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Size or position sensing of intermixed sheets in a sheet stacking tray with sheet edge shadow detection

  • US 5,847,405 A
  • Filed: 09/04/1997
  • Issued: 12/08/1998
  • Est. Priority Date: 09/04/1997
  • Status: Expired due to Term
First Claim
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1. A non-contact optical sheet size or position detection system for a sheet stacking tray in which thin document sheets of different sizes or positions are stacked on top of one another;

  • said sheet detection system detecting the position of at least one sheet edge of an outside (top or bottom) sheet of said stack, comprising;

    an illumination source for illuminating for light reflection therefrom an area of the surface of said outside sheet of said stack,said illuminated area including at least said one sheet edge,said illumination from said illumination source being at a sufficiently shallow illumination angle to the surface of said outside sheet to generate a detectable edge shadow directly adjacent to said sheet edge, which edge shadow is relatively darker than reflected said illumination of said top sheet adjacent thereto,said illumination angle being substantially greater than a grazing angle to not form shadows from said surface of said sheet,and an optical detection system positioned to remotely detect said detectable edge shadow without contacting said outside sheet or said stack,said optical detection system providing location information for the location of said edge shadow so as to provide location information for said sheet edge of said outside sheet of said stack,wherein said sheet stacking tray is part of a document sheet feeder for sequentially feeding said outer sheet from said stack by moving said outer sheet away from said stack to be imaged, and wherein said optical detection system is responsive only to a detected said sheet edge shadow which is detected as moving, so as to determine the size of the sheet being fed to be imaged relative to other sheets in said stack irrespective of different sizes of document sheets in said stack.

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