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The Next Step in TV Backlighting

As published in Display Daily

Mar 23, 2010

As published in Display Daily

LED backlighting is in the process of replacing conventional LCD-TV backlighting that uses cold-cathode fluorescent  lamps (CCFLs). Some of the Tier 1 TV makers are saying that 30% to 50% of the sets they sell this year will be LED-lit.

For the most part, “LED backlighting” means edge-lighting with white LEDs. That’s what Samsung was doing last year in the extremely successful sets it labeled as “LED TV.” That moniker is incorrect and confusing, but it smacks of marketing genius in the concise way it let Samsung differentiate between its three flat-screen product categories: plasma, LCD-TV (with CCFL backlighting), and “LED-TV” (LCD-TV with LED backlighting), while implying that the new category was more revolutionary than it really was. Samsung charged a healthy premium for its “LED-TVs” last year, and people paid it. Other manufacturers have picked up the designation, and it looks like we’re stuck with it.

All of this is part of the passion panel-makers and TV makers have for pulling themselves out of the commoditization trap, which seemed inescapable only a couple of years ago. Now, TV makers are implementing a slew of value-added features and designs, such as 3D-TV, IPTV, Toshiba’s Cell TV, Sharp’s QuadPixel multi-primary TV, and, of course, LED backlighting.

But last year’s exciting premium feature is next year’s box on a buyer’s checklist. The cost premium for white-LED edge-lighting is dropping rapidly and is likely to less than $50 more than CCFL for 40-inch sets by the beginning of 2012, according to DisplaySearch. (Some panel-makers have projections that are far more aggressive than that.) This year, Westinghouse Digital has positioned itself as the company to bring LED edge-lighting to value-priced sets in the 24- to 32-inch range.

The next step in LCD-TV backlighting is direct or full-matrix LED backlighting, in which there is an array of LEDs distributed evenly behind the entire active area of the liquid-crystal display. This was actually the first approach to TV LED backlighting that was implemented by Sony and Samsung several years ago, but it was too expensive for volume products. Insight Media was quick to point out the appeal of LED edge-lighting, at least as an interim solution, but the industry was slow to give up the benefits of full-matrix backlighting: sharply extended color gamut with the use of red, green, and blue LEDs; and the ability to dim the LEDs zone by zone (local area dimming) to enhance contrast ratio and reduce power consumption.

Now, advancing technology is allowing the industry to move back to full-matrix LED backlighting, and Vizio, Sony, Samsung, Toshiba and Sharp (and perhaps others by now) have models available for sale or close to it. Vizio’s 55-inch offering in the category is priced at $2100, which is a startlingly low price. Sharp’s offering uses white LEDs rather than RGB to keep the cost down.

But direct-matrix LED backlights have their problems. They are still considerably more expensive than edge-lights, they are considerably thicker than edge-lights, and measures must be taken to compensate for the different rates at which the red, green, and blue LEDs age, as well as for the different ways their outputs vary with temperature.

Panel makers are working on these issues, but an Israeli company called Oree (www.oree-inc.com) has developed an elegant integrated solution for all of them at once. In an extensive exclusive interview, Oree CEO Eran Fine explained his company’s approach. Oree makes backlight modules, currently 50 cm2. The company purchases its RGB LEDs in chip form, and integrates them with a controller IC and temperature, luminance, and color sensors. Color mixing is accomplished with proprietary optics in less than a cm in the plane of the module, and a light guide conducts the light throughout the module and directs toward the viewer with greater than 90% uniformity. The module is built on an aluminum plate that serves as heat sink and heat conductor. Thus, the module handles optical, mechanical, electrical, and thermal issues all at once, and is application-ready, Fine said. A 46-inch TV would require 288 modules of the current design to produce 10,000 nits at the backlight surface and approximately 500 nits out of the LCD. Thickness is of the total BLU is 7.6mm, including chassis, 2D dimming is supported, and cost is 50% of other full-matrix RGB approaches, Fine said.

Fine showed me working modules, and photos of a prototype TV set with full-up BLU. He was careful not to indicate which Tier 1 companies he was talking to, but said that discussions had reached an advanced level.

Oree is also working on general and architectural lighting applications. Because the modules convert LEDs into planar light sources, they blur the previously distinct application spaces for LED and OLED luminaires.

We will continue to track Oree and other developers of innovative LED backlighting solutions.

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