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SAR (Synthetic Aperture Radar) image speckle reduction method based on sparse representation

A technology of coherent speckle suppression and sparse representation, applied in the field of image processing, it can solve the problems of loss of image details, blurred edges, serious problems, etc., and achieve the effect of noise suppression and integrity assurance.

Active Publication Date: 2013-06-26
XIDIAN UNIV
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Problems solved by technology

S.Foucher made a preliminary attempt to suppress SAR coherent speckle by using sparse redundant representation. He reconstructed the logarithmically transformed image by modifying the objective function, but the details of the processed image were seriously lost, and certain edges appeared. Vague

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  • SAR (Synthetic Aperture Radar) image speckle reduction method based on sparse representation
  • SAR (Synthetic Aperture Radar) image speckle reduction method based on sparse representation
  • SAR (Synthetic Aperture Radar) image speckle reduction method based on sparse representation

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Embodiment Construction

[0033] refer to figure 1 , the specific implementation process of the present invention is as follows:

[0034] Step 1. Input the SAR image Y to be subjected to speckle suppression, and perform logarithmic operation on it to obtain the logarithmically transformed image Y′.

[0035] Step 2. Split the log-transformed image Y′ into overlapping blocks.

[0036] Select the size of n as 64, that is, divide the image into overlapping blocks with a size of 8×8, take each pixel in the image as the starting point to extract image blocks with a size of 8×8 to the right and downward, and use The coordinates of the starting pixel point to mark the position of the block in the original image. The size of the SAR image used in the experiment is 256×256, then the number of segmented image blocks is (256-7)×(256-7)=249 2 = 62001 pieces.

[0037] Step 3. Sparse coding is performed on each segmented overlapping block, and the pixel information of the image block is introduced as a control ...

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Abstract

The invention discloses an SAR (Synthetic Aperture Radar) image speckle reduction method based on sparse representation, which mainly solves the problems of incomplete detail information and unsmooth homogeneous regions for SAR image speckle reduction in the prior art. The method comprises the following steps of: carrying out logarithmic transformation on an original SAR image Y; carrying out overlapping blocking on an image Y' subjected to logarithmic transformation; taking the own information of the image blocks as control factors and carrying out sparse representation on the control factors; carrying out dictionary learning by adopting an approximate KSVD (K Singular Value Decomposition) algorithm to obtain a self-adaptive dictionary and updated sparse representation coefficients; obtaining an image W by adopting the self-adaptive dictionary and the updated sparse representation coefficients, and carrying out exponential transformation on the image W to obtain an image R; and carrying out nonlinear anisotropic diffusion on a difference image V obtained from the original SAR image Y and the image R subjected to the exponential transformation, thereby obtaining a final speckle-reduced image. The method disclosed by the invention has the advantages that the homogeneous regions of speckle reduction results are smooth, point targets are clear and visible, and edge information iskept complete and the like, besides, the method is suitable for a preprocessing process of SAR image understanding.

Description

technical field [0001] The invention belongs to the technical field of image processing, and relates to a method for suppressing coherent speckles of SAR images, which can be used for scene analysis and image understanding preprocessing of SAR images. Background technique [0002] Synthetic Aperture Radar (SAR) has been widely used in military and civilian fields due to its advantages of all-weather, all-time imaging and strong penetration. In the imaging process of SAR, due to the influence of the fading effect produced by the coherence of electromagnetic waves, speckle noise randomly distributed in the image, that is, coherent speckle. The existence of coherence speckle seriously affects the understanding and automatic interpretation of images, and reduces the effectiveness of image segmentation and target recognition and extraction. Therefore speckle suppression for SAR images is a necessary prerequisite for other operations. [0003] One of the main methods of speckle ...

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G06T5/00G06T5/50G06T7/00
Inventor 侯彪焦李成蒋继光王爽刘芳尚荣华
Owner XIDIAN UNIV
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