Reconstruction of three-dimensional conductivity variations from eddy current (electromagnetic induction) data

A direct linear inverse method for eddy current nondestructive evaluation is presented. The method is based on inverting the impedance change measured in an eddy current probe, placed above a conducting half-space containing a three-dimensional (3D) conductivity anomaly. The eddy current probe used for this purpose consists of a spatially periodic, time-harmonic current sheet. The Born approximation is used to linearize the relevant integral equations used for inversion. It is found that a coupled Fourier-Laplace transform has to be inverted to provide a 3D reconstruction of the inhomogeneity in the conventional frequency domain; however, the transforms decouple in the time domain.

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