Advanced Imaging


Industry News

Updated: July 8th, 2008 05:26 PM CDT

LEDs in LCDs

Video Systems
via NewsEdge Corporation

Without inputs for analog component video or SDI, however, the LCD2180WG-LED is certainly not yet ready for video reference monitor status, so editors will need to hang on to their bulky CRTs for at least a little longer. But if this month's CES show was any indication, we'll soon see LED backlighting in many different types of flat panels, including those that feature the proper video I/O.

A brighter white

If you can imagine the color depth that three-beam CRT projectors used to achieve by that blended red, green, and blue light, you'll start to appreciate what's (literally) behind NEC's LCD. By blending light beams of the pure primary colors, those projectors were able to create a pure and even white ? and by extension a full range of grays all the way down to black.

Naturally, there's a big difference between those CRT projectors and a panel. That's because the LEDs themselves don't create the color, just the white light. The LCD panel still filters portions of the red, green, and blue light out of that white, thereby producing different shades of color. However, getting a full range of accurate colors is mathematically impossible if you start filtering or subtracting red, green, and blue from less-than-pure ?white,? and that's a common problem of typical LCDs backlit by CCFL (Cold Cathode Fluorescent Lamp).

If you don't start with 100 percent of white, you'll never achieve 100 percent of anything else. However, by combining pure red, green, and blue LEDs to produce something very close to pure white, an LED-backlit LCD can reproduce a fuller range of colors ? even by the subtractive, or filtering, method used by LCDs. The result is a very steady and full range of grayscales with a consistent color temperature and very strong color reproduction.

In the NEC model, I found both primary and secondary to be very accurate, with the exception of magenta, which leaned toward blue. Green and red were actually outside the color gamut triangle on the CIE chart in my tests, although blue (almost always a difficult color) was inside and a little less saturated than ideal.

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