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Sony's XBR-84X900 4K television. (Courtesy Sony)

Sony plans to soon start selling TV sets with four times the resolution of today's best HDTVs.

The company's first "4K" sets, named XBR-84X900, will measure 84 inches on the diagonal, making the screen area four times as large as the common 42-inch set. They will go on sale in North America by December, Sony said, and prices will be announced next week.

The resolution of the 4K television sets is 3,840 by 2,160 pixels. The technology is known as "4K" because it has nearly 4,000 pixels on the horizontal edge. That compares with 1,920 by 1,080 pixels in "1080p" sets. More pixels allow TV makers to make bigger screens without compromising sharpness.

There is, for now, very little video content available that can take advantage of the higher resolution. With some work and know-how, a computer connected to the set can display video in the ultra-HD "4K" resolution. The set will also do its best to "upscale" TV, DVD and Blu-ray movies, so they look better.

Sony already makes digital projectors operating at 4K resolution for movie theaters.

The TV industry has been looking for a technology that will get consumers to upgrade their HDTV sets. Sales are slumping after an initial wave of upgrades from standard-definition sets, and 3-D sets attract only a small number of consumers.