The invention relates to a device for keeping optical elements (1) clean in motor vehicles, in particular sensor or camera covers. This is done according to the present invention by applying a directed stream of gas, in particular a stream of air (4), to the transparent cover (2) in such a way that when the cover moves (6) relative to the surroundings no ambient atmosphere (10), in particular no ambient air, reaches the surface (20) of the cover. According to one embodiment, using a nozzle (3) pressurized air (4) is blown in, producing a transverse air stream (9). It is also possible, using a cover, to form a buffer space in front of the cover in addition to the transverse air stream. In a further refinement, a cleaning nozzle and a heater for the cover can be provided, in order to also be able to perform cleaning when soiling has occurred during stationary operation and to remove icing at low temperatures. To this end the cleaning fluid and / or the supplied air may also be pre-heated.