To commonly use, and miniaturize piezoelectric ultrasonic microphones of a short distance sensor and a long distance sensor, reduce the cost, and ensure an approximately same detection area width irrespective of the detection distance in a periphery monitoring device for a vehicle.
The periphery monitoring device for the vehicle is equipped with both sensors of the short distance sensor 3 having a main detection range of short distance and the long distance sensor 4 having a main detection range of short, middle, and long distance which are composed of the approximately same piezoelectric ultrasonic microphones 2 transmitting/receiving the ultrasonic, a transmission drive circuit 20 causing them to transmit the ultrasonic sound, amplifier circuits 5, 6 amplifying a received wave signal, a threshold circuit 7 outputting the signal based on the intensity of the signal, and a central control part 9 which detects an obstacle by controlling the transmission drive circuit 20 and outputs an alarm signal based on the output from the threshold circuit 7. The detection gain is controlled by the amplifier circuit 6 and gain control signals G1, G2, G3 to make the detection area width in the short distance, middle distance, and long distance of the long distance sensor 4 approximately equal.
COPYRIGHT: (C)2007,JPO&INPIT
Koji Urase
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Katsumi Taguchi
Shinichi Mizuta