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New Applications Of Modulated Digital Images In Document Security, Robert A. Lee, Patrick W. Leech, Lawrey D. Mccarthy, Gerhard F. Swiegers

Faculty of Science - Papers (Archive)

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 …