NONDESTRUCTIVE EVALUATION OF SOLIDS AND DEPOSITED FILMS BY THERMAL-WAVE INTERFEROMETRY

In order to investigate heat diffusion processes in dielectric or meta llic materials, a differential interferometer was constructed allowing phase-sensitive measurement of the thermal expansion of periodically excited solid surfaces. To get insight into the physical process of he at propagation, a three-dimensional model of temperature diffusion wil l be introduced. This theoretical model may be considered as a first s tep for the understanding of signal formation in case of investigating the homogeneity or adhesion properties of deposited films by means of thermal-wave interferometry. First measurements will be presented and thermal parameters evaluated using the model mentioned above.