Circular synthetic aperture radar imaging method, system, device, medium and terminal

Abstract

The present invention belongs to the field of radar signal processing technology, and discloses a circular synthetic aperture radar imaging method and system, equipment, medium and terminal, which performs aperture segmentation on complete CSAR data, and uses a fast algorithm to image sub-aperture data respectively in combination with the data to obtain sub-images; local images located in different elevation planes in the sub-aperture images are used as references for registration to obtain a group of CSAR images with different depths of field; the obtained images with different depths of field are multi-focus fused to obtain a fully focused image. The present invention draws on the principle of multi-focus fusion imaging of optical images, is suitable for CSAR imaging in terrain undulating areas, reduces local area defocusing caused by elevation errors in CSAR two-dimensional imaging, is easy to use, performs imaging processing only once, obtains multiple CSAR images with different focus depths, reduces the amount of algorithm calculation, solves the image focusing problem without external elevation auxiliary data, and obtains high-quality CSAR two-dimensional imaging results.

Description

Technical Field

[0001] The present invention belongs to the technical field of radar signal processing, and in particular relates to a circular synthetic aperture radar imaging method and system, equipment, medium and terminal. Background Art

[0002] At present, Synthetic Aperture Radar (SAR) imaging is an important high-resolution earth observation technology. Due to its characteristics of working around the clock and in all weather conditions, it has been rapidly developed and widely concerned in recent years. In order to meet the growing military and civilian needs, SAR technology has evolved in multiple directions. Circular SAR (CSAR) technology is the main representative of the evolution of radar synthetic aperture manifolds. Aperture manifold refers to the trajectory shape formed by the radar transceiver channel during the imaging process. Compared with the linear aperture manifold represented by the traditional linear trajectory SAR, CSAR imaging forms a 360° circular aperture manifold around the observation scene, which can obtain the omnidirectional scattering characteristics of the observed target. In addition, the increase in the observation angle (azimuth accumulation angle) broadens the target azimuth spectrum, so that CSAR can theoretically obtain image resolution far superior to LSAR.

[0003] Terrain undulation has an impact on SAR imaging, especially high-frequency and high-precision CSAR imaging, which cannot be ignored. At present, domestic and foreign researchers mainly rely on the Digital Elevation Model (DEM) data of the observation area obtained by other means to reduce the impact of terrain undulation. In addition, judging from the results of airborne CSAR imaging experiments and measured data processing that have been made public at home and abroad, most of the selected experimental observation scenes are flat areas with small changes in terrain undulation, which reduces the impact of terrain undulation on CSAR imaging to a certain extent. However, the algorithms studied based on these data have limitations in observation areas with severe terrain undulation. Therefore, in order to expand the practical scope of CSAR, it is necessary to study effective methods to solve the CSAR imaging problem in areas with high terrain undulation.

[0004] Through the above analysis, the problems and defects of the existing technology are as follows: In the existing technology, the algorithm studied based on the digital terrain elevation data of the observation area has limitations in the observation area with drastic terrain fluctuations.

[0005] The difficulty of solving the above problems and defects is: without the assistance of digital elevation data, the existing CSAR imaging technology mainly adopts the method of estimating the terrain elevation of the observation scene to reduce the impact of terrain fluctuation errors. However, the elevation estimation based on the CSAR system not only brings a lot of additional calculations, but also has limited estimation accuracy and can only reduce the impact of fluctuations to a limited extent.

[0006] Solving the above problems can solve the CSAR imaging problem in areas with high terrain relief and expand the practical scope of CSAR. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a circular synthetic aperture radar imaging method and system, equipment, medium and terminal, and more particularly, relates to a circular synthetic aperture radar imaging method and system, equipment, medium and terminal based on multi-layer focusing.

[0008] The present invention is implemented as follows: a circular synthetic aperture radar imaging method, the circular synthetic aperture radar imaging method comprising:

[0009] The complete CSAR data is segmented by aperture, and the sub-aperture data is imaged separately using a fast algorithm in combination with the data to obtain sub-images; local images located in different elevation planes in the sub-aperture images are used as references for alignment to obtain a set of CSAR images with different depths of field; finally, the images with different depths of field are multi-focus fused to obtain a fully focused image.

