate of the OCT system itself, it can image cells in human tissue without the use of external contrast agents. However, as mentioned earlier, it has a natural imaging depth disadvantage, so it can only form cross-sectional images, but not tomographic images. (2) Dynamic focusing (C-mode scanning) can also effectively improve resolution and depth of field [1], it generates multiple focal areas arranged along the axial direction, thus forming an axial focus with high resolution. Since the coherence transfer function (CTF) corresponding to each focus is optimal, the resolution and contrast of the image are equivalent to the focused image generated by the standard focusing scheme. The lateral and longitudinal resolution can reach 5-10 microns. Its limitation is that the illumination path must be in free space, and the imaging speed is slow. (3) The principle of beam shape adjustment is to produce a non-Gaussian focus (also called Micro OCT) by controlling the pupil function of the focusing lens. Usually, the annular aperture produces a Bessel focus [2] , which is super-resolved in the lateral direction and extended in the axial direction relative to the Gaussian focus. A pure phase mask or phase pupil filter combined with a spherical lens can moderately extend the axial focusing range, but at the expense of light intensity and a corresponding decrease in image contrast. (4) In 2019, Duke University proposed a multi-scanning method similar to CT (Computed Tomography) for image reconstruction, thereby achieving high-resolution and large depth of field imaging requirements. [3] However, it requires the sample to be rotated 360°, and image averaging is used in the reconstruction algorithm. Only when the rotation angle reaches 360° can the isotropy of lateral and longitudinal resolution be achieved, which limits the application prospects of this method in the field of clinical medicine.

[0004] Imaging speed is another important parameter that affects the application of OCT systems in clinical medicine. Fast imaging speed can reduce artifacts caused by human body jitter in live detection. The first generation of OCT systems detected the delay of optical echoes by mechanically scanning the path length of the interferometer reference arm (time domain OCT). The development of Fourier domain detection has made breakthroughs in the sensitivity and speed of OCT imaging. The performance advantages of frequency domain OCT were independently recognized by several research groups in 2003. [4], most commercial OCT instruments currently use spectrometers and line scan cameras (spectral domain OCT). Swept-frequency OCT is an OCT system developed from spectral domain OCT. It uses high-speed photodetectors instead of the spectrometers and line scan cameras used in spectral domain OCT. Due to the higher detection efficiency of photodetectors, the detection loss of swept-frequency OCT is reduced compared with spectral domain OCT. In addition, the imaging of swept-frequency OCT systems at wavelengths of 1000nm and 1300nm, which is longer than the 840nm wavelength commonly used in spectral domain OCT, can better penetrate light and improve the imaging depth of scattering tissue. Advances in swept laser technology have helped achieve high scan rates, and high speed can reduce the acquisition time of in vivo imaging to reduce motion artifacts. High speed can also obtain more data, thereby achieving denser sampling density or wider field of view within a given acquisition time. High-speed imaging can also extract additional functional imaging parameters from OCT data. High speed facilitates Doppler OCT and angiography without the need for exogenous contrast agents. Finally, dynamic structural and functional processes can also be measured using 4D (3D+time) imaging, which requires repeated acquisition of volumetric data sets as a function of time. Another way to increase imaging speed is line scanning OCT, which can capture the entire cross-sectional image (Bscan) in a single scan instead of just a single Ascan, thereby increasing scanning speed compared to traditional single-point scanning systems. [5] . Parallel measurement of Ascans in line-field OCT offers several advantages over conventional frequency-domain OCT systems, in addition to better phase stability. First, motion-related image distortion and artifacts in Bscans can be significantly reduced due to the lack of time differences between Ascans. Second, since the detection beam is focused as a straight line on the sample surface, it can achieve higher imaging speeds (and signal-to-noise ratios) at lower illumination intensities. This enables faster in vivo imaging with less risk of damage to the human body.

[0005] In summary, it is difficult to take into account both lateral and longitudinal resolution in the existing technology. Therefore, it is necessary to design an OCT system solution that can achieve high-resolution and large depth of field imaging requirements.

[0006] References:

[0007] [1] J.Mo, M.de Groot, and JFJOede Boer, "Focus-extension by depth-encoded synthetic aperture in Optical Coherence Tomography," vol.21, no.8, pp.10048-10061, 2013.

[0008] [2]R.Huber,M.Wojtkowski,J.G.Fujimoto,J.Jiang,and A.J.O.e.Cable,"Three-dimensional and C-mode OCT imaging with a compact,frequency swept lasersource at 1300nm,"vol.13,no.26,pp.10523-10538,2005.

[0009] [3]K.C.Zhou,R.Qian,S.Degan,S.Farsiu,and J.A.J.N.P.Izatt,"Opticalcoherence refraction tomography,"vol.13,no.11,pp.794-802,2019.

[0010] [4]J.F.de Boer,B.Cense,B.H.Park,M.C.Pierce,G.J.Tearney,andB.E.Bouma,"Improved signal-to-noise ratio in spectral-domain compared withtime-domain optical coherence tomography,"Optics Letters,vol.28,no.21,pp.2067-2069,Nov2003.

[0011] [5]S.Lawman et al.,"Supercontinuum ultra-high resolution line-fieldOCT;experimental spectrograph comparison and comparison with current clinicalOCT systems by the imaging of a human cornea,"in 2nd Canterbury Conference onOCT with Emphasis on Broadband Optical Sources,2018,vol.10591,p.1059104:International Society for Optics and Photonics. Summary of the Invention

[0012] The purpose of the present invention is to provide a multi-angle composite optical coherence tomography system and method in order to overcome the defects of the prior art.

[0013] The purpose of the present invention can be achieved by the following technical solutions:

[0014] According to a first aspect of the present invention, there is provided a multi-angle composite optical coherence tomography system, comprising an OCT system, wherein a sample arm of the OCT system comprises a multi-angle scanning component and a Bscan scanning component, the OCT system is used to project a parallel light beam to the sample arm, the multi-angle scanning component is used to implement multi-angle scanning of a sample, and the Bscan scanning component is used to implement Bscan scanning of a sample.

