Vision system for a motor vehicle and method of controlling a vision system

A vision system for a motor vehicle, comprising a pair of imaging devices forming a stereo imaging apparatus and a data processing device adapted to perform a rectification of images captured by the stereo imaging apparatus, a stereo matching of rectified images to produce stereo matched images, and to detect an object in an area surrounding the motor vehicle from the stereo matched images, the data processing device is adapted to perform, for image elements of a rectified image from one of the imaging devices, a search for a best-matching image element in a rectified image from the other of the imaging devices, the search covering a two-dimensional search area, the search yielding vertical shift information from which a vertical shift from an image element to the best-matching image element is derivable, wherein the vertical shift information comprises a plurality of match related scores indicating a degree of match in the vertical shift information from one of the imaging devices between the image element and a plurality of image elements of a corresponding image from the other of the imaging devices shifted with different vertical components relative to the image element from one of the imaging devices, yielding a vertical matching cost cube, the plurality of the image elements from the imaging devices are bundled into larger image regions and for each vertical shift the match related scores from each image element in the image regions are accumulated, yielding a reduced size version of the matching cost cube, wherein the data processing device is adapted to calculate a pitch angle error or a roll angle error of or between the imaging devices from the vertical shift information.