[0010] Furthermore, the circular synthetic aperture radar imaging method comprises the following steps:

[0011] Step 1: divide the sub-aperture data according to CSAR system parameters, imaging geometry and image resolution;

[0012] Step 2, using a high-resolution fast imaging algorithm to perform sub-aperture imaging on the sub-aperture data;

[0013] Step 3: The sub-aperture images are directly accumulated to obtain the original CSAR image, and the "focus" area is selected;

[0014] Step 4: perform registration according to the selected focus area to obtain CSAR images with multiple “focus depths”;

[0015] Step 5: Fusion process multiple “focus depth” CSAR images to obtain the final imaging result.

[0016] Furthermore, in the step 1, according to the CSAR system parameters, imaging geometry and required image resolution, the complete circular aperture data is equally divided into N sub-aperture data according to the observation azimuth angle.

[0017] Furthermore, in step 2, a high-resolution fast imaging algorithm is used to perform imaging processing on the sub-aperture data to obtain corresponding N sub-images.

[0018] Furthermore, in the step three, the sub-images are directly accumulated to obtain a CSAR imaging result with a reference plane as the depth of field, and M unfocused local areas in the image are selected as the focus.

[0019] Furthermore, in the step 4, the selected local area "focus" is used as an image matching reference to perform sub-image registration and fusion processing to obtain CSAR imaging results of M different "focus depths".

[0020] In the step 5, CSAR images with different “focusing depths” are fused to obtain a fully focused imaging result.

[0021] Another object of the present invention is to provide a circular synthetic aperture radar imaging system using the circular synthetic aperture radar imaging method, the circular synthetic aperture radar imaging system comprising:

[0022] The circular aperture data division module is used to divide the complete circular aperture data into N sub-aperture data according to the observation azimuth angle according to the CSAR system parameters, imaging geometry and required image resolution;

[0023] An aperture data imaging processing module is used to perform imaging processing on the sub-aperture data using a high-resolution fast imaging algorithm to obtain corresponding N sub-images;

[0024] A sub-image accumulation module is used to directly accumulate sub-images to obtain CSAR imaging results with a reference plane as the depth of field, and select M unfocused local areas in the image as the focus;

[0025] The registration and fusion processing module is used to perform registration and fusion processing of sub-images using the selected local area "focus" as an image matching reference to obtain CSAR imaging results of M different "focus depths";

[0026] The full-focus imaging result acquisition module is used to fuse CSAR images of different "focus depths" to obtain full-focus imaging results.

[0027] Another object of the present invention is to provide a computer device, the computer device comprising a memory and a processor, the memory storing a computer program, and when the computer program is executed by the processor, the processor performs the following steps:

[0028] According to the CSAR system parameters, imaging geometry and required image resolution, the complete circular aperture data is divided into N sub-aperture data according to the observation azimuth; the sub-aperture data is imaged and processed using a high-resolution fast imaging algorithm to obtain the corresponding N sub-images; the sub-images are directly accumulated to obtain the CSAR imaging results with the reference plane as the depth of field, and M unfocused local areas in the image are selected as the focus;

[0029] The selected local area "focus" is used as the image matching reference to perform sub-image registration and fusion processing to obtain CSAR imaging results with M different "focus depths". The CSAR images with different "focus depths" are fused to obtain the full-focus imaging result.

[0030] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the following steps:

[0031] According to the CSAR system parameters, imaging geometry and required image resolution, the complete circular aperture data is divided into N sub-aperture data according to the observation azimuth; the sub-aperture data is imaged and processed using a high-resolution fast imaging algorithm to obtain the corresponding N sub-images; the sub-images are directly accumulated to obtain the CSAR imaging results with the reference plane as the depth of field, and M unfocused local areas in the image are selected as the focus;

[0032] The selected local area "focus" is used as the image matching reference to perform sub-image registration and fusion processing to obtain CSAR imaging results with M different "focus depths". The CSAR images with different "focus depths" are fused to obtain the full-focus imaging result.

[0033] Another object of the present invention is to provide an information data processing terminal, which is used to implement the circular synthetic aperture radar imaging system.