[0015] Furthermore, when the OCT system is a line scanning OCT system, the sample arm includes a collimator, a focusing mirror and a rotating stage, the sample is placed on the rotating stage and rotates with the rotating stage, the parallel light beam emitted from the collimator is incident on the focusing mirror, the focusing mirror is configured to focus the light beam and incident on the sample, the rotating stage is a multi-angle scanning component, the rotation of the rotating stage is used to achieve multi-angle scanning of the sample, and the linear array light beam formed by the frequency domain line scanning OCT system is used to achieve Bscan scanning of the sample;

[0016] When the OCT system is a frequency domain point scanning OCT system, the sample arm includes a collimator, a scanning head, a focusing mirror and a rotating table. The scanning head is provided with a galvanometer. The sample is placed on the rotating table and rotates with the rotating table. The galvanometer is configured to reflect the parallel light beam emitted from the collimator to the focusing mirror. The focusing mirror is configured to focus the light beam and inject it into the sample. The rotating table is a multi-angle scanning component. The rotation of the rotating table is used to achieve multi-angle scanning of the sample. The galvanometer is a Bscan scanning component. The rotation of the galvanometer is used to achieve Bscan scanning of the sample.

[0017] Furthermore, when the OCT system is a frequency domain line scanning OCT system, the sample arm includes a collimator, a translation stage and a focusing mirror, the collimator is fixed on the translation stage and moves linearly with the translation stage, the parallel light beam emitted from the collimator is emitted to the focusing mirror, the focusing mirror is configured to focus the light beam and inject it into the sample, the translation stage is a multi-angle scanning component, the translation of the translation stage is used to achieve multi-angle scanning of the sample, and the linear array light beam formed by the frequency domain line scanning OCT system is used to achieve Bscan scanning of the sample;

[0018] When the OCT system is a frequency domain point scanning OCT system, the sample arm includes a collimator, a scanning head, a translation stage and a focusing mirror. The scanning head is provided with a galvanometer, the scanning head is fixed on the translation stage and translates linearly with the translation stage, the galvanometer is configured to reflect the parallel light beam emitted from the collimator to the focusing mirror, the focusing mirror is configured to focus the light beam and inject it into the sample, the translation stage is a multi-angle scanning component, the translation of the translation stage is used to achieve multi-angle scanning of the sample, the galvanometer is a Bscan scanning component, and the rotation of the galvanometer is used to achieve Bscan scanning of the sample.

[0019] Further, when the OCT system is a frequency domain line scanning OCT system, the sample arm includes a collimator, a galvanometer, a first focusing mirror, a reflector, and a second focusing mirror. The galvanometer and the reflector are respectively arranged at the focal points on both sides of the first focusing mirror, the optical axes of the first focusing mirror and the second focusing mirror are perpendicular, and the reflector is arranged at the common focus of the first focusing mirror and the second focusing mirror. The galvanometer is configured to reflect the parallel light beam emitted from the collimator to the first focusing mirror, the first focusing mirror is configured to refract the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror and project it to the reflector, the reflector is configured to reflect the parallel light beam parallel to the optical axis of the first focusing mirror to the second focusing mirror, the second focusing mirror focuses the light beam and then projects it to the sample, the galvanometer is a multi-angle scanning component, the rotation of the galvanometer is used to realize multi-angle scanning of the sample, and the linear array light beam formed by the frequency domain line scanning OCT system is used to realize Bscan scanning of the sample;

[0020] When the OCT system is a frequency domain point scanning OCT system, the sample arm includes a collimator, a first galvanometer, a first focusing mirror, a second galvanometer and a second focusing mirror, the first galvanometer and the second galvanometer are respectively arranged at the focal points on both sides of the first focusing mirror, the optical axes of the first focusing mirror and the second focusing mirror are perpendicular, and the second galvanometer is arranged at the common focus of the first focusing mirror and the second focusing mirror, the first galvanometer is configured to reflect the parallel light beam emitted from the collimator to the first focusing mirror, the first focusing mirror is configured to refract the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror and emit it to the second galvanometer, the second galvanometer is configured to reflect the parallel light beam parallel to the optical axis of the first focusing mirror to the second focusing mirror, the second focusing mirror focuses the light beam and then incident on the sample, the first galvanometer is a multi-angle scanning component, and the rotation of the first galvanometer is used to realize multi-angle scanning of the sample, the second galvanometer is a Bscan scanning component, and the rotation of the second galvanometer is used to realize Bscan scanning of the sample.

[0021] Furthermore, when the OCT system is a frequency domain line scanning OCT system, the sample arm further comprises a beam splitter, a third focusing mirror and a light receiving component, wherein the beam splitter is arranged between the first focusing mirror and the reflecting mirror, and the light returned from the sample passes through the beam splitter and is focused by the third focusing mirror before entering the light receiving component;

[0022] When the OCT system is a frequency domain point scanning OCT system, the sample arm also includes a spectrometer, a third focusing mirror and a light receiving component. The spectrometer is arranged between the first focusing mirror and the second galvanometer. The light returned from the sample passes through the spectrometer and is focused by the third focusing mirror before entering the light receiving component.

[0023] Further, when the OCT system is a frequency domain line scanning OCT system, the sample arm includes a collimator, a cylindrical lens, a first focusing mirror, a reflector, and a second focusing mirror. The cylindrical lens and the reflector are respectively arranged at the focal points on both sides of the first focusing mirror, the optical axes of the first focusing mirror and the second focusing mirror are perpendicular, and the reflector is arranged at the common focus of the first focusing mirror and the second focusing mirror. The cylindrical lens is configured to reflect the parallel light beam emitted from the collimator to the first focusing mirror, the first focusing mirror is configured to refract the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror and project it to the reflector, the reflector is configured to reflect the parallel light beam parallel to the optical axis of the first focusing mirror to the second focusing mirror, the second focusing mirror focuses the light beam and then incident on the sample, the cylindrical lens is a multi-angle scanning component, the up and down movement of the cylindrical lens is used to realize multi-angle scanning of the sample, and the linear array light beam formed by the frequency domain line scanning OCT system is used to realize Bscan scanning of the sample;

[0024] When the OCT system is a frequency domain point scanning OCT system, the sample arm includes a collimator, a cylindrical lens, a first focusing mirror, a second galvanometer and a second focusing mirror. The cylindrical lens and the second galvanometer are respectively arranged at the focal points on both sides of the first focusing mirror, the optical axes of the first focusing mirror and the second focusing mirror are perpendicular, and the second galvanometer is arranged at the common focus of the first focusing mirror and the second focusing mirror. The cylindrical lens is configured to reflect the parallel light beam emitted from the collimator to the first focusing mirror, the first focusing mirror is configured to refract the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror and emit it to the second galvanometer, the second galvanometer is configured to reflect the parallel light beam parallel to the optical axis of the first focusing mirror to the second focusing mirror, the second focusing mirror focuses the light beam and then incident on the sample, the cylindrical lens is a multi-angle scanning component, and the up and down movement of the cylindrical lens is used to realize multi-angle scanning of the sample, the second galvanometer is a Bscan scanning component, and the rotation of the second galvanometer is used to realize Bscan scanning of the sample.

