Patent ID: 6369378
Filing Date: 2002-04-09
Classification: B60S

Abstract:
A device for detecting wetting of a pane of glass, or a windshield, said device comprising a rain sensor includinga measurement circuit comprising a light-radiating transmitter (12) for generating radiated light, a light receiver (14) arranged to receive a portion of the radiated light according to the wetting of the pane of glass or windshield as well as extraneous light and to generate a sensor signal depending on a light amount of the portion of the radiated light and the extraneous light reaching the receiver, an integration stage (16) for integrating the sensor signal from the light receiver and for generating an integrated sensor signal and a comparator (20) for generating a trigger signal (21) when the integrated sensor signal exceeds a predetermined threshold; and an evaluating circuit (22) including means for turning on said light-radiating transmitter (12) during a plurality of first predetermined time intervals (Tg) and for turning off said light-radiating transmitter (12) during another plurality of second predetermined time intervals (Tf;Tfâ€²) for evaluating the extraneous light and for day-night detection; means for determining an integrated light quantity reaching said light receiver (14) during each of said time intervals when a respective one of said trigger signals is received; means for adjusting said predetermined threshold of said comparator to a first threshold value (S1) during each of said first predetermined time intervals during which the light-radiating transmitter is turned on and to a respective second threshold value (S2) during each of said second predetermined time intervals during which the light-radiating transmitter is turned off for evaluating the extraneous light and for day-night detection and means for adjusting each of said second predetermined time intervals to a first time interval value (Tf) for evaluating the extraneous light and to a second time interval value (Tfâ€²) for day-night detection after a predetermined number of extraneous light measurements, said second time interval value (Tfâ€²) being longer than said first time interval value (Tf).