There is no doubt that the near-term future of lighting belongs to the LED.
Inexorably, LEDs have replaced traditional lighting sources in our homes, offices and workplaces. The urban landscape has been forever altered by bright, white LED street and pedestrian lighting. Buildings soar into the sky illuminated as beacons to be seen for miles.
Not all of these improvements come without controversy: light pollution, glare, the disruption of migratory patterns and circadian rhythms, to name but a few. It seems that in the rush to develop all things LED, one of our best tools got left behind … glare control.
Don’t blame it on the manufacturers; blame it on science. There is this theoretical thing called a point source. It’s really small. In fact, it’s impossible (or improbable) to achieve in a luminaire. The smaller the source the better the optical system performs.
Traditional sources used glowing filaments or electric arcs to produce light. These relatively small sources were then manipulated by reflection and refraction to do our bidding. Add shielding and you could get a lot of light to go a long way with minimal objectionable glare, as long as the fixture was properly placed. These were big fixtures with big bulbs, but because they had a point source, they could be controlled.
Today, many modern lighting sources create white light by exciting phosphors – think about the white powder in a broken fluorescent lamp. The lamp emits blue or ultraviolet light; this light, in turn, causes the phosphor powders to glow. The more blue light energy you pump into the phosphors, the brighter they glow. Unfortunately, current LED output is restricted by size and thermal issues, so at a certain point you have to add more emitters if you want more light. More emitters make a larger source, a larger source is less optically efficient, and you end up with the glare bombs we have come to accept in architecture and area lighting applications.
What if we could pump more light into a smaller phosphor?
What if we could regain optical control of our tools?
We need a new source.
Enter the laser diode. Like a light-emitting diode, the laser diode is a solid state device that emits light. In the case of the laser diode, it emits coherent light in a very tight beam. Laser diodes have been around for a long time (they are in CD and DVD players), and like all solid state devices, they continue to improve as technology advances.
The laser diode allows more blue light to be delivered to a smaller area of phosphor. This, in turn, allows the source to produce more light from a smaller package. How much more remains to be seen, but this technology is definitely on the horizon. BMW has shown a concept car with prototype laser-based headlamps, and a major LED lamp manufacturer has just spun off a laser division to pursue this technology.
They say everything old is new again.
I’ve got my fingers crossed.