Typical eddy-current system test data consist of the values of the system's probe impedance. The wave theory that links the phase response of the eddy-current probe impedance to the defect location relative to the probe is presented. The technique of phase multiplying the diffraction-limited hologram generated from the probe impedance is discussed. The effects and limitations of this technique are illustrated with a mathematical model of the eddy-current probe. Experimental data are presented that confirm the theoretical analysis and illustrate the ability to focus eddy-current holographic data by using backward wave propagation.
© 1993 Optical Society of America
J. M. Prince and B. P. Hildebrand, "Low-frequency electromagnetic (eddy-current) holography for imaging in conductors," Appl. Opt. 32, 4960-4971 (1993)