Driven by Lumus' patented Light-guide Optical Element, a micro-display pod, and the Optical Engine which projects light into the lens -- where it is reflected back to the user's eye via reflectors embedded in the lens -- the Lumus' DK-32 delivers a bright 720p 3D-capable display that only weighs 27 grams.

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The Economist's Big Mac Index, a light-hearted guide to how far currencies are from fair value, provides some answers.

ECONOMIST: Food for thought about exchange-rate controversies

IX, in contrast, uses fibre-optic strands to guide the light from its lamp to the individual holes in its star-masks.

ECONOMIST: The joys of indoor star-gazing

Until now, these have relied on what are known as "metamaterials" - artificially-produced materials that have microscopic variations in their properties that guide incoming light waves around or over a hidden object.

BBC: Invisibility cloaking benefits from crystal-clear idea