Image Denoising for Phased Array Total Focusing Based on Wavelet Transform
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摘要: 针对相控阵全聚焦技术的成像背景噪声问题，提出了一种基于小波变换的相控阵全聚焦图像去噪声方法。利用离散小波变换将全聚焦图像信号分解到小波域，变换后的高频子带系数采取无偏似然估计的自适应阈值处理。对处理完的高、低频子带系数进行小波逆变换，重构全聚焦图像。试验结果表明，该方法能有效去除全聚焦图像的背景噪声，保留被检工件内部的真实缺陷信号。Abstract: In order to solve the problem of the imaging background noise of the phased array total focusing method, this paper presents a method to eliminate the noise of phased array total focusing method image based on wavelet transform. The focusing image signal is decomposed into wavelet domain by the discrete wavelet transform, and the high frequency sub band transformed coefficients is subjected with adaptive threshold processing based on unbiased risk estimation. Inverse wavelet transform is then implemented on the processed high and low frequency sub band coefficients, and hence total focusing method image is reconstructed. The experimental results show that the proposed method can effectively remove the background noise of the total focusing method image, and retain the real defect signal inside the inspected workpiece.
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Keywords:
- total focusing method /
- denoising /
- wavelet transform /
- subband coefficient /
- adaptive threshold
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[1] LINES D, WHARRIE J, HOTTENROTH J, et al. Real-time ultrasonic array imaging using full matrix capture and the total focusing method[C]//Aircraft Airworthiness & Sustainment Conference. San Diego:[s.n.], 2011.
[2] HOLMES C, DRINKWATER B W, WILCOX P D. Post-processing of the full matrix of ultrasonic transmit-receive array data for non-destructive evaluation[J].NDT&E International,2005,38:701-711.
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