| 摘要 |
PROBLEM TO BE SOLVED: To provide an obstacle detector which suppresses the variance of a detection area as much as possible while preventing false notification due to external noise and radio interference in transmission to or reception from a sensor. SOLUTION: A sensor 5 including a microphone 21 and a circuit part 23 switches, by a frequency adjustment circuit 32, the mode to either a reference frequency mode or a shift frequency mode for avoiding external noise in which an ultrasonic wave at a frequency different from that of the reference frequency mode is transmitted, transmits an ultrasonic wave, and changes the sound pressure in a microphone driving circuit 33 or the reception sensitivity of a gain adjustment circuit 36 upon transmission in the reference frequency mode and transmission in the shift frequency mode. With this structure, a false operation due to external noise is prevented, and the change of the detection area is suppressed. COPYRIGHT: (C)2011,JPO&INPIT |
