奥島 基良, 大槻 茂雄

Motoyoshi OKUJIMA, Shigeo OHTSUKI

東京工業大学精密工学研究所

Tokyo Institute of Technology

キーワード : lateral resolution, dynamic focusing, Fresnel’s division, variable aperture

To improve lateral resolution on ultrasonotomography, it is desirable to employ dynamic focusing technique of circular concave transducer divided along concentric circulars.
In this paper, dynamic focusing transducer with Fresnel’s division is discussed. Its beam width is estimated from calculated sound pressure on the axis of the transducer, and its practical design method is shown.
In case of variable aperture transducer, dynamic focusing technique enables us to get ultrasonic narrow beam easily. That is, variable aperture transducer with two elements and one delay circuit forms preferable narrow beam over wide range. This paper also discusses the transducer and its design method.