Importance

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Abstract

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 receiver. In order to prevent spurious beams caused by an extremely thin intermediate layer located in the pane from having a noticeable influence on the signal used to control the windscreen wiper system, the beam guide element comprises a further beam exit window in the central region of its rear surface facing away from the pane. The region is located between the two beam windows. The further beam exit window is allocated to the measuring path and cooperates with an additional beam detector. Only those irrelevant beams reflected at the extremely thin metallic intermediate layer located in the pane exit therefrom. The signal resulting from the existing irrelevant beams which is detected by the additional beam detector is used to correct the signal supplied by the actual beam detector. Alternatively; signal correction can be achieved by an electrical circuit.

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First Claim