[0025] Furthermore, when the OCT system is a frequency domain line scanning OCT system, the sample arm further comprises a beam splitter, a third focusing mirror and a light receiving component, wherein the beam splitter is arranged between the first focusing mirror and the reflecting mirror, and the light returned from the sample passes through the beam splitter and is focused by the third focusing mirror before entering the light receiving component;

[0026] When the OCT system is a frequency domain point scanning OCT system, the sample arm also includes a spectrometer, a third focusing mirror and a light receiving component. The spectrometer is arranged between the first focusing mirror and the second galvanometer. The light returned from the sample passes through the spectrometer and is focused by the third focusing mirror before entering the light receiving component.

[0027] According to a second aspect of the present invention, a multi-angle composite optical coherence tomography method is provided, which uses the above-mentioned multi-angle composite optical coherence tomography system to collect multiple spectra returned from different angles in the imaging area, and uses a time-delayed accumulation beam synthesis method in the spatial domain to accumulate the obtained data, and takes the arithmetic average based on the corresponding position and angle of each Bscan in space to obtain a reconstructed image, specifically, including:

[0028] Extract the amplitude information I0, obtain the propagation trajectory of the ray according to the spatial geometric relationship and refractive index distribution of the components in the multi-angle composite optical coherence tomography system, calculate the delay from the scattered signal to the objective lens based on the propagation trajectory, time-shift the extracted amplitude information I0 based on the time difference, and calculate the Ascan signal time-shifted from each offset angle:

[0029] I(k)=I0(τ k ), k = 1, 2, ... N

[0030] Where τ is the time difference, k represents the beam, and N represents the number of beams;

[0031] The multi-frame Ascan signals of the same target imaging object obtained from multiple symmetrical angles are superimposed to obtain a coherent composite image. n Perform the arithmetic averaging process to obtain the characterization of the scattering points in space:

[0032]

[0033] Wherein, z(k) represents the Ascan signal after superposition and averaging.

[0034] Furthermore, the A-scan formula of the OCT system is expressed as:

[0035]

[0036] In the formula, r(z) represents, represents the imaginary part, R S(z) represents the back reflection of each layer structure in the depth direction of the object, N represents the N-layer structure in the depth direction, and F -1 represents the inverse Fourier transform, represents the optical path from the nth layer to the beam splitter position, k represents the beam, Indicates the optical path difference between different layers of the sample and the reference light, z R is the optical path length of the reference arm, R S (z) includes amplitude and phase information.

[0037] Furthermore, it also includes:

[0038] The mean square error between the original Ascan and the Ascan reconstructed based on the environment matching high resolution is calculated, and the refractive index distribution is optimized based on the mean square error.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention realizes a multi-angle scanning mode in the system, and the sample remains motionless during the detection process, which is more conducive to the application of the system in the field of clinical diagnosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the imaging system structure of the frequency domain line scanning OCT system;

[0042] Figure 2 It is a schematic diagram of the imaging system structure of the frequency domain point scanning OCT system;

[0043] Figure 3 This is a schematic diagram of the design of the sample arm rotating stage in Example 2;

[0044] Figure 4 Schematic diagram of the design of the sample arm translation stage in Example 3;

[0045] Figure 5 Schematic diagram of the sample arm galvanometer design in Example 4;

[0046] Figure 6 Schematic diagram of the design of the sample arm galvanometer in Example 5;

[0047] Figure 7 Schematic diagram of the sample arm column lens design in Example 6;

[0048] Figure 8 Schematic diagram of the design of the sample arm column lens in Example 7;

[0049] Fig. 9 Schematic diagram of reconstructed images at different deflection angles;

[0050] Fig.10Schematic diagram of the change of lateral resolution with compound angle;

[0051] Fig.11 Schematic diagram of the change of contrast with composite angle;

[0052] Fig.12 It is a schematic diagram of the overall process of the image reconstruction method;

[0053] Reference numerals:

[0054] 1-1, light source, 1-2, emitter (including beam expander), 1-3, cylindrical mirror, 1-4, beam splitter, 1-5, focusing mirror ①, 1-6, reference mirror, 1-7, focusing mirror ②, 1-8, sample, 1-9, focusing mirror ③, 1-10, spectrometer crack, 1-11, focusing mirror ④, 1-12, grating, 1-13, focusing mirror ⑤, 1-14, camera;

[0055] 2-1, light source, 2-2, optical fiber, 2-3, collimator ①, 2-4, galvanometer ①, 2-5, galvanometer ②, 2-6, objective lens, 2-7, sample, 2-8, collimator ②, 2-9, focusing lens, 2-10, reference lens, 2-11, spectrometer, 2-12, computer;

[0056] 101, scanning head, 102, focusing lens, 103, rotating stage, 104, sample;

[0057] 210, translation stage, 202, scanning head, 203, focusing lens, 204, sample;

[0058] 301, collimator, 302, first galvanometer, 303, first focusing mirror, 304, second galvanometer, 305, second focusing mirror, 306, sample, 307, spectroscope, 308, third focusing mirror, 309, light receiving component;

[0059] 401. collimator, 402. cylindrical lens, 403. first focusing mirror, 404. second galvanometer, 405. second focusing mirror, 406. sample, 407. spectroscope, 408. third focusing mirror, 409. light receiving component. DETAILED DESCRIPTION

[0060] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given. Obviously, the described embodiment is only an embodiment of a part of the present invention, not all embodiments, and the protection scope of the present invention is not limited to the following embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work should fall within the scope of protection of the present invention.

[0061] In the drawings, components with the same structure are indicated by the same numerical reference numerals, and components with similar structures or functions are indicated by similar numerical reference numerals. The size and thickness of each component shown in the drawings are arbitrarily shown, and the present invention does not limit the size and thickness of each component. In order to make the illustration clearer and show the matching relationship between the various components, some parts in the drawings are appropriately scaled, and the distance between the components is increased or decreased.

