Light sheet fluorescence microscopic imaging system and method

Abstract

The invention is applicable to the field of microscopic imaging, and discloses a light sheet fluorescence microscopic imaging system and method.The system comprises a laser generator, a first semi-transparent and semi-reflecting mirror, a first micromirror array, a light beam scanning assembly, an object carrying platform, an imaging device, a second semi-transparent and semi-reflecting mirror, a camera and a second micromirror array; a laser beam generated by the laser generator is transmitted to the first micro-mirror array through the first semi-transparent and semi-reflecting mirror to be adjusted to generate an emergent beam, the emergent beam is reflected to the beam scanning assembly through the first micro-mirror array, and the beam scanning assembly scans the emergent beam in the X-axis direction and the Z-axis direction to generate a light sheet. After the light sheet irradiates a measured object placed on the object carrying platform, excited fluorescence is imaged through the imaging device and then is transmitted to the second micro-mirror array through the second semi-transparent and semi-reflecting mirror, the fluorescence adjusted by the second micro-mirror array is reflected to the camera through the second semi-transparent and semi-reflecting mirror, and high-speed tomography can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of microscopic imaging, and in particular to a light-sheet fluorescence microscopic imaging system and method. Background Art

[0002] Light-sheet fluorescence microscopy, also known as selected plane illumination microscopy or orthogonal plane fluorescence optical sectioning microscopy, is a novel three-dimensional microscopic imaging technique. It utilizes an orthogonal optical path design, using a thin light sheet to excite the sample from the side. A two-dimensional fluorescence image of the sample is captured perpendicular to the light sheet using a microscope objective and a digital camera. By axially scanning the light sheet or moving the sample to image each surface, tomographic images at different depths can be obtained, enabling three-dimensional reconstruction of the sample. It offers the advantages of fast 3D imaging, high contrast, and minimal photodamage, making it particularly suitable for long-term 3D imaging of living biological samples.

[0003] In light-sheet fluorescence microscopy, microscopic imaging performance is closely tied to the characteristics of the light sheet. The system's axial resolution is determined by the numerical aperture of the detection objective and the thickness of the excitation light sheet. The field of view is limited by the width of the light sheet. Achieving a larger field of view typically comes at the expense of axial resolution and three-dimensional tomographic imaging capabilities. Existing light-sheet fluorescence microscopy systems use spatial light modulators to modulate the light beam, control the movement of the light sheet, and expand the field of view. This approach also suffers from high cost and low refresh rate. Using less expensive binary phase spatial light modulators, however, results in system complexity.

[0004] Therefore, the existing technology still needs to be improved and developed. Summary of the Invention

[0005] A first object of the present invention is to provide a light sheet fluorescence microscopy system, which aims to solve the technical problem of high cost of existing light sheet fluorescence microscopy systems.

[0006] To achieve the above object, the present invention provides the following solutions: A light sheet fluorescence microscopy imaging system includes a laser generator, a first semi-transparent and semi-reflective mirror, a first micromirror array, a beam scanning assembly, a loading platform, an imaging device, a second semi-transparent and semi-reflective mirror, a camera, and a second micromirror array. The laser generator generates a laser beam, which is transmitted through the first semi-transparent and semi-reflective mirror to the first micromirror array for adjustment to generate an output beam. The output beam is reflected by the first micromirror array to the beam scanning assembly. The beam scanning assembly scans the output beam in the X-axis and Z-axis directions to generate a light sheet. After the light sheet is irradiated onto an object to be measured placed on the loading platform, the excited fluorescence is imaged by the imaging device and transmitted through the second semi-transparent and semi-reflective mirror to the second micromirror array. The fluorescence adjusted by the second micromirror array is reflected by the second semi-transparent and semi-reflective mirror to the camera. The zoom height of the second micromirror array corresponds to the scanning height of the beam scanning assembly in the Z-axis direction.

[0007] Preferably, the beam scanning assembly includes an X-axis scanning device and a Z-axis scanning device, the X-axis scanning device is used to scan the outgoing beam in the X-axis direction to generate a light sheet, and the Z-axis scanning device is used to scan the outgoing beam in the Z-axis direction to achieve tomographic imaging.

