Title Dot-matrix hologram rendering algorithm and its validation through direct laser interference patterning /
Authors Tamulevičius, Tomas ; Juodėnas, Mindaugas ; Klinavičius, Tomas ; Paulauskas, Andrius ; Jankauskas, Kęstutis ; Ostreika, Armantas ; Žutautas, Andrius ; Tamulevičius, Sigitas
DOI 10.1038/s41598-018-32294-5
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Is Part of Scientific reports.. London : Springer. 2018, vol. 8, art. no. 14245, p. 1-11.. ISSN 2045-2322. eISSN 2045-2322
Keywords [eng] dot-matrix hologram ; computational methods ; laser material processing ; micro-optics
Abstract [eng] The fight against forgery of valuable items demands efficient and reasonably priced solutions. A security tag featuring holographic elements for anti-counterfeiting is one of them. However, the content and colours of a diffraction image that would be seen by an observer are often counterintuitive in the design stage. Here, we propose an original algorithm based on the conical diffraction formalism, which can be used to describe the variations of a diffraction image with respect to all aspects of observation. We validate the output of the algorithm by comparing it to test holograms, which we have produced by employing direct laser interference patterning (DLIP) in electrochemically grown nickel foil. We have employed a motorized femtosecond laser system to micro-machine arrays of 65 μm × 65 μm sized diffraction gratings with a defined orientation and pitch on the order of 1 μm. Based on completed diffraction efficiency measurements, we determined optimal ablation parameters, i.e. 57.4 mJ/cm2 fluence per pulse and 1100 pulses/pixel. Furthermore, we show how accurate the proposed algorithm is through measured diffraction spectra as well as captured diffraction images of test holograms produced using the obtained parameters. Finally, we showcase anti-counterfeiting tag prototypes with complex holographic effects, i.e. colour reconstruction, animation effects, and image multiplexing. The proposed algorithm can severely shorten the time between design and production of a holographic tag, especially when realizing it via a competitive origination technology—DLIP.
Published London : Springer
Type Journal article
Language English
Publication date 2018
CC license CC license description