Method of forming integral transducer and impedance matching layers

Abstract

A method of forming a transducer device having integral transducer and impedance matching portions includes forming grooves partially through a thickness of a piezoelectric member. A groove volume fraction at the impedance matching portion controls the electrical impedance. The impedance matching portion may be at either or both of the front and rear surfaces of the transducer portion, which generates acoustic wave energy in response to application of a drive signal. The drive signal is introduced by electrodes. In one embodiment, the electrode at the impedance matching portion extends into the grooves, but preferably a filler material is selected and deposited to allow use of a planar electrode. An alternative embodiment to fabricating the transducer device is to assemble piezoelectric material. For example, an integral transducer and impedance matching portions may be formed by using molding techniques or by stacking dimensionally different thin piezoelectric layers. The acoustic impedance of the matching layer can be varied spatially to provide apodization of a radiating aperture. Moreover, a graded impedance matching layer can be formed, resulting in a tapered variation in the acoustic impedance of the matching layer.