| 摘要 |
<P>PROBLEM TO BE SOLVED: To enable distance measurement to a further distant object while enhancing the reliability of distance measurement by avoiding an effect by noise outside and inside a distance measuring environment and an effect of the other object that is an obstacle. Ž<P>SOLUTION: A transmission signal that is, for example, an ultrasonic signal obtained by performing frequency-shift modulation with two frequencies is transmitted from an ultrasonic transmitter, a receiving signal including a reflection signal from an object is received by an ultrasonic receiver, the frequency shift of the receiving signal is detected, and the distance to the object is detected based on a time difference ΔT between timing t1 thereof and transmitting timing t0. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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