| 摘要 |
<p>An ultrasonic transducer (10) for use in medical imaging systems includes a piezoelectric element (11) having an active electrode (12) formed as a series of concentric annular segments (14-22). Each segment is separately driven by a transmitter (31) in which the amplitude and phase of the drive signals produce an ultrasonic wave having a pressure profile that approximates a zeroth order Bessel function. A nondiffracting beam of ultrasonic waves is produced.</p> |
