Abstract: In order also to allow the detection, for example, of condensation of the inner side of an interface (window) using motor-vehicle rain sensors that exploit the interference, at a window wetted with moisture, with total reflection of light irradiated by a transmitter, several sensors are proposed that are sufficiently variable in terms of configuration and function that they contain, without complex adaptation actions, an implementable possibility for selectable inside/outside detection simultaneously with good discrimination between outside and inside wetting.

Abstract: In an optical sensor for detecting moisture on a windshield of a motor vehicle, in which the light radiation is deflectable to a detection area on the windshield situated in the light path between transmitter and receiver, the transmitter and/or the receiver have a transparent design and are integrated into the windshield. The transparent optical elements may thus be situated in the area of a wiped field of the windshield cleaned by the windshield wiper.