| 摘要 |
<p>An ultrasonic transducer comprises an acoustic wave propagation medium (150), a piezoelectric element (145) mounted on a surface of the propagation medium (150), and an ultrasonic lens (155) formed in the opposite surface of the progagation medium (150) and having a predetermined focal distance. The ultrasonic radiation generated from the piezoelectric element (145) is propagated through the propagation medium (150) and focused by the lens (155). The axial length of the propagation medium is selected to be 1/N (N: odd number) of a Fresnel focal distance.</p> |
