Behind the Screens
Brighter, purer lights give flat-panel and rear-projection TVs a boost
Pricey plasmas aside, most types of big-screen TVs and projectors are lit by an incandescent bulb or fluorescent lamp, which lasts anywhere from 1,500 to 8,000 hours and isn´t pure enough to reproduce the full spectrum of colors available in HDTV. By the time your bulb burns out, though, you might have better options: TVs illuminated by LEDs and lasers can last 10,000 to 15,000 hours and create a wider color gamut. Engineers are working on boosting LED light into a beam bright enough to illuminate ever-larger flat screens. As for lasers, whose concentrated beam is bright enough to light up an 80-plus-inch screen, the trick is making them cost-efficient (a 52-inch laser TV made with today´s components would run $300,000). Coherent´s new laser system coherentinc.com reduces cost by minimizing the number of parts needed to build green and blue lasers, which could lead to laser-based TVs in two or three years. There would be a small premium in price and a huge payoff in picture quality.
Click here to find out how to build a laser on the cheap.
by Stephen Rountree
Start with an inexpensive 808-nanometer (nm) infrared laser . Focus its light through a pair of lenses  onto a crystalline semiconductor  that re-emits light at either 920nm (when making blue) or 1060nm (when making green). Halve the resulting wavelength by sending it through a second crystal  to produce visible blue (460nm) or visible green (530nm) laser light as it exits the output coupler .