An optical sensor has an optical plate which is adapted to make surface contact on a pane, in particular a windshield of a motor vehicle. It further has one or preferably a plurality of photoreceivers arranged on the side of the optical plate facing away from the pane. An optical mask is arranged in the optical path upstream of each photoreceiver, the optical mask having light-blocking and light-transmissive surface areas. The light-transmissive surface areas each allow an optical path to traverse the optical plate, impinging on the photoreceiver and is delimited by the light-blocking surface areas.