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Optical Engineering

Anticounterfeiting method for a dot-matrix hologram composed of grating dots with different fringe orientations
Author(s): Sheng Lih Yeh; Shyh Tsong Lin
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Paper Abstract

A method for identifying a dot-matrix hologram composed of grating dots with different fringe orientations is proposed. Two neighboring grating dots, Dot 1 and Dot 2, are selected. The intersection angle between the two sets of fringes of the two grating dots must be smaller than a threshold angle, e.g., 50 deg. The overlapping region of Dot 1 and Dot 2 can show a moiré pattern composed of many stripes. Some of the stripes contain the same fringe orientation as that of Dot 1, some of the stripes contain the same fringe orientation as that of Dot 2, and some of the stripes contain special fringe orientations different from those of Dot 1 and Dot 2. The stripes which contain special fringe orientations are called transition stripes here, and the number of transition stripes (transition stripe number) is used to identify Dot 1 and Dot 2. Because the transition stripe number for a dot pair is sensitively affected by the distance between the dot pair and the grating brightness distributions of the two dots, it is difficult to correctly reproduce the transition stripe numbers for the grating dot pairs on a dot-matrix hologram, i.e., counterfeiting the hologram is not easy.

Paper Details

Date Published: 16 November 2015
PDF: 5 pages
Opt. Eng. 54(11) 113106 doi: 10.1117/1.OE.54.11.113106
Published in: Optical Engineering Volume 54, Issue 11
Show Author Affiliations
Sheng Lih Yeh, Lunghwa Univ. of Science and Technology (Taiwan)
Shyh Tsong Lin, National Taipei Univ. of Technology (Taiwan)


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