[0008] Preferably, the camera is a high-speed CMOS camera.

[0009] Preferably, the light sheet fluorescence microscopy system further includes a shaping component, which is disposed between the beam scanning component and the object loading platform. The light sheet shapes the intensity distribution of the laser through the shaping component and then irradiates the laser onto the object to be measured placed on the object loading platform.

[0010] A second object of the present invention is to provide a light sheet fluorescence microscopy imaging method, which is implemented based on the light sheet fluorescence microscopy imaging system as described above, and comprises: obtaining a range of an object to be observed, and determining a range of a change step of the first micromirror array from a pre-constructed calibration file according to the range of observation; sequentially adjusting the micromirror array state of the first micromirror array according to the determined range of change step, so that the micromirrors in the first micromirror array are combined into different equivalent curved surfaces, so that the light beam scanning component performs X-axis scanning on the outgoing light beam. The focusing position of the light sheet generated after scanning on the Y axis corresponds to each step length; the outgoing light beam is scanned in the Z axis direction by the beam scanning component to adjust the height of the light sheet generated after scanning in the X axis direction; at the same time, the second micromirror array is synchronized with the beam scanning component to zoom according to a preset adjustment step length within the height range of the object to be measured, and the zoom height corresponds to the adjustment height of the light sheet; the camera is used to collect fluorescence images of the object to be measured at different zoom heights at each focusing position; all the collected fluorescence images are spliced and fused to generate a multi-layer tomography scanning image of the object to be measured.

[0011] Preferably, the method of obtaining the observation range of the object to be measured and determining the range of the change step of the first micromirror array from a pre-constructed calibration file according to the observation range also includes: calibrating the state of the first micromirror array and recording each state as a step; obtaining the focal position in the Y-axis direction of the outgoing light beam corresponding to each step; and establishing a connection between all the steps and the focal positions to generate a calibration file.

[0012] Preferably, the stitching and fusing of all collected fluorescence images to generate a multi-layer tomographic scanning image of the object to be measured includes: preprocessing all collected images to obtain multiple preprocessed images; extracting features of the multiple preprocessed images to obtain feature points and feature descriptors of each preprocessed image; based on the extracted feature descriptors, using a brute force matching method to find matching feature point pairs between the multiple processed images; based on the matched feature point pairs, using an image registration algorithm to spatially align the different processed images to obtain a registered image; and fusing the image information of the overlapping areas of the registered images to generate a multi-layer tomographic scanning image of the object to be measured.

[0013] Preferably, extracting features of multiple preprocessed images to obtain feature points and feature descriptors of each preprocessed image includes: using any one of scale-invariant feature transform, accelerated robust feature, and fast directional brief algorithms to extract features of multiple preprocessed images to obtain feature points and feature descriptors of each preprocessed image.

[0014] In this solution, in terms of expanding the light-sheet scanning range, the light sheet is moved flatly in the beam propagation direction (Y-axis) by adjusting the micromirror array state of the first micromirror array. This greatly widens the light-sheet scanning range without increasing the thickness of the light sheet. Compared with the traditional solution using a spatial light modulator, this solution avoids the complex modulation process and greatly improves the scanning speed by leveraging the fast response characteristics of the first micromirror array. At the same time, the high-precision micromirror operation ensures higher positioning accuracy and effectively reduces costs by simplifying the hardware structure. In the tomographic imaging link, the beam scanning component is used to synchronize the zoom with the second micromirror array, discarding the Z-axis displacement platform in the traditional light-sheet microscopy system, eliminating the speed bottleneck and precision loss caused by mechanical movement. The two work together to quickly and accurately adjust the light-sheet height and focus position, significantly improving the scanning speed of tomographic imaging at different zoom heights. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0016] Figure 1 is a schematic structural diagram of a light sheet fluorescence microscopy imaging system provided by an embodiment of the present invention; Figure 2 is a calibration principle diagram of a first micromirror array provided by an embodiment of the present invention; Figure 3 4 is a flow chart of a light-sheet fluorescence microscopy method provided by an embodiment of the present invention. Description of the drawings: 10. Laser generator; 20. First semi-transparent and semi-reflective mirror; 30. First micromirror array; 40. Light beam scanning assembly; 50. Object loading platform; 60. Imaging device; 70. Second semi-transparent and semi-reflective mirror; 80. Camera; 90. Second micromirror array; 100. Shaping assembly; 110. Object to be measured. DETAILED DESCRIPTION

[0018] The terms "first," "second," "third," "fourth," and so on (if any) in the description and claims of the present invention and in the accompanying drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or precedence. It should be understood that the terms used in this manner are interchangeable where appropriate, so that the embodiments described herein can be implemented in an order other than that shown or described herein. In addition, the terms "including" or "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus that includes a series of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, product, or apparatus.

