| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide a rain droplet sensing device using light capable of detecting only a signal component corresponding to a rain droplet accurately by cutting external light in accordance with a frequency on a light emitting side without changing an internal circuit even if the frequency on the light emitting side is changed due to characteristics of a vehicle. SOLUTION: Light is received in light receiving elements 23a, 23b by driving light emitting elements 22a, 22b of a rain droplet sensor by pulse signals from an oscillation part 21, an external light quantity signal generation part 25 turns this received signal into a rain droplet signal, and an inversion signal of the pulse signal of the oscillation part is synchronized with this rain droplet signal to sample a voltage of external light component from the rain droplet signal and hold it. A rain droplet amount signal sampling part 26 obtains a difference in voltage between the voltage of the external light component and the rain droplet signal received by the,light receiving element.</p> |
