A three-dimensional imaging method and device based on multi-angle trajectory

Abstract

This application belongs to the field of 3D imaging technology and relates to a 3D imaging method and apparatus based on multi-angle trajectories. The method includes: acquiring a 2D image of a wireless device to obtain slant-range-azimuth 2D SAR images of the target at different viewpoints on the current trajectory; converting the slant-range-azimuth 2D SAR images into height-azimuth 2D SAR images; converting the height-azimuth 2D SAR images in the original coordinate system into height-azimuth 2D SAR images in a reference coordinate system and using them as echoes; stacking echoes at the same height from different viewpoints of the wireless device to obtain slices at corresponding heights; stacking slices at different heights to obtain 3D information of the target on the current trajectory; and projecting the 3D information of the target on multiple trajectories onto the reference coordinate system to obtain a 3D image of the target. This application can perform 3D imaging quickly and accurately within a local area while maintaining the simplicity and computational efficiency of the algorithm.

Description

Technical Field

[0001] This application relates to the field of three-dimensional imaging technology, and in particular to a three-dimensional imaging method and apparatus based on multi-angle trajectories. Background Technology

[0002] With the rapid development of science and technology, 3D imaging technology has become an indispensable part of modern industry, scientific research, and daily life. From medical imaging to Geographic Information Systems (GIS) and sensor systems for autonomous vehicles, the application range of 3D imaging technology is wide, and its importance is increasingly prominent. Among the many 3D imaging technologies, imaging methods based on wireless devices have attracted much attention due to their advantages such as the ability to penetrate various materials, independence from lighting conditions, and the ability to provide real-time dynamic information.

[0003] Current 3D SAR imaging technologies mainly include: Multi-Baseline SAR (MBSAR), Circular SAR (CSAR), Holographic Synthetic Aperture Radar (HoloSAR), CurviLinear SAR (CLSAR), and Linear Array Synthetic Aperture Radar (LASAR).

[0004] Tomographic SAR is an information inversion technique developed based on Interferometric Synthetic Aperture Radar (InSAR). However, to ensure high resolution and imaging accuracy in the elevation direction, more flight data is required, and multi-baseline tomographic SAR images are generally obtained by repeated flight passes, which is expensive.

[0005] Circular SAR technology acquires 360° omnidirectional 3D scattering information of the observation area by having a platform orbit around it in a circular motion. Its imaging principle relies on this circular trajectory to obtain omnidirectional information about the target and reconstruct a 3D image. Although CSAR can achieve subwavelength resolution in the range-azimuth plane, the limitation of its effective bandwidth in the elevation direction results in very low elevation resolution, severely restricting the practical engineering application of single-loop CSAR 3D imaging.

[0006] Holographic SAR is a special form of multi-baseline SAR that solves the problem of overlapping anisotropic targets by simultaneously observing from all directions. HoloSAR uses multiple motion trajectories (i.e., multiple baselines) to acquire three-dimensional information of the target. These baselines can be circular trajectories at different heights or angles. This imaging technology requires a radio equipment platform capable of continuous 360° observation of the target from different heights. While such omnidirectional observation trajectories are suitable for airborne platforms, their implementation involves high system complexity. Furthermore, the observation equations of holographic SAR may become larger or even enormous due to increased dimensionality and integrity requirements, leading to theoretical problems regarding the feasibility and convergence of solutions, as well as engineering implementation issues related to efficiency.

[0007] Curved SAR technology involves defining the flight path of a moving platform in three-dimensional space and using the non-linear motion of the platform's trajectory to synthesize a virtual sparse array to reconstruct the 3D information of the scene. To achieve better parameter estimation performance, CLSAR requires high-performance curved trajectories for the platform. For example, large apertures and complex apertures with higher nonlinearity are more conducive to forming dense data sets, thereby improving the accuracy of parameter estimation. However, due to limitations in platform flight performance and safety considerations, overly complex trajectories are impractical.

[0008] Linear array SAR technology involves fixing a linear array antenna to the wing of an aircraft and using the linear array antenna positioned along the flight path and the linear motion of the platform to synthesize a virtual array to reconstruct the 3D information of the scene. However, linear array 3D SAR imaging algorithms are affected by the Nyquist sampling theorem and array grating lobes, requiring uniform distribution of array elements and the smallest possible element spacing. This results in an excessive number of array elements, and traditional algorithms have high sidelobes in the cross-heading resolution function. At the same time, the Rayleigh limit limits the system resolution.

