LEDs Fueling New Lampless Projectors
LED technology is behind new projectors which offer brighter colors and a longer life-span.
Earlier this year, we profiled LED-based rear projection TVs using Luminus Devices’ PhlatLight technology. Several readers also expressed interest in LED-based front projectors. Well, after returning from the 2008 CEDIA show, I can definitely say that LED-based front projectors will be coming to a home theater near you in the not-so-distant future.
At this time, LED illumination seems to be focused solely on those projectors utilizing Texas Instruments’s DLP imaging technology. But Epson, who created the competing 3LCD display technology, believes that LED illumination will also be used in their projectors sometime in the future (but would not specify if it was next year or a couple of years from now).
Arc Lamps and Color Wheels
Currently, front projectors that use DLP technology require an arc lamp, color wheel, and mechanical shutter to produce images. Lamps offer terrific brightness, but burn out after a couple of thousand hours or so, and need to be replaced. Replacement bulbs can run several hundred dollars. LEDs, on the other hand, offer a stable light output solution during the entire life of the projector. Whereas, arc lamps decrease in brightness over time because of fading (and become dimmer), LEDs offer a constant and consistent light source over time. And, unlike arc lamps, there is no mercury in LEDs so there’s no replacement hazard or stockpiling of hazardous materials in landfills. LEDs are also an energy-efficient and green technology.
Color wheels have always been problematical in my mind. They spin at high RPMs, but can be subject to noise and mechanical degradation over time. Color wheels may also contribute to the annoying (for some people) “rainbow” effect that has plagued DLP projection displays for years. In my life as a product reviewer, I’ve even had sets with color wheels that wobbled distorting the on-screen image. Employing a stable light source such as LED (rated at somewhere between 50,000 and 100,000 hours of viewing) to illuminate front projectors eliminates another potential defect by taking away the color wheel entirely. Lastly, LED illumination also takes away the mechanical shutter, which has its own set of problems. Overall, the LED illumination system replaces the lamp, the color wheel and the shutter of a traditional projector. What is crucial here is that various companies have come together to produce a precise and complex control algorithm that allows the LED to work with the DMD to get high image quality.
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[Link: electronichouse.com]
