ABSTRACT
Acoustic microscopy involves imaging the elastic properties of surface or subsurface regions using acoustic waves as well as measuring the mechanical properties on a microscopic scale. In the early days of acoustic microscopy, it was discovered that slight defocusing is needed to obtain high-contrast images. A theoretical understanding of this phenomenon quickly leads to the realization that one could obtain quantitative information from the scanning acoustic microscope (SAM) by continuously defocusing and bringing the sample toward the lens for a fixed x, y position of the lens axis. For SAM, an acoustic lens of this type at the end of a buffer rod is used for focusing and reception of the ultrasonic signal. Lens design for the SAM is a pinnacle of achievement in ultrasonic science and engineering.
