Cree and Osram show off LED-based TV backlights
Osram Opto Semiconductors says that it has made an LED backlight unit that can illuminate an 82-inch LCD display.
According to the company the backlight, which is the size of a door but only 40 mm thick, is the largest such system ever built.
The backlight is based on Osram's Golden Dragon LEDs. A total of 1120 chips are used altogether, and these are arranged in clusters of four. Each cluster contains one red chip emitting at 625 nm, one blue chip emitting at 458 nm, and two green chips that peak at 527 nm.
These emission wavelengths have been slightly shifted from the regular Golden Dragon output, to improve the so-called "color gamut", or fidelity of color reproduction on-screen.
While Osram's massive light engine consumes 1 kW in power, its US rival Cree is concentrating on an energy-efficient approach to display backlighting.
The Durham, NC, company has just released substantially brighter versions of its blue and green LED chips, which are specifically targeted at the future market for LED-based backlights for PC monitors and televisions.
Cree's blue XB900 chips are said to be 38% brighter than the previous generation, with a minimum radiant flux of 65-90 mW. The new green chips in the same product family produce a minimum radiant flux of 30-40 mW - a 33% increase.
This extra brightness means that less power is needed to meet the specifications laid down for large-scale display backlighting applications, thereby reducing energy consumption.
"LED-based solutions for televisions were applauded initially for significantly improving color rendering," said Jerry Simmons, who manages the solid-state lighting program at Sandia National Laboratories.
"It's now clear that energy savings can also be significant if the backlighting system is designed for high energy efficiency," added Simmons.
Cree claims that its backlight has a power consumption of only 40 W, compared with 100 W for similar LED solutions and 45 W for traditional cold-cathode backlights that are used in today's LCD displays.
The company, which is demonstrating the system privately at the Society for Information Display (SID) show in Boston this week, plans to make it available commercially by late 2005.
