摘要 |
<p>A flexible technique that is robust in the presence of noise and distortion is disclosed for locating and utilizing fiducial markings to locate predetermined areas within an image. Initially, a set of candidate markings is determined, one marking from within each of a plurality of predesignated areas of a scanned image. Thereafter, an estimate of a set of image distortion factors relative to an ideally registered image of the same type as the scanned image is derived. Predicted locations for the fiducial markings are derived using this estimated set of image distortion factors. If the difference in location between the actual location of any candidate marking and its predicted location is greater than a predetermined threshold, at least one such candidate is removed from the set of candidate markings. The estimation and removal processes are repeated, utilizing the new current set of candidate fiducial markings until all remaining candidate markings are within a predetermined distance of their predicted locations. Predetermined areas within the scanned image can thereafter be accurately located by combining the known location of the area within an ideal image with the final estimated set of image distortion factors. The predicted location may be further improved by using a weighted average of the ideal versus the actual fiducial marking differences, to account for local non-linear variations [FIG. 2]. <IMAGE></p> |