The classical holographic procedure uses a transducer with single coil considered as a source of spheric electromagnetic waves, the modification of the transducer impedance representing the information by whose means the holographic image is obtained.

This work is dedicated to the study of the possibility to obtain holographic images by using an eddy current transducer with orthogonal coils [1]. We present the analytical model for the operation of this transducer and the way in which the discontinuities scattering the electromagnetic waves influence the electromotive voltage induced in the coil perpendicular to the inspected surface when using as sender the coil parallel to the surface.

The information for obtaining the holograms can be taken from the correlation of the response signal of the transducer connected to a classical eddy current installation, with a test function which is both a spatial and temporal correlation. The response signal is measured along an artificial aperture and is transformed by means of a bi-dimensional Fourier transform.

The hologram is reconstructed by the inverse Fourier transform using the phase multiplication procedure to artificially reduce the wave length.

The intensity of the holographic signal is calculated as the square of the inverse Fourier transform.

The theoretical results are compared with the experimental ones originating from a discontinuity of the type of blind hole with flat bottom machined in aluminium blocks. The holes diameter was 3 mm, the distance between the bottom of the hole and the surface ranging between 0.5 and 0.7 mm, while the distances between the holes centers were different. REFERENCE

1. A. Savin, E. Radu, O. Mihalache, B. Bradu, A. Andreescu, R. Grimberg, "Transducer with Orthogonal Coils Used to Control Flat Products", The International Symposium on Nonlinear Electromagnetics Systems, Cardiff, Wales, UK, 17-20 September 1995