PURPOSE:To detect direction of and distance from an obstacle, by providing plural signal-receiving units, which are capable of receiving signals from at least one of ultrasonic wave pulse generators mounted on a car, in the direction of a car axis by keeping a distance between them and thereby comparing situations of receiving of reflected waves. CONSTITUTION:Ultrasonic wave oscillators 13a and 13b and also ultrasonic wave receiving units 21a and 21b are provided on front section (or rear section) of a car by keeping a distance between them in the direction of the car axis. Ultrasonic wave pulses received by the receivers 21a and 21b are amplified, rectified and shaped to obtain pulse wave shapes from circuits 25a and 25b. Time of occurrence of these pulses are differed by distance from an obstacle. These pulses are put into a logic circuit consisting of an AND circuit, a flip-flop and an OR circuit, etc. When the pulses are away, the OR circuit 39(40) is turned on to light a lamp LA(LB), indicating that the obstacle is on the right (left) side, and when the pulses are approaching, the both lamps are turned on to indicate that the obstacle is located on the center. A distance from the obstacle is sought by counting clock pulse until the first received pulse. It is thereby possible to determine position of the obstacle.
展开▼
