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Improved red color with cholesteric liquid crystals in Bragg reflection mode
Auteur(s)
Kipfer, Peter
Klappert, Rolf
Grupp, Joachim
Date de parution
2002
In
Optical Engineering, International Society for Optical Engineering (SPIE), 2002/41/3/638-646
Résumé
The helical pitch of the cholesteric liquid crystal (CLC) can be adjusted to reflect the colors red, green, and blue. Additive mixing of these colors in displays results in multicolor images and it is easy to use pure primary blue and green colors, but the red color is in general very unsaturated. We show by simulations that this poor red color performance is due to reflection sidebands on the smaller wavelength side of the normal red Bragg reflection band. We discuss five approaches to improve the red color performance, namely, two types of spectral filtering (dyes or filters), a very low birefringence CLC, a gradient in the birefringence of the CLC, and the use of a bluish reflector. The two methods of spectral filtering are also experimentally tested.
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Type de publication
journal article
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