[0009] In summary, traditional 3D imaging methods often rely on complex algorithms and computationally expensive hardware (e.g., limitations in data acquisition, requiring specific flight conditions and trajectories, posing a challenge for practical operation; existing 3D SAR systems are often bulky and heavy, limiting their application on more platforms, especially in situations with strict requirements on equipment size and weight; their high system complexity and development difficulty make system miniaturization and widespread application challenging; the massive data volume, complex processing, and low target imaging resolution lead to reduced accuracy and reliability of imaging results). For current SAR systems, this limits their feasibility in real-time applications and broader fields. Furthermore, for large-scale or dynamically changing scenarios, traditional centralized radio systems may struggle to provide sufficient coverage and flexibility. In other words, traditional 3D SAR technology often faces problems such as high cost, low elevation resolution, low timeliness, complex flight paths, and low imaging quality. Summary of the Invention

[0010] Therefore, it is necessary to provide a three-dimensional imaging method and device based on multi-angle trajectories to address the above-mentioned technical problems. This method and device can perform three-dimensional imaging quickly and accurately in local areas while maintaining the simplicity and computational efficiency of the algorithm. It can also provide sufficient coverage and flexibility for large-scale or dynamically changing scenes.

[0011] A three-dimensional imaging method based on multi-angle trajectories includes:

[0012] Two-dimensional images of the wireless equipment are acquired, and a back projection algorithm is used to obtain slant range-azimuth two-dimensional SAR images of the target under different viewpoints on the current trajectory.

[0013] Based on the slant distance of the imaging plane center from different viewpoints, the angle between the wireless equipment and the slant distance of the imaging plane center is obtained; based on the angle, the slant range-azimuth 2D SAR image is converted into an altitude-azimuth 2D SAR image.

[0014] Obtain the angles between different radio devices and the reference coordinate axes, calculate the coordinate axis transformation matrix and translation matrix, so as to convert the height-azimuth 2D SAR image in the original coordinate system into a height-azimuth 2D SAR image in the reference coordinate system, and use it as an echo.

[0015] Echoes from the same height at different viewpoints of the radio equipment are stacked to obtain slices at the corresponding heights; slices from different heights are stacked to obtain the three-dimensional information of the target under the current trajectory.

[0016] The three-dimensional information of the target under multiple trajectories is projected onto the reference coordinate system to obtain a three-dimensional image of the target.

[0017] In one embodiment, the slant-range-azimuth 2D SAR images of the target at different viewpoints on the current trajectory include:

[0018]

[0019] In the formula, For wireless equipment a Slant range-azimuth 2D SAR image from the perspective of view. for a Complex scattering coefficients at the viewpoint The impulse response is in the slant range direction. For wireless equipment a Slant range coordinates from the viewpoint For target to wireless equipment a Slant distance from the viewpoint For the azimuth impulse response, For wireless equipmenta Orientation coordinates from the viewpoint For wireless equipment a The target's orientation and location from the viewpoint. The imaginary unit, For wireless equipment wavelength;

[0020]

[0021] In the formula, For wireless equipment b Slant range-azimuth 2D SAR image from the perspective of view. for b Complex scattering coefficients at the viewpoint For wireless equipment b Slant range coordinates from the viewpoint For target to wireless equipment b Slant distance from the viewpoint For wireless equipment b Orientation coordinates from the viewpoint For wireless equipment b The target's orientation and location from the viewpoint.

[0022] In one embodiment, the angle between the wireless device and the center slope distance of the imaging plane is obtained based on the slope distance of the imaging plane center from different viewpoints, including:

[0023]

[0024]

[0025]

[0026]

[0027] In the formula, For the target's altitude position, For wireless equipment a The angle between the viewing angle and the oblique distance from the center of the imaging plane. For wireless equipment b The angle between the viewing angle and the oblique distance from the center of the imaging plane.

[0028] In one embodiment, converting a slant-range-azimuth 2D SAR image into a height-azimuth 2D SAR image based on the included angle includes:

[0029] When the target satisfies the far-field condition:

[0030]

[0031]

[0032] but:

[0033]

[0034] We can obtain:

[0035]

[0036]

[0037] In the formula, This represents the error between the target height and the estimated value when the target is not centered on the imaging plane. For wireless equipment a Two-dimensional SAR image with elevation and azimuth from the viewpoint. For height coordinates, For wireless equipment b Two-dimensional SAR image with elevation and azimuth from the viewpoint.

[0038] In one embodiment, the angles between different radio devices and the reference coordinate axes are obtained, and the coordinate axis transformation matrix and translation matrix are calculated to convert the height-azimuth 2D SAR image in the original coordinate system into a height-azimuth 2D SAR image in the reference coordinate system, which is then used as an echo, including:

[0039] Obtain the angles between different wireless devices and the reference coordinate axes, and calculate the coordinate axis transformation matrix based on the principle of basis transformation;

[0040] Obtain the geometric relationship between the coordinate axis transformation matrix and the translation matrix, and calculate the translation matrix by combining the coordinate axis transformation matrix and the relationship between the original coordinate system and the reference coordinate system;

[0041] Based on the coordinate axis transformation matrix and translation matrix, the 2D SAR image in the original coordinate system is transformed into a 2D SAR image in the reference coordinate system using the axis shifting formula, and the 2D SAR image in the reference coordinate system is used as the echo.

