Optical differential interferometry, initially developed to characterize planar recording media surfaces and subsequently used to detect continuous and pulsed ultrasonic elastic waves, has recently been applied to the measurement of the interface properties of bonded transparent solids. Acousto-optic interaction between dual laser probe beams and periodic particle displacement fields induced by acoustic waves on the boundary permits the qualitative identification of surface conditions at the interface. In this paper, the theory and operation of the real-time interferometric measurement system, an analysis of the acousto-optic interaction, and surface testing results for bonded glass specimens are presented.
Richard O. Claus,
"Boundary Surface Testing Via Differential Interferometric Measurements Of Interface Waves," Optical Engineering 19(4), 194590 (1 August 1980). https://doi.org/10.1117/12.7972564