Television
is something we all know and love -- sometimes without good reason. Critics
routinely argue that shows like Temptation Island and WWF Smackdown! have
pushed us several steps down the evolutionary ladder, but people still
watch them. One thing that has evolved is the technology for displaying
video images. We’re all familiar with the classic cathode-ray tube
(CRT), an analog technology that’s been around since TV’s earliest
days. The CRT served us well for over 50 years, but in this digital era,
when video can be broken down into ones and zeros and routed through countless
conduits, it’s become something of a dinosaur.
Enter Digital Light Processing (DLP), a video display technology based on the proprietary Digital Micromirror Device (DMD) from Texas Instruments. Though DLP has been around for a few years, it’s only recently started to gain recognition as movie theaters contemplate a move away from traditional film projection. A handful of theaters installed DLP systems to project the much-hyped Star Wars: Episode I – The Phantom Menace when it was released in 1999, and it continues to gain momentum. Worldwide, 30 theaters had made the switch at this writing in late March.
DLP is now starting to show up on the home front in the form of front and rear projectors. The advantage of a DLP-based display is that the video signal remains in the digital domain from the moment it enters the set until it’s reflected as light onto the screen. DLP’s fully digital signal path not only holds the promise of higher-quality images than CRTs currently deliver but also makes it the ideal display technology for folks who want to mix up their TV viewing with videogames and Web surfing.
Compared with CRT displays, which generate images using high-voltage electron guns and bulky glass tubes, the technology behind DLP is elegantly refined. At the heart of a DLP display is the DMD, an integrated circuit covered with an array of tiny mirrors. A lamp inside the set throws light at the DMD chip, and the mirrors pivot up to 50,000 times a second, switching between on and off states in which light is either reflected toward a projection lens or deflected toward light-absorbing material. The amount of time that each mirror, or pixel, reflects light at the lens determines the pixel’s brightness -- that is, where it falls in the scale between black and white.
DLP displays handle color in two ways. In three-chip DLP projectors, which are found in movie theaters and a few ultra-expensive home installations, a prism splits the light from the lamp into red, green, and blue components. Each color is directed to a separate DMD chip, and the reflections are optically recombined before the image hits the projection lens. In less expensive one-chip models -- the kind intended for home use -- a rotating color wheel filters the light into red, green, and blue. Although the three separate beams are reflected off the DMD sequentially, the rate at which they flash onscreen is so fast that the eye perceives a full-color image.
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.
Hitachi’s DLP Rear Projector
With
its silver case and glassy, sculptured stand, Hitachi’s first DLP
projection set looks good even when it’s turned off. The 55DMX01W
has a 55-inch (diagonal) 16:9 aspect ratio screen and converts all incoming
video signals, including 480i (interlaced) and 480p (progressive) standard
definition and 1080i high-definition digital TV, to the native 720p resolution
of its DMD chip. The set also displays XGA, SVGA, and VGA signals from
a connected computer, so you can use it to surf the Web or play games
on CD-ROM and DVD-ROM.
It might be an example of cutting-edge technology, but the Hitachi set has also been outfitted with many traditional TV features and functions. There’s a wealth of connections, including two wideband component-video inputs and two VGA jacks for computer signals. The remote control has a partially backlit keypad. While I eventually got used to working with it, the many buttons on the remote intimidated me at first.
With no convergence controls to mess with, setting up the Hitachi was a cakewalk -- just turn it on, and you get a crisp image with perfect geometry and focus. A company representative encouraged me to engage the set’s Movie mode before any critical viewing because that turns on the upconverter’s 3:2-pulldown feature -- an important detail the manual fails to mention. (This feature eliminates artifacts that result from transferring 24-frame-per-second, or fps, film to 30-fps video.) After selecting the Movie mode and Warm color-temperature setting, I adjusted the picture controls with Ovation Software’s Avia DVD. The Hitachi’s picture at this point measured pretty close to the 6,500-K NTSC standard, but an additional half hour of tweaking via the service menu brought it up to perfect spec.
When I played The Fifth Element, one of my standard reference DVDs, I was impressed by the Hitachi set’s excellent color rendition -- flesh tones were dead-on accurate, and heavily saturated colors (like Leeloo’s orange hair) came across vividly but without any softening of detail. With 3:2 pulldown engaged, the set’s upconverter was a force to be reckoned with. In shots with vertical camera motion, straight lines looked completely solid, without any of the stairstep artifacts that the line doublers in many other HDTVs introduce.
When I switched over to the murky opening scenes of Gladiator, however, I was given a taste of DLP technology’s current limitations. As the Roman warriors waged battle in the forests of Germania, the shadowy landscape came across as a flat, uniform dark gray, with no deep blacks. The compressed contrast range robbed the image of the 3-D illusion that came across so well in the movie’s better-lit scenes.
| Hitachi 55DMX01W |
| KEY
FEATURES:
DIMENSIONS
51 1/2 inches wide, 40 inches high, 24 inches deep |
When converting 1080i signals to the DMD’s native 720p, the Hitachi generated a faint noise pattern visible on flat patches of color -- a problem I corrected by setting our Dish Network 6000 HDTV tuner to convert all incoming signals to 720p. Displaying a high-def satellite transmission of The Talented Mr. Ripley, the Hitachi did a credible job of rendering the detailed wall decorations in the hotel Ripley checks into after assuming his murdered friend’s identity. Unfortunately, the set had the same limitations with HDTV that I had observed with DVDs --
reduced contrast in scenes containing lots of shadows. One workaround I discovered was to increase the level of ambient light in the room, which helped to improve the set’s apparent contrast. Although I’m used to watching movies in fairly dark rooms, I can’t say that I minded the light. For once I could find the remote without groping about like a blind man.
