As the prices for plasma TVs continue to drop, demand is starting to skyrocket. That's because plasma technology offers excellent picture quality (including high-definition on many models), super-thin designs that can be mounted right on a wall and screen size options that rival standard projection CRTs.

The technology of a plasma TV is similar to the idea behind a fluorescent light bulb. In a fluorescent light bulb, an electric current excites gas contained in a glass tube causing the release of ultraviolet photons. These photons hit the phosphor coating inside of a fluorescent tube, and this phosphor creates visible light. However, since this is not an article about light bulbs, let's talk plasma TV.

Plasma is a highly ionized gas-like substance that is an excellent conductor of electricity. A plasma TV consists of thousands (and sometimes millions) of tiny glass, plasma-filled chambers, which are layered between two wired glass panels. On one panel the wires are arranged in rows. In the other the wires are arranged in columns, creating a grid. Directing a charge to the desired wire intersection activates individual pixels.

Behind each of the glass chambers are three phosphors that emit red, green, or blue light, and combine to create the images on the screen.

An image is displayed when a digitally controlled electric current excites the plasma, causing it to give off invisible ultraviolet light. This ultraviolet light strikes the phosphors on the back of the display and makes them display the appropriate color. Plasma TVs eliminate the need for a back light source because they produce their own light.

The result of plasma technology is an evenly focused, realistic picture with a wide viewing angle. Plasma displays perform well regardless of lighting conditions and are not affected by magnetic fields. That means you can set one next to your home speaker system without affecting the picture. Most models accept both video and computer inputs, allowing you to watch your favorite movies or display images from the DVD-ROM drive of your computer. One past criticism of plasma technology has been a problem with poor contrast - blacks had a slightly whitish hue and appeared to be more of a dark gray than a true black. However, the quality of contrast has improved significantly since the original plasma displays were introduced, and the images produced by plasma technology today are noticeably cleaner and more defined. Just like LCDs, plasmas are capable of displaying a palate of almost 16.8 million colors, giving images a more lifelike quality.

Like a CRT television, the phosphors and gases deteriorate over time, causing brightness to fade. The life span of a TV with regard to brightness is measured in terms of a half-life. To put it simply, this is the amount of time it takes for the display to lose half of its original brightness. If you happen to have an older CRT television sitting around your house, you can see how the picture has slowly become darker over time. The life span of a plasma display averages 30,000 hours (compared to 20,000 hours for a CRT). If you were to watch 6 hours of television per day, the half-life of your plasma TV would average 13.7 years. This doesn't mean the TV stops working smack dab in the middle of your favorite rerun of "Cop Rock", only that the picture loses some of its brightness over a period of several years.

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