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Proceedings Paper

New applications of modulated digital images in document security
Author(s): Robert A. Lee; Patrick W. Leech; Lawry D McCarthy; Gerhard F. Swiegers
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Paper Abstract

In previous work we have demonstrated that selective masking, or modulation, of digital images can be used to create documents and transparent media containing covert or optically variable, overt images. In the present work we describe new applications and techniques of such "modulated digital images" (MDI's) in document security. In particular, we demonstrate that multiple hidden images can be imperceptibly concealed within visible, host images by incorporating them as a new, half-tone, printing screen. Half-toned hidden images of this type may contain a variety of novel features that hinder unauthorized copying, including concealed multiple images, and microprinted-, color-, and various fadeeffects. Black-and-white or full color images may be readily used in this respect. We also report a new technique for the embossing of multiple, covert- or optically variable, overt-images into transparent substrates. This method employs an embossing tool that is prepared using a combination of electron beam and greytone lithography. Two approaches may be used: (i) a double-sided "soft" emboss into curable, transparent, lacquer layers, and (ii) a single-sided "hot" emboss in which multiple, dithered images consisting of distinctly-sloped microprisms are impressed into the substrate. Technique (ii) requires a novel, electron-beam-originated master dye.

Paper Details

Date Published: 9 February 2006
PDF: 13 pages
Proc. SPIE 6075, Optical Security and Counterfeit Deterrence Techniques VI, 60750C (9 February 2006); doi: 10.1117/12.642440
Show Author Affiliations
Robert A. Lee, Commonwealth Scientific and Industrial Research Organisation (Australia)
Patrick W. Leech, Commonwealth Scientific and Industrial Research Organisation (Australia)
Lawry D McCarthy, Commonwealth Scientific and Industrial Research Organisation (Australia)
Gerhard F. Swiegers, Commonwealth Scientific and Industrial Research Organisation (Australia)


Published in SPIE Proceedings Vol. 6075:
Optical Security and Counterfeit Deterrence Techniques VI
Rudolf L. van Renesse, Editor(s)

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