If Digital Light Processing is TV’s destiny, the Hitachi 55DMX01W
rear-projection TV is a promising sign of things to come. Not only will
it look great sitting in your living room, but it delivers exceptionally
bright, finely detailed images and accurate color.
Runco’s DLP Front Projector
Who
invented home theater? Although lots of companies would like to claim
to have been the first to deliver a taste of the movie theater experience
in the home, a good case can be made for Runco. As far back as 1991, the
company pioneered aspect ratio control for CRT front projectors so that
widescreen movies on laserdisc could be viewed at home in a theatrical
format. With widescreen HDTVs on the market now, aspect ratio control
is something we take for granted, but when Runco first developed it, it
was a revolutionary idea.
A decade later, Runco is still pushing the home theater envelope with DLP projectors like the VX-1c, which includes the outboard VHD video processor/aspect ratio controller. Licensing agreements previously prohibited Texas Instruments from selling 16:9 aspect ratio DMDs to front-projector manufacturers, but that didn’t stop Runco, which developed a neat workaround in the VHD. The VX-1c’s 4:3 aspect ratio DMD has a native resolution of 1,024 x 768 pixels. If the projector is mated with a screen that has a wide aspect ratio, however, the VHD controller scales images down to a 16:9 area on the DMD’s surface. This allows the VX-1c to operate like a native widescreen display, switching effortlessly between HDTV, anamorphic widescreen DVDs, and standard 4:3 sources.
Although the VX-1c/ VHD package consists of two separate, stylistically undistinguished pieces, the way they seamlessly communicate is a thing of beauty. A phone-type cable carries commands from controller to projector -- press the power button on the controller’s remote, and the entire system turns on. And once you’ve set up the projector on a table or the ceiling and aligned its lens with the screen, you can forget about it and turn your attention to the VHD controller.
Inputs on the VHD include composite-, component-, and S-video jacks. Although the component-video jack won’t accept signals from a progressive-scan DVD player, the VHD’s scaler, which features 3:2 pulldown for film-based video sources, performs as well as the best progressive-scan DVD players I’ve tested. A 15-pin VGA-jack pass-through input lets you connect an HDTV tuner, and there’s an RGB+ H/V output to the projector.
Having labored for hours setting up CRT front projectors in the past, I found getting the VX-1c to look good absurdly easy. After positioning it so its image filled a 92-inch 16:9 Da-Lite High Contrast Da-Mat screen, which is designed specifically for DLP projection, I selected the warmest setting on the projector’s slider-type color-temperature control and used the Avia disc to adjust the picture settings on the VHD.
With the Runco VX-1c projecting Gladiator, I felt as though I was sitting beside Emperor Commodus in the Colosseum during the movie’s bloody battle scenes -- the image was that crisp, lifelike, and large. And the combined one-two punch of the VHD’s clean video processing and the Da-Lite screen’s contrast enhancement delivered satisfying shadows in the movie’s dark opening scenes. Although the contrast wasn’t as punchy as from the $25,000 Runco DTV-991 CRT projector we use in our reference video system, the VX-1c’s overall brightness was nearly double -- and that’s with an even larger screen than we normally use!
| Runco VX-1c/VHD |
| KEY
FEATURES
DIMENSIONS
VX-1c projector, 14 1/2 inches wide, 5 3/4 inches high, 18 1/2 inches
deep; VHD controller, 17 1/2 inches wide, 13/4 inches high, 11 inches
deep |
On the other hand, the projector could use a little improvement with its color rendition. It has a single global color-temperature control, so there’s no easy way to achieve a precise grayscale. I found the colors vibrant and reasonably accurate in both the Gladiator DVD and the high-def satellite transmission of The Talented Mr. Ripley, but in a few scenes the flesh tones were a bit too orange.
Runco’s VX-1c/VHD controller combo is a great choice if you want the ultra-big-screen experience of a front projector along with DLP’s simplicity and eye-pleasing brightness. The VHD controller in particular deserves praise for its seamless integration with the VX-1c projector. I was also impressed by its high-quality scaling and the clever way of adapting the projector’s native 4:3 aspect ratio DMD for widescreen display. CRT-based projectors might still dominate home theater’s high end, but with the arrival of DLP projectors like the Runco VX-1c/VHD system, that could soon change.
Will your next TV be a DLP projector? That depends on the progress Texas Instruments makes in getting the word out about its technology and getting the price of DLP displays down to more affordable levels. To judge by these offerings from Hitachi and Runco, DLP is closing in on the CRT. It’s only a matter of time before the traditional TV tube becomes a thing of the past.