| 摘要 |
<p>PURPOSE: To accurately measure the distance to an obstacle by setting a larger compari son reference value in the case where the propagation time from the application of light to reception of a signal is shorter than in the case where it is longer, setting a time when a reception signal exceeds it as a point when detecting the reception of signal, and measuring a time from the application of light to a detection point. CONSTITUTION: A threshold is set large for a case where a propagation delay time is longer than in the case where the propagation delay time is shorter by a propagation delay time measuring means 10 and a time when the light reception signal of a light reception circuit 4 is equal to or more than the threshold is set as a signal reception detection point, thus measuring a plurality of propagation delay time. An averaging means 6 averages them and a distance operation means 7 calculates the distance between an own vehicle and an obstacle 3 based on it. A light reception signal due to such disturbance as mist and rain is generated at a part with a shorter delay time, and reflection light due to disturbance results in smaller intensity than that of the reflection light of the obstacle 3. Therefore, by setting the threshold in this manner, the obstacle 3 can be positively detected.</p> |
