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

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Inventors: Bares, Jan, Acquaviva, Thomas
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): PYO, KEVIN K
• Application Number:
  US08/923,588
• Time in Patent Office: 460 Days
• Field of Search: 250/559.36, 250/223 R, 250/559.24, 250/559.25, 356/384, 356/385, 356/386
• US Class Current: 250/559.36
• CPC Class Codes: B65H 2220/01 indicating an entity as a function of which control, adjustment or change is performed, i.e. input
• CPC Class Codes: B65H 2220/03 indicating an entity which is measured, estimated, evaluated, calculated or determined but which does not constitute an entity which is adjusted or changed by the control process per se
• CPC Class Codes: B65H 2511/10 Size; Dimensions
• CPC Class Codes: B65H 2511/11 Length
• CPC Class Codes: B65H 2511/20 Location in space
• CPC Class Codes: B65H 2511/23 Coordinates, e.g. three dimensional coordinates
• CPC Class Codes: B65H 2511/514 Particular portion of element
• CPC Class Codes: B65H 2515/60 Optical characteristics, e.g. colour, light
• CPC Class Codes: B65H 2553/414 involving receptor receiving light reflected by a reflecting surface and emitted by a separate emitter
• CPC Class Codes: B65H 2553/416 Array arrangement, i.e. row of emitters or detectors
• CPC Class Codes: B65H 2701/131 Edges
• CPC Class Codes: B65H 7/14 by photoelectric feelers or detectors
• CPC Class Codes: G01B 11/2433 for measuring outlines by shadow casting
• CPC Class Codes: G03G 15/607 for detecting size, presence or position of original
• CPC Class Codes: G03G 2215/00215 Mixed types handled
• CPC Class Codes: G03G 2215/00324 Document property detectors
• CPC Class Codes: G03G 2215/00329 Document size detectors
• CPC Class Codes: H04N 1/00681 Detecting the presence, position or size of a sheet or correcting its position before scanning H04N1/047 takes precedence; mode signalling H04N1/333; skew detection or correction in image signals H04N1/3878

Abstract

A non-contact optical sheet size and/or position detection system for detecting the position of at least one edge of an outside (top or bottom) document sheet stacked in a sheet stacking tray in which thin document sheets of different sizes and/or positions are stacked on top of one another; with an illumination source for illuminating the potential sheet edge areas at an angle generating detectable sheet edge shadows, and an optical detection system remotely detecting the edge shadow positions to provide sheet edge location information to a control system for the imaging or offsetting of the sheet. In a document feeder for sequentially feeding a top or bottom sheet to be imaged, the detection system may be responsive only to a moving sheet edge shadow to determine the size of the sheet being fed to be imaged relative to other sheets in the stack irrespective of intermixed different sizes of sheets in the stack. For a bottom feeder the detection may be through an elongate aperture in the tray. For an output stacking system with a system for offsetting alternately printed sets of sheets in a stacking tray the detected edge shadow(s) of the top sheet may be used to control the offsetting.

Claims

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.

2. The sheet detection system of claim 1, wherein said sheet stacking tray has an elongate aperture and said optical detection system is mounted to detect the movement of the trailing edge of the bottom sheet of a range of mixed sizes of plural document sheets stacked in said sheet stacking tray of said document sheet feeder to provide a control signal to said document sheet feeder indicative of the size of the document sheet being fed by said document sheet feeder.

4. The sheet detection system of claim 1, wherein said optical detection system is intermittently activated only in time periods in which said edge shadow detection is needed for said location information.

5. The sheet detection system of claim 1, wherein said optical detection system comprises a low resolution photodetector array bar.

6. The sheet detection system of claim 1, wherein said optical detection system comprises a low resolution photodetector array bar with an optical resolution of only approximately 3 mm or greater.

7. The sheet detection system of claim 1, wherein said optical detection system is intermittently activated upon the actuation of said document sheet feeder for said document sheet being fed by said document sheet feeder.

3. 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 an output stacking system with a stacking tray in which thin printed sheets are sequentially stacked on top of other such sheets, and having an offsetting system for offsetting alternate stocks of sheets in said stacking tray, wherein said offsetting system is operatively controlled by said optical detection system sheet edge location information from a detected edge shadow of the top sheet in said stacking tray for controlling said offsetting of alternately printed stacks of sheets.