[0062] In the description of the embodiments of the present application, it should be understood that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the products of the application are conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0063] Furthermore, the terms “first”, “second”, “third”, etc. are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0064] In the description of the embodiments of the present application, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0065] Embodiment 1:

[0066] The present invention provides a multi-angle composite optical coherence tomography system, comprising an OCT system. The sample arm of the OCT system comprises a multi-angle scanning component and a Bscan scanning component. The OCT system projects a parallel light beam to the sample arm. The multi-angle scanning component realizes multi-angle scanning of the sample, and the Bscan scanning component realizes Bscan scanning of the sample.

[0067] Specifically, multi-angle scanning can be implemented on both frequency domain line scanning OCT systems and frequency domain point scanning OCT systems. For the selection of light sources, in order to achieve good axial resolution, a wide-wavelength SLED light source can be selected, because SLED is between semiconductors and lasers, has the advantages of high power stability, relatively flat spectrum, and moderate price. In this embodiment,

[0068] In this embodiment, the structure of the multi-angle composite optical coherence tomography imaging system using the frequency domain line scanning OCT system is as follows: Figure 1 As shown, it includes a light source, a transmitter (including a beam expander), a cylindrical mirror, a beam splitter, a focusing mirror ①, a reference mirror, a focusing mirror ②, a sample, a focusing mirror ③, a focusing mirror ④, a focusing mirror ⑤, a camera, etc. A frequency domain line scanning OCT system based on a Michelson interferometer built using a cylindrical lens, a parallel light beam is emitted by a light source 1-1, and after the parallel light beam passes through a cylindrical mirror 1-3 through a transmitter 1-2, the longitudinal axis of the light beam remains parallel and the transverse axis is focused, and after the light beam passes through any objective lens, a linear array of illumination will be formed at the focal plane position. The beam splitter 1-4 divides the light beam into two paths, which are irradiated to the reference arm and the sample arm respectively. The reference arm includes focusing mirror ①1-5 and reference mirror 1-6, etc., which are consistent with the prior art structure and will not be described in detail here. The design of the sample arm is the key to achieving multi-angle scanning. The specific design is shown in Example 2-7 below, which is simplified here to focusing mirror ③1-9 and sample 1-8. The light on the reference arm passes through focusing mirror ①1-5 and reference mirror 1-6 in turn, and the reflected light returns to beam splitter 1-4 along the original path. The light signals returned from sample 1-8 and reference mirror 1-6 are mixed and interfered on beam splitter 1-4, and the light signals are received by the spectrometer through the collecting arm, which converts the light signals into electrical signals. The spectrometer part is mainly composed of three components: transmission grating, cylindrical lens (focusing mirror ④1-11, focusing mirror ⑤1-13) and photoelectric receiver (camera 1-14). Because it is a two-dimensional frequency domain system, a planar array camera needs to be selected. Because the light beam of the frequency domain line scanning OCT becomes a line in front of the beam splitter, the Bscan scanning component is no longer needed on the sample arm, so only the multi-angle scanning component needs to be retained.

[0069] In addition, the structure of the multi-angle composite optical coherence tomography imaging system using the frequency domain point scanning OCT system is as follows Figure 2 As shown, it includes a light source, a detector, a sample arm and a reference arm. The light beam of the light source 2-1 is divided into two paths through the optical fiber 2-2, and enters the sample arm and the reference arm respectively. The reference arm is basically the same as the existing structure, and is simplified here to a collimator ②2-8, a focusing mirror 2-9 and a reference mirror 2-10. The design of the sample arm is shown in Example 2-7 below, and is simplified here to a collimator ①2-3, a galvanometer ①2-4, a galvanometer ②2-5, an objective lens 2-6 and a sample 2-7. The multi-layer tissue sample will scatter the incident photons back, and interfere with the light reflected back in the reference arm at the spectrometer 2-11, and the resulting spectrum will be recorded to obtain an image of the sample.

[0070] The multi-angle scanning component on the sample arm is used to realize multi-angle scanning, and the Bscan scanning component is used to realize lateral scanning (Bscan). Multi-angle scanning of samples can be realized by various methods, and for the frequency domain point scanning OCT system, the Bscan scanning component can be realized by a galvanometer.

[0071] The present invention realizes a multi-angle scanning mode on the OCT system, and the sample remains motionless during the detection process, which is conducive to the application of the system in the field of clinical diagnosis.

[0072] The present invention also provides a multi-angle composite optical coherence tomography method, using a multi-angle composite optical coherence tomography system, such as the above-mentioned linear array-based system-constructed OCT system, to achieve a single scan and simultaneously obtain the entire Bscan spectrum, and design a multi-angle scanning configuration in the sample arm of the OCT to achieve fast and stable multi-angle scanning of the same position of the target. The imaging algorithm is high-resolution OCT image reconstruction, because there are differences in lateral and longitudinal resolutions, in Fourier space, the transfer function of the corresponding point spread function is anisotropic, which means that the high-frequency information in one direction is weakened. By collecting cross-sectional images at multiple angles, the missing high-frequency information can be filled.

[0073] In this embodiment, the reconstruction algorithm is based on the imaging principle of multi-angle plane wave coherent compounding, that is, collecting spectra returned from multiple different angles in the imaging area, and completing beam synthesis, combining image information from different angles, which is equivalent to high NA focusing at the spectrum receiving end, thereby effectively improving the lateral resolution of the image. This application adopts beam synthesis technology in the spatial domain, taking the arithmetic average based on the corresponding position and angle of each Bscan in space, so as to obtain a reconstructed image.

[0074] The A-scan formula of frequency domain point scanning OCT can be simply expressed as:

[0075]

[0076] Among them, r(z) represents, represents the imaginary part, R S (z) represents the back reflection of each layer structure in the depth direction of the object, N represents the N-layer structure in the depth direction, and F -1 represents the inverse Fourier transform, represents the optical path from the nth layer to the beam splitter position, k represents the beam, Indicates the optical path difference between different layers of the sample and the reference light, z R is the optical path length of the reference arm, R S (z) includes amplitude and phase information.

