Piezopolymer ultrasonic transducer

The invention relates to a piezopolymer ultrasonic transducer for generating and detecting ultrasound in (coupling) liquid, comprising at least one layer 3, situated between a front and a rear electrode 2, 2', of a piezoelectric high polymer, a rear end body 1 and a protective layer 4 on the transducer side situated adjacently to the transmitting medium. The object of the invention is to provide an ultrasonic transducer which is intended for the working or nominal frequency arranged between 1 and 10 MHz, and which can be fabricated by a simple procedure from thin high-polymer piezoelectric layers whose thickness produces a resonance frequency which is at least twice the working or nominal frequency of the ultrasonic transducer and whose impedance is consequently reduced so that an electrical impedance matching to the low-impedance output of commercial ultrasonic units is possible. According to the invention, the object can be achieved in that the protective layer 4 is designed by dimensioning, in accordance with the invention, the relationships between the acoustic impendance of the protective-layer material and that of the piezoelectric material and between the ratios of layer thickness to sound velocity for protective layer and piezoelectric layer as a frequency-relevant or frequency-determining element, the total thickness of the piezoelectric layer being less than the limit value specified in Claim 1.