Using Excitation Invariance in the Characterization of Defects by Eddy Current Image Constructions

In this article the eddy current method is used to characterize defects in conductive non-ferromagnetic plates. A special attention is paid to the presentation of results in the form of images. An inverse problem with Tikhonov regularization is solved to obtain the two-dimensional distribution of currents inside the material under test. With this purpose a uniform field probe is used to guarantee a spatially invariant excitation field for probe scanning translations. The probe contains a magnetic field detector based on high sensitivity giant magneto-resistors which reads the magnetic field component parallel to the excitation and induction currents.