Laser reflection tomography three-dimensional imaging method and system

Abstract

The invention discloses a laser reflection tomography three-dimensional imaging method and system, and relates to the technical field of three-dimensional imaging. The method is used for realizing high-resolution imaging of a three-dimensional contour structure of a space target and accurate recognition description of the target. Comprising the steps of obtaining target multi-angle echo information, completing fly-around plane two-dimensional image reconstruction, and efficiently and accurately resolving to obtain target fly-around axial reflectivity distribution based on multiple groups of fly-around plane two-dimensional images, so that accurate reconstruction of a target three-dimensional image is completed, and the problem that high-resolution three-dimensional reconstruction of a space target external structure is difficult is solved. In the method, the three-dimensional laser reflection tomography provides information of one dimension and is used for reconstructing the three-dimensional image; therefore, the appearance, the size and the structure details of the target can be reflected more comprehensively, and the next-step processing of the target image at the cognitive end can be facilitated.

Description

Technical Field

[0001] The present invention relates to the field of three-dimensional imaging technology, and in particular, to a three-dimensional imaging method and system for laser reflection tomography. Background Art

[0002] Laser Reflective Tomography (LRT) imaging technology is a new type of laser imaging technology developed on the basis of Computed Tomography (CT) technology in the medical field. In the case of relative angular motion between the detection system and the target, modulated laser echo pulse signals can be accurately acquired from multiple angles. After reconstruction processing by a dedicated algorithm, target projection imaging in the laser vertical axis direction can be achieved. Essentially, it is a method of restoring the image contour in a scene where distance is resolvable and angle is not resolvable by introducing multi-angle echo information. The imaging mechanism of RTL determines that under the condition of sufficient laser echo signal-to-noise ratio, its imaging resolution is independent of the detection distance and system aperture, and is mainly related to the laser pulse width, detection circuit bandwidth, and acquisition system sampling rate. It has great potential in long-distance space target laser detection and space-based laser imaging detection.

[0003] As early as in 1988, Parker, Marino, etc. at MIT Lincoln Laboratory began to study the combination of tomography technology and lidar, and built non-coherent / coherent lidar systems respectively to verify the feasibility of distance-resolved and Doppler-resolved RTL imaging (F.K. Knight, S.R. Kulkarni, R.M. Marino. Tomographic techniques applied to laser radar reflective measurements[J]. Lincoln Laboratory Journal, 1989(No.2):143-160.). From 1998 to 2001, Matson, etc. at the US Air Force Laboratory designed the HI-CLASS coherent lidar for long-distance detection, tracking, and imaging of the MSSS space monitoring station. Since then, domestic and foreign scholars such as Henriksson (Henriksson Markus, Olofsson Tomas, Christina, et al. Optical reflectance tomography using TCSPC laser radar [C] / / Kamerman G W, Steinvall O, Bishop G J, et al. SPIE Security+Defence. Edinburgh, United Kingdom, 2012: 85420E. doi: 10.1117 / 12.974493.), Hu Yihua's team (Hu Yihua, Zhang Xinyuan, Han Fei, etc. Super-resolution imaging of small and distant targets by reflection tomography lidar [J]. Chinese Journal of Lasers, 2023 (Issue 3): 214-215.) and others have all carried out research on RTL imaging. However, the existing research currently only stays at the two-dimensional tomography imaging of the target, and can only obtain the two-dimensional contour image of the target, without carrying out research on the three-dimensional tomography imaging of the target.

[0004] The closest prior art to the present invention is the laser reflection tomography method and device based on sparse regularization iteration proposed by Northwestern Polytechnical University (Guo Rui, Jiang Zheyi, Zhang Zhao, Zhang Shuangxi, Guo Liang. A laser reflection tomography method and device for non-cooperative targets [P]. Chinese Patent: CN114820846A, July 29, 2022). This scheme provides a two-dimensional laser reflection tomography iterative algorithm that is superior to the traditional filtered back projection (FBP) and algebraic reconstruction technique (ART), and can achieve better two-dimensional reconstruction results for incomplete projection data. <T

[0005] As Figure 1 shown, this technology obtains the reflection projection data of non-cooperative targets through lidar, then transforms the reflection projection data into transmission data, obtains the first image through the ART algorithm, and obtains the second image, that is, the final result, through sparse regularization iteration.

