Quantitative characterization of material inhomogeneities by thermal waves

Photothermal measurement techniques offer the possibility to determine thermal properties on and below the sample’s surface. Thus, subsurface thermal inhomogeneities such as defects, buried structures, and continuous profiles of thermal parameters become accessible by photothermal means. Our special interest is focused on the quantitative characterization of material modifications in near-surface layers that are induced by thermal (such as hardening) or mechanical (such as grinding) treatments of the surface as well as the reconstruction of a subsurface structure’s depth, size, and defect strength. Altogether, these investigations are aimed to develop photothermal techniques toward a true quantitative and noncontact inspection method for the nondestructive evaluation of opaque solids. © 1997 Society of Photo-Optical Instrumentation Engineers.