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METHOD TO PREVENT THE COPYING OF CLASSIFIED DOCUMENT

IP.com Disclosure Number: IPCOM000027356D
Original Publication Date: 1996-Jun-30
Included in the Prior Art Database: 2004-Apr-07
Document File: 2 page(s) / 64K

Publishing Venue

Xerox Disclosure Journal

Abstract

Fluorescent chemicals that emit light of characteristic fiequencies when excited can be used to encrypt paper for classified documents. The paper can be so treated either before or after printing to enable a detection and alert mechanism against copying. The copier can be equipped with light detectors that are sensitive to very narrow bandwidths. If the light emitted by the document is detected to be modulated in schronization with an excitation light, a signal is sent to the copier's electronics to reject copying.

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XEROX DISCLOSURE JOURNAL

METHOD TO PREVENT THE COPYING OF CLASSIFIED DOCUMENT U. S. C1.355/201 Richard H. Boerger

Proposed Classification

Int. C1. G03g 21/00

Fluorescent chemicals that emit light of characteristic fiequencies when excited can be used to encrypt paper for classified documents. The paper can be so treated either before or after printing to enable a detection and alert mechanism against copying. The copier can be equipped with light detectors that are sensitive to very narrow bandwidths. If the light emitted by the document is detected to be modulated in schronization with an excitation light, a signal is sent to the copier's electronics to reject copying.

The decay time for fluorescent materials can be very short, for example, lo-' seconds, allowing the detection scheme to be quick and not delay routine copying processes. The wavelengths selected for excitation and emission should be preferably similar in order to make it impossible to filter the light at the platen and circumvent the device. Multilayer filters on the light sensor(s) permit very tight bandwidths to be selected.

Two preferred detection schemes are wherein the modulation of the excitation light being compared to the demodulated waveform of the fluorescent light; and wherein a comparison is made of the demodulated waveform of the excitation light and the demodulated waveform of the fluorescent light, using two light sensors filtered to the two slightly different wavelengths.

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