Two-component white color synthesis using diffractive structures

Najdek, David; Fiala, Pavel; Richter, Ivan

doi:10.1117/1.2789643

Cited by 1 publication

(3 citation statements)

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“…Better results might be obtained by carefully selecting the illumination source as described in 12 . By mixing particular colour channels and tuning their intensities, even white light can be obtained 33 , 49 . It should be noted, that the colour purity is directly related to the observation distance and aperture size (which in our case was 60 cm and 72 mm respectively), as the further the observer’s position, the smaller the range of the wavelengths that get through an aperture, resulting in narrower diffraction intensity peaks, i.e.…”

Section: Discussionmentioning

confidence: 99%

“…It is assumed that the observer is looking at the hologram at a normal angle and the light is illuminating the hologram at 30° and 45° angles of incidence. The selected range of angles used to describe colours was also reported in 12 , 32 , 49 and represents typical illumination conditions in real life applications. The range of typical pitches—that in the case of classical grating configuration reconstruct visible colours—usually spans 940–1254 nm for the angle of incidence of 30° 12 and 667–944 nm for 41–45° 32 , 49 .…”

Section: Discussionmentioning

confidence: 99%

“…The selected range of angles used to describe colours was also reported in 12 , 32 , 49 and represents typical illumination conditions in real life applications. The range of typical pitches—that in the case of classical grating configuration reconstruct visible colours—usually spans 940–1254 nm for the angle of incidence of 30° 12 and 667–944 nm for 41–45° 32 , 49 . Similar image multiplexing performance was demonstrated on chiral metasurface structures 8 , dot-matrix holograms in photoresist 10 , 32 , electron resist 33 .…”

Section: Discussionmentioning

confidence: 99%

See 2 more Smart Citations

Dot-Matrix Hologram Rendering Algorithm and its Validation through Direct Laser Interference Patterning

Tamulevičius¹,

Juodėnas²,

Klinavičius³

et al. 2018

Sci Rep

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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.

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Section: Discussionmentioning

confidence: 99%