Techworthy - Business Traveler - Presentation Projectors: LCD or DLP?

Image is everything. When making a presentation, flip charts are death. Bound, color printouts of your PowerPoint presentation make good leave-behinds, but to wow your audience, nothing beats projecting an active presentation on a screen or bare wall.

Portable projectors use either of two competing technologies: LCD and DLP. Each camp has its die-hard devotees who will tell you their way is best. How do you choose?

Liquid Crystal Display (LCD) technology pushes light through colored LCD filters to generate an onscreen image. Digital Light Processing (DLP), on the other hand, uses a tiny digital micromirror device to reflect light onto a screen.

The liquid crystal used by the LCD is an oddball material that sometimes acts like a solid and sometimes like a liquid. Described simply, electricity controls the state of the liquid crystal. An electric charge straightens out liquid crystals to allow light to pass through. When the charge is taken away, the crystals arrange randomly, thereby blocking light.

In an LCD, liquid crystals are sandwiched on an electrical grid between two panes of glass. By controlling the density of red, green, and blue in a trio of closely packed dots, a pixel with any of 65,000 different colors can be created.

In an LCD projector, instead of a single large LCD, there are three tiny ones--one each for red, green, and blue. Each tiny, light-permeable LCD has an electrical grid that creates individual pixels. When light is funneled through each LCD, combined prismatically, and shot through a lens, it forms a moving image.

DLP projection works a little differently. Rather than filter light through permeable LCDs, a DLP projector uses a device developed by Texas Instruments called a Digital Micromirror Device (DMD).

About the size of a postage stamp, a DMD is a Microelectrical Mechanical System (MEMS). It is composed of about a quarter of a million tiny mirrors suspended on microscopic hinges. When an electrical charge is applied, the mirrors tilt on their hinges. In this manner, light reflected off each mirror can be directed through a lens.

In larger DLP projectors, three DMDs (one each for red, green, and blue) are used in an arrangement similar to the LCD arrangement mentioned above. In an ultraportable DLP projector, a single DMD may be used.

In order to create color in a single-DMD projector, light is passed through a rotating color wheel that flashes short bursts of red, green, and blue in front of the DMD. The result is 65,000 different hues.

DLP projectors have one major advantage: since only a single DMD is required, DLP projectors can be manufactured as light as three pounds. (The Compaq MP2800, InFocus LP130, and PLUS U-1080 all hit the three-pound mark.) On the other hand, the lightest LCD projectors weigh in at around 5.5 pounds. DLP units are smaller, too.

DLP has another advantage when it comes to moving images: DLP systems donât ghost. Ghosting is that eerie visual phenomenon when a projectorâs refresh cycle isnât quite fast enough to keep up with the image being projected onscreen.

Ghosting is a traditional drawback of LCD. Letâs take a simple example of a football moving across a screen. As the football moves from left to right, pixels must turn on and off in rapid succession. If they donât turn off quickly enough, it looks like the football has a tail (or a ghost) following it.

With DLP, this isnât a problem. The mirrors tilt quickly on their hinges, so pixels go off instantaneously. However, the liquid crystals of an LCD donât turn off that quickly, which is why ghosting is traditionally a problem.

Modern LCD projectors are not affected by ghosting nearly as much as older LCD projectors were. By putting an extra twist in the crystal structure, itâs possible to make them snap off a little faster. However, action movies and sporting events look better on DLP than LCD, as do fast-paced computer presentation graphics.

Ultraportable DLP, on the other hand, is sometimes adversely affected by the color wheel. In less expensive units, a wavy motion is detectable on still, dark colors. This is an artifact created by the color wheel architecture. LCD units generally have better color saturation.

Consider your budget and how you want to use the ultraportable projector. The better DLP units are premium-priced at $4,000 to $5,000. A decent portable LCD unit can cost almost half of that. Do you need the superior quality of an ultraportable DLP? Can your budget bear it?

If the answer is yes to both these questions, consider the three units mentioned above. If itâs no, by all means go LCD. Youâll still get yourself a high-quality piece of equipment. Check out the NEC LT-156 for a top-of-the-line ultraportable LCD unit, or the Sharp NoteVision PG-C20XU for an affordable alternative.

Whichever technology you choose, youâll find that a multimedia projector adds a lot of punch to your presentation without adding a lot of weight to your travel package. At low cost and low weight, portable projectors are a great way to differentiate yourself from the competition.

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Compaq

Computer Corp.

(800) OK-COMPAQ

www.compaq.com

InFocus Corp.

(800) 294-6400

www.infocus.com

NEC USA, Inc.

(212) 326-2400

www.nec.com

PLUS Corp. of America