8. Ultrasonic Imaging and Microscope
The Metrology and Imaging modes of the acoustic reflection microscope are applied to spherically shaped specimens. Metrology is usually practiced by translating the specimen along the acoustic beam axis. This operation yields a measurement of the local Rayleigh velocity at a single location in the specimen plane. Imaging is accomplished through raster-scanning in the plane transverse to the beam axis. The two modes are, in effect, simultaneously employed when a nonplanar surface of' known curvature is scanned. The resulting image reveals nearly concentric rings with radial, periodic brightness variation, if the surface is spherical in shape. Stainless steel bearing balls of the type used in gyros are used to demonstrate the technique. It is suggested that the obtained images represent a two-dimensional map of elastic properties applicable to convex (bearing ball) and concave (bearing raceway) surfaces.
Weglein, R. D., "Acoustic Microscopy of Curved Surfaces" (1981). Proceedings of the DARPA/AFWAL Review of Progress in Quantitative NDE, October 1979–January 1981. 35.