Browse Prior Art Database

Edge Detector for Variable Length Document Conveyer

IP.com Disclosure Number: IPCOM000079074D
Original Publication Date: 1973-May-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Fitch, EL: AUTHOR [+2]

Abstract

Documents are carried by a carrier (transport) member 12 (also not shown is an optional vacuum actuation) thru a processing position 14. The, for instance, not shown optics scans printed or other matter on the document and converts the same to electrical (video) signals. If the documents have variable length it is desirable to ascertain precisely the instant of passage of initial and trailing edges of each document, in order to properly operate the scanner or other processing apparatus.

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Edge Detector for Variable Length Document Conveyer

Documents are carried by a carrier (transport) member 12 (also not shown is an optional vacuum actuation) thru a processing position 14. The, for instance, not shown optics scans printed or other matter on the document and converts the same to electrical (video) signals. If the documents have variable length it is desirable to ascertain precisely the instant of passage of initial and trailing edges of each document, in order to properly operate the scanner or other processing apparatus.

For this purpose, a pair of photocells 16,17 mounted beneath the carrier communicates through staggered holes 20 in the carrier, with respective light beams conducted by light pipes 22,23. The staggered holes overlap so that in the absence of a document, at least one of the photocells is illuminated for all positions of the carrier. Only at the instant that an edge of a document passes the photocell sensing position will both photocells be effectively occluded. This then provides an unambiguous indication of the instant of edge passage relative to the photocells, and inferentially relative to processing position 14 since the document velocity or distance to the processing station is known.

With a single photocell and single row of holes, the edge of the document could be situated between holes or the instant of passage over the photocell position; giving rise to positional uncertainty proportionate to the spacing between holes. B...