Thinner, flatter CRTs are on the horizon

Summary:A new CRT technology known as the field emitter display should make

When will the CRT disappear and leave us with a world of flat-panel displays (FPDs)? No time soon, the way things look. The CRT manufacturing process is well-established, and CRTs are inexpensive to make. And unless China abandons the concept of becoming an even cheaper producer, the world will be flooded with cheap CRTs for years. But a variation—a flat CRT—will be in our hands this year.

This topic comes to mind after two recent experiences. In one, a guest on my TV show, Silicon Spin, hinted everyone should wait six months before buying a color PDA. Apparently, he learned under nondisclosure of a new, bright, visible-in-sunlight, color display.

The other was a demonstration of a new Texas Instruments technology. Researchers were showing off a wireless OS on a mock color phone display. As I took my eyes from the screen, I noticed the strobe and realized the dinky little display wasn't an LCD. They told me it was a "thin-film CRT." They used it because it was bright. In fact, this was a field emitter display (FED).

The FED has been under development by two companies, Candescent and Pixtech, each with a different approach. The idea is to use an array of tiny cathodes placed directly behind the phosphor. Although TI told me this wasn't an FED but a thin-film CRT, I found the answer on Candescent's Web site (www.candescent.com). The company renamed the technology "ThinCRT."

Aside from the cost differential between CRTs and FPDs, another factor keeps FPDs from dominating the market. FPD technologies are manifold and in flux. Although the CRT may have added a few pixels over time, we won't see the kind of developmental changes we're seeing with FPDs. The FED takes advantage of much of the work already done on CRTs.

FEDs have been in development for nine years and in discussion for decades. Four years ago I was told they could be cheaper to produce than LCDs, and could be made small or large with no scalability problems. The LCD was limited in size. The plasma display was an alternative, but it was too power-hungry and could only be large. It would never be cost-effective. The FED would solve all this and become the rage. Then came the various problems with phosphor burnout, manufacturing, and other glitches. Until I saw this display, I didn't think I'd ever see an FED in operation.

This could be the "bright" display my guest was discussing. It's supposed to be low power, and it could be used in a handheld application. And there must have been some reason TI was using one in a demo.

Because FED technology is fashioned after that of CRTs, it has both its advantages and disadvantages. The glass vessel is flattened, and instead of having a gun that scans the screen to hit various phosphors through holes in a shadow mask, it puts a panel of tiny emitters behind the phosphors. A "focusing grid" acts in much the same way as a CRT's shadow mask. The package is 8mm thick when sandwiched together. The resulting brightness is identical to that of a normal tube.

The displays should deliver a brighter image with better viewing angles than any LCD and with none of the smearing you get with plasma, according to Candescent. They also consume less power than LCDs, likely because the LCD backlight is a power hog. Claims say it uses less wattage than an LCD "at equivalent brightness." Because the FED is inherently bright, this claim is dubious. To pump up an LCD to equivalent brightness means jacking up the backlight.

I'd recommend a visit to the Candescent Web site for more details. I was amused by the company's argument that "no independent source" is a drawback to LCDs: "The major FPD producers are captive operations of companies such as Fujitsu, Hitachi, IBM, Matsushita, NEC, Samsung, Sharp, and Toshiba. These companies give first pick of their latest FPD products to their own in-house system groups, leaving customers at a distinct disadvantage." Please! A company such as Samsung could never suck up its own supply of LCDs for Samsung-branded products. And are vendors supposed to believe eight suppliers of LCDs is a bad thing, while one supplier of FEDs is a good thing?

Marketing hype aside, unmentioned issues of flicker and durability do exist. The FED display I saw flickered noticeably. Perhaps the prototype I looked at was an exception, but if not, that's not good. And the display is glass under a vacuum. Although I've cracked a few screens myself, most LCDs can withstand some abuse. This screen looks very susceptible to damage.

Apparently, the FED is finally making its way toward us and will be marketed as a ThinCRT. I'd prefer they call it a cathode array tube, or CAT, which is what it is. Whatever it's called, lots of hype will surround its introduction.

Topics: Hardware

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