Optical interferometry for measurement of Rayleigh and dilatational waves

Two-beam optical interferometry provides a highly sensitive new technique for the measurement of both Rayleigh waves and dilatational waves. A new optical arrangement overcomes previous objections to interferometry by its differential nature. The acoustically perturbed surface need not be exceptionally flat and the specimen need not be exactly aligned. The technique can be used to measure the phase and amplitude of Rayleigh waves to within a fraction of a wavelength from a discontinuity on any fully or partly reflecting surface. Dilatational waves are measureable in any transparent medium.