A sensor system is described for detecting wetting of a window includes a photodetector having multiple light-sensitive elements and a light source for emitting light to a detection region of the window in such a way that a portion of the light is reflected at the window, and another portion of the light passes through the window. The light source and the light-sensitive element are situated in such a way that a portion of the light from the light source which passes through the window is reflected at the wetting and strikes a portion of the light-sensitive elements. The light source includes a lighting element which is set up to irradiate into a transparent body. The transparent body has a surface which has defined unevennesses for the diffuse radiation of the irradiated light.