[0006] This method only stays at the two-dimensional cross-section for the contour imaging of objects. Three-dimensional laser reflection tomography provides an additional dimension of information, and the reconstructed image is three-dimensional. It can more comprehensively reflect the shape, size and structural details of the target, and is more conducive to the next-step processing of the target image at the cognitive end. Moreover, the prior art does not have a signal deconvolution and projection registration process. When the laser pulse width is greater than the sampling period (after the laser is broadened) and the object has random rigid motion, and the projection angle deviates from the projection center, the imaging will be distorted and the imaging resolution will decrease. Summary of the Invention

[0007] In view of the deficiencies in the prior art, the present invention proposes a three-dimensional imaging scheme (method and system) for laser reflection tomography.

[0008] In the first aspect of the present invention, a method for three-dimensional imaging of laser reflection tomography is proposed, and the method includes:

[0009] Step S1: A narrow-pulse picosecond laser emits laser light, and a spatial distribution signal suitable for reflection tomography is collected from a hypersensitive high-speed detection module.

[0010] Step S2: The high-precision scanning pointing system performs axial overlapping scanning on a long-distance spatial target, and step S1 is repeated to obtain the spatial distribution signal of the entire axis at the current flying-around angle.

[0011] Step S3: Fly around according to a predetermined route, and repeat step S2 within a certain angle range to obtain the spatial distribution signal suitable for reflection tomography of a certain axial angle.

[0012] Step S4: Reconstruct the tomographic imaging spatial distribution signals at different axial scanning angles and each flying-around angle into multiple groups of two-dimensional tomographic images.

[0013] Step S5: Combine the multiple groups of two-dimensional tomographic images into a three-dimensional tomographic image in the order of axial scanning.

[0014] In the method: After obtaining the laser echo information at a fixed position on the target's flying-around axis, reconstruct the two-dimensional image of the flying-around plane at the corresponding axial position according to the predetermined route; repeat the processing of the laser echo information on the target's flying-around axis at multiple positions to obtain the two-dimensional image of the flying-around plane at the target's axial position.

[0015] In the method: According to the field of view and scanning range, calculate the reflectivity distribution on the target's flying-around axis, thereby correct the two-dimensional images of the flying-around plane at different axial positions, and complete the calculation of the reflectivity distribution on the flying-around axis and the reconstruction of the two-dimensional images of the flying-around plane.

[0016] In the method: The signal intensity in the laser echo signal is expressed as the integral of the echo signals at each point along a specific path, and the laser echo intensity signal at this moment is projected onto each point of this integral path through back-projection transformation; multiple groups of laser detection data are obtained at different observation angles, and the echo signal intensity at each point inside the target is regarded as the gray level of the target, and it is regarded as the superposition of the signal intensities on the integral paths corresponding to each angle, thereby realizing the image reconstruction of each point inside the target and obtaining a high-resolution planar image of the target.

[0017] In the method: In the axial dimension orthogonal to the flying-around orbit, extract the stratified signals of the target in this direction through spatial scanning and signal reconstruction, and realize three-dimensional high-resolution imaging of the target through multi-layer signal image reconstruction.

[0018] In the second aspect of the present invention, a three-dimensional imaging system for laser reflection tomography is proposed. The system includes: a narrow-pulse picosecond laser, an ultrasensitive high-speed detection module, a high-precision scanning and pointing system, and a processing unit. When the system is in the working state, it performs the following steps:

[0019] Step S1: The narrow-pulse picosecond laser emits laser light, and a spatial distribution signal suitable for reflection tomography imaging is collected from the ultrasensitive high-speed detection module.

[0020] Step S2: The high-precision scanning and pointing system performs axial overlapping scanning on a long-distance spatial target, and step S1 is repeated to obtain the spatial distribution signal of the entire axial direction at the current flying-around angle.

[0021] Step S3: Fly around according to a predetermined route, and step S2 is repeated within a certain angle range to obtain the spatial distribution signal of a certain axial direction suitable for reflection tomography imaging.

[0022] Step S4: The processing unit reconstructs the tomography imaging spatial distribution signals at different axial scanning angles and each flying-around angle into multiple groups of two-dimensional tomography images.

[0023] Step S5: The processing unit combines the multiple groups of two-dimensional tomography images in the order of axial scanning into a three-dimensional tomography image.

