Ultrasonic transducer arrays and methods for the fabrication thereof

Abstract

This invention provides a method for fabricating ultrasonic transducer arrays and various transducer arrays produced utilizing such methods. The method includes the steps of cutting a block of piezoelectric material to form a plurality of wafers, each wafer being of a predetermined thickness; forming the wafers into a spaced parallel array with a center-to-center spacing between the wafers substantially equal to one-half of the object wavelength (as this term is defined in the specification); and causing the space between the wafers to be filled with a substance having an acoustic impedance which differs from that of the piezoelectric material by an amount such that the reflection coefficient between the piezoelectric material and the substance is greater than 0.9. The predetermined thickness of the wafers may be equal to one-half the piezoelectric wavelength and the substance between the wafers may be formed at least mostly of air. A material of a depth substantially equal to the spacing between wafers required to achieve the desired periodicity may be affixed to one of the adjacent wafer surfaces of each space, and this material may either be etchable and etched away to form a precise air gap between the wafers, or the material may be formed in a pattern with substantially more area without material than with material. Alternatively, a material having the required acoustic impedance mismatch, and preferably also having a relatively high absorption coefficient, is placed between each two adjacent wafers when the wafers are formed into the array.