[0077] The first step of the image reconstruction algorithm is to calculate the delay from the scattered signal to the objective lens based on the trajectory of ray propagation derived from the geometric relationship in space and the refractive index distribution, and use the time difference to perform a corresponding time shift on the amplitude information (I0) extracted from formula (1) at each angle:

[0078] I(k)=I0(τm ), m=1,2,…N (2)

[0079] Where τ is the time difference, m represents the number of incident angles for multi-angle scanning, and the distance from a scattering point to the objective lens is shown in a simplified diagram as follows: Figure 8 As shown, the transmission signal delay of the scattered signal at each point is determined by the deflection angle of the incident light. The time required for the central beam and the deflected beam to reach the scattering point (P) is:

[0080] τ(P cen )=f / c (3)

[0081] τ(P side )=f / c·cosθ (4)

[0082] θ is the deflection angle of the deflection beam, f is the focal length, and c is the speed of light, so that the Ascan signal shifted at each offset angle is obtained.

[0083] The second step is to stack and sum. By stacking multiple frames of Ascan signals from multiple symmetrical angles of the same target imaging object, a coherent composite image can be obtained. n Perform the arithmetic averaging process to obtain the final representation of the scattering points in space:

[0084]

[0085] Corresponding calculations are performed on each scattering point in the imaging area until the entire image in the imaging space is obtained. Figure 9-11 The simulation results of composite coherent image reconstruction in the sound field are shown. Fig. 9 The reconstructed images with deflection angles ranging from 0° to 23° are shown. Fig.10 and Fig.11 It respectively shows that as the composite angle increases, the lateral resolution and contrast are significantly improved, and the image quality is improved.

[0086] In fact, in the imaging system, the spatial geometric relationship can be determined based on the positions of the sample, objective lens, and various optical components, but the refractive index distribution is difficult to obtain accurately. In order to improve the imaging quality, this application also designs a feedback mechanism.

[0087] In order to provide feedback on the accuracy of the time-shifted Ascan obtained in the first step to help optimize it, a differentiable metric is needed to quantify the degree of joint registration between all Ascans. The present application describes an intensity-based metric that is used to calculate the mean square error (MSE) between the original Ascan and the Ascan reconstructed based on environmental matching high-resolution. The forward model starts with the current estimate based on OCT high-resolution reconstruction. For each Bscan direction, the current estimate is then rotated, distorted according to the same trajectory, blurred by the OCT PSF, deeply attenuated, and readjusted according to the local intensity of the incident direction. The result constitutes a forward prediction of the Ascan, in which the forward model parameters (such as RI distribution, attenuation parameters, etc.) between the MSE and the original Ascan data are minimized. The present application also regularizes the refractive index distribution to impose spatial smoothness, stabilize the solution and optimize. The refractive index distribution is improved by gradually minimizing the difference iteratively, and finally the best reconstructed image is obtained. Fig.12 The entire image reconstruction process is demonstrated.

[0088] This application effectively improves the lateral resolution under limited scanning angles. The coherent plane wave composite imaging method is a commonly used method in ultra-fast ultrasound imaging. The algorithm is based on the plane wave delay accumulation beamforming algorithm. The signal after the echo data beamforming under different plane wave transmission angles is coherently composited and processed into an image display. In the overlapping area of ​​different transmission angles, the image resolution and quality are improved. The acoustic field simulation results are shown in Figure 1. Fig. 9 As shown, when the composite angle reaches 20-25°, the image quality is significantly improved. Because OCT and ultrasound technology are similar, this application applies coherent composite algorithm imaging to the OCT field for high-resolution and large depth of field image reconstruction, and effectively improves the lateral resolution under limited scanning angles.

[0089] Embodiment 2:

[0090] In this embodiment, the OCT system is a frequency domain point scanning OCT system, such as Figure 3 As shown, the sample arm includes a collimator, a scanning head 101, a focusing mirror 102 and a rotating table 103. A galvanometer is provided in the scanning head 101. The sample 104 is placed on the rotating table 103 and rotates with the rotating table 103. The galvanometer reflects the parallel light beam emitted from the collimator to the focusing mirror 102. The focusing mirror 102 focuses the light beam and makes it incident on the sample 104. The rotating table 103 is a multi-angle scanning component. The rotation of the rotating table 103 realizes multi-angle scanning of the sample 104. The galvanometer is a Bscan scanning component. The rotation of the galvanometer realizes Bscan scanning of the sample 104. Figure 3In the embodiment, the sample 104 is placed at the focus of the focusing mirror 102 , and the rotation of the rotating stage 103 causes the focused light beam to irradiate the sample 104 at different incident angles, while the rotation of the galvanometer shifts the angle of the light beam, forming a linear scan on the sample 104 .

[0091] Under the design scheme of this embodiment, if the OCT system is a frequency domain line scanning OCT system, the Bscan scanning component is removed, and the sample arm includes a collimator, a focusing mirror and a rotating stage. The sample is placed on the rotating stage and rotates with the rotating stage. The parallel light beam emitted from the collimator is projected to the focusing mirror, and the focusing mirror focuses the light beam and injects it into the sample. The rotating stage is a multi-angle scanning component. The rotation of the rotating stage realizes multi-angle scanning of the sample, and the linear array light beam formed by the frequency domain line scanning OCT system realizes Bscan scanning of the sample.

[0092] The advantage of this solution lies in the system sample arm design. Multi-angle scanning is completed by only one rotating stage, without changing the configuration of the original OCT system, which is more convenient to implement. In addition, under this solution, multi-angle scanning can reach the theoretical maximum scanning value, that is, 180°, which maximizes the resolution.

[0093] Embodiment 3:

[0094] Compared with Embodiment 2, this embodiment improves the multi-angle scanning component. Figure 4 As shown, the OCT system is a frequency domain point scanning OCT system, and the sample arm includes a collimator, a scanning head 202, a translation stage 201 and a focusing mirror 203. A galvanometer is provided in the scanning head 202, and the scanning head 202 is fixed on the translation stage 201 and translates linearly with the translation stage 201. The galvanometer reflects the parallel light beam emitted from the collimator to the focusing mirror 203, and the focusing mirror 203 focuses the light beam and makes it incident on the sample 204. The translation stage 201 is a multi-angle scanning component, and the translation of the translation stage 201 realizes multi-angle scanning of the sample 204. The galvanometer is a Bscan scanning component, and the rotation of the galvanometer realizes Bscan scanning of the sample 204. Figure 4 In the example, the sample 204 is placed at the focus of the focusing mirror 203. It is known that the focus of the focusing mirror is f, and the distance the platform is offset from the center of the focusing mirror is l. Then the incident angle (field of view) is:

[0095]

[0096] Under the design scheme of this embodiment, if the OCT system is a frequency domain line scanning OCT system, the Bscan scanning component is removed, and the sample arm includes a collimator, a translation stage and a focusing mirror. The collimator is fixed on the translation stage and moves linearly with the translation stage. The parallel light beam emitted from the collimator is directed to the focusing mirror, and the focusing mirror focuses the light beam and injects it into the sample. The translation stage is a multi-angle scanning component, and the translation of the translation stage realizes multi-angle scanning of the sample. The linear array light beam formed by the frequency domain line scanning OCT system realizes Bscan scanning of the sample.

