METHOD FOR DETECTING PRECIPITATION ON A WINDSCREEN

摘要

The invention relates to a method for detecting precipitation, especially rain and fog, on a windscreen, which is not based on an active illumination of the windscreen or a measurement of the reflectivity, but on a camera using a plurality of adjacent pixels for detecting an image of a target area. Said target area is located in the surroundings of the vehicle, and the windscreen is thus represented in a blurred manner. In the event of a blurred representation, raindrops or fog on the windscreen produce a soft-focus effect in the image. The sharpness of the image and/or the difference in contrast of adjacent pixels is evaluated and the presence of precipitation is detected therefrom, the image is then preferably subjected to a two-dimensional Fourier transformation and the spatial frequencies are evaluated. A first image is recorded especially for a low contrast target area, a windscreen wiper passing over the windscreen in the visual region of the camera or a heating process is activated, and a second image is then recorded, and both images are evaluated according to changes.