Directional Acoustic Microscope with Electrical Reference Signals

Abstract

The acoustic microscopes have been expected to be widely used in the fields of biological science, material characterization, nondestructive evaluation and others1–2. For the quantitative measurements, several types of scanning acoustic interference microscope (SAIM) have been developed so far, to measure the velocity distributions in thin materials and/or topological profiles on the solid surfaces3–8. In most imaging systems including SAIMs, a point-focus-beam has been employed for high resolution. On the other hand, with the nonscanning reflection acoustic microscope, a line-focus-beam has been introduced for the quantitative measurement of acoustic properties including anisotropy on various solid surfaces. A measurement system for the anisotropic materials have been successfully established with high accuracy10. However, the line-focus-beam usually has a line width wider than 1mm, so that the results obtained by the system show the mean values over the line width. A directional scanning acoustic microscope has been already proposed, which reveals elastic anisotropy with high spatial resolution11. In that acoustic microscope, however, directly reflected waves from the sample is necessary to interfere with re-radiated leaky surface waves on the sample for the V(z) curve establishment.