Abstract
This paper presents an image processing method for eddy-current testing for the detection of the defects with a specific orientation. The method utilizes the fact that a line-shaped signal is, throught the Fourier transform, mapped onto a line passing through the origin and perpendicular to the orientation of the original signal. Hence, nonseparable fan filters is used to select the frequency components corresponding to the defects orientated in a specific direction. This approach enables more precise control of the extraction characteristics of signals compared to the iterative application of one-dimensional (1-D) filtering in the vertical and horizontal directions, in which the shape of the pass band is restricted to a geometry made from squares. The effectiveness of the proposed method is shown by a demonstration using a metallic sample with a defect aligned in a number of directions.