PURPOSE: To achieve an accurate judgement in the identification of an obstacle by prohibiting the current identification processing with the first reception of ultrasonic waves after transmitted to delay the subsequent transmission timing by the time from the transmission to the reception thereof before performing the intended identification of obstacle.
CONSTITUTION: A time ultrasonic wave from an ultrasonic wave receiver 4 is transmitted backward from a vehicle and received at a reference transmission cycle T0 until a signal received is inputted through an ultrasonic wave receiver 5. Thereafter, as the ultrasonic wave receiver 5 detects the reflected ultrasonic wave with the backward movement of the vehicle, a time measuring section 11 measures the time from the point of transmitting ultrasonic waves to the point of receiving them. A memory circuit 12 provides a signal corresponding to the total time of the measured time and a mask time to transmission cycle decision circuit 9 which determines the output timing of the subsequent trigger signal at the point of the time delayed by said total time. In a decision circuit 13, comparison processing is performed by a comparison between the preset reference time T1 and the measured time (t).
HIRAMATSU SEIICHIROU
MAENO TAKESHI
OOTSUKA MITSUGI
| JPS5390800A | 1978-08-09 | |||
| JPS5682626A | 1981-07-06 | |||
| JP56082626B |