[0024] When the system is in the working state, it is configured to perform: after obtaining the laser echo information at a fixed position of the target flying-around axis, reconstruct the two-dimensional image of the flying-around plane at the corresponding axial position according to a predetermined route; repeat the processing of the laser echo information of the target flying-around axis at multiple positions to obtain the two-dimensional image of the flying-around plane at the target axial position.

[0025] When the system is in the working state, it is configured to perform: according to the field of view and the scanning range, calculate the reflectivity distribution of the target flying-around axis, so as to correct the two-dimensional images of the flying-around plane at different axial positions, and complete the calculation of the reflectivity distribution of the flying-around axis and the reconstruction of the two-dimensional images of the flying-around plane.

[0026] When the system is in the working state, it is configured to perform: the signal intensity in the laser echo signal is the integral of the echo signals of each point along a certain specific path, and the laser echo intensity signal at this moment is projected onto each point of this integral path through back-projection transformation; multiple groups of laser detection data are obtained at different observation angles, and the echo signal intensity of each point in the target is regarded as the gray level of the target, and it is regarded as the superposition of the signal intensities on the corresponding integral paths at each angle, thereby realizing the image reconstruction of each point inside the target and obtaining a high-resolution planar image of the target.

[0027] In this regard, when the system is in the working state, it is configured to perform: extracting the layered signals of the target in this direction through spatial scanning and signal reconstruction in the axial dimension orthogonal to the orbiting trajectory, and realizing three-dimensional high-resolution imaging of the target through multi-layer signal image reconstruction.

[0028] A third aspect of the present invention proposes an electronic device. The electronic device includes a memory and a processor. The memory stores a computer program. When the processor executes the computer program, a three-dimensional imaging method of laser reflection tomography according to the first aspect of the present disclosure is realized.

[0029] A fourth aspect of the present invention proposes a computer-readable storage medium. A computer program is stored on the computer-readable storage medium. When the computer program is executed by a processor, a three-dimensional imaging method of laser reflection tomography according to the first aspect of the present disclosure is realized.

[0030] In summary, the present invention realizes high-resolution imaging of the three-dimensional contour structure of a space target and accurate identification and description of the target. In the solution proposed by the present invention: obtaining the echo information of the target from multiple angles, completing the two-dimensional image reconstruction of the orbiting plane, and efficiently and accurately calculating the axial reflectivity distribution of the target's orbiting based on multiple groups of two-dimensional images of the orbiting plane, so as to complete the accurate reconstruction of the target's three-dimensional image, and solve the problem that it is difficult to perform high-resolution three-dimensional reconstruction of the external structure of space targets. Due to the additional dimension of information provided by three-dimensional laser reflection tomography, the reconstructed image is three-dimensional and stereoscopic. It can more comprehensively reflect the shape, size and structural details of the target, and is more conducive to the next-step processing of the target image at the cognitive end. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0032] Figure 1 It is a flowchart of the prior art implementation.

[0033] Figure 2 It is a schematic diagram of a three-dimensional imaging scene of laser reflection tomography according to an embodiment of the present invention.

[0034] Figure 3 It is a schematic diagram of the three-dimensional imaging process of laser reflection tomography according to an embodiment of the present invention.

[0035] Figure 4 (including (a)-(d)) It is a schematic diagram of the imaging result according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0037] Abbreviations and definitions of key terms (the following English abbreviations and terms are provided with their corresponding English full names and Chinese translations, or detailed explanations of Chinese professional terms):

[0038] LRT: Laser Reflective Tomography, i.e., Laser Reflective Tomography;

[0039] APD: Avalanche photodiode, i.e., Avalanche Photodiode;

[0040] CT: Computer Tomography, i.e., Computerized Tomography;

[0041] RTL: Reflective Tomography LiDAR, i.e., Reflective Tomography LiDAR.

