An ultrasonic micro-spectrometer for the evaluation of elastic properties with microscopic resolution

The authors describe a novel technique for the quantitative measurement of elastic properties, including the anisotropy, on a small surface area of a specimen. Specifically, an ultrasonic microspectrometer (UMSM) is introduced. In the UMSM, a pulsed ultrasonic wave with an oblique incidence is focused on the specimen surface by a spherical lens, and a plane wave component with a specific wave vector is extracted by a planar transducer from a reflected divergent wave. The Fourier spectrum of the received signal reveals the frequency dependence of the reflection coefficient of a small spot of the specimen surface. A prototype system operates in a frequency range from 20 to 150 MHz, and in the incidence angle range from 20° to 40°