An Acoustic Gray Scale for Scanning Acoustic Microscopy and Diagnostic Ultrasound

The principle of a true acoustic gray scale standard is presented and experimentally applied to the Scanning Acoustic Microscope (SAM). The implementation is based on the impedance matching property of a quarter wave impedance transformer through which precise changes in reflection coefficient may be produced in a single material. The performance of the first implementation designed for 375 MHz operation is described and the implications of its use are discussed in detail. The application of the principle to diagnostic ultrasound is also treated.