Method for detecting the width and position of documents using image information in a large-format scanner system

摘要

Documents in a large-format scanning system are scanned by coarsely recognizing longitudinal or transverse transition regions between a reflector roller and a document by the substeps of dividing the scanning image transversely into uniform image strips, determining statistical parameters for each image strip, examining the scanning image in the image strips with fixed threshold values for deviations such that, if a value of one the statistical parameters of an image strip exceeds the threshold value, this region is recognized as being a transverse transition region between the reflector roller and the document, and examining the image strips to determine the longitudinal transition region by line-by-line generation of an average value and determining sufficiently strong and steep edges, the image strips being rotated incrementally from the transverse of the document to an acute angle. Then longitudinal or transverse document edges within the transition regions detected by coarse recognition are finely recognized.

主权项

1. A method of recognizing the width and position of documents in a large-format scanning system having at least one image-detecting element that records image information from an original passing in a direction past the element, a transparent plate in front of the element, and at least one roller opposite the image-detecting element, the method comprising the steps of:
S1) before the document reaches the roller, preprocessing the recorded image information in order to reduce interference factors due to contamination of the transparent plate and roller; S2) coarsely recognizing longitudinal or transverse transition regions between the roller and the document by the substeps of: S2a) dividing a scanning image transversely into uniform image strips, S2b) determining statistical parameters for each image strip, S2c) examining the scanning image in the image strips with fixed threshold values for deviations such that, if a value of one the statistical parameters of an image strip exceeds the threshold value, this region is recognized as being a transverse transition region between the roller and the document, and S2d) examining the image strips to determine the longitudinal transition region by line-by-line generation of an average value and determining sufficiently strong and steep edges, the image strips being rotated incrementally from the transverse of the document to an angle of at most 90°; and S3) finely recognizing longitudinal or transverse document edges within the transition regions detected in step S2 by coarse recognition.