SELECTABLE FOCUS ULTRASONIC TRANSDUCERS FOR DIAGNOSTIC IMAGING

摘要

Dual focus ultrasonic transducers are provided having an effective aspheric radiating surface (312, 314). The transducers exhibit an elongated focal zone in which the radiated ultrasonic energy is concentrated. An annular groove separates the piezoelectric material into an inner disc region (312) and an outer annular region (314) for simultaneous activation or activation of the inner disc alone. When the focus is switched, both the near field limit and the geometric focus are changed to provide near and far focal zones of good lateral resolution. The focus is changed by a reed switch (316) connection to the two transducer regions, which permits proximity switch control of the transducer operation in a shielded environment for good noise performance.