| 摘要 |
A system for detecting the presence of rain droplets on a windshield (17) employs a source of light, such as an LED (11), and a photodetector (12) installed on the dashboard (13) of a vehicle. The LED (11) and the photodiode (12) are arranged with respect to one another such that light from the LED (11) cannot reflect directly off the windshield into the photodiode (12). Only when the light from the LED is backscattered by an environmental condition, such as the raindrops (25) on the exterior of the windshield (17), the condensation of moisture on the interior of the windshield (17), or the presence of smoke in the cabin, will the photodiode (12) receive the light from the LED (11). Each of these environmental conditions has a predeterminable characteristic signature which permits the processing of data to detect same. An ambient light signal is subtracted from the combination of the rain and ambient light signals by pulsed operation of the LED (11) and subtracting the ambient light signal, which is detected when the LED (11) is dark, from the combined LED (11) and ambient light signal which is present when the LED (11) is illuminated. |
