Ultrasonic probes

摘要

Disclosed is an ultrasonic probe which is capable of externally and selectively controlling the conversion efficiency of an electroacoustic conversion portion. For the electroacoustic conversion portion is used a material which does not exhibit or exhibit the piezoelectricity depending on the absence or the presence of bias electric field, for example, a certain kind of ferroelectric material which is maintained at a temperature in the vicinity of the phase transition temperature thereof or a material having high electrostrictive effect. The electroacoustic conversion efficiency is controlled by applying bias electric field to such a material.