Application of the wavelet packet transform to flaw detection in ultrasound B-scans

An important issue in ultrasonic nondestructive evaluation is the detection of flaw echoes in the presence of coherent background noise associated with the microstructure of materials. Many signal processing techniques have proven to be useful for this purpose. However, when considering B-scan images, it appears that fully two-dimensional robust flaw detection techniques remain desirable. In this paper, we describe a novel automatic flaw detection method based on the wavelet packet transform, which is particularly well adapted to B-scan image analysis. Some experimental detection results in B-scan images of austenitic stainless steel samples comprising artificial flaws are also presented.