Home Theaters Employ Big, Bright LEDs

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

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

"The next logical step after rear projection televisions is home theater systems," notes Matt Mazzuchi, general manager of the Projection Display Business Group at Luminus Devices. "A lot of consumers are starting to invest in high-definition projection systems for the home. And they want the benefits of LED technology so they can get the best bang for their buck."

The LEDs serve as a replacement for conventional mercury vapor arc lamps, commonly employed in DLP-based projectors. LEDs are said to offer several advantages over the mercury lamps, including instant start-up and no warm-up time. They also last the lifetime of the projector, and maintain their color stability over time.

Up to now, however, LEDs have more often been integrated into smaller applications, such as Christmas lights and flashlights. They haven't typically served in home theater projectors because they weren't big enough or bright enough.

Luminus engineers say they've solved those problems because their devices are significantly larger and can operate at higher current levels. Unlike many LEDs that 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 out enormously more light than other LEDs," Mazzuchi says. "And that light can be used in these large panel projection systems very efficiently."

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

"If you're an optical systems designer and you have to shoot all your light into a pipe, the Lambertian system could be unusable for you because the light shoots off at all angles," Mazzuchi says. "In ours, all the light shoots out of the top, so you can get more of the light into the system."

Delta Electronics is employing the PhlatLight technology in its HT-8000 projector, which serves in Vivitek USA's H6080FD home theater system. Similarly, Chi Lin is combining the PT-120 chipset with TI's DLP technology in its new home theater system.

Both projector manufacturers worked closely with Luminus and with Texas Instruments on the construction of the optical engines, which process the light from the LEDs through separate channels for red, green and blue light devices. Projectors from both companies are due out in 2009.

Luminus engineers predict that large LEDs like theirs will be key in driving the move toward LED-based projectors in home theater systems.

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