Assembling the Perfect DVD Presentation System: Getting Visual - Buyers Guide

Emedia Professional, Nov, 1999 by Mark Fritz

CRT projectors are the type you usually see in sports bars projecting the latest ball game or boxing match. They are big and heavy and mounted to the ceiling and employ CRTs. This is the same basic technology used in TV sets and computer monitors, except instead of using just one tube, CRT projectors use three, one for each primary color. Because of their size and weight, almost all CRT projectors fall into the large venue category.

LCD projection panels use Liquid Crystal Display technology. Essentially an LCD employs a special liquid sandwiched between two pieces of glass. Liquid crystals are rod-shaped nematic molecules (equaling one pixel) that selectively block or let light pass, under control of an electric signal. In an active matrix LCD system, liquid crystals are controlled by pairing each with a transistor. More advanced LCDs also pair a "micro-lens," with each liquid crystal or pixel.

Cheaper LCD projectors employ only one panel, while more expensive models use three overlapping panels, one for each primary color. Assigning a panel for each color like this results in better color reproduction and saturation, but the down side is that the more panels you put between the bulb and the lens, the more light gets blocked, reducing your brightness. Manufacturers then have to compensate by using bigger power supplies and more powerful bulbs.

The lightness and simplicity of LCD projectors has made them so popular that, according to Sweta Dash, senior analyst for San Jose-based Standford Resources: "They've wiped out CRT from the portable presentations market completely," forcing CRT manufacturers to compete for a portion of the large venue market. Even in that niche, CRTs are feeling pressure from advanced LCD and DLP products, she says. Her fellow analyst Bill Coggshall agrees. "We'll continue to see CRTs, especially lower-priced ones in the home theater market, because they are good at handling video; but the overall market for CRTs is stagnant. They're dying out."

The latest multimedia projector technology, DLP, has only been around since 1996, and yet it has managed to capture nearly 30 percent of the market. DLP projectors are based on digital chip technology from Texas Instruments. Also known as Micro Mirror Devices (DMD), these postage stamp-sized chips contain over half-a-million microscopic mirrors (one for each pixel) that can be opened and closed to reflect varying amounts of light. In a DLP projector, light from the bulb is focused on the DMD and reflected off the mirrors, through a color wheel, and eventually through the lens to a screen on the wall. The best (and more expensive) DLP projector uses three chips, one for each color, which eliminates the slight flicker that the color wheel causes in one-chip DLP projectors.

Over 30 companies sell DLP projectors including ASK, Boxlight, Buhl, Davis, DreamVision, Electrohome, InFocus, Megapower, NEC, nview, Polaroid, Proxima, and Sony.

Another technology you'll hear mentioned when high-priced, large venue systems are discussed is ILA, which stands for Image Light Amplification. This is a reflective technology from Hughes-JVC that combines CRT and LCD technologies for extremely bright projector performance.