PURPOSE: To seek a distance of up to an obstacle so accurately without entailing any misconception between the already transmitted reflected wave and the newly transmitted one by outputting any distance information individually on the basis of a time difference ranging from the transmission time of each ultrasonic wave to the reception time of the reflected wave of corresponding frequency.
CONSTITUTION: Respective reflected waves of each ultrasonic wave are individually received at each one different in frequency by those of first, second and third receiving sensors 8a, 8b and 8c, and distance information is outputted individually at each one different in frequency by those of first, second and third distance arithmetic circuits 9a, 9b and 9c on the basis of a time difference ranging from the transmission time of each ultrasonic wave to the reception time of corresponding reflected waves respectively. Therefore, it is not necessary to synchronize the transmission timing of each ultrasonic wave and the detection timing of electric signals corresponding to the reflected waves, any distance of up to an obstacle is accurately measurable without entailing any misconception between the already transmitted ultrasonic waves and the reflected waves of the newly transmitted ones.
CHITOKU MINORU
GOTO YOSHIHIRO
NISHIZAKI KATSUTOSHI
KADA TOMOYASU
OBATA YOSHIFUMI
