Abstract: An apparatus for detecting obstructions behind a vehicle, employing ultrasonic waves is disclosed. The apparatus comprises an ultrasonic transmitting and receiving device disposed on the rear portion of the vehicle, an electric motor for rotating the transmitting and receiving device at a constant velocity, an angle sensor for detecting the rotating angle of the transmitting and receiving device and a sonar circuit for emitting ultrasonic waves through the transmitting and receiving device at predetermined rotating angles, receiving ultrasonic waves reflected from obstructions through the transmitting and receiving device at predetermined rotating angles and measuring the distance to the obstructions from the time taken from the transmission to the reception of the ultrasonic waves.

Abstract: Obstacles in the path of a vehicle are detected by an ultrasonic radar system which measures the time between the instance of transmission of an ultrasonic wave pulse and another instance of reception of an echo signal. The transmitting period is controlled to be retarded from a reference or standard transmitting period by a time length including the measured time at every other transmitting period. The measured time is compared with a reference time to check whether a detected obstacle is within a dangerous range. This comparison is effected at every other transmitting period so that a false detection signal caused from a far obstacles is prevented from being produced. As a result of the comparison an alarming device is energized to alert the vehicle driver when necessary.

Abstract: An ultrasonic detector for roadway vehicles comprises an array of electroacoustic transducers mounted on the rear of the vehicle. The transducers are sequentially driven by a transmitter circuit to transmit a pulsed, laterally shifting ultrasonic energy toward an object located behind the vehicle in one of plural regions defined by partially overlapped directivity patterns of adjacent transducers. A receiver circuit is coupled to the transducer array to receive echos returning from the object during the interval between successive beam transmissions. A logic circuit detects the lateral position of and the distance to the object for giving relevant indications on a display unit, the audible tone being variable depending on object distance. An audible warning device is optional.

Abstract: A device for detecting failure of an ultrasonic apparatus having an ultrasonic pulse generator, an ultrasonic transmitter and an ultrasonic receiver utilizes a damped oscillation signal which is produced at the junction point between the ultrasonic pulse generator and the ultrasonic transmitter when the ultrasonic transmitter or the ultrasonic receiver is excited by applying thereto an ultrasonic pulse generated by the ultrasonic pulse generator. A level discriminator compares the damped oscillation signal with a reference level and determines whether the damped oscillation signal has a sufficient magnitude and duration indicating that the ultrasonic transmitter or the ultrasonic receiver is in a normal operating condition.