[0042] In one embodiment, the angles between different wireless devices and the reference coordinate axes are obtained, and the coordinate axis transformation matrix is ​​calculated according to the basis transformation principle, including:

[0043]

[0044] In the formula, The coordinate axis transformation matrix. This represents the angle between different wireless devices and the reference coordinate axis.

[0045] In one embodiment, the geometric relationship between the coordinate axis transformation matrix and the translation matrix is ​​obtained, and the translation matrix is ​​calculated by combining the coordinate axis transformation matrix and the relationship between the original coordinate system and the reference coordinate system, including:

[0046]

[0047]

[0048]

[0049] In the formula, The position of the image origin projected onto the reference coordinate system. This represents the position of the target in the original coordinate system. This represents the position of the target in the reference coordinate system. It is a translation matrix. Project the image origin onto the reference coordinate system The position of direction, The origin of the image is in the reference coordinate system The location of the direction.

[0050] In one embodiment, the height-azimuth 2D SAR image in the reference coordinate system includes:

[0051]

[0052]

[0053] In the formula, For wireless equipment a A two-dimensional SAR image with reference coordinate system height-azimuth orientation from the viewpoint. In order to be in Selecting the first height slice indivual, It is half the total number of slices in the height direction. For the first A height-oriented slice, For wireless equipment b Two-dimensional SAR image with reference coordinate system height-azimuth orientation from the viewpoint.

[0054] In one embodiment, echoes from the same height at different viewpoints of a wireless device are stacked to obtain slices at the corresponding heights, including:

[0055]

[0056] In the formula, This is a slice at the corresponding height.

[0057] A three-dimensional imaging device based on multi-angle trajectories, comprising:

[0058] The acquisition module is used to acquire two-dimensional images of the wireless device and use a back projection algorithm to obtain slant range-azimuth two-dimensional SAR images of the target under different viewpoints on the current trajectory.

[0059] The conversion module is used to obtain the angle between the slant range of the imaging plane center and the wireless equipment and the slant range of the imaging plane center based on the slant range of the imaging plane center from different perspectives; and to convert the slant range-azimuth 2D SAR image into an altitude-azimuth 2D SAR image based on the angle.

[0060] The echo module is used to obtain the angle between different radio devices and the reference coordinate axis, calculate the coordinate axis transformation matrix and translation matrix, so as to convert the height-azimuth 2D SAR image in the original coordinate system into a height-azimuth 2D SAR image in the reference coordinate system, and use it as an echo.

[0061] The stacking module is used to stack echoes from the same height at different viewpoints of the radio equipment to obtain slices at the corresponding height; and to stack slices from different heights to obtain the three-dimensional information of the target under the current trajectory.

[0062] The projection module is used to project the three-dimensional information of targets under multiple trajectories onto a reference coordinate system to obtain a three-dimensional image of the target.

[0063] The above-mentioned three-dimensional imaging method and device based on multi-angle trajectories have the following beneficial effects:

[0064] 1) It considers the importance of local area imaging, allowing users to flexibly select the size of the imaging area based on the error curve to adapt to different application scenarios and accuracy requirements; in addition, it adopts a distributed wireless equipment configuration, which is not limited by fixed geometry and can be arbitrarily configured according to actual needs, thus providing greater flexibility and adaptability; through the selection of local areas and the deployment of distributed wireless equipment, this method can significantly improve imaging speed and efficiency while ensuring imaging accuracy, which is particularly important for application scenarios that require rapid response, such as emergency rescue, environmental monitoring or traffic management, where fast and accurate 3D imaging capabilities can greatly improve decision-making efficiency and response speed.

[0065] 2) It can form an image with just two lines at any angle, unlike existing technologies that require at least a surface. This simplifies the imaging process and improves imaging speed while ensuring image quality. It enables rapid data processing and imaging, which not only reduces the demand for computing resources and lowers computing costs, but also makes the entire imaging process more efficient. It effectively solves the problems of low imaging speed and high cost in 3D imaging. It has great application value and broad application prospects in practical engineering, and is particularly suitable for application scenarios that require real-time or near-real-time feedback, such as the rapid deployment and dynamic monitoring of UAV swarms.

[0066] 3) The 3D imaging method of this application is particularly suitable for UAV swarms. The configuration of the UAV swarm can be arbitrarily and flexibly configured according to mission requirements. Whether it is a linear, grid-like, or arbitrary-shaped flight formation, it can effectively collect 3D data. This arbitrariness of configuration provides great flexibility for the deployment of UAV swarms, enabling them to adapt to various complex terrains and environmental conditions, while improving the coverage and efficiency of data acquisition. Attached Figure Description

[0067] Figure 1 This is a flowchart illustrating a three-dimensional imaging method based on multi-angle trajectories in one embodiment;

[0068] Figure 2 This is a schematic diagram of the wireless device configuration in one embodiment;

[0069] Figure 3 This is a schematic diagram of basis transformation and translation transformation in one embodiment;

[0070] Figure 4 This is a schematic diagram of a height-oriented slice in one embodiment;