[0019] See also Figure 1 As shown, an embodiment of the present invention provides a light sheet fluorescence microscopy system, comprising a laser generator 10, a first semi-transparent and semi-reflective mirror 20, a first micromirror array 30, a beam scanning assembly 40, a loading platform 50, an imaging device 60, a second semi-transparent and semi-reflective mirror 70, a camera 80, and a second micromirror array 90. The laser generator 10 generates a laser beam, which is transmitted through the first semi-transparent and semi-reflective mirror 20 to the first micromirror array 30 for adjustment to generate an outgoing beam, which is reflected by the first micromirror array 30 to the beam scanning assembly 40. The light beam scanning component 40 scans the outgoing light beam in the X-axis direction and the Z-axis direction to generate a light sheet. After the light sheet is irradiated onto the object to be measured 110 placed on the object loading platform 50, the excited fluorescence is imaged by the imaging device 60 and then transmitted to the second micromirror array 90 via the second semi-transparent and semi-reflective mirror 70. The fluorescence adjusted by the second micromirror array 90 is reflected by the second semi-transparent and semi-reflective mirror 70 to the camera 80. The zoom height of the second micromirror array 90 corresponds to the scanning height of the light beam scanning component 40 in the Z-axis direction.

[0020] In this embodiment, the generator generates a collimated and expanded laser beam.

[0021] In this embodiment, the first micromirror array 30 is controlled by a controller, and the micromirrors in the first micromirror array 30 can be rotated and translated to form different curved surfaces. When the laser beam passes through the first micromirror array 30, the focus position of the outgoing beam moves in the Y-axis direction compared to the original laser beam, as shown in FIG. Figure 2 shown.

[0022] In this embodiment, by adjusting the angle or position of each micro-mirror in the first micro-mirror array 30, the first micro-mirror array 30 is combined into a group of equivalent curved surfaces G={G1, G2, ..., G N}, and record the corresponding micromirror array state as Step={1, 2, …, N}.

[0023] The focal position of the incident light beam changes after passing through the first micromirror array 30. If the current micromirror array state is Step=i (1≤i≤N), the equivalent surface is G i , the generated output beam is O i , the focus position of the corresponding outgoing light beam in the Y-axis direction is recorded as Y i .

[0024] By changing the micromirror array state of the first micromirror array 30, the focus position of the outgoing light beam on the Y axis is changed. Each time the micromirror array state of the first micromirror array 30 is changed, the focus position of the outgoing light beam is moved along the Y axis by a certain distance ∆y, so that the light beams obtained from the N states of Step1-N can be flatly spread over the entire calibration range. When Step=1, Y1 is the position closest to the light source system, and Y1 is the origin (Y1=0). Y2-Y N Moving along the direction of beam propagation, its value is the difference with Y1.

[0025] In this embodiment, the beam scanning assembly 40 includes an X-axis scanning device and a Z-axis scanning device. The X-axis scanning device is used to scan the outgoing beam in the X-axis direction to generate a light sheet, and the Z-axis scanning device is used to scan the outgoing beam in the Z-axis direction to achieve tomographic imaging.

[0026] In this embodiment, the zoom height of the second micromirror array 90 corresponds to the scanning height of the beam scanning assembly 40 in the Z-axis direction. The second micromirror array 90 can be adjusted in up to 320 steps (steps 1-319) along the depth direction (Z-axis), synchronizing with the Z-axis scanning device in the beam scanning assembly 40 to achieve focused imaging of the light sheet position.

