US Patent 9319637 Vehicle vision system with lens pollution detection

A vision system for a vehicle includes a camera and a processor operable to process image data captured by the camera. When the vehicle is moving, the processor at least one of (a) reads a selected set of imager register values and compare a contrast of auto exposure control zones, and wherein, responsive to a determination that a range of contrast levels is less than a threshold level, the processor determines that there are contaminants at the lens or cover of the camera, and (b) monitors outputs of photosensing elements of the camera and, when the outputs fit a Gaussian distribution, the processor classifies the photosensing elements as blocked elements and, responsive to a determination that a number of the blocked photosensing elements is greater than a threshold level, the processor determines that there are contaminants at the lens or cover of the camera.