[0034] Combining all the above technical solutions, the advantages and positive effects of the present invention are as follows: the circular synthetic aperture radar imaging method provided by the present invention is suitable for CSAR imaging in terrain undulating areas. It draws on the principle of multi-focus fusion imaging of optical images, uses the local plane as the "focus", obtains a group of images with different "focus depths" by aligning the sub-images, and then obtains a fully focused image by fusing this group of images, thereby solving the image focusing problem without external elevation auxiliary data and obtaining high-quality CSAR two-dimensional imaging results. The present invention not only reduces the local area defocusing caused by elevation errors in CSAR two-dimensional imaging, but is also easy to use. It only performs imaging processing once, obtains multiple CSAR images with different focus depths, and reduces the amount of calculation of the algorithm. At the same time, the method of the present invention has been verified by measured radar echo data, and the experimental results prove the effectiveness of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0036] Figure 1 It is a flow chart of a circular synthetic aperture radar imaging method provided by an embodiment of the present invention.

[0037] Figure 2 It is a schematic diagram of a circular synthetic aperture radar imaging method provided by an embodiment of the present invention.

[0038] Figure 3 It is a structural block diagram of a circular synthetic aperture radar imaging system provided by an embodiment of the present invention.

[0039] Figure 4a 4b is a CSAR image of different focus depths provided by an embodiment of the present invention.

[0040] Figure 5 It is a schematic diagram of the CSAR image result obtained after fusion of the proposed algorithm provided in an embodiment of the present invention.

[0041] In the figure: 1. Circular aperture data division module; 2. Aperture data imaging processing module; 3. Sub-image accumulation module; 4. Registration and fusion processing module; 5. Full focus imaging result acquisition module. DETAILED DESCRIPTION

[0042] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] In view of the problems existing in the prior art, the present invention provides a circular synthetic aperture radar imaging method and system, equipment, medium and terminal. The present invention is described in detail below with reference to the accompanying drawings.

[0044] like Figure 1 As shown, the circular synthetic aperture radar imaging method provided by the embodiment of the present invention comprises the following steps:

[0045] S101, dividing sub-aperture data according to CSAR system parameters, imaging geometry and image resolution;

[0046] S102, performing sub-aperture imaging on the sub-aperture data using a high-resolution fast imaging algorithm;

[0047] S103, directly accumulating the sub-aperture images to obtain the original CSAR image, and selecting the "focus" area;

[0048] S104, performing registration according to the selected focus area to obtain a CSAR image with multiple “focus depths”;

[0049] S105, performing fusion processing on multiple “focus depth” CSAR images to obtain a final imaging result.

[0050] The principle diagram of the circular synthetic aperture radar imaging method provided by the embodiment of the present invention is as follows: Figure 2 shown.

[0051] like Figure 3 As shown, the circular synthetic aperture radar imaging system provided by the embodiment of the present invention includes:

[0052] The circular aperture data division module 1 is used to divide the complete circular aperture data into N sub-aperture data according to the observation azimuth angle according to the CSAR system parameters, imaging geometry and required image resolution;

[0053] Aperture data imaging processing module 2, used to perform imaging processing on sub-aperture data using a high-resolution fast imaging algorithm to obtain corresponding N sub-images;

[0054] The sub-image accumulation module 3 is used to directly accumulate the sub-images to obtain the CSAR imaging results with the reference plane as the depth of field, and select M unfocused local areas in the image as the focus;

[0055] The registration and fusion processing module 4 is used to perform registration and fusion processing of sub-images using the selected local area "focus" as an image matching reference to obtain CSAR imaging results of M different "focus depths";

[0056] The full-focus imaging result acquisition module 5 is used to perform fusion processing on CSAR images with different “focus depths” to obtain the full-focus imaging result.

[0057] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0058] Example 1

[0059] The present invention proposes a CSAR imaging method suitable for terrain undulating areas. By drawing on the principle of multi-focus fusion imaging of optical images, the local plane is used as the "focus", and a group of images with different "focus depths" are obtained by aligning sub-images. Then, a fully focused image is obtained by fusing this group of images, thereby solving the image focusing problem without external elevation auxiliary data and obtaining high-quality CSAR two-dimensional imaging results.

