| 摘要 |
<p>A water droplet detection apparatus is disclosed which detects raindrops (23) on the outer surface of a windshield (22) of a vehicle even in the presence of fog droplets on the inner surface of the windshield. A first light beam (12) is transmitted through the windshield to the raindrops which redirect the light beam and cause a portion of it to be transmitted to a photodetector (20), which causes a detector circuit (Figures 5, 6A and 6B) to produce a rain output signal that increases in the amount of raindrops on the windshield. The first light beam strikes the inner surface of the windshield at an acute angle of about 40 degrees or less so that it is not redirected by the fog droplets to the photodetector to produce a false rain signal. A second light beam (14) may be transmitted through the windshield to the photodetector to determine the light transmissivity of the windshield.</p> |