[0042] The present invention proposes a method and system for three-dimensional imaging of laser reflective tomography. As Figure 2 shown, three-dimensional imaging of laser reflective tomography obtains echo information from multiple angles of the target, completes the reconstruction of a two-dimensional image of the circumferential flight plane, and then combines the one-dimensional scanning information in the circumferential flight axis to achieve the reconstruction of a three-dimensional image of the spatial target. Obtain the one-dimensional scanning laser echo information of the target in the circumferential flight axis, and complete the reconstruction of multiple groups of two-dimensional images of the circumferential flight plane at different axial positions; according to the field of view and scanning range, calculate the reflectivity distribution of the target in the circumferential flight axis, so as to correct the two-dimensional images of the circumferential flight plane at different axial positions; combine multiple groups of corrected two-dimensional images of the circumferential flight plane, and use the method for reconstructing a three-dimensional image of a spatial target to complete the high-resolution reconstruction of the three-dimensional image of the target; the system generates a detection laser signal through a high-repetition-rate picosecond laser, obtains a spatial distribution signal suitable for reflective tomography imaging through beam spatial shaping and control, and then performs axial-dimensional overlapping scanning on a long-distance spatial target through a high-precision scanning and pointing system. The weak echo signal of the target is received by a super-sensitive high-speed detection module, and the waveform distribution information of the target echo signal is obtained through the target echo signal preprocessing module. Combined with the pointing information provided by the high-precision scanning and pointing module, the axial-dimensional echo signal calculation module obtains the super-resolution reconstruction data of the axial-dimensional target echo information. Through accompanying circumferential flight observation at a certain angle with the target, process the multi-angle information, and finally obtain the three-dimensional super-resolution imaging result of the spatial target.

[0043] Three-dimensional imaging of laser reflection tomography obtains echo information of the target from multiple angles, completes the reconstruction of the two-dimensional image of the fly-around plane, and then combines the one-dimensional scanning information of the fly-around axis to realize the reconstruction of the three-dimensional image of the spatial target. After completing the reconstruction of multiple groups of two-dimensional images of the fly-around plane at different axial positions, it is necessary to calculate the reflectivity distribution of the target fly-around axis according to the field of view and scanning range, so as to correct the two-dimensional images of the fly-around plane at different axial positions. The correction effect of the two-dimensional image will directly affect the quality of the three-dimensional image reconstruction of the target.

[0044] The operation of the system and obtaining the three-dimensional super-resolution imaging results can be summarized into 5 steps:

[0045] Step 1: The narrow-pulse picosecond laser emits laser light, and the spatial distribution signals suitable for reflection tomography imaging are collected from the ultra-sensitive high-speed detection module.

[0046] Step 2: Through the high-precision scanning and pointing system, the axial overlap scanning of the long-distance space target is carried out. Repeat Step 1 to obtain the spatial distribution signals of the entire axis at this fly-around angle.

[0047] Step 3: Fly around according to the route, repeat Step 2 at a certain angle, and finally obtain the spatial distribution signals of the axis at a certain angle that are suitable for reflection tomography imaging.

[0048] Step 4: Reconstruct the tomographic imaging spatial distribution signals at different scanning angles of the axis and at each fly-around angle into multiple groups of two-dimensional tomographic images.

[0049] Step 5: Combine multiple groups of two-dimensional tomographic images into a three-dimensional tomographic image according to the order of axial scanning.

[0050] In some embodiments, after obtaining the laser echo information at a fixed position of the target fly-around axis, the reconstruction of the two-dimensional image of the fly-around plane at the corresponding axial position is completed according to the above route. Repeat the processing of the laser echo information of the target fly-around axis at multiple positions to obtain the two-dimensional image of the fly-around plane at the target axial position. Then, according to the field of view and scanning range, use the same method to calculate the reflectivity distribution of the target fly-around axis, so as to correct the two-dimensional images of the fly-around plane at different axial positions, and complete the calculation of the reflectivity distribution of the fly-around axis and the reconstruction of the two-dimensional image of the fly-around plane.

[0051] In some embodiments, the basic principle of realizing three-dimensional imaging of laser reflection tomography of a spatial target is as Figure 2As shown in the figure, the signal intensity at a certain moment in the laser echo signal is expressed as the integration of the echo signals of each point along a specific path. Through back-projection transformation, the laser echo intensity signal at this moment is projected onto each point of this integration path. By using multiple sets of laser detection data obtained at different observation angles, the echo signal intensity of each point inside the target (manifested as the target gray level) can be regarded as the superposition of the signal intensities on the corresponding integration paths at each angle. Thus, the image reconstruction of each point inside the target can be realized, and a high-resolution planar image of the target can be obtained. In the axial dimension orthogonal to the orbiting path, through spatial scanning and signal reconstruction, the layered signals of the target in this direction are extracted, and through multi-layer signal image reconstruction, the three-dimensional high-resolution imaging of the target is finally realized.