[0097] The advantage of this solution is that the multi-angle scanning is completed by the translation stage, and the sample can be fixed, which is suitable for application in the biomedical field.

[0098] Embodiment 4:

[0099] Compared with Embodiment 2, this embodiment improves the multi-angle scanning component and the Bscan scanning component. Figure 5 As shown, the OCT system is a frequency domain point scanning OCT system, the sample arm includes a collimator 301, a first galvanometer 302, a first focusing mirror 303, a second galvanometer 304 and a second focusing mirror 305, the first galvanometer 302 and the second galvanometer 304 are respectively arranged at the focal points on both sides of the first focusing mirror 303, the optical axes of the first focusing mirror 303 and the second focusing mirror 305 are perpendicular, and the second galvanometer 304 is arranged at the common focus of the first focusing mirror 303 and the second focusing mirror 305, the first galvanometer 302 reflects the parallel light beam emitted from the collimator 301 to the first focusing mirror 30 3. The first focusing mirror 303 refracts the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror 303 and projects it to the second galvanometer 304. The second galvanometer 304 reflects the parallel light beam parallel to the optical axis of the first focusing mirror 303 to the second focusing mirror 305. After being focused by the second focusing mirror 305, the light beam is incident on the sample 306. The first galvanometer 302 is a multi-angle scanning component. The rotation of the first galvanometer 302 realizes multi-angle scanning of the sample 306. The second galvanometer 304 is a Bscan scanning component. The rotation of the second galvanometer 304 realizes Bscan scanning of the sample 306. Figure 5 In the embodiment, the sample 306 is placed at the focus of the second focusing mirror 305.

[0100] In the design scheme of this embodiment, if the OCT system is a frequency domain line scanning OCT system, the Bscan scanning component is removed, and the sample arm includes a collimator, a galvanometer, a first focusing mirror, a reflector, and a second focusing mirror. The galvanometer and the reflector are respectively arranged at the focal points on both sides of the first focusing mirror, the optical axes of the first focusing mirror and the second focusing mirror are perpendicular, and the reflector is arranged at the common focus of the first focusing mirror and the second focusing mirror. The galvanometer reflects the parallel light beam emitted from the collimator to the first focusing mirror, the first focusing mirror refracts the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror and emits it to the reflector, the reflector reflects the parallel light beam parallel to the optical axis of the first focusing mirror to the second focusing mirror, and is focused by the second focusing mirror and incident on the sample. The galvanometer is a multi-angle scanning component, and the rotation of the galvanometer realizes multi-angle scanning of the sample. The linear array light beam formed by the frequency domain line scanning OCT system realizes Bscan scanning of the sample.

[0101] The advantage of this solution is that both multi-angle scanning and Bscan scanning are completed by the galvanometer, the scanning speed is faster than mechanical operation, and the system size is smaller. The sample can also be fixed, and there are more application scenarios.

[0102] Embodiment 5:

[0103] This embodiment further improves the system structure based on the embodiment 4. Figure 6 As shown, the OCT system is a frequency domain point scanning OCT system. The sample arm also includes a beam splitter 307, a third focusing mirror 308 and a light receiving component 309. The beam splitter 307 is arranged between the first focusing mirror 303 and the second galvanometer 304. The light returned from the sample 306 passes through the beam splitter 307 and is focused by the third focusing mirror 308 before entering the light receiving component 309.

[0104] Under the design scheme of this embodiment, if the OCT system is a frequency domain line scanning OCT system, the sample arm also includes a beam splitter, a third focusing mirror and a light receiving component. The beam splitter is arranged between the first focusing mirror and the second galvanometer. The light returned from the sample passes through the beam splitter and is focused by the third focusing mirror before entering the light receiving component.

[0105] The advantages of this solution, in addition to those mentioned in Example 4, are that the light receiving component can be an optical fiber, and the design of the beam splitter + the third focusing mirror + the light receiving component allows the light returned from the sample to be focused on the light receiving component, and the light signal returned from the sample no longer passes through the first galvanometer 302, which makes the phase information of the returned light signal more accurate.

[0106] Embodiment 6:

[0107] Compared with Embodiment 4, this embodiment improves the multi-angle scanning component. Figure 7As shown, the OCT system is a frequency domain point scanning OCT system, the sample arm includes a collimator 401, a cylindrical lens 402, a first focusing mirror 403, a second galvanometer 404 and a second focusing mirror 405, the cylindrical lens 402 and the second galvanometer 404 are respectively arranged at the focal points on both sides of the first focusing mirror 403, the optical axes of the first focusing mirror 403 and the second focusing mirror 405 are perpendicular, and the second galvanometer 404 is arranged at the common focus of the first focusing mirror 403 and the second focusing mirror 405, the cylindrical lens 402 reflects the parallel light beam emitted from the collimator 401 to the first focusing mirror 403, The first focusing mirror 403 refracts the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror 403 and projects it to the second galvanometer 404. The second galvanometer 404 reflects the parallel light beam parallel to the optical axis of the first focusing mirror 403 to the second focusing mirror 405. After being focused by the second focusing mirror 405, it is incident on the sample 406. The cylindrical lens 402 is a multi-angle scanning component. The up and down movement of the cylindrical lens 402 realizes multi-angle scanning of the sample 406. The second galvanometer 404 is a Bscan scanning component. The rotation of the second galvanometer 404 realizes Bscan scanning of the sample 406. Figure 7 In the embodiment, the sample 406 is placed at the focus of the second focusing mirror 405.

