Affiliations: [a] Faculty of Electronic Engineering, The University of
Electro-Communications, 1-5-1 Chofuga-oka, Chofu, Tokyo, 182-8585 Japan | [b] Laboratory of Magnetic Field Control and Applications,
Faculty of Engineering, Kanazawa University, 2-40-20 Kodatsu-no, Kanazawa,
920-8667 Japan
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.