[0052] The overall implementation scheme of the system is as follows Figure 3 As shown in the figure, a detection laser signal is generated by a high-repetition-rate picosecond laser. Through beam spatial shaping and control, a spatial distribution signal suitable for reflection tomography imaging is obtained. Then, through a high-precision scanning and pointing system, axial-dimensional overlapping scanning of a long-distance space target is performed. The weak echo signal of the target is received by a super-sensitive high-speed detection module, and the waveform distribution information of the target echo signal is obtained through the target echo signal preprocessing module. Combined with the pointing information provided by the high-precision scanning and pointing module, through the axial-dimensional echo signal calculation module, super-resolution reconstruction data of the target echo information in the axial dimension is obtained. By accompanying and orbiting the target at a certain angle for observation and processing the multi-angle information, the three-dimensional super-resolution imaging result of the space target is finally obtained.

[0053] In some embodiments:

[0054] (1) A narrow-pulse picosecond laser emits laser light, and a spatial distribution signal suitable for reflection tomography imaging is collected from a super-sensitive high-speed detection module.

[0055] (2) Through a high-precision scanning and pointing system, axial-dimensional overlapping scanning of a long-distance space target is performed. Repeat (1) to obtain the entire axial spatial distribution signal suitable for reflection tomography imaging at this orbiting angle, and finally obtain the spatial distribution signal suitable for reflection tomography imaging in a certain axial direction.

[0056] (4) Combine the tomographic imaging spatial distribution signals at different axial scanning angles and each orbiting angle into a tomographic imaging spatial distribution signal at one axial angle.

[0057] (5) Perform deconvolution operation on the tomographic imaging spatial distribution signal at a certain axial angle to restore the waveform of the tomographic imaging spatial distribution signal, thereby restoring the true reflectivity distribution of the target.

[0058] (6) On the basis of (5), through the method of projection registration, register and correct the spatial distribution signal with the projection center

[0059] (7)On the basis of the registration in (6), use the filtered back-projection method to reconstruct the two-dimensional image of this axial angle.

[0060] (8)Repeat steps (5)-(7) to obtain tomographic images of two-dimensional laser reflection distributions at different axial angles, extract the two-dimensional image contours, and convert the two-dimensional contours into two-dimensional scatter points according to the axial angles. See Figure 4 (Specifically see Figure 4 the (a)-(d) images in) Combine the two-dimensional scatter points at different axial angles into the three-dimensional point cloud image in (b), or the continuous three-dimensional surface image in (d) can also be reconstructed according to the three-dimensional point cloud image.

[0061] In summary, the present invention realizes high-resolution imaging of the three-dimensional contour structure of a spatial target and accurate identification and description of the target. In the solution proposed by the present invention: obtain the multi-angle echo information of the target, complete the reconstruction of the two-dimensional image of the fly-around plane, and efficiently and accurately calculate the axial reflectivity distribution of the target's fly-around based on multiple groups of two-dimensional images of the fly-around plane, so as to complete the accurate reconstruction of the three-dimensional image of the target and solve the problem of difficult high-resolution three-dimensional reconstruction of the external structure of the spatial target. Three-dimensional laser reflection tomography provides an additional dimension of information, and the reconstructed image is three-dimensional and stereoscopic. It can more comprehensively reflect the shape, size, and structural details of the target, and is more conducive to the next-step processing of the target image at the cognitive end.

[0062] Please note that the technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as the combinations of these technical features do not conflict, they should be considered as within the scope described in this specification. The above embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be pointed out that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application should be subject to the appended claims.

Claims

1. A three-dimensional imaging method for laser reflection tomography, characterized in that The method includes: Step S1: A narrow-pulse picosecond laser emits laser light, and a spatial distribution signal suitable for reflection tomography is collected from a hypersensitive high-speed detection module. Step S2: The high-precision scanning pointing system performs axial overlapping scanning on a long-distance space target, and step S1 is repeated to obtain the spatial distribution signal of the entire axis at the current orbiting angle. Step S3: Orbit around according to a predetermined route, and repeat step S2 within a certain angle range to obtain the spatial distribution signal suitable for reflection tomography of a certain axial angle. Step S4: Reconstruct the tomography spatial distribution signals at different axial scanning angles and each orbiting angle into multiple groups of two-dimensional tomography images. Step S5: Combine the multiple groups of two-dimensional tomography images into a three-dimensional tomography image in the order of axial scanning.

