Determination of the presence of moisture on a windscreen

A sensor device for detecting a wetting condition on a windshield where radiation emitted by a radiation transmitter is coupled with the windshield by a coupling element with a beam acceptance surface designed as focusing lens and where, following at least one total reflection from the windshield via a decoupling element which has a beam emission surface that is also a focusing lens. The radiation is decoupled to a radiation receiver and the axial transmitter radiation is totally reflected on a level first limiting surface, and the radiation acceptance surface has a spherical shape. The radiation transmitter is arranged such that the diverging transmitter radiation is essentially focused axis-parallel toward the first limiting surface and that the dimensions of the first limiting surface are at least big enough so that it detects the complete parallel-focused beam of rays.