[0108] In the design scheme of this embodiment, if the OCT system is a frequency domain line scanning OCT system, the Bscan scanning component is removed, and the sample arm includes a collimator, a cylindrical lens, a first focusing mirror, a reflector, and a second focusing mirror. The cylindrical lens and the reflector are respectively arranged at the focal points on both sides of the first focusing mirror, the optical axes of the first focusing mirror and the second focusing mirror are perpendicular, and the reflector is arranged at the common focus of the first focusing mirror and the second focusing mirror. The cylindrical lens reflects the parallel light beam emitted from the collimator to the first focusing mirror, the first focusing mirror refracts the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror and emits it to the reflector, the reflector reflects the parallel light beam parallel to the optical axis of the first focusing mirror to the second focusing mirror, and is focused by the second focusing mirror and incident on the sample. The cylindrical lens is a multi-angle scanning component, and the up and down movement of the cylindrical lens realizes multi-angle scanning of the sample. The linear array light beam formed by the frequency domain line scanning OCT system realizes Bscan scanning of the sample;

[0109] The advantage of this solution is that the sample can be fixed and there are more application scenarios.

[0110] Embodiment 7:

[0111] This embodiment further improves the system structure based on Embodiment 6. Figure 8As shown, the OCT system is a frequency domain point scanning OCT system. The sample arm also includes a beam splitter 407, a third focusing mirror 408 and a light receiving component 409. The beam splitter 407 is arranged between the first focusing mirror 403 and the second galvanometer 404. The light returned from the sample 406 passes through the beam splitter 407 and is focused by the third focusing mirror 408 before entering the light receiving component 409.

[0112] Under the design scheme of this embodiment, if the OCT system is a frequency domain line scanning OCT system, the sample arm also includes a beam splitter, a third focusing mirror and a light receiving component. The beam splitter is arranged between the first focusing mirror and the second galvanometer. The light returned from the sample passes through the beam splitter and is focused by the third focusing mirror before entering the light receiving component.

[0113] The advantage of this solution is that the light receiving component can be an optical fiber, and the design of the beam splitter + the third focusing mirror + the light receiving component allows the light returned from the sample to be focused on the light receiving component. The light signal returned from the sample no longer passes through the first galvanometer 302, which makes the phase information of the returned light signal more accurate.

[0114] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A multi-angle composite optical coherence tomography system, characterized in that: It comprises an OCT system, wherein the sample arm of the OCT system comprises a multi-angle scanning component and a Bscan scanning component, the OCT system is used to irradiate a parallel light beam to the sample arm, the multi-angle scanning component is used to realize multi-angle scanning of the sample, and the Bscan scanning component is used to realize Bscan scanning of the sample.

2. The multi-angle composite optical coherence tomography system according to claim 1, characterized in that: When the OCT system is a line scanning OCT system, the sample arm includes a collimator, a focusing mirror and a rotating stage. The sample is placed on the rotating stage and rotates with the rotating stage. The parallel light beam emitted from the collimator is incident on the focusing mirror. The focusing mirror is configured to focus the light beam and incident on the sample. The rotating stage is a multi-angle scanning component. The rotation of the rotating stage is used to achieve multi-angle scanning of the sample. The linear array light beam formed by the frequency domain line scanning OCT system is used to achieve Bscan scanning of the sample. When the OCT system is a frequency domain point scanning OCT system, the sample arm includes a collimator, a scanning head, a focusing mirror and a rotating table. The scanning head is provided with a galvanometer. The sample is placed on the rotating table and rotates with the rotating table. The galvanometer is configured to reflect the parallel light beam emitted from the collimator to the focusing mirror. The focusing mirror is configured to focus the light beam and inject it into the sample. The rotating table is a multi-angle scanning component. The rotation of the rotating table is used to achieve multi-angle scanning of the sample. The galvanometer is a Bscan scanning component. The rotation of the galvanometer is used to achieve Bscan scanning of the sample.

3. The multi-angle composite optical coherence tomography system according to claim 1, characterized in that: When the OCT system is a frequency domain line scanning OCT system, the sample arm includes a collimator, a translation stage and a focusing mirror. The collimator is fixed on the translation stage and moves linearly with the translation stage. The parallel light beam emitted from the collimator is emitted to the focusing mirror. The focusing mirror is configured to focus the light beam and inject it into the sample. The translation stage is a multi-angle scanning component. The translation of the translation stage is used to achieve multi-angle scanning of the sample. The linear array light beam formed by the frequency domain line scanning OCT system is used to achieve Bscan scanning of the sample. When the OCT system is a frequency domain point scanning OCT system, the sample arm includes a collimator, a scanning head, a translation stage and a focusing mirror. The scanning head is provided with a galvanometer, the scanning head is fixed on the translation stage and translates linearly with the translation stage, the galvanometer is configured to reflect the parallel light beam emitted from the collimator to the focusing mirror, the focusing mirror is configured to focus the light beam and inject it into the sample, the translation stage is a multi-angle scanning component, the translation of the translation stage is used to achieve multi-angle scanning of the sample, the galvanometer is a Bscan scanning component, and the rotation of the galvanometer is used to achieve Bscan scanning of the sample.

4. The multi-angle composite optical coherence tomography system according to claim 1, characterized in that: When the OCT system is a frequency domain line scanning OCT system, the sample arm includes a collimator, a galvanometer, a first focusing mirror, a reflector, and a second focusing mirror. The galvanometer and the reflector are respectively arranged at the focal points on both sides of the first focusing mirror, the optical axes of the first focusing mirror and the second focusing mirror are perpendicular, and the reflector is arranged at the common focus of the first focusing mirror and the second focusing mirror. The galvanometer is configured to reflect the parallel light beam emitted from the collimator to the first focusing mirror, the first focusing mirror is configured to refract the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror and project it to the reflector, the reflector is configured to reflect the parallel light beam parallel to the optical axis of the first focusing mirror to the second focusing mirror, the second focusing mirror focuses the light beam and then projects it to the sample, the galvanometer is a multi-angle scanning component, the rotation of the galvanometer is used to realize multi-angle scanning of the sample, and the linear array light beam formed by the frequency domain line scanning OCT system is used to realize Bscan scanning of the sample; When the OCT system is a frequency domain point scanning OCT system, the sample arm includes a collimator, a first galvanometer, a first focusing mirror, a second galvanometer and a second focusing mirror, the first galvanometer and the second galvanometer are respectively arranged at the focal points on both sides of the first focusing mirror, the optical axes of the first focusing mirror and the second focusing mirror are perpendicular, and the second galvanometer is arranged at the common focus of the first focusing mirror and the second focusing mirror, the first galvanometer is configured to reflect the parallel light beam emitted from the collimator to the first focusing mirror, the first focusing mirror is configured to refract the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror and emit it to the second galvanometer, the second galvanometer is configured to reflect the parallel light beam parallel to the optical axis of the first focusing mirror to the second focusing mirror, the second focusing mirror focuses the light beam and then incident on the sample, the first galvanometer is a multi-angle scanning component, and the rotation of the first galvanometer is used to realize multi-angle scanning of the sample, the second galvanometer is a Bscan scanning component, and the rotation of the second galvanometer is used to realize Bscan scanning of the sample.