2. The three-dimensional imaging method of laser reflection tomography according to claim 1, characterized in that, In the method: After obtaining the laser echo information at a fixed axial position of the target orbit, reconstruct the two-dimensional image of the orbiting plane at the corresponding axial position according to the predetermined route; repeat the processing of the laser echo information of the target orbiting axially at multiple positions to obtain the two-dimensional image of the orbiting plane at the target axial position.

3. A three-dimensional imaging method for laser reflection tomography according to claim 2, characterized in that, In the method: According to the field of view and scanning range, calculate the axial reflectivity distribution of the target orbit, so as to correct the two-dimensional images of the orbiting plane at different axial positions, and complete the calculation of the axial reflectivity distribution of the orbit and the reconstruction of the two-dimensional images of the orbiting plane.

4. A three-dimensional imaging method of laser reflection tomography according to claim 3, characterized in that, In the method: The signal intensity in the laser echo signal is the integral of the echo signals of each point along a specific path. The laser echo intensity signal at this moment is projected onto each point of this integral path through back-projection transformation; multiple groups of laser detection data are obtained at different observation angles. The echo signal intensity of each point in the target is regarded as the gray level of the target, and it is regarded as the superposition of the signal intensities on the corresponding integral paths at each angle. Thus, the image reconstruction of each point inside the target is realized, and a high-resolution planar image of the target is obtained.

5. A three-dimensional imaging method of laser reflection tomography according to claim 4, characterized in that, In the method: In the axial dimension orthogonal to the orbiting orbit, extract the layered signals of the target in this direction through spatial scanning and signal reconstruction, and realize three-dimensional high-resolution imaging of the target through multi-layer signal image reconstruction.

6. A three-dimensional imaging system for laser reflection tomography, characterized in that, The system includes: a narrow-pulse picosecond laser, a hypersensitive high-speed detection module, a high-precision scanning pointing system, and a processing unit; the system performs the following steps in the working state: Step S1: A narrow-pulse picosecond laser emits laser light, and a spatial distribution signal suitable for reflection tomography is collected from a hypersensitive high-speed detection module. Step S2: The high-precision scanning pointing system performs axial overlapping scanning on a long-distance space target, and step S1 is repeated to obtain the spatial distribution signal of the entire axis at the current orbiting angle. Step S3: Orbit around according to a predetermined route, and repeat step S2 within a certain angle range to obtain the spatial distribution signal suitable for reflection tomography of a certain axial angle. Step S4: The processing unit reconstructs the tomography spatial distribution signals at different axial scanning angles and each orbiting angle into multiple groups of two-dimensional tomography images. Step S5: The processing unit combines the multiple groups of two-dimensional tomography images into a three-dimensional tomography image in the order of axial scanning.

7. The three-dimensional imaging system of laser reflection tomography according to claim 6, characterized in that, When in operation, the system is configured to: obtain laser echo information of a target's axially fixed position, and then reconstruct a two-dimensional image of the corresponding axial position's fly-around plane according to a predetermined route; and repeatedly process the axial laser echo information of the target's fly-around plane at multiple positions to obtain a two-dimensional image of the target's axial position's fly-around plane.

8. A three-dimensional imaging system for laser reflection tomography according to claim 7, wherein, When in operation, the system is configured to perform the following operations: calculating the target fly-by axial reflectivity distribution according to the field of view and the scanning range, thereby correcting the fly-by plane two-dimensional image at different axial positions, and completing the fly-by axial reflectivity distribution calculation and the fly-by plane two-dimensional image reconstruction.

9. The three-dimensional imaging system of laser reflection tomography according to claim 8, wherein, When in operation, the system is configured to perform the following: the signal intensity in the laser echo signal is expressed as the integral of the echo signals at each point along a specific path, and the laser echo intensity signal at that moment is projected onto each point of the integral path through back-projection transformation; multiple sets of laser detection data are obtained at different observation angles, and the echo signal intensity at each point within the target is expressed as the target grayscale, which is regarded as the superposition of the signal intensities on the integral path corresponding to each angle, thereby achieving image reconstruction of each point inside the target and obtaining a high-resolution planar image of the target.

10. The three-dimensional imaging system for laser reflection tomography according to claim 9, wherein, When in operation, the system is configured to perform: extracting the target's layered signals in the axial dimension orthogonal to the orbit through spatial scanning and signal reconstruction, and achieving three-dimensional high-resolution imaging of the target through multi-layer signal image reconstruction.

Images