| 摘要 |
PURPOSE:To make the search area constant independently of the distance, by changing the receiving wave beam directional angle from a wide angle to a narrow angle at the receiving time according to the elapse of the time. CONSTITUTION:The signal from transmission part 3 is applied through T/R switching circuit 2 to oscillating element 1, which is constituted with three oscillator parts 1a-1c of concentric rounds to transmit ultrasonic waves. Next, T/R switching circuit 2 is switched to the receiving side, and first, only center oscillator part 1a is used to perform receiving at a wide directional angle. Next, two oscillator parts 1a and 1b are used to perform receiving at a narrow directional angle. Finally, three oscillator parts 1a-1c are used to lead the signal, which is received at a narrower directional angle, to receiving part 5. The receiving signal obtained by receiving part 5 is supplied to recorder 6. |
