Acoustic Phase Conjugation Using Nonlinear Electroacoustic Interaction and its Application to Scanning Acoustic Imaging Systems

Abstract

Scanning acoustic imaging systems such as acoustic microscopes and acoustic flaw detectors are now widely used in industrial and medical researches. The advantage of acoustic imaging is its ability of visualizing the inside of optically opaque materials. These systems, however, are still accompanied with a common drawback. That is, when we observe a sample which has a non-flat surface, the surface image is always superposed on the internal image. This is caused by the refraction of the acoustic beam at the surface of the sample. It induces the deflection of the beam and/or the distortion of the wavefront, and then the shape of the wavefront of the detected beam becomes different from the shape of the transducer. This fact restricts the reliable usage of acoustic imaging to flat-topped samples and the removal of the surface roughness effect has been a target of study in acoustic imaging [1].