| 摘要 |
<p>An ultrasonic transmitting and/or receiving transducer (18) which includes a piezoelectric body (20) with electrodes (22, 24) at opposite faces thereof. At least one of the electrodes is in the form of an elongated strip conductor (22) such that the transducer als functions as a lossy delay line. The beam pattern of the transducer is dependent upon the delay of the delay line. A high permeability member such as a ferrite body (100) is located adjacent the elongated strip conductor (22) to increase the distributed inductance of the delay line and, consequently, the delay thereof. The permeability of the ferrite body is controlled by use of a drive coil (102) adjacent thereto. By time varying the drive current to the coil, the acoustic beam pattern is time varied. By using a spiral shaped elongated strip conductor on a cylindrical shaped piezoelectrical body, a focusing transducer is provided. </p> |
