Browse Prior Art Database

Control Logic for White Document Sensor

IP.com Disclosure Number: IPCOM000082017D
Original Publication Date: 1974-Sep-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 51K

Publishing Venue

IBM

Related People

Hubbard, JH: AUTHOR [+2]

Abstract

A white document sensor is used in copying machines to eliminate the black leading edge that normally occurs on copy sheets, when copies are made of a small document. The document sensor senses the leading edge position of the original document with respect to the edge of the document glass and controls the turnoff of an erase lamp. Control logic is employed to provide an accurate time delay independent of the tolerance of electrical components employed.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 3

Control Logic for White Document Sensor

A white document sensor is used in copying machines to eliminate the black leading edge that normally occurs on copy sheets, when copies are made of a small document. The document sensor senses the leading edge position of the original document with respect to the edge of the document glass and controls the turnoff of an erase lamp. Control logic is employed to provide an accurate time delay independent of the tolerance of electrical components employed.

A copying machine employs a rotating photoreceptive drum 11 which is electrostatically charged by charging apparatus 13, and discharged in image pattern configuration at imaging station 15. An erase lamp 17 is employed to discharge interimage areas on drum 11. The erase lamp is actuated and deactuated under the control of an emitter rotating with drum 11, which defines the image and nonimage (interimage) areas.

The image of document 19 placed on document glass 21 is scanned by an optical scanning system, not shown, onto mirrors 22 and 23 which reflect the image to the imaging station 15. A white cover, not shown, is normally placed behind the document 19 to thereby discharge the areas bordering the image area on the drum 11. When a book or the like is placed on document glass 21, the area surrounding the document 19 on document glass 21 not covered thereby is nonreflective, thereby causing a nondischarged border area to be located about the image of document 19 on the surface of drum 11.

In order to discharge the drum 11 at the portion which receives an image of area 25 (leading edge margin), a scanning photodetector 27 is employed to provide an output signal to control logic 36 to indicate the position of the leading edge of document 19 with respect to the edge of document glass 21. Photodetector 27 scans document 19 and can be mounted on the same carriage as the optical scanning device, not shown.

Since sensor 27 views the document 18 at the same time that the document is imaged on drum 11 at station 15, it is necessary for the control logic 36...