5. The multi-angle composite optical coherence tomography system according to claim 4, characterized in that: When the OCT system is a frequency domain line scanning OCT system, the sample arm further comprises a beam splitter, a third focusing mirror and a light receiving component, wherein the beam splitter is arranged between the first focusing mirror and the reflecting mirror, and the light returned from the sample passes through the beam splitter and is focused by the third focusing mirror before entering the light receiving component; When the OCT system is a frequency domain point scanning OCT system, the sample arm also includes a spectrometer, a third focusing mirror and a light receiving component. The spectrometer is arranged between the first focusing mirror and the second galvanometer. The light returned from the sample passes through the spectrometer and is focused by the third focusing mirror before entering the light receiving component.

6. The multi-angle composite optical coherence tomography system according to claim 1, characterized in that: When the OCT system is a frequency domain line scanning OCT system, the sample arm includes a collimator, a cylindrical lens, a first focusing mirror, a reflector, and a second focusing mirror. The cylindrical lens and the reflector are respectively arranged at the focal points on both sides of the first focusing mirror, the optical axes of the first focusing mirror and the second focusing mirror are perpendicular, and the reflector is arranged at the common focus of the first focusing mirror and the second focusing mirror. The cylindrical lens is configured to reflect the parallel light beam emitted from the collimator to the first focusing mirror, the first focusing mirror is configured to refract the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror and project it to the reflector, the reflector is configured to reflect the parallel light beam parallel to the optical axis of the first focusing mirror to the second focusing mirror, the second focusing mirror focuses the light beam and then incident on the sample, the cylindrical lens is a multi-angle scanning component, and the up and down movement of the cylindrical lens is used to realize multi-angle scanning of the sample, and the linear array light beam formed by the frequency domain line scanning OCT system is used to realize Bscan scanning of the sample; When the OCT system is a frequency domain point scanning OCT system, the sample arm includes a collimator, a cylindrical lens, a first focusing mirror, a second galvanometer and a second focusing mirror. The cylindrical lens and the second galvanometer are respectively arranged at the focal points on both sides of the first focusing mirror, the optical axes of the first focusing mirror and the second focusing mirror are perpendicular, and the second galvanometer is arranged at the common focus of the first focusing mirror and the second focusing mirror. The cylindrical lens is configured to reflect the parallel light beam emitted from the collimator to the first focusing mirror, the first focusing mirror is configured to refract the parallel light beam into a parallel light beam parallel to the optical axis of the first focusing mirror and emit it to the second galvanometer, the second galvanometer is configured to reflect the parallel light beam parallel to the optical axis of the first focusing mirror to the second focusing mirror, the second focusing mirror focuses the light beam and then incident on the sample, the cylindrical lens is a multi-angle scanning component, and the up and down movement of the cylindrical lens is used to realize multi-angle scanning of the sample, the second galvanometer is a Bscan scanning component, and the rotation of the second galvanometer is used to realize Bscan scanning of the sample.

7. The multi-angle composite optical coherence tomography system according to claim 6, characterized in that: When the OCT system is a frequency domain line scanning OCT system, the sample arm further comprises a beam splitter, a third focusing mirror and a light receiving component, wherein the beam splitter is arranged between the first focusing mirror and the reflecting mirror, and the light returned from the sample passes through the beam splitter and is focused by the third focusing mirror before entering the light receiving component; When the OCT system is a frequency domain point scanning OCT system, the sample arm also includes a spectrometer, a third focusing mirror and a light receiving component. The spectrometer is arranged between the first focusing mirror and the second galvanometer. The light returned from the sample passes through the spectrometer and is focused by the third focusing mirror before entering the light receiving component.

8. A multi-angle composite optical coherence tomography method, characterized in that: The multi-angle composite optical coherence tomography system as claimed in any one of claims 1 to 7 is used to collect a plurality of spectra returned from different angles in an imaging area, and the obtained data are accumulated by using a time-delayed accumulation beam synthesis method in a spatial domain, and an arithmetic average is taken based on the corresponding position and angle of each Bscan in space to obtain a reconstructed image, specifically, including: Extract the amplitude information I0, obtain the propagation trajectory of the ray according to the spatial geometric relationship and refractive index distribution of the components in the multi-angle composite optical coherence tomography system, calculate the delay from the scattered signal to the objective lens based on the propagation trajectory, time-shift the extracted amplitude information I0 based on the time difference, and calculate the Ascan signal time-shifted from each offset angle: I(k)=I0(τ k ), k=1, 2,...N Where τ is the time difference, k represents the beam, and N represents the number of beams; The multi-frame Ascan signals of the same target imaging object obtained from multiple symmetrical angles are superimposed to obtain a coherent composite image. n Perform the arithmetic averaging process to obtain the characterization of the scattering points in space: Wherein, z(k) represents the Ascan signal after superposition and averaging.

9. The multi-angle composite optical coherence tomography method according to claim 8, characterized in that: The A-scan formula of the OCT system is expressed as: In the formula, r(z) represents, represents the imaginary part, R S (z) represents the back reflection of each layer structure in the depth direction of the object, N represents the N-layer structure in the depth direction, and F -1 represents the inverse Fourier transform, represents the optical path from the nth layer to the beam splitter position, k represents the beam, Indicates the optical path difference between different layers of the sample and the reference light, z R is the optical path length of the reference arm, R S (z) includes amplitude and phase information.

10. The multi-angle composite optical coherence tomography method according to claim 8, characterized in that: Also includes: The mean square error between the original Ascan and the Ascan reconstructed based on the environment matching high resolution is calculated, and the refractive index distribution is optimized based on the mean square error.

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