With incandescent light bulbs in the process of being phased out around the world, LEDs are one of the most promising technologies for taking over our day-to-day lighting needs - they use less energy, provide more light, contain less toxic substances, and are tougher than incandescents. That said, they may not be the one and only best choice. Lasers are even more efficient than LEDs at high amperages, although scientists have long believed that the quality of white light produced by diode lasers would be unpleasing to the human eye. According to a study recently carried out by Sandia National Laboratories, however, the human eye appears to like their light just fine.
To create white light, the beams of blue, red, green, and yellow diode lasers are merged, combining their four very narrow-band wavelengths. Sunlight, by contrast, incorporates a much wider light spectrum, with no gaps between wavelengths - even LEDs have a spectrum that is ten times wider than that of white laser light. For this reason, it had been assumed that people would find laser light unpleasant.
The study was performed at the University of New Mexico's Center for High Technology Materials. A total of 40 volunteers were individually shown two identical bowls of fruit, set side-by-side but in separate chambers. Each bowl was randomly lit by warm, cool, or neutral white LEDs; a tungsten-filament incandescent light bulb; or by the four combined diode lasers. In each case, the volunteers had to state which type of light they preferred, without knowing which was which - the people administering the tests were also unaware of what particular combination each volunteer was viewing.
The volunteers came from a wide range of age groups, with each person having to choose a total of 80 times between two types of light.
When all was said and done, it turned out that there was a "statistically significant preference" for the laser light over that of the warm and the cool LEDs. There was little difference between preferences for the laser, neutral LED or incandescent lights.
Laser-based lighting (left) and incandescent lighting (right)
While the apparent acceptance of the laser-based light is surprising, it doesn't necessarily mean that such technology will be usurping LEDs any time soon. Diode lasers are still more expensive to produce than LED bulbs, plus the yellow and green lasers aren't yet efficient enough for commercial use.
Sandia's Jeff Tsao, who proposed the experiment, has suggested that it might instead make sense to combine the two technologies - creating white light using blue and red diode lasers with yellow and green LEDs, for example. The combinations of the different colors could then be tweaked by users, to produce multiple color temperatures of light from one source.
In the meantime, BMW is already planning on using blue diode lasers to produce white light in the headlights of its i8 concept car.
