Home Theaters Employ Big, Bright LEDs

Home theater projector makers at the recent Consumer Electronics Show (CES) demonstrateda new technological twist: using light-emitting diodes (LEDs) to power theiroptical engines.

At least twomanufacturers at CES showed off LED-based home projectors. Chi Lin Technology Co. Ltd.and Delta Electronics, Inc. are said tobe the first of a wave of manufacturers making digital light processing (DLP)projectors and using high-powered LEDs as a source of illumination. Bothcompanies employed DLP technology from Texas Instruments and PhlatLight PT-120 LED chipsetsfrom Luminus Devices in their hometheater projectors.

"The nextlogical step after rear projection televisions is home theater systems," notesMatt Mazzuchi, general manager of the Projection Display Business Group atLuminus Devices. "A lot of consumers are starting to invest in high-definitionprojection systems for the home. And they want the benefits of LED technologyso they can get the best bang for their buck."

The LEDsserve as a replacement for conventional mercury vapor arc lamps, commonlyemployed in DLP-based projectors. LEDs are said to offer several advantagesover the mercury lamps, including instant start-up and no warm-up time. Theyalso last the lifetime of the projector, and maintain their color stabilityover time.

Up to now, however, LEDs have moreoften been integrated into smaller applications, such as Christmas lights andflashlights. They haven't typically served in home theater projectors becausethey weren't big enough or bright enough.

Luminusengineers say they've solved those problems because their devices aresignificantly larger and can operate at higher current levels. Unlike many LEDsthat measure about 1 mm² and operate at about 350 mA, Luminus'PT-120 measures about 12 mm on a side and can run at currents as high as 30 A.

"We put outenormously more light than other LEDs," Mazzuchi says. "And that light can beused in these large panel projection systems very efficiently."

Luminussays that its technology is also significant for home theater projectorsbecause it employs a so-called "photonic lattice" - a micro-structure embeddedin the surface of the LED that affects the light output of the device. Incontrast to conventional LEDs, which use a "Lambertian" method of lightreflectance that allows light to be equally distributed across a 180° plane,Luminus' PhlatLight systems maximize light extraction out of the top of theLED. The effect is that the light is more concentrated.

"If you'rean optical systems designer and you have to shoot all your light into a pipe, theLambertian system could be unusable for you because the light shoots off at allangles," Mazzuchi says. "In ours, all the light shoots out of the top, so you canget more of the light into the system."

Delta Electronicsis employing the PhlatLight technology in its HT-8000 projector, which servesin Vivitek USA'sH6080FD home theater system. Similarly, Chi Lin is combining the PT-120 chipsetwith TI's DLP technology in its new home theater system.

Bothprojector manufacturers worked closely with Luminus and with Texas Instruments onthe construction of the optical engines, which process the light from the LEDsthrough separate channels for red, green and blue light devices. Projectorsfrom both companies are due out in 2009.

Luminusengineers predict that large LEDs like theirs will be key in driving the movetoward LED-based projectors in home theater systems.

"Up to now,the LEDs simply weren't big enough and didn't offer enough brightness to makeit happen," Mazzuchi says. "But the big LEDs work because they deliver a lot ofbrightness into the optical aperture of the system."