Computer Aided Interpretation of Radiographic Images Using a Wavelet Transform Procedure

The x-ray radiographic testing method is often used for detecting defects as a non-destructive testing method (NDT). In many cases, NDT is used for aircraft components, welds, etc. Hence, the backgrounds are always more complex than a piece of steel. It is difficult to detect defects using classical image processing methods. In this paper, we apply wavelet algorithms with a digital X-ray image to extract defects to aid automated radiography inspection. In our algorithms, after obtaining the x-ray image, we firstly use wavelet thresholding to reduce image noise to improve the quality of the radiographic image. Then we extract defects from the radiographic image. In the process of extracting edge features, according to the wavelet multi-scale character obtained from edge information at different scales, we integrate the coefficients of wavelet transforms on a series of scales to look for the best scale where the edges are well discriminated from noise to extract edge features. With the help of wavelet algorithm, an objective and fast computer based evaluation of defect indications is possible.