[0027] In this embodiment, the camera 80 is a high-speed CMOS camera 80, which is used to capture fluorescence images to obtain a series of fluorescence images of different regions and different zoom heights, and then stitch and fuse the series of fluorescence images of different regions and different zoom heights into a multi-layer tomography scanning image through an image fusion algorithm.

[0028] In this embodiment, the light sheet fluorescence microscopy system also includes a shaping component 100, which is arranged between the beam scanning component 40 and the object loading platform 50. The light sheet shapes the intensity distribution of the laser through the shaping component 100 and then irradiates it onto the object to be measured 110 placed on the object loading platform 50.

[0029] The light-sheet fluorescence microscopy system of this embodiment expands the light-sheet scanning range by adjusting the micromirror array state of the first micromirror array 30 to achieve tiled movement of the light sheet in the beam propagation direction (Y-axis). This significantly broadens the light-sheet scanning range without increasing the thickness of the light sheet. Compared with conventional solutions using spatial light modulators, this solution avoids the complex modulation process and significantly improves scanning speed by leveraging the fast response characteristics of the first micromirror array 30. Furthermore, the high-precision micromirror operation ensures higher positioning accuracy and effectively reduces costs by simplifying the hardware structure. In the tomographic imaging process, the beam scanning assembly 40 and the second micromirror array 90 are used for synchronous zooming, eliminating the Z-axis displacement stage in conventional light-sheet microscopy systems and the speed bottleneck and precision loss caused by mechanical movement. The two work together to quickly and accurately adjust the light-sheet height and focus position, significantly improving the scanning speed of tomographic imaging at different zoom heights.

[0030] See also Figure 3 As shown, the present invention also provides a light sheet fluorescence microscopy method, comprising: S101, obtaining a range of the object to be observed 110, and determining a range of a change step of the first micromirror array 30 from a pre-built calibration file according to the range of the object to be observed; S102, sequentially adjusting the micromirror array state of the first micromirror array 30 according to the determined range of step size change, so that the micromirrors in the first micromirror array 30 are combined into different equivalent curved surfaces, so that the focus position on the Y axis of the light sheet generated by the light beam scanning assembly 40 scanning the outgoing light beam in the X-axis direction corresponds to each step size; S103: Scanning the outgoing light beam in the Z-axis direction by the beam scanning assembly 40 to adjust the height of the light sheet generated by scanning in the X-axis direction. Simultaneously, the second micromirror array 90 synchronizes with the beam scanning assembly 40 to zoom within the height range of the measured object 110 according to a preset adjustment step size, with the zoom height corresponding to the adjusted height of the light sheet. S104, collecting fluorescence images of the object 110 at different zoom heights at each focus position through the camera 80; S105 , stitching and fusing all collected fluorescence images to generate a multi-layer tomographic scanning image of the object 110 to be measured.

[0031] In this embodiment, in step S101, the observation range of the object to be measured 110 is obtained, and the range of the step size change of the first micromirror array 30 is determined from a pre-built calibration file based on the observation range. The process also includes: calibrating the state of the first micromirror array 30 and recording each state as a step size; obtaining the focal position in the Y-axis direction of the outgoing light beam corresponding to each step size; and establishing a relationship between all step sizes and focal positions to generate a calibration file.

[0032] In this embodiment, the calibration range of the focus position of the outgoing light beam in the Y-axis direction is L.

[0033] For example, by adjusting the angle or position of each micro-mirror in the first micro-mirror array 30, the first micro-mirror array 30 is combined into a set of equivalent curved surfaces G={G1, G2, ..., G N}, and record the corresponding state of the first micromirror array 30 as Step={1, 2, ..., N}.

[0034] For example, the focus position corresponding to Step={1, 2, ..., N} is Y={Y1, Y2, ..., Y N}.

[0035] In this embodiment, it is assumed that the observation range of the object 110 to be measured is the focus position Y1-Y2 of the outgoing light beam on the Y axis. N , then according to the focus position Y1–Y N From the calibration file, determine the change step range S of the first micromirror array 30 = {S1, S2, ..., S N}.

[0036] In this embodiment, in step S102, the beam scanning assembly 40 includes an X-axis scanning device and a Z-axis scanning device. After the X-axis scanning device scans the outgoing beam in the X-axis direction, the focusing position of the light sheet generated on the Y-axis corresponds to each step size.

