Patent ID: 6888346

Claim:
An eddy current device for non-destructive evaluation of an electrically conductive material, comprising: an excitation coil for inducing eddy currents within the electrically conductive material, the excitation coil having windings wherein the excitation coil's longitudinal axis is perpendicular to the surface of the electrically conductive material; a giant magnetoresistive sensor having a longitudinal axis perpendicular to the surface of the electrically conductive material and surrounded by the windings of the excitation coil; a tubular flux focusing lens disposed between the excitation coil and the giant magnetoresistive sensor, composed of a conductive material having a high magnetic permeability, having a first opening opposite the surface of the electrically conductive material and having a second opening adjacent to the surface of the electrically conductive material and which prevents magnetic coupling between the excitation coil and the giant magnetoresistive sensor and which produces high flux density at the outer edge of the giant magnetoresistive sensor; a feedback source; and a feedback coil electrically connected to the feedback source and positioned adjacent to the giant magnetoresistive sensor along the longitudinal axis thereof and surrounded by the windings of the excitation coil and the flux focusing lens, the feedback coil receiving a feedback current from the feedback source having the same frequency as the excitation coil frequency but 180 degrees out of phase with the output of the giant magnetoresistive sensor, such that leakage magnetic fields are canceled.