[0060] The basic idea of ​​the present invention is: first, perform aperture segmentation on the complete CSAR data, and use a fast algorithm to image the sub-aperture data separately in combination with the data to obtain sub-images; then, perform registration with reference to the local images located in different elevation planes in the sub-aperture images to obtain a group of CSAR images with different depths of field; finally, perform multi-focus fusion on the images with different depths of field to obtain a fully focused image.

[0061] The circular synthetic aperture radar imaging method based on multi-layer focusing proposed in the present invention comprises the following processing steps:

[0062] In the first step, according to the CSAR system parameters, imaging geometry and required image resolution, the complete circular aperture data is divided into N sub-aperture data according to the observation azimuth;

[0063] The second step is to use a high-resolution fast imaging algorithm to process the sub-aperture data and obtain the corresponding N sub-images;

[0064] The third step is to directly accumulate the sub-images to obtain the CSAR imaging results with the reference plane as the depth of field, and select M unfocused local areas in the image as the focus;

[0065] The fourth step is to use the selected local area "focus" as the image matching reference to perform sub-image registration and fusion processing to obtain CSAR imaging results of M different "focus depths";

[0066] The fifth step is to fuse the CSAR images with different “focusing depths” to obtain the full-focus imaging results.

[0067] The present invention provides a method for two-dimensional high-resolution circular synthetic aperture radar imaging without the assistance of digital elevation data. The method not only reduces the local area defocusing caused by elevation error in CSAR two-dimensional imaging, but is also easy to use. Only one imaging process is performed to obtain multiple CSAR images with different focusing depths, thereby reducing the calculation amount of the algorithm.

[0068] Example 2

[0069] Figure 2 The method for suppressing radio frequency interference signals based on adaptive alternating sparse reconstruction provided by an embodiment of the present invention comprises the following steps:

[0070] The first step is to divide the sub-aperture data according to the CSAR system parameters, imaging geometry and required image resolution; the second step is to use a high-resolution fast imaging algorithm to perform sub-aperture imaging on the sub-aperture data; the third step is to directly accumulate the sub-aperture images to obtain the original CSAR image, and select the "focal" area; the fourth step is to align the selected focal area to obtain CSAR images with multiple "focus depths"; the fifth step is to fuse the CSAR images with multiple "focus depths" to obtain the final imaging result.

[0071] The method of the present invention is verified by measuring radar echo data, and the experimental results prove the effectiveness of the present invention.

[0072] Figure 4 is a schematic diagram of the working mode of the test radar system. The results of image matching processing of the L-band CSAR sub-aperture image of a certain town area with local planes of different heights as the focus center. Figure 4(a) is the matching result obtained with area A as the "focus" plane, and Figure 4(b) is the matching result obtained with area B as the "focus" plane. By observing the two images, it can be found that the upper and lower images are well focused in the area near their respective "focus" planes, while the areas with a large height difference from the "focus" plane are severely defocused.

[0073] Figure 5 This is a CSAR image obtained after multi-layer focus fusion using the proposed method. It can be seen that in the defocused area of ​​the original image, after fusion, effective focus is obtained, and the local area defocus problem caused by inconsistent image terrain undulation is effectively corrected, indicating that the method of the present invention has a good inhibitory effect on the defocus caused by imaging terrain undulation without elevation data.

[0074] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When the use is implemented in whole or in part in the form of a computer program product, the computer program product includes one or more computer instructions. When the computer program instructions are loaded or executed on a computer, the process or function described in the embodiment of the present invention is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium, or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from one website site, computer, server or data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL) or wireless (e.g., infrared, wireless, microwave, etc.) mode) to another website site, computer, server or data center. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid-state hard disk Solid State Disk (SSD)), etc.

