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, subsurfac e thermal inhomogeneities such as defects, buried structures, and cont inuous profiles of thermal parameters become accessible by phototherma l means. Our special interest is focused on the quantitative character ization of material modifications in near-surface layers that are indu ced by thermal (such as hardening) or mechanical (such as grinding) tr eatments of the surface as well as the reconstruction of a subsurface structure's depth, size, and defect strength. Altogether, these invest igations are aimed to develop photothermal techniques toward a true qu antitative and noncontact inspection method for the nondestructive eva luation of opaque solids. (C) 1997 Society of Photo-Optical Instrument ation Engineers.