Disclosed are Power Encoder means for imprinting MICR characters on checks, with optical check-sensing means disposed along a check-transport path, including optical skew-sensor means including a pair of area-photo-sensor means, one on each side of the check whereby the differential output thereof indicates...http://www.google.fr/patents/US5021676?utm_source=gb-gplus-shareBrevet US5021676 - Document-skew detection with photosensors
