Patent ID: 6946777

Claim:
A composite piezoelectric ultrasonic transducer, comprising: a ribbon-wound piezoelectric element having a winding of a piezoelectric film ribbon against an elastomer material; wherein the piezoelectric film ribbon has three layers: two outer conductive layers and an inner polymer layer; wherein the elastomer material is a material having a lower modulus of elasticity than that of the polymer layer, and forms an elastic layer between the conductive layers as the film ribbon is wound, and wherein a material property of the elastomer is such that the velocity of an acoustic wave through the elastic layer is substantially lower than through the film ribbon; wherein the winding has width selected such that the resonant frequency is an ultrasonic frequency, said width being calculated substantially as an average of the velocity of sound through the film ribbon and the elastomer material divided by four times the ultrasonic frequency; a face plate covering the top surface or bottom surface of the winding, the face plate operable for low impedance matching of ultrasonic wave detection or generation between the winding and the environment external to the transducer; and a rigid backing on the surface of the winding opposing the face plate, operable to confine radiation and detection of ultrasonic waves to the face plate.