[0071] Figure 5 This is a schematic diagram of the target projected at various heights in one embodiment;

[0072] Figure 6 A wireless device in one embodiment a Two-dimensional SAR image obtained from the viewpoint: slant range-azimuth direction;

[0073] Figure 7 A wireless device in one embodiment b Two-dimensional SAR image obtained from the viewpoint: slant range-azimuth direction;

[0074] Figure 8 A wireless device in one embodiment a Two-dimensional SAR image with height and azimuth obtained from the viewpoint;

[0075] Figure 9 A wireless device in one embodiment bTwo-dimensional SAR image with height and azimuth obtained from the viewpoint;

[0076] Figure 10 A wireless device in one embodiment a , b The same height slices are obtained by basis transformation and translation transformation. x - y Two-dimensional SAR image;

[0077] Figure 11 A wireless device in one embodiment a , b A top view of the obtained three-dimensional imaging results of the target;

[0078] Figure 12 A wireless device in one embodiment a , b A front view of the obtained three-dimensional result of the target;

[0079] Figure 13 In one embodiment Figure 12 The target x A slice diagram of the direction;

[0080] Figure 14 In one embodiment Figure 12 The target y A slice diagram of the direction;

[0081] Figure 15 In one embodiment Figure 12 The target z A slice diagram of the direction;

[0082] Figure 16 A wireless device in one embodiment a , b , c The obtained three-dimensional result image of the target;

[0083] Figure 17 In one embodiment Figure 16 The target x A slice diagram of the direction;

[0084] Figure 18 In one embodiment Figure 16 The target y A slice diagram of the direction;

[0085] Figure 19 In one embodiment Figure 16 The target z A slice diagram of the direction;

[0086] Figure 20This is a structural block diagram of a three-dimensional imaging device based on multi-angle trajectories in one embodiment. Detailed Implementation

[0087] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0088] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of those features. In the description of this application, "multiple sets" means at least two sets, such as two sets, three sets, etc., unless otherwise explicitly specified.

[0089] In this application, unless otherwise expressly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection, an electrical connection, a physical connection, or a wireless communication connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two elements or the interaction between two elements, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0090] Furthermore, the technical solutions of the various embodiments of this application can be combined with each other, but only if they are based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this application.

[0091] This application provides a three-dimensional imaging method based on multi-angle trajectories, such as... Figure 1 The flowchart shown, in one embodiment, includes:

[0092] Step 101: Acquire a two-dimensional image of the radio device and use a back projection algorithm to obtain slant range-azimuth two-dimensional SAR images of the target under different viewpoints on the current trajectory.

[0093] Specifically, the slant range-azimuth 2D SAR images of the target at different viewpoints on the current trajectory include:

[0094]

[0095] In the formula, For wireless equipment a Slant range-azimuth 2D SAR image from the perspective of view. for a Complex scattering coefficients at the viewpoint The impulse response is in the slant range direction. For wireless equipment a Slant range coordinates from the viewpoint For target to wireless equipment a The slant range from the viewpoint (also the slant range position of target P). For the azimuth impulse response, For wireless equipment a Orientation coordinates from the viewpoint For wireless equipment a The target's orientation and location from the viewpoint. The imaginary unit, For wireless equipment wavelength;

[0096]

[0097] In the formula, For wireless equipment b Slant range-azimuth 2D SAR image from the perspective of view. for b Complex scattering coefficients at the viewpoint For wireless equipment b Slant range coordinates from the viewpoint For target to wireless equipment b Slant distance from the viewpoint For wireless equipment b Orientation coordinates from the viewpoint For wireless equipment b The target's orientation and location from the viewpoint.

[0098] In this step, such as Figure 2 As shown, I is the imaging plane, and W is the side length of the imaging plane. The angles between different wireless devices and the reference coordinate axes. For wireless equipment a The angle between the viewing angle and the oblique distance from the center of the imaging plane (which is also the angle of incidence for different viewing angles). For wireless equipment b The angle between the viewing angle and the oblique distance from the center of the imaging plane, the azimuth coordinates of the radio equipment. a This can be represented as a coordinate system in the figure. y .

[0099] Radio equipment can be radar.

[0100] As for how to obtain two-dimensional images of wireless devices and the back projection algorithm, these are existing technologies and will not be elaborated here.

[0101] Step 102: Based on the slant range of the imaging plane center from different perspectives, obtain the angle between the slant range of the radio equipment and the slant range of the imaging plane center; based on the angle, convert the slant range-azimuth 2D SAR image into an altitude-azimuth 2D SAR image.

