The theory and performance of a two beam differential interferometer for measurement of both surface and bulk waves are described. The system is insensitive to small errors (<1 mm) in focus or in specimen flatness. Both amplitude and phase measurements are demonstrated. The system has been absolutely calibrated and can detect 6 x 10(-4)-A surface wave displacements on glass.
A Doppler-shifted light-scattering technique, long used in velocimetry to yield 3-D flow information about liquids and gases, has been used for the first time to measure ultrasonic fields in solids. Unlike Bragg diffraction and interferometric methods previously used in solids, Doppler methods require no a priori assumptions about the sound field in order to obtain 3-D resolution. In addition, Doppler methods determine not refractive index changes but particle motion directly; thus the need to use the photoelastic constants of the medium to calculate strain data is eliminated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.