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Copier Security System

IP.com Disclosure Number: IPCOM000083973D
Original Publication Date: 1975-Aug-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 13K

Publishing Venue

IBM

Related People

Galli, G: AUTHOR [+2]

Abstract

An office copier is equipped with a security system with provision for distinguishing confidential documents from normal document material. A document is coded as confidential by coating or impregnating the paper with a dye having strong optical absorption over a narrow wavelength region. Three light detectors are provided in the copier in a position to intercept light reflected from the document. By the use of proper filters each of these detectors is set to measure the reflectance of the document over a narrow band corresponding to red, green or blue light, for example.

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Copier Security System

An office copier is equipped with a security system with provision for distinguishing confidential documents from normal document material. A document is coded as confidential by coating or impregnating the paper with a dye having strong optical absorption over a narrow wavelength region. Three light detectors are provided in the copier in a position to intercept light reflected from the document. By the use of proper filters each of these detectors is set to measure the reflectance of the document over a narrow band corresponding to red, green or blue light, for example.

Since the confidential document has strong absorption over only one band (green, for example), the diffuse reflection from the paper will be uniquely coded. The signals from each of the three detectors are then compared. When the coded signal is less than either of the other two, this is an indication that an attempt is being made to copy a confidential document and an electronic circuit is provided to abort the copy cycle.

This security system utilizes the exposure light in a copy machine to illuminate the document. The dye used to code the confidential document should have a narrow absorption band so that for ease of detection, light detected from the coded paper will be reduced in intensity by an order of magnitude or more within the absorption band of the dye. However, since the absorption band is narrow, the reflection density for white light is low and the information on the document can be easily read in ordinary light. Many organic dyes in solution have such an absorption spectrum. These dyes can be incorporated into the paper in solid solution or coated on the paper in a supporting resin.

A subtractive color process is used so that the co...