A device and a method for detecting rain on a pane, e.g. of a motor vehicle, use a camera or other light sensor and a lighting source. The camera is disposed behind an inner surface of the pane and focused onto a far range that lies in front of an outer surface of the pane. The lighting source generates a source light beam and directs it onto the inner surface of the pane such that at least one resultant reflected beam (r2; r2′) that is reflected from the outer surface of the pane impinges on the camera. The light quantity of the at least one resultant reflected beam is measured by the camera.