1. A system which inspects pattern-bearing material that is subject to topical distortions, comprising: means for scanning in a first direction a plurality of predefined local regions of a pattern to be inspected to provide an image of each local region, said means for scanning having a scan width, in a second direction, greater than the width in the second direction of each said local region; means for generating a reference image for each of said local regions; means for shifting the position of the image of each said local region and the position of its corresponding reference image relative to each other to align as a pair the images in the second direction; means for modifying in the first direction at least one of the dimension of the image of each said local region and the dimension of its corresponding reference image relative to each other to align as a pair the images in the first direction; and means for comparing each pair of aligned images to detect errors in the pattern independent of misalignment of and topical distortions of each said local region.