| 摘要 |
PURPOSE:To enable simple recognition of the type of a obstacle, by a method wherein a comparison level, is automatically set according to the reflection time of an echo wave and an obstacle is discriminated by comparing the reception level of the echo wave with the comparison level to emit a voice alarm. CONSTITUTION:An ultrasonic wave which is reflected on an obstacle after being emitted from a transmission sensor 5a of an ultrasonic unit 5 is received with a reception sensor 5b to be introduced to a programable gain amplifier 13. The PGA13 changes the gain according to the reflection time of the ultrasonic wave to compensate for attenuation and the received signal is introduced into a computer 2 through a PPH14 and an A/D converter 15. As the reflected ultrasonic wave changes in the reception level with the obstacle, the reception level and the reflection time of the reflected wave are compared with an internal table within the computer 2 to discriminate the presence, type and the position of the obstacle and a voice alarm is emitted from a speaker 22. |
