News & Views | Published:


Darkened light

Naturevolume 417page914 (2002) | Download Citation


'Dayglo' dyes look brighter than they should. They absorb invisible ultraviolet, and re-emit that energy in a lower visible band, perhaps as green, orange or red. Normal dyestuffs, with a broad visible band, must also be fluorescent. Illuminated with sharp, narrow-band light, a dye will be raised to its excited electronic state, and will re-radiate that energy over its whole broad visible band. This range of re-emitted frequencies is much wider than those inserted by the narrow-band source. Luckily, the Sun and most lamps are such broad-band sources that we notice no effect.

Yet 'same-band fluorescence' should be far commoner and more efficient than the two-band variety of Dayglo dyes. So Daedalus is now lighting targets with modern narrow-band sources: lasers, metal-vapour lamps, LEDs. For each source, he has a matching pair of narrow-band rejector spectacles, whose 'notch' cuts out just the frequency of the source. Although mildly coloured, they darken the lamp itself for the wearer. But the pigment — DREADCO's Lampglo dye — fluoresces either side of that region in almost full wide-band glory. Unblinded by lamps, the wearer will see the dye very brightly.

In an ordinary room lit by broad-band tungsten bulbs, Lampglo dye will seem unexceptional. Its novel power will be felt only in rooms lit by narrow-band emitters, and to wearers of DREADCO spectacles with a coincident absorptive 'notch'. The lamps will hardly be visible, but Lampglo-dyed domestic objects will shine brightly indeed. Computer and TV screens will be quite black, but for their own light.

Daedalus plans to transform night driving as well. Sodium street lamps are narrow-band metal-vapour emitters already, so properly notched spectacles will hardly see them. DREADCO sodium headlamps on approaching cars will also fail to dazzle. But Lampglo-coloured cars will show up well, as will the Lampglo road itself.

A rethink of the content of News & Views means that this is David Jones's last Daedalus column for Nature. The column has appeared for the past 14 years, apart from a five-month break at one point, and was published for 24 years before that in New Scientist. We owe David thanks for his consummate professionalism as a columnist, and for entertaining, stimulating, provoking and — sometimes — perplexing Nature readers over so many years. He can be contacted at, Nature


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