木村 友久, 浅井 仁, 金井 浩, 中鉢 憲賢

Tomohisa KIMURA, Hitoshi ASAI, Hiroshi KANAI, Noriyoshi CHUBACHI

東北大学工学部電気工学科

Department of Electrical Engineering Tohoku University Faculty of Engineering

キーワード : Acoustic input impedance, Cascade matrix, Reflection characteristic, 2-Terminal-pair network, Ultrasonic transducer

We propose a new method for improving the characteristics of the piezoelectric transducer using by the inverse matrix of the cascade system so that time resolution in the determination of transit time of ultrasound signals in a thin layer is increased. The complete set of characteristic of the pulse-echo system is described by a cascade of distributed-constant systems for the ultrasonic transducer, matching layer, and acoustic medium. Acoustic input impedance and reflection characteristics are estimated by using the inverse matrix of the cascade system and the voltage and the current signal at the electrical port. From the inverse Fourier transform of the resultant reflection characteristic, transit time in an object that forms a thin layer is accurately determined with high time-resolution. The principle of the method was confirmed by simulation experiments and experiments using a water tank.