Camera system, method for operation of a camera system and sensor device of a camera system

aThe invention concerns a camera system, especially a camera system in a camera-based analysis system and/or assistance system of a vehicle, comprising a camera with an optical beam path, which has at least one optical element to guide image information to a light-sensitive image sensor. At least one test beam can be coupled into a transparent test element arranged on the input side in front of beam path and, depending on a degree of soiling of the test element, at least one partial beam indicating soiling can be directed from the test element onto a sensor to receive the partial beam indicating soiling.