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March 2006

This chapter is from the book

FRIDAY: MARCH 10, 2006

THIS WEEK’S FOCUS: Choosing a Big-Screen TV

PLASMA FLAT-SCREEN DISPLAYS

As popular as rear projection sets are, what a lot of people want is a TV they can hang on the wall. Two different types of flat panel display are available today: plasma and LCD. Of these, plasma is by far the most popular today.

Most plasma display are only about six inches deep. It’s that thin because it contains no picture tubes or projection devices. Instead, it sandwiches a layer of ionized xenon and neon gas between two thin layers of glass. The gas is contained in hundreds of thousands of tiny cells and made up primarily of uncharged particles. When an electrical voltage is applied to the gas, negatively charged particles rush toward the positively charged area of the plasma and positively charged particles rush toward the negatively charged area. The rapidly moving particles collide with each other, exciting the gas atoms in the plasma and releasing photons of energy—which we see as light. When enough sub-pixels light up in a pattern, a picture is created; color intensity is increased or decreased by varying the pulses of current flowing through the different cells.

Plasma displays are popular because they’re becoming quite affordable. Plasmas also deliver the closest picture to that of a traditional CRT, with excellent off-axis viewing. But beware of some low-priced 42-inch plasmas that promise "enhanced definition" or EDTV picture quality; these displays can’t reproduce high-definition signals.

The primary downside—and it’s a big one—to plasma display technology is the danger of burn-in. If you leave a static image on the screen for an extended period of time, the phosphors will burn in to that image, leaving a ghost image on the screen after the fact. This is a big issue if you watch a lot of letterboxed movies or if you watch your 4:3 programming unstretched on a 16:9 display. (The pillars on either side of the picture burn in.) For this reason, many cautious videophiles avoid plasma displays.

ON THIS DAY: URANUS HAS RINGS (1977)

On March 10, 1977, astronomers discovered that the planet Uranus has rings—at least 11 of them. They can’t be seen from Earth because the rings get lost in the planet’s glare. The rings were discovered when Uranus passed in front of a star and scientists noted a dip in the brightness of the star. By the way, most of Uranus’ rings are not quite circular, and most are not exactly in the plane of the equator.

WEBSITE OF THE WEEK: AVS FORUM

One of my favorite home theater/consumer electronics websites is the Audio Video Science (AVS) Forum, located at http://www.avsforum.com. This site has tons of different forums devoted to different types of audio/video equipment and specific brands; users typically are well versed in the technology and prone to posting very detailed reviews. This is definitely the site to go to when you’re considering buying a new big-screen TV.

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