Method for fabricating an annular ring transducer

A method for fabricating an annular ring transducer, comprising the steps of:

• providing a cylindrical piece of piezoelectric member;
• removing an outer portion of said piezoelectric member to form a slanted outer face that is approximately 45 degrees, said slanted outer face is located at a distance from the center of said cylindrical piece;
• removing a center portion of said piezoelectric member, said center portion having a radius smaller than said distance;
• removing an inner portion of said piezoelectric member to form a slanted inner face that is approximately 45 degrees, wherein a portion of said piezoelectric member positioned between said slated outer face and said slanted inner face formed an angled ring transducer with a thickness t, where t is given by f=V/2 t, and where f is a resonant frequency of the annular ring transducer, and V is an ultrasonic velocity of propagation in said piezoelectric member;
• forming a layer of base material over said slanted inner face and said slanted outer face;
• forming a layer of matching material over said base material layer;
• beating said piezoelectric member to a first temperature below a Curie temperature of said piezoelectric member;
• applying a voltage to said slanted inner face and said slanted outer face;
• heating said piezoelectric member at a second temperature that is less than said first temperature;
• and
• allowing said piezoelectric member to cool down to room temperature while applying said voltage to said slanted inner face and said slanted outer face.