Not long ago, consumer electronics giants were clamoring to get out of the microdisplay market. Sub-par technology, combined with high manufacturing costs and a stiff price tag, all contributed to the demise of the microdisplay.
No longer on the back burner, today's microdisplay market is on fire, and they're back with a vengeance. And at the center of it all is the realm of microdisplays that drive high-definition (HD) rear-projection TVs (RPTVs) with screen diagonal sizes upwards of 50 in. and an equally impressive price tag.
Three technologies contend for supremacy in this space: LCDs, Texas Instruments' digital light processing (DLP), and liquid crystal on silicon (LCoS). A smaller fourth category includes near-to-eye displays for camera viewfinders, headmounted displays, and video games (see "The Other Microdisplay," p. 60).
Designers of HD RPTV home theater systems have a wealth of choices at their disposal. In varying degrees, each method offers vast improvements over previous technology, from higher resolutions to brighter images, lower maintenance requirements, increased viewing angles, and much slimmer sizes and lighter weights.
The different microdisplay definitions may seem confusing. Some experts say that microdisplays have a diagonal of less than 1 in. Many of these devices are direct-view displays. By that definition, some cell-phone displays fit into this category. Yet most experts agree that microdisplays use a projection system that provides high-density content of at least 800 by 1000 lines/in. and a magnification system that enlarges the image from a tiny light source.
Most microdisplays are used in HD RPTVs and other projection products, like home and office projectors. Unlike LCDs, plasma panels, and other front-view displays, though, large rear-projection displays don't cost disproportionally more. That's because LCD and plasma panel manufacturers must construct more pixels on larger sheets of glass to create larger displays, which isn't the case with rear-projection display manufacturers.
MARKET MATTERS
Market research firm Quixel Research reports that the U.S. HD RPTV microdisplay market surged from $4.7 billion in 2004 to $5.8 billion in 2005. Many other estimates peg the RPTV microdisplay market as high as $8 billion. Though that figure pales in comparison with the overall HD RPTV market (which includes the venerable CRT), microdisplay sales are definitely on the upswing (Fig. 1).
A microdisplay uptick is remarkable, considering Intel Corp. and Philips both gave up on LCoS a couple of years ago. Thomson (under the RCA brand name) and Toshiba (which used Hitachi LCoS panels) gave up, too. A number of factors contributed to these decisions, but they were due in part to technical and scaling limitations, such as display lifetimes. At the time, it seemed that microdisplays were doomed.
So what changed? First, the technology is better. Use of high-intensity LEDs as light sources has led to higher resolution and brightness levels for HD RPTVs. Optics subsystems improved their performance, and manufacturing glitches were overcome. And prices dropped—considerably. As a result, top-tier Japanese HD RPTV suppliers like Sony and JVC are making a strong push into the LCoS microdisplay market.
Another change is standardization. Microdisplays use an optical subsystem between the light source, or "light engine," and the image seen by the viewer. Vendors other than the display chip manufacturers supply many of these optical systems, though, with few standardized formats available. With demand on the rise for the latter, we're now seeing efforts under way for a more standardized approach.
But perhaps the biggest turning point was the market introduction of 1920- by 1080-pixel progressive resolution (1080p) microdisplays. Also referred to as "true HDTV" and "ultra HD," the 1080p progressive format successors to the 720p displays provide not only the maximum lines of resolution possible, but also the best image quality in the HDTV standard.
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