Transducer acoustic lens

Claim 1

A transducer for use in transmitting acoustic signals into a body of a patient to be examined and translating reflections thereof into electrical signals, comprising a base, an array of crystals mounted on said base, a metal shield covering the ends of the said crystals remote from said base and in electrical contact therewith, a first lens element comprised of electrically insulating material having an acoustic impedance approximating that of the tissue under examination and an acoustic propagation velocity greater than that of the tissue under examination, said first element having a concave inner surface and an outer surface, said surfaces being shaped so that parallel rays approaching said inner surface are focussed on the other side of said outer surface, means for mounting said first lens element with its concave inner surface facing said metal shield and on the side of said shield opposite said crystals, and a second lens element comprised of electrically insulating material contained between the inner concave surface of said first lens element and said metal shield, said latter material having an acoustic impedance and propagation velocity approximating those of the tissue under examination.