Ultrasonic scanning and imaging appts. - has organic piezoelectric transducer detector, between sample and ceramic transducer transmitter, with matched acoustic impedance

摘要

The appts. generates ultrasonic images of e.g. parts of the human body and has a transmitter transducer of a ceramic piezoelectric and a receiver transducer of organic piezoelectric. The ceramic is e.g. PZT and the organic material is e.g. a film polymer piezoelectric of an acoustic impedance near to that of the body to be examined. The receiver transducer is interposed between the transmitter and the body. The polymer is conveniently a vinylidene polyfluoride rendered piezoelectric by the single action of an electric field normal to the film principal faces while the organic material is a film of thickness determined as a function of the frequency of electric pulses applied to the transmitter transducer. The principal transducer faces are metallised with that of the receiver in body contact and at earth potential while that of the transmitter is secured to a backing which strongly attenuates reverse transmitted sound waves.