| 摘要 |
<p>PURPOSE:To accurately detect the short distance to an obstacle through ultrasonic waves, by mounting a contact detector of prescribed length on a bumper or the like so that a predetermined length is indicated when the detector generates an output signal. CONSTITUTION:A signal of ultrasonic waves or the like from a transmitter 23 is reflected on an obstacle and detected by a receiver 24. A flip-flop 30 generates an output signal showing the time H from the reflection to the detection, so that a measuring unit 31 calculates the distance to the obstacle. The switch 13 of a contact detector provided on a bumper is located at the tip of the detector of prescribed length so that the switch puts a delaying circuit 42 in operation when the switch is brought into contact with the obstacle. As a result, a distance display unit indicates a predetermined length. A switch 16, which is turned on when the distance to the obstacle has become zero, acts not through the delaying circuit 42 so that the display unit indicates that the distance is zero.</p> |