[0037] In this embodiment, in step S103, the light sheet is adjusted m times in height by the Z-axis scanning device, and the corresponding height is recorded as H={H1, H2, ..., H m}, the second micromirror array 90 is synchronously zoomed within the object height range, and a total of m steps are adjusted, which are recorded as {B1, B2, ..., B m}, the corresponding scanning height is H = {H1, H2, …, H m}.

[0038] In this embodiment, in step S104, at each focus position and corresponding zoom height, the system control signal triggers the camera 80 to capture an image. The camera 80 performs photoelectric conversion on the fluorescence excited by the object 110, converting the optical signal into an electrical signal, which is then converted into a digital image signal through analog-to-digital conversion.

[0039] In this embodiment, the final result is Fluorescence images of different areas at different zoom heights.

[0040] In this embodiment, in step S104, all the collected fluorescence images are spliced and fused to generate a multi-layer tomographic scanning image of the object to be measured 110, including: preprocessing all the collected images to obtain multiple pre-processed images; extracting features of the multiple pre-processed images to obtain feature points and feature descriptors of each pre-processed image; based on the extracted feature descriptors, using a brute force matching method to find matching feature point pairs between the multiple processed images; based on the matched feature point pairs, using an image registration algorithm to spatially align the different processed images to obtain a registered image; and fusing image information of overlapping areas of the registered images to generate a multi-layer tomographic scanning image of the object to be measured 110.

[0041] In this embodiment, in light-sheet fluorescence microscopy, the collected images are easily affected by factors such as noise and uneven illumination. Preprocessing operations such as denoising, brightness and contrast adjustment can effectively improve image quality, enhance the accuracy of subsequent feature extraction and matching, and provide a basis for high-quality image stitching and fusion.

[0042] In this embodiment, feature extraction algorithms such as SIFT (Scale-Invariant Feature Transform), SURF (Speeded Up Robust Features), or ORB (Oriented Brief) are used to extract feature points and feature descriptors from each preprocessed image. Feature points contain key image information, such as corners and edges, while feature descriptors describe the local characteristics of feature points for subsequent image matching.

[0043] In this embodiment, based on the matched feature point pairs, an image registration algorithm (such as affine transformation or perspective transformation based on a transformation matrix) is used to spatially align the different pre-processed images so that they are in the same coordinate system. Simultaneously, by adjusting image parameters such as translation, rotation, and scaling, the image content in the overlapping areas is accurately aligned, eliminating image misalignment caused by differences in shooting angle and position.

[0044] In this embodiment, the overlapping areas of the registered images are fused to eliminate stitching traces, generate continuous and natural multi-layer tomography images, and fully present the internal structure of the object 110 under test, which meets the goal of the light-sheet fluorescence microscopy system to obtain clear and accurate images.

[0045] The light-sheet fluorescence microscopy method of this embodiment expands the light-sheet scanning range by adjusting the micromirror array state of the first micromirror array 30 to achieve tiled movement of the light sheet in the beam propagation direction (Y-axis). This significantly broadens the light-sheet scanning range without increasing the thickness of the light sheet. Compared with conventional solutions using spatial light modulators, this solution avoids the complex modulation process and significantly improves scanning speed by leveraging the fast response characteristics of the first micromirror array 30. Furthermore, the high-precision micromirror operation ensures higher positioning accuracy and effectively reduces costs by simplifying the hardware structure. In the tomographic imaging process, the beam scanning assembly 40 and the second micromirror array 90 are used for synchronous zooming, eliminating the Z-axis displacement stage in conventional light-sheet microscopy systems and the speed bottleneck and precision loss caused by mechanical movement. The two work together to quickly and accurately adjust the light-sheet height and focus position, significantly improving the scanning speed of tomographic imaging at different zoom heights.