[0102] Specifically:

[0103] Based on the slant distance of the imaging plane center from different viewpoints, the angle between the radio equipment and the slant distance of the imaging plane center is obtained:

[0104]

[0105]

[0106]

[0107]

[0108] In the formula, For the target's altitude position, For wireless equipment a The angle between the viewing angle and the oblique distance from the center of the imaging plane (which is also the angle of incidence for different viewing angles). For wireless equipment b The angle between the viewing angle and the oblique distance from the center of the imaging plane;

[0109] Based on the angle between the slant range of the radio equipment and the center of the imaging plane, the slant range-azimuth 2D SAR image is converted into a height-azimuth 2D SAR image:

[0110] When the target satisfies the far-field condition:

[0111]

[0112]

[0113] but:

[0114]

[0115] We can obtain:

[0116]

[0117]

[0118] In the formula, This represents the error between the target height and the estimated value when the target is not centered on the imaging plane. For wireless equipment a Two-dimensional SAR image with elevation and azimuth from the viewpoint. For height coordinates, For wireless equipment b Two-dimensional SAR image with elevation and azimuth from the viewpoint.

[0119] In this step, the target's current coordinate system is generally an oblique coordinate system.

[0120] Step 103: Obtain the angle between different radio devices and the reference coordinate axis, calculate the coordinate axis transformation matrix and translation matrix to convert the height-azimuth 2D SAR image in the original coordinate system into a height-azimuth 2D SAR image in the reference coordinate system, and use it as an echo.

[0121] Specifically:

[0122] Obtain the angles between different wireless devices and the reference coordinate axes, and calculate the coordinate axis transformation matrix based on the principle of basis transformation;

[0123] Obtain the geometric relationship between the coordinate axis transformation matrix and the translation matrix, and calculate the translation matrix by combining the coordinate axis transformation matrix and the relationship between the original coordinate system and the reference coordinate system;

[0124] Based on the coordinate axis transformation matrix and translation matrix, the 2D SAR image in the original coordinate system is transformed into a 2D SAR image in the reference coordinate system using the axis shifting formula, and the 2D SAR image in the reference coordinate system is used as the echo.

[0125] More specifically:

[0126] Obtain the angles between different wireless devices and the reference coordinate axes, and calculate the coordinate axis transformation matrix according to the basis transformation principle:

[0127]

[0128] In the formula, The coordinate axis transformation matrix. The angle between different wireless devices and the reference coordinate axis;

[0129] like Figure 3 As shown, the geometric relationship between the coordinate axis transformation matrix and the translation matrix is ​​obtained:

[0130]

[0131] Considering the relationship between the original coordinate system and the reference coordinate system (which is also the relationship between the base of the coordinate system and the base of the rectangular coordinate system):

[0132]

[0133] And by combining the coordinate axis transformation matrix, calculate the translation matrix:

[0134]

[0135] In the formula, The position of the image origin projected onto the reference coordinate system. This represents the position of the target in the original coordinate system. This represents the position of the target in the reference coordinate system. It is a translation matrix. Project the image origin onto the reference coordinate system The position of direction, The origin of the image is in the reference coordinate system The position of direction;

[0136] Based on the coordinate axis transformation matrix and translation matrix, the 2D SAR image in the original coordinate system is converted into a 2D SAR image in the reference coordinate system using the axis shift formula. The 2D SAR image in the reference coordinate system is then used as the echo.

[0137]

[0138]

[0139] In the formula, For wireless equipment a A two-dimensional SAR image with reference coordinate system height-azimuth orientation from the viewpoint. In order to be in Selecting the first height slice The total number of height-oriented slices is [number]. indivual, It is half the total number of slices in the height direction. For the first A height-oriented slice, For wireless equipment b Two-dimensional SAR image with reference coordinate system height-azimuth orientation from the viewpoint.

[0140] In this step, the original coordinate system is the oblique coordinate system, and the reference coordinate system is the rectangular coordinate system.

[0141] because The influence of the transformation from the oblique coordinate system to the reference coordinate system results in a translation. The new basis vectors are rotated or scaled relative to the old basis vectors. Therefore, in the reference coordinate system, a point that was originally located at the origin in the original coordinate system may no longer be located at the origin.

[0142] As for the basis transformation principle and axis shift formula, these are existing technologies and will not be elaborated here.

[0143] Step 104: Stack echoes from the same height at different viewpoints of the radio equipment to obtain slices at the corresponding heights; stack slices from different heights to obtain the three-dimensional information of the target under the current trajectory.

[0144] Specifically:

[0145] By stacking echoes from the same height at different viewpoints of the radio equipment, slices at the corresponding heights are obtained:

[0146]

[0147] In the formula, Slices at the corresponding height;

[0148] By stacking slices at different heights, the three-dimensional information of the target under the current trajectory can be obtained.

[0149] In this step, the projection theorem is used to reconstruct the target's two-dimensional coordinate information from different slices (a slice at the same height is a picture, which is the radio equipment). a Slicing of perspectives and b (Obtained by multiplying slices of viewpoint), and then by continuously stacking height-oriented slices, the height-oriented information of the target (i.e., the three-dimensional information of the target) is obtained, such as... Figure 4 and Figure 5 As shown, XOZ is a wireless device. b The projection plane of the viewpoint, YOZ is a wireless device. a The projection plane of the viewpoint, YOX is the radio device. ab The projection plane of the viewpoint.

