Lockin thermography with eddy current excitation

Abstract

A new lockin thermography method is presented where inductive heating by eddy current is used for periodical sample excitation. In conventional eddy current testing damages like cracks in metals are detected with a coil which changes its impedance over defect areas. The disadvantage of this method is its time consuming point-by-point scanning over the surface of the sample. Induction-Lockin-Thermography (ILT), however, uses a thermography camera with a detector array to monitor induction heated areas. Temperature patterns and their time dependence responding to the coded excitation allow for fast phase angle imaging of defects in larger areas.