杏吧原创

ANYONE planning to ditch their conventional cathode-ray tube TV in favour of a much wider flat panel TV will be spoilt for choice. With the rewards so great for companies who can dominate this market, competition between manufacturers is intense. The result is that flat panel TVs are being enhanced so rapidly that any performance comparisons quickly go out of date.

Take a simple measure like screen size. At Japan鈥檚 leading consumer electronics show, CEATEC, held in Makuhari on Tokyo bay in September, hundreds of would-be home cinema owners crowded around Panasonic鈥檚 new 65-inch plasma panel TV, which was being billed as 鈥渢he largest commercial TV set in the world鈥�. But just two weeks later, the company had to withdraw the claim when its bitter rivals, South Korean firms Samsung and LG Electronics, leapfrogged it with 67-inch and 71-inch plasma panel TVs respectively.

And if constantly shifting specifications are not enough of a problem, there is the small matter of which of the three available large screen technologies is best: plasma display panel (PDP), liquid crystal display (LCD) or rear projection. And then there are the forthcoming 鈥渜uantum effect鈥� surface-conduction emission displays (SEDs) that are due out next year, and still in the pipeline are flat screens based on organic LEDs (see 鈥淚s TV鈥檚 future organic?鈥�).

Driving this confusing multiplicity of formats is the desire of screen makers to grab a share of the estimated $30 billion per annum market that flat panel TV sets are expected to command by 2007.

It is too early to say which technology will win: each has its own advantages and disadvantages, stemming from the way an image is produced.

A plasma panel display is made up of millions of phosphor-coated gas-filled pixel cells. When excited by a voltage, the gas emits UV light that makes the cell鈥檚 red, green or blue phosphor coating emit visible light. There have been significant improvements in brightness and picture quality since the first 40-inch-plus plasma screens were launched in the mid-1990s. Proponents say that the technology produces more natural colours and a softer picture than the stark brightness of a uniformly backlit LCD 鈥� making viewing easier for tired eyes. However, PDP screens have a shorter lifetime than an LCD and consume more power.

At the moment LCDs are the most popular, according to US market research firm DisplaySearch (see Graphic). That鈥檚 in part due to the maturity of the technology and wide variety of sizes available.

An electric field controls the orientation of liquid crystal molecules in an LCD cell so that they either block the passage of polarised light from a backlight or let it pass through. Red, green and blue filters on top of the cell determine its colour.

LCDs have lagged behind plasma displays in size because they are harder to make. The process is more akin to making an enormous microchip: any flaw and you have to start over. Consequently screen size used to taper off at around 45 inches. But LG Electronics has just launched a 55-inch screen and Sharp has a 65-inch one in the works.

An LCD鈥檚 polarised light is highly directional, making it harder to view from the side than a cathode-ray tube (CRT) or plasma display. And the speed at which picture frames are refreshed is slower than a plasma display, causing blurring in some fast action scenes.

In rear projection TVs a small image is projected onto a device at the back of the TV 鈥� a CRT, LCD or micromirror chip 鈥� and then shone onto a large screen at the front. These TVs are the most competitively priced and come in sizes as large as 82 inches. On the downside, they are typically about 12 inches thick and are not as bright as rival technologies.

The drawbacks of plasma displays, LCD and projection TVs have driven research and development on the new SED and OLED technologies.

SEDs, newly developed by Canon and Toshiba, work much like CRTs. But instead of one electron gun, an SED has a flat array of hundreds of thousands of minuscule low-voltage electron guns that use a quantum tunnelling effect to jump across a gap to excite a phosphor (New 杏吧原创, 24 April, p 24).

The 36-inch prototype SED on show at CEATEC produced very impressive pictures, crisp and equal in brightness to a CRT. The makers claim it has a faster video response time and better colour reproduction than either an LCD or plasma display of comparable size. It should also consume a lot less power as there is no backlight and no gas to ionise. SED TVs of over 40 inches are promised for next year and, on the evidence available at CEATEC, they may well be worth waiting for.

The manufacturers鈥� claims and counterclaims of superiority will doubtless continue, making it hard for the consumer to make the right choice. And the new technologies on the horizon won鈥檛 make it any easier.