Self-propelled harvesters may be designed as combine harvesters with crop gathering machines adapted to the respective crop. In spite of a plurality of automatic settings of crop gathering machines, such as for example, cutting height, reel position and cutter bar position, the driver of the combine harvester must continuously visually monitor the crop flow within the crop gathering machine. For example, the driver must make certain that a uniform crop flow speed is present within the crop gathering machine, since in the case of a non-uniform crop flow, the vehicle speed and thus crop collection must be reduced in order to prevent crop jams. If a crop jam occurs (e.g., a blocking of the crop flow), the harvesting operation must be terminated and a time-consuming elimination of the crop jam must be performed. The time required for this significantly impairs the efficiency of the harvesting. One problem in avoiding a crop jam is that by the time a completely developed crop jam can be clearly recognized, it is frequently too late to correct the operation of the crop gathering machine.
Published application DE 10 2008 032 191 A1 describes a self-propelled harvester with a sensor unit for monitoring the crop flow within a crop gathering machine of the harvester. A camera is provided which creates images of the crop flow. These images are then subjected to a motion blur method or an image comparison method. In the case of the motion blur method, by setting the exposure times of the cameras, irregularities in the crop flow are recorded by means of the image sharpness.