[0075] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. A circular synthetic aperture radar imaging method, characterized in that: The circular synthetic aperture radar imaging method comprises: performing aperture segmentation on complete CSAR data, imaging sub-aperture data respectively using a fast algorithm in combination with the data to obtain sub-images; performing registration with reference to local images located at different elevation planes in the sub-aperture images to obtain a group of CSAR images with different depths of field; and finally performing multi-focus fusion on the obtained images with different depths of field to obtain a fully focused image; The circular synthetic aperture radar imaging method comprises the following steps: Step 1: divide the sub-aperture data according to CSAR system parameters, imaging geometry and image resolution; Step 2, using a high-resolution fast imaging algorithm to perform sub-aperture imaging on the sub-aperture data; Step 3: The sub-aperture images are directly accumulated to obtain the original CSAR image, and the focus area is selected; Step 4: perform registration according to the selected focus area to obtain a multi-focus depth CSAR image; Step 5: Fusion process the multi-focus depth CSAR images to obtain the final imaging results.

2. The circular synthetic aperture radar imaging method according to claim 1, characterized in that: In the step 1, according to the CSAR system parameters, imaging geometry and required image resolution, the complete circular aperture data is equally divided into N sub-aperture data according to the observation azimuth angle.

3. The circular synthetic aperture radar imaging method according to claim 1, characterized in that: In the step 2, a high-resolution fast imaging algorithm is used to perform imaging processing on the sub-aperture data to obtain corresponding N sub-images.

4. The circular synthetic aperture radar imaging method according to claim 1, characterized in that: In the step three, the sub-images are directly accumulated to obtain a CSAR imaging result with a reference plane as the depth of field, and M unfocused local areas in the image are selected as the focus.

5. The circular synthetic aperture radar imaging method according to claim 1, characterized in that: In the step 4, the selected local area focus is used as an image matching reference to perform sub-image registration and fusion processing to obtain CSAR imaging results of M different focus depths; In the step 5, the CSAR images with different focus depths are fused to obtain a full focus imaging result.

6. A circular synthetic aperture radar imaging system for implementing the circular synthetic aperture radar imaging method according to any one of claims 1 to 5, characterized in that: The circular synthetic aperture radar imaging system comprises: The circular aperture data division module is used to divide the complete circular aperture data into N sub-aperture data according to the observation azimuth angle according to the CSAR system parameters, imaging geometry and required image resolution; An aperture data imaging processing module is used to perform imaging processing on the sub-aperture data using a high-resolution fast imaging algorithm to obtain corresponding N sub-images; A sub-image accumulation module is used to directly accumulate sub-images to obtain CSAR imaging results with a reference plane as the depth of field, and select M unfocused local areas in the image as the focus; A registration and fusion processing module is used to perform registration and fusion processing of sub-images using the selected local area focus as an image matching reference to obtain CSAR imaging results of M different focus depths; The full-focus imaging result acquisition module is used to fuse CSAR images of different focus depths to obtain full-focus imaging results.

7. A computer device, characterized in that: The computer device includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor performs the following steps: According to the CSAR system parameters, imaging geometry and required image resolution, the complete circular aperture data is divided into N sub-aperture data according to the observation azimuth; the sub-aperture data is imaged and processed using a high-resolution fast imaging algorithm to obtain the corresponding N sub-images; the sub-images are directly accumulated to obtain the CSAR imaging results with the reference plane as the depth of field, and M unfocused local areas in the image are selected as the focus; The selected local area focus is used as the image matching reference to perform sub-image registration and fusion processing to obtain CSAR imaging results with M different focus depths; the CSAR images with different focus depths are fused to obtain the full focus imaging result.

8. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the following steps: According to the CSAR system parameters, imaging geometry and required image resolution, the complete circular aperture data is divided into N sub-aperture data according to the observation azimuth; the sub-aperture data is imaged and processed using a high-resolution fast imaging algorithm to obtain the corresponding N sub-images; the sub-images are directly accumulated to obtain the CSAR imaging results with the reference plane as the depth of field, and M unfocused local areas in the image are selected as the focus; The selected local area focus is used as the image matching reference to perform sub-image registration and fusion processing to obtain CSAR imaging results with M different focus depths; the CSAR images with different focus depths are fused to obtain the full focus imaging result.

9. An information data processing terminal, characterized in that: The information data processing terminal is used to implement the circular synthetic aperture radar imaging system as described in claim 6.

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