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Volume 10, Number 23
6 April 2004

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Digital Projection: A New Way to See Incredible Pictures

Most of us are familiar with projection devices. They are everywhere: in the cinemas, offices, and now increasingly in the home. Donít think of projection as only front projection, since rear projection TVs use a very similar technology. Until now, CRT based projectors were dominating the market.
CRT, which has existed for decades, stands for Cathode Ray Tube and is the analogue technology of conventional TVs. Now there are serious rivals to CRT coming from the digital domain. The first rival to CRT was the well-known LCD. But now there are better-performing technologies, like LCoS and DLP, which have revolutionized the technology. Let us look at their features.
LCD Projection: In LCD projection devices, there are small TFT LCD panels. The image that is formed in the panel is projected to the screen with lamps that emit light through the panel. The main advantage of LCD panels is that they are cheap and the devices containing them are lightweight. Some of the drawbacks are that their contrast is low, blacks seem like grey, and as their resolution increases, their brightness and overall image quality decreases. The LCD projection is widely used, especially in front projectors. Most of the projectors in the classrooms at Bilkent University are LCD.
LCoS Projection: Stands for Liquid Crystal on Silicon. The main difference between LCoS and LCD is that the small panel in LCoS is reflective rather than transmissive. This fact helps maintain brightness and resolution. The LCoS panels give superb image quality but are very expensive. Some companies have enhanced this technology, giving it names D-ILA or SXRD.
DLP Projection: DLP stands for Digital Light Processing. It consists of a lamp that projects light on to a chip that has microscopic mirrors. As these microscopic mirrors tilt, a grayscale image is created. Then this grayscale image passes through a color wheel and is reflected on to the screen. This technology allows very high contrast ratios to be achieved and superb images to be created. As time goes on, more and more companies will invest in these technologies. This will eventually cause the price of the devices to drop and make them more obtainable for the average consumer.

Eren Tezmen (MAN/III)

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