[0150] Step 105: Project the three-dimensional information of the target under multiple trajectories onto the reference coordinate system to obtain a three-dimensional image of the target.

[0151] In this step, steps 101 to 104 are repeated for each trajectory to obtain the 3D information of the target under each trajectory. That is, each trajectory can be calculated using two perspectives to obtain a 3D image. Then, all the 3D information of the target under all trajectories is projected onto the reference coordinate system, and all the 3D information is multiplied to obtain the 3D image of the target under multiple perspectives (multiple angles). a , b , c This method can also be used, for example, with a , b 3D image and b , cMultiplying three-dimensional images, if the viewpoints are respectively a , b , c , d You can randomly select combinations, as long as all perspectives are used. For example, using... a , b 3D image and b , c 3D images and c , d (3D image multiplication).

[0152] The above-mentioned three-dimensional imaging method based on multi-angle trajectories has the following beneficial effects:

[0153] 1) It considers the importance of local area imaging, allowing users to flexibly select the size of the imaging area based on the error curve to adapt to different application scenarios and accuracy requirements; in addition, it adopts a distributed wireless equipment configuration, which is not limited by fixed geometry and can be arbitrarily configured according to actual needs, thus providing greater flexibility and adaptability; through the selection of local areas and the deployment of distributed wireless equipment, this method can significantly improve imaging speed and efficiency while ensuring imaging accuracy, which is particularly important for application scenarios that require rapid response, such as emergency rescue, environmental monitoring or traffic management, where fast and accurate 3D imaging capabilities can greatly improve decision-making efficiency and response speed.

[0154] 2) It can form an image with just two lines at any angle, unlike existing technologies that require at least a surface. This simplifies the imaging process and improves imaging speed while ensuring image quality. It enables rapid data processing and imaging, which not only reduces the demand for computing resources and lowers computing costs, but also makes the entire imaging process more efficient. It effectively solves the problems of low imaging speed and high cost in 3D imaging. It has great application value and broad application prospects in practical engineering, and is particularly suitable for application scenarios that require real-time or near-real-time feedback, such as the rapid deployment and dynamic monitoring of UAV swarms.

[0155] 3) The 3D imaging method of this application is particularly suitable for UAV swarms. The configuration of the UAV swarm can be arbitrarily and flexibly configured according to mission requirements. Whether it is a linear, grid-like, or arbitrary-shaped flight formation, it can effectively collect 3D data. This arbitrariness of configuration provides great flexibility for the deployment of UAV swarms, enabling them to adapt to various complex terrains and environmental conditions, while improving the coverage and efficiency of data acquisition.

[0156] It should be understood that, although Figure 1The steps in the flowchart are shown sequentially as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order in which these steps are executed, and they can be performed in other orders. Figure 1 At least some of the steps in the process may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.

[0157] In one specific embodiment, a simulation experiment was conducted, and the simulation parameters used are shown in Table 1.

[0158] Table 1: Simulation Parameters

[0159]

[0160] Wireless equipment a , b The slant range-azimuth 2D SAR image obtained from the viewpoint is represented as follows: Figure 6 , Figure 7 As shown. You can see that, b From this perspective, the target's azimuth position is not at 300 meters, because... a , b The angle between them is not 90°, so the target is... b The upward projection is:

[0161]

[0162] in, , The values ​​are 300 meters and 0 meters respectively. Substituting these values ​​into the calculation, the azimuth of direction b is 259.8076 meters, which is basically consistent with the result.

[0163] Using wireless equipment a , b The angular relationship between the slant distance and the height obtained from the viewpoint , Obtain wireless equipment a , b The height-azimuth 2D SAR image obtained from the viewpoint, such as Figure 8 , Figure 9 As shown, the target altitude is approximately 10,800 meters, which is basically consistent with the actual location.

[0164] Figure 10 Showcasing wireless equipment a ,b The same height slices are obtained by basis transformation and translation transformation. x - y The directional 2D SAR image shows that after basis transformation and axis shifting, the target coordinates are basically consistent with the true position, verifying the effectiveness of the above transformation matrix and translation matrix.

[0165] Figure 11 and Figure 12 The three-dimensional imaging result of the target is shown below. A slice analysis is performed on the three-dimensional imaging of the target, and the theoretical resolution of the target in each direction is calculated as follows:

[0166] The theoretical resolution of the direction is:

[0167]

[0168] The theoretical resolution of the direction is:

[0169]

[0170] The theoretical resolution of the direction is:

[0171]

[0172] Actual resolution as Figure 13 , Figure 14 , Figure 15 The slice image shows that the resolution is basically consistent with the theoretical resolution, verifying the effectiveness of the method.

