Browse Prior Art Database

Unauthorized Copy Prevention

IP.com Disclosure Number: IPCOM000083511D
Original Publication Date: 1975-Jun-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Bruce, GD: AUTHOR

Abstract

Document security is provided by recording not-to-be-copied information onto plain paper, which has been overprinted with a cyclic repeating background pattern. This background patter produces a detectable cyclic signal during a subsequent attempt to copy the document by the use of a scanning type office copier. Detection of this signal patter by a detector housed within the copier inhibits copying by the copier.

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Unauthorized Copy Prevention

Document security is provided by recording not-to-be-copied information onto plain paper, which has been overprinted with a cyclic repeating background pattern. This background patter produces a detectable cyclic signal during a subsequent attempt to copy the document by the use of a scanning type office copier. Detection of this signal patter by a detector housed within the copier inhibits copying by the copier.

Fig. 1 shows such a sheet 10. This sheet contains two orthogonally oriented varying patterns which cyclically vary from light gray to darker gray. This patter is contrast has been exaggerated in Fig. 1, and in fact the contrast may be as subtle as a watermark in paper, such that overprinted information is very clear. However, the patter remains detectable.

If sheet 10 is scanned in direction 11, the patter represented by dark-to-light gradations between lines 12 produces a cyclic signal shown in Fig. 2, wherein the two lines 13 and 14 represent white and black, respectively.

Fig. 3 shows this sheet, with its recorded information, placed on the document glass 15 of a scanning type office copier. Light source 16 scans the document by movement in direction 17. Light 18, reflected off the document, includes the cyclic pattern of Fig. 2.

The office copier is constructed to first scan the document as sensor 19 monitors light 18 reflected therefrom. If a pattern-produced signal is detected by bandpass detector or matched filter 20,...