A sensor device for detecting the degree of wetting of a multi-layer transparent pane, made in particular of glass, by an, in particular, drop-shaped precipitation. The sensor device is provided with a beam guide element which comprises two beam windows and cooperates with a beam transmitter and a beam...http://www.google.se/patents/US5498866?utm_source=gb-gplus-sharePatent US5498866 - Optoelectronic sensor for detecting moisture on a windshield with means to compensate for a metallic layer in the windshield
