LCD and DLP projectors
Mar 1, 1999 12:00 PM, Peter H. Putman
There is a trend sweeping through the professional A-V industry. Slowly but surely, plug-and-play LCD and DLP projectors are making their way into the fixed-in stallation market, displacing the venerable CRT projector. Some companies already offer a full range of installation-grade display systems. Others, without a competitive product, scurry around making OEM deals.
In my October 1998 column, I talked about this new wave of projection systems and how their features measured up to the rigors of the installation marketplace. Since then, the trickle of products has grown. Sanyo, the company that kick-started the plug-and-play LCD projector revolution with its XGA-resolution PLC-9000N, is working to stay in the lead with its higher-brightness PLC-9000NA and the upcoming PLC-EF10N. Sony responded with the quad-lamped VPL-X2000, 2,000 lumen boardroom projector, while Barco has taken a long-anticipated step into the smaller, brighter, lighter arena with the BarcoGraphics 6300. Epson, a company long identified with portable projectors for desktop presenters, now has the 1,000 lumen, 12 pound (5.4 kg) PowerLite 7300 with 5xBNC connectivity, and Hughes-JVC continues to improve its D-ILA G1000 SXGA box, currently rated at 1,000 lumens but shooting for double that in the next year.
Proxima, another company long associated with desktop projectors, made a strong entry into the boardroom market with its version of the Sanyo projector (Pro AV 9310) and is currently touring a totally integrated A-V room exhibit, "The Conference Room of The Millennium," in conjunction with Da-Lite and Crestron. Eiki, a reseller of Sanyo products, is also making bold gestures toward system integrators with its version of the PLC-9000 series, forsaking numbers for the catchy "Powerhouse" moniker.
Sharp continues to ship the full-featured XG-3500, a real eye-catcher at this year's INFOCOMM Shoot-Out that is aimed at the boardroom market. Electrohome, AmPro and Telex are in the fray with their respective private labelings of Fujitsu's 1,000 lumen desktop design, and, of course, Mitsubishi continues to make waves with the LVP-X200, one of the better designs in terms of sync compatibility and a nice picture-in-picture function, well-suited for videoconferencing.
This surge towards the fixed-install market has caught more than a few companies off-guard. Davis North America, which just a couple of years ago turned its back on LCD projectors in favor of DLP engines, recently announced the new DPB 1200 boardroom LCD projector with 1,200 lumens, wide sync capability and picture-in-picture. Score 100 points if you correctly guessed that it is the Mitsubishi X200.
An even bigger puzzle is presented by In Focus, who is single-handedly responsible for most of the buzz about the LCD boardroom invasion. Its full-featured, 1,000 lumen Lite Pro 1000 previewed to favorable comments at COMDEX 1997, but shipments did not begin until almost 6 months later. As of early February, In Focus has decided to hedge its bets with the new Lite Pro 1200, another full-featured boardroom projector with 1,200 lumens, wide sync capability and picture-in-picture. Score another 100 points if you again guessed that it is the Mitsubishi X200.
Replacing years of CRT technology with a plug-and-play box is not as easy as many companies would have you believe. CRT projectors certainly have their drawbacks; they are heavy, take up a lot of space, require convergence, have virtually no lens options and cannot produce nearly as much light as even a simple ultraportable projector.
On the other hand, the ability of a CRT projector to trace an infinite number of picture resolutions and aspect ratios with no strings attached, combined with complete control over optical alignment and picture geometry, still makes them a standard of comparison for other display systems, and do not not forget the purity and color quality of CRT-generated images either, still preferred by virtual-reality and simulator designers.
If you are caught up in the installation-projector wave, there are a few things you will want to consider before you start swapping out tubes for TFTs. For some applications, the functionality of a slide projector is all that is required. For others (particularly retrofits), we will demand a lot more from our projection system.
