Patent ID: 6952967

Claim:
An ultrasonic transducer comprising a transduction element formed into a ring and inclined so as to define a truncated conical shape having an open interior, said transduction element having a bottom edge which defines a base plane, and having an active surface, wherein said active surface is disposed at an angle φ with respect to said base plane such that, during operation of said ultrasonic transducer, substantially all of the acoustic energy incident upon a surface of a target will be refracted as surface waves, wherein said active surface of said transduction element has a width q, said width being equal to: q = D 2 ⁢ cos ⁢ ⁢ ϕ - a ⁢ ⁢ sin ⁢ ⁢ ϕ wherein D is an outer diameter of said transduction element, and a is a lift-off distance from said bottom edge of said transduction element to said surface of said target.