[0046] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention description and drawings under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A light sheet fluorescence microscopy system, characterized in that: The invention comprises a laser generator, a first semi-transparent and semi-reflective mirror, a first micromirror array, a light beam scanning component, a loading platform, an imaging device, a second semi-transparent and semi-reflective mirror, a camera and a second micromirror array, wherein the laser generator generates a laser beam, the laser beam is transmitted to the first micromirror array through the first semi-transparent and semi-reflective mirror for adjustment to generate an outgoing light beam, the outgoing light beam is reflected to the light beam scanning component through the first micromirror array, the light beam scanning component scans the outgoing light beam in the X-axis direction and the Z-axis direction to generate a light sheet, after the light sheet is irradiated onto the object to be measured placed on the loading platform, the excited fluorescence is imaged by the imaging device and transmitted to the second micromirror array through the second semi-transparent and semi-reflective mirror, the fluorescence adjusted by the second micromirror array is reflected to the camera through the second semi-transparent and semi-reflective mirror, and the zoom height of the second micromirror array corresponds to the scanning height of the light beam scanning component in the Z-axis direction.

2. The light sheet fluorescence microscopy system according to claim 1, wherein: The beam scanning assembly includes an X-axis scanning device and a Z-axis scanning device. The X-axis scanning device is used to scan the outgoing light beam in the X-axis direction to generate a light sheet, and the Z-axis scanning device is used to scan the outgoing light beam in the Z-axis direction to achieve tomographic imaging.

3. The light sheet fluorescence microscopy system according to claim 1, wherein: The camera is a high-speed CMOS camera.

4. The light sheet fluorescence microscopy system according to claim 1, wherein: The light sheet fluorescence microscopy system further includes a shaping component, which is disposed between the beam scanning component and the object loading platform. The light sheet shapes the intensity distribution of the laser through the shaping component and then irradiates the laser onto the object to be measured placed on the object loading platform.

5. A light sheet fluorescence microscopy method, characterized in that: The light-sheet fluorescence microscopy method is implemented based on the light-sheet fluorescence microscopy system according to any one of claims 1 to 4, and the light-sheet fluorescence microscopy method comprises: Obtaining a range of the object to be observed, and determining a range of a change step of the first micromirror array from a pre-built calibration file according to the range of the object to be observed; sequentially adjusting the micromirror array state of the first micromirror array according to the determined range of step length variation, so that the micromirrors in the first micromirror array are combined into different equivalent curved surfaces, so that the focus position on the Y axis of the light sheet generated by the light beam scanning component scanning the outgoing light beam in the X-axis direction corresponds to each step length; The outgoing light beam is scanned in the Z-axis direction by the beam scanning assembly to adjust the height of the light sheet generated after scanning in the X-axis direction. At the same time, the second micromirror array is synchronized with the beam scanning assembly to zoom according to a preset adjustment step within the height range of the measured object, and the zoom height corresponds to the adjusted height of the light sheet; Collecting fluorescence images of the object under test at different zoom heights at each focus position by the camera; All collected fluorescence images are stitched and fused to generate a multi-layer tomographic scanning image of the object being measured.

6. The light sheet fluorescence microscopy method according to claim 5, wherein: The step of obtaining the observed range of the object to be measured and determining the change step range of the first micromirror array from a pre-built calibration file according to the observed range may also include: The first micromirror array is calibrated in state, and each state is recorded as a step length: Obtain the focus position of the outgoing light beam in the Y-axis direction corresponding to each step size; Associate all step sizes with focus positions and generate a calibration file.

7. The light sheet fluorescence microscopy method according to claim 5, wherein: The step of stitching and fusing all collected fluorescence images to generate a multi-layer tomographic scanning image of the object under test includes: Preprocessing all collected images to obtain multiple preprocessed images; Extract features of multiple preprocessed images to obtain feature points and feature descriptors of each preprocessed image; Based on the extracted feature descriptors, a brute force matching method is used to find matching feature point pairs between multiple processed images; According to the matched feature point pairs, the image registration algorithm is used to spatially align the different processed images to obtain the registered image; The image information of the overlapping areas of the registered images is fused to generate a multi-layer tomographic scanning image of the object being measured.

8. The light sheet fluorescence microscopy method according to claim 7, wherein: The extracting features of the plurality of preprocessed images to obtain feature points and feature descriptors of each preprocessed image includes: using any one of scale-invariant feature transform, accelerated robust feature, and fast directional brief algorithms to extract features of the plurality of preprocessed images to obtain feature points and feature descriptors of each preprocessed image.

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