[0173] Introduction of wireless equipment c To verify the improvement in imaging quality caused by multiple wireless devices and multiple angles, the target 3D result image is shown below. Figure 16 As shown, it can be seen that due to wireless equipment a , b , c The gain is much greater than that of radio equipment. a , b , Figure 12 and Figure 16 At the same -25dB level, Figure 16 The side lobes were severely suppressed. A slice analysis of the above results was performed, as follows: Figure 17 , Figure 18 , Figure 19 The slice images all have better image quality metrics than Figure 12 .

[0174] This application also provides a three-dimensional imaging device based on multi-angle trajectories, such as... Figure 20As shown, in one embodiment, it includes: an acquisition module 2002, a conversion module 2004, an echo module 2006, a stacking module 2008, and a projection module 2010, wherein:

[0175] The acquisition module 2002 is used to acquire two-dimensional images of the wireless device and use a back projection algorithm to obtain slant range-azimuth two-dimensional SAR images of the target under different viewpoints on the current trajectory.

[0176] The conversion module 2004 is used to obtain the angle between the slant distance of the radio equipment and the center slant distance of the imaging plane based on the slant distance of the imaging plane center from different viewpoints; and to convert the slant range-azimuth two-dimensional SAR image into an altitude-azimuth two-dimensional SAR image based on the angle.

[0177] The echo module 2006 is used to obtain the angle between different radio devices and the reference coordinate axis, calculate the coordinate axis transformation matrix and translation matrix, so as to convert the height-azimuth 2D SAR image in the original coordinate system into a height-azimuth 2D SAR image in the reference coordinate system, and use it as an echo.

[0178] Stacking module 2008 is used to stack echoes from the same height at different viewpoints of the radio equipment to obtain slices at the corresponding height; and to stack slices at different heights to obtain the three-dimensional information of the target under the current trajectory.

[0179] The projection module 2010 is used to project the three-dimensional information of targets under multiple trajectories onto a reference coordinate system to obtain a three-dimensional image of the target.

[0180] For specific limitations regarding a 3D imaging device based on multi-angle trajectories, please refer to the limitations of a 3D imaging method based on multi-angle trajectories mentioned above, which will not be repeated here. Each module in the above device can be implemented entirely or partially through software, hardware, or a combination thereof. These modules can be embedded in hardware or independently of the processor in a computer device, or stored in software in the memory of a computer device, so that the processor can call and execute the operations corresponding to each module.

[0181] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0182] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0183] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A three-dimensional imaging method based on multi-angle trajectories, characterized in that, include: Two-dimensional images of the wireless equipment are acquired, and a back projection algorithm is used to obtain slant range-azimuth two-dimensional SAR images of the target under different viewpoints on the current trajectory. Based on the slant distance of the imaging plane center from different viewpoints, the angle between the wireless equipment and the slant distance of the imaging plane center is obtained; based on the angle, the slant range-azimuth 2D SAR image is converted into an altitude-azimuth 2D SAR image. Obtain the angles between different radio devices and the reference coordinate axes, calculate the coordinate axis transformation matrix and translation matrix, so as to convert the height-azimuth 2D SAR image in the original coordinate system into a height-azimuth 2D SAR image in the reference coordinate system, and use it as an echo. Echoes from the same height at different viewpoints of the radio equipment are stacked to obtain slices at the corresponding heights; slices from different heights are stacked to obtain the three-dimensional information of the target under the current trajectory. The three-dimensional information of the target under multiple trajectories is projected onto the reference coordinate system to obtain a three-dimensional image of the target; Based on the included angle, the slant range-azimuth 2D SAR image is converted into an altitude-azimuth 2D SAR image, including: When the target satisfies the far-field condition: but: We can obtain: In the formula, This represents the error between the target height and the estimated value when the target is not centered on the imaging plane. For wireless equipment Two-dimensional SAR image with elevation and azimuth from the viewpoint. For height coordinates, For wireless equipment Two-dimensional SAR image with elevation and azimuth from the viewpoint. For the target's altitude position, For wireless equipment The target's orientation and location from the viewpoint. For target to wireless equipment Slant distance from the viewpoint For wireless equipment The angle between the viewing angle and the oblique distance from the center of the imaging plane. For target to wireless equipment Slant distance from the viewpoint For wireless equipment The angle between the viewing angle and the oblique distance from the center of the imaging plane. for Complex scattering coefficients at the viewpoint The impulse response is in the slant range direction. The impulse response is in the azimuth direction. For wireless equipment Orientation coordinates from the viewpoint The imaginary unit, For wireless equipment wavelengths, for Complex scattering coefficients at the viewpoint For wireless equipment Orientation coordinates from the viewpoint For wireless equipment The target's orientation and location from the viewpoint; Echoes from the same height at different viewpoints of the radio equipment are stacked to obtain slices at the corresponding heights, including: In the formula, For slices at the corresponding height, For the first A height-oriented slice.

