| 摘要 |
PURPOSE:To reduce period and to detect exactly an obstruction by operating plural ultrasonic wave receivers simultaneously with each other, operating successively the same time-dividedly when modulation arises in the acoustic wave and operating simultaneously the same when there is no influence of interference. CONSTITUTION:For example, an obstruction is assumed to exist only in 11 among detection regions 11-14 set by wave transmitter and receivers 21-24. A transmission signal, a control signal for transmission and reception, etc. are obtd. in a circuit 5 for generating control signal. The transmission signal of a transmission circuit 5 is inputted to the transmitter and receivers 21, 23, which emit simultaneously ultrasonic waves to the respective regions 11, 13. Since the obstruction exists only in the region 11 to be detected, the wave reflected from the region 11 is received and is inputted with an analog switch for reception to an amplifier by a control signal. |
