TOFD (time of flight diffraction) is a kind of weld defect detection technology by using ultrasonic diffraction wave signal. Because\nthe diffraction intensity is far less than ultrasonic echo wave intensity, thus, the noise contained in TOFD signal is fairly large, and\nthe formed image is not clear enough. Therefore, it is difficult to determine the size of defects accurately. In this paper, a method of\nnoise reduction of TOFD signal and improving the resolution of the image are discussed based on the combination of wavelet\nthresholding and image registration. Wavelet multiresolution analysis method is adopted and the A-scan signal is decomposed\ninto different frequency components. We propose a new threshold function to process the wavelet coefficients, which guarantees\nto denoise while preserving the useful information as much as possible. Setting up the ultrasonic TOFD inspection system and\nthe image data with randomly distributed noise can be obtained via fine shake of the probes during testing. Then, image\nregistration based on maximum correlation and blending is adopted to eliminate the noise in further step. The result shows that\nthe proposed method can achieve denoising, together with resolution enhancement.
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