1 October 1991 Frequency modulation of printed gratings as a protection against copying
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Proceedings Volume 1509, Holographic Optical Security Systems; (1991) https://doi.org/10.1117/12.47113
Event: ECO4 (The Hague '91), 1991, The Hague, Netherlands
Abstract
A method for generating half-tone images on binary (i.e., paper and ink) systems using different (frequency-) modulation techniques is described. Security gratings and patterns are designed to generate 'alias' images or detectable codes, due to undersampling by the digital scanner.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Sybrand Spannenburg, Sybrand Spannenburg, } "Frequency modulation of printed gratings as a protection against copying", Proc. SPIE 1509, Holographic Optical Security Systems, (1 October 1991); doi: 10.1117/12.47113; https://doi.org/10.1117/12.47113
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