Seeing the Digital Light Page 2
When it comes to watching movies at home, DLP projectors improve in several areas on the performance of CRT projectors as well as the liquid-crystal-display (LCD) projectors that have become a popular alternative to CRTs. The most obvious benefit is image uniformity. With CRTs, brightness usually falls off as you move from the center to the edge of the screen -- the farther you stray from the central viewing axis, the worse it gets. LCD projectors are also prone to color shifting, where the same colors in the image vary in hue on different areas of the screen. With DLP projectors, brightness and color remain consistent over the whole screen whether you're sitting dead center or off to one side of the couch.
DLP also offers near-perfect convergence and image geometry. Both front and rear CRT projectors require three tubes to beam images onto a screen -- one each for the red, green, and blue components of the video signal. Unless each tube's output is perfectly converged with the others, you'll see color fringing, or "halos," on the edges of objects and text. Since DLP projectors use a single lens, you don't have to worry about convergence errors. As shipped from the factory, CRT projectors often display poor image geometry -- an uneven ratio of width to height, or vice versa, at the edges of the screen. But since the spacing of the mirrors (pixels) on a DMD chip is fixed, DLP projectors have perfect geometry at both the center and edges of the screen. While DLP has significant advantages over both CRT and LCD projectors, there's still one key area where Texas Instruments needs to improve the technology. Although DLP projectors deliver exceptionally bright images, their contrast ratio -- the range between the whitest white and the blackest black -- falls short compared with CRTs, which can deliver deep blacks and fine gradations of gray. Shadow areas in DLP projections appear to taper off at the threshold of true black. That's why the images tend to have less depth and dimensionality than those of their tube-based brethren.
But Texas Instruments is working to improve DLP performance. The company recently developed a DMD with a 16:9 aspect ratio and has struck deals with Hitachi, Mitsubishi, and Panasonic to use it in widescreen HDTV sets. And the company's next round of efforts will focus on extending DLP's contrast ratio -- a feat it hopes to pull off by increasing the absorption of stray light from the individual mirrors on the DMD. Once contrast is improved, even the fussiest of videophiles may be hard pressed to find fault with the technology. DLP's future is so promising that even Sharp, a company long identified with LCD development, has licensed the technology. According to Sharp, its first DLP product -- a front projector employing the same 16:9 DLP chips found in widescreen rear-projection TVs -- will be available sometime this summer.
To get a handle on what kind of DLP displays are out there and how they perform, we rounded up a widescreen rear-projection HDTV monitor from Hitachi and a front projector from Runco. With prices well in excess of ten grand each, these products aren't aimed at casual TV watchers but at video enthusiasts who like to be on the cutting edge. But don't be scared off: both represent the state of the art in video technology, and that always costs more. As with plasma TVs, which are slowly becoming more affordable, prices for DLP projectors will come down.