2. The three-dimensional imaging method based on multi-angle trajectories according to claim 1, characterized in that, Two-dimensional SAR images of the target from different viewpoints on the current trajectory, including: In the formula, For wireless equipment Slant range-azimuth 2D SAR image from the perspective of view. for Complex scattering coefficients at the viewpoint The impulse response is in the slant range direction. For wireless equipment Slant range coordinates from the viewpoint For target to wireless equipment Slant distance from the viewpoint The impulse response is in the azimuth direction. For wireless equipment Orientation coordinates from the viewpoint For wireless equipment The target's orientation and location from the viewpoint. The imaginary unit, For wireless equipment wavelength; In the formula, For wireless equipment Slant range-azimuth 2D SAR image from the perspective of view. for Complex scattering coefficients at the viewpoint For wireless equipment Slant range coordinates from the viewpoint For target to wireless equipment Slant distance from the viewpoint For wireless equipment Orientation coordinates from the viewpoint For wireless equipment The target's orientation and location from the viewpoint.

3. The three-dimensional imaging method based on multi-angle trajectories according to claim 2, characterized in that, Based on the slant distance of the imaging plane center from different viewpoints, the angle between the radio equipment and the slant distance of the imaging plane center is obtained, including: In the formula, For the target's altitude position, For wireless equipment The angle between the viewing angle and the oblique distance from the center of the imaging plane. For wireless equipment The angle between the viewing angle and the oblique distance from the center of the imaging plane.

4. A three-dimensional imaging method based on multi-angle trajectories according to any one of claims 1 to 3, characterized in that, The angles between different radio devices and the reference coordinate axes are obtained, and the coordinate axis transformation matrix and translation matrix are calculated to convert the original coordinate system's height-azimuth 2D SAR image into the reference coordinate system's height-azimuth 2D SAR image, which is then used as the echo, including: Obtain the angles between different wireless devices and the reference coordinate axes, and calculate the coordinate axis transformation matrix based on the principle of basis transformation; Obtain the geometric relationship between the coordinate axis transformation matrix and the translation matrix, and calculate the translation matrix by combining the coordinate axis transformation matrix and the relationship between the original coordinate system and the reference coordinate system; Based on the coordinate axis transformation matrix and translation matrix, the 2D SAR image in the original coordinate system is transformed into a 2D SAR image in the reference coordinate system using the axis shifting formula, and the 2D SAR image in the reference coordinate system is used as the echo.

5. The three-dimensional imaging method based on multi-angle trajectory according to claim 4, characterized in that, Obtain the angles between different wireless devices and the reference coordinate axes, and calculate the coordinate axis transformation matrix according to the basis transformation principle, including: In the formula, The coordinate axis transformation matrix. This represents the angle between different wireless devices and the reference coordinate axis.

6. The three-dimensional imaging method based on multi-angle trajectories according to claim 5, characterized in that, Obtain the geometric relationship between the coordinate axis transformation matrix and the translation matrix, and calculate the translation matrix by combining the coordinate axis transformation matrix and the relationship between the original coordinate system and the reference coordinate system, including: In the formula, The position of the image origin projected onto the reference coordinate system. This represents the position of the target in the original coordinate system. This represents the position of the target in the reference coordinate system. It is a translation matrix. Project the image origin onto the reference coordinate system The position of direction, The origin of the image is in the reference coordinate system The location of the direction.

7. A three-dimensional imaging method based on multi-angle trajectories according to any one of claims 1 to 3, characterized in that, Two-dimensional SAR images in the reference coordinate system, including height-azimuth orientation, include: In the formula, For wireless equipment A two-dimensional SAR image with reference coordinate system height-azimuth from the viewpoint. In order to be in Selecting the first height slice indivual, It is half the total number of slices in the height direction. For the first A height-oriented slice, For wireless equipment Two-dimensional SAR image with reference coordinate system height-azimuth orientation from the viewpoint.

8. A three-dimensional imaging device based on multi-angle trajectories, characterized in that, A three-dimensional imaging method based on multi-angle trajectory as described in any one of claims 1 to 7, comprising: The acquisition module is used to acquire two-dimensional images of the wireless device and use a back projection algorithm to obtain slant range-azimuth two-dimensional SAR images of the target under different viewpoints on the current trajectory. The conversion module is used to obtain the angle between the slant range of the imaging plane center and the wireless equipment and the slant range of the imaging plane center based on the slant range of the imaging plane center from different perspectives; and to convert the slant range-azimuth 2D SAR image into an altitude-azimuth 2D SAR image based on the angle. The echo module is used to obtain the angle between different radio devices and the reference coordinate axis, calculate the coordinate axis transformation matrix and translation matrix, so as to convert the height-azimuth 2D SAR image in the original coordinate system into a height-azimuth 2D SAR image in the reference coordinate system, and use it as an echo. The stacking module is used to stack echoes from the same height at different viewpoints of the radio equipment to obtain slices at the corresponding height; and to stack slices from different heights to obtain the three-dimensional information of the target under the current trajectory. The projection module is used to project the three-dimensional information of targets under multiple trajectories onto a reference coordinate system to obtain a three-dimensional image of the target.

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