Acoustic phase conjugation by nonlinear piezoelectricity. II. Visualization and application to imaging systems

Phase conjugate waves of ultrasound were generated in PZT ceramics through nonlinear piezoelectric interaction between an incident ultrasonic field at omega and an electric field at 2 omega. The amplitude reflectivity of the phase conjugator was 23% at 10 MHz. The behavior of the incident waves and the phase conjugate waves were visualized by stroboscopic schlieren technique. Time-reversal property and the automatic correction of wavefront distortion in the phase conjugate process were confirmed. A scanning ultrasonic imaging system with a PZT phase conjugator has. been built. This system was used to visualize test samples composed of solid plates and phase disturbers. Images by phase conjugate reflection yielded clear figures of the solid plates in spite of the existence of phase disturbers made of agarose gel with rough surfaces, whereas conventional images showed serious distortion. (C) 1999 Acoustical Society of America. [S0001-4966(99)02809-X].