Optical correction Because of a ceiling-mounted pro-jector's requirements, there has to be a way to adjust the focal plane to compensate for off-axis imaging that typically leads to keystoned images. CRT projectors compensate by not only tilting the angle of their three lenses slightly (about 12 degrees), but also providing keystone adjustment of the electron beams. By effectively keystoning the rasters in the opposite plane, the tilt is compensated, and viewers see a perfectly rectangular image.
Not so with LCD and DLP projectors. Tilt a projector off its center axis, and you will get a keystoned image. There are two ways to compensate for this. The first (and sensible) method is to provide a motorized lens shift, changing the vertical alignment of the projection lens with respect to the projector's image plane, the same process used in view cameras to correct for perspective distortion when tilting up or down.
The second, less effective method is to re-map the image electronically across less or more pixels in a trapezoid shape. This is a similar approach to shifting the electron beams in a CRT projector, except that the resolution of a CRT projector is unaffected by keystone correction. Re-mapping images across more or less pixels in a trapezoid shape affects resolution and results in a jagged, aliased edge to the image, not a solution expected in a professional installation. Although this re-mapping problem becomes less apparent at higher resolution, it is still inadequate. Optical lens shift is the way to go, and having the ability to tilt the image-forming plane of the projector (typically, the combining prism) several degrees would help even more.
Sync compatibility This is a no-brainer for CRT projectors, which have no native or fixed resolution; just tell them the horizontal scan rate and vertical refresh, and they do the rest. Not so with LCD and DLP projectors, who must continually sample and time incoming signals to make sure they fit into the available resolution of their imaging panels. Now, we must be concerned with pixel clocks and sync frequencies and phase.
Various names have been given to auto-synching circuits used by the many contenders for the boardroom flat-matrix projector market, but not all circuits are created equal. In my tests, I have found a wide disparity among projectors in their abilities to sense, grab and lock up a perfect image from various SVGA, XGA and SXGA sources. Even repeated manual adjustment may not clear up the problem entirely.
Although not as apparent with still photos and simple test charts, images with high detail and fine text will suffer the most from sync compatibility problems. This has been particularly true with some of the higher sync rates, like XGA-5 (57 kHz, 70 Hz refresh) and XGA-6 (61 kHz, 76 Hz refresh). Even SVGA rates like SVGA-6 (48 kHz, 72 Hz) have been problematic for boardroom projectors.
If you are considering a flat-matrix projector for an installation project, you cannot be certain your customer will not ever cross paths with a problematic image source. XGA notebooks are becoming more commonplace, and it is not unusual to haul a workstation into a meeting these days. One way to head off trouble beforehand is to use an outboard sync pattern generator (like Extron's VTG-200) when you demo a projector. Step through every possibly needed sync rate, and take careful note of the results, particularly on the small "H" text pattern. If the projector passes this test, you are probably safe.
Video quality More and more clients are expecting top-notch video quality from installation-grade projection systems. In terms of color quality and grayscale rendering, they may already be spoiled if they were previously using a CRT projector. Spreadsheets with 256 colors are one thing, but a video-conference is far more demanding in terms of image realism.
Video quality will be affected by everything from the projection lamp to the video decoder. If the projector uses a metal-halide light source, check to see how much control you have over not only red, green and blue drive, but also bias. About presetting white balance, some lamps will not yield a clean white field, no matter how hard you try to balance colors. Xenon projection lamps do a much better job, but they are more costly to operate and replace. Projectors made by companies long used to the installation market will generally provide better color control.
How about the video decoder? In my own tests, about 25% of the fixed-install projectors I have seen use decoders inferior to commercially available, low-end video scalars. Do not assume you can just pump video through the projector as easily as an RGB signal. If your application is heavy on video (videoconferencing, stand-alone kiosks, museum exhibits, image magnification come to mind), processing it outboard is better
Line doublers, triplers and quadruplers are slowly giving way to digital video scalars, and there are some good models available. Granted, a quality scalar will increase installations cost, but there is a direct correlation between price and image quality with scalars, and the difference is apparent in controlled viewing environments.
