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THERE’S ALWAYS A BETTER MOUSETRAP |
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| The market for flat panel displays may be maturing,
Last month, I covered several significant product and technology announcements at CES 2005. While much of the press coverage of this show was fixated on such oddities as Samsung’s 102-inch plasma TV, there were less obvious but far more important exhibits that are worth a second and more detailed look. Three in particular stood out in my mind. The first was Samsung’s introduction of a 46-inch LCD TV that uses LEDs for backlights, not conventional cold-cathode (fluorescent) lamps. This technology promises to bring a wider and more accurate color gamut to LCD imaging, something that is essential if this technology is to replace the venerable CRT and successfully compete with plasma. The second was the Toshiba-Canon joint venture into a new flat panel technology, the Surface-conduction Electron-emitter Display (SED for short). The 36-inch prototype shown at CES delivered the closest thing I’ve seen to CRT imaging while achieving a thin profile and low power consumption. Can it compete with LCD and plasma? The final demonstration was tucked away in a hotel suite far from the show floor, but well worth the trip. It detailed the ongoing development of plasma tube technology by Fujitsu (and by extension, manufacturing partner Hitachi). The plasma tube design is a radical departure from the traditional crossed ribs and ‘waffle’ pixel structures now in common use by other plasma manufacturers. LIKE SOUP AND SANDWICH The use of LEDs for backlights certainly isn’t a new idea; various display engineers have considered them for some time. But it took a partnership between Philips Lighting and Agilent Technologies in 1999 to bring a new company – LumiLEDs – into existence and accelerate the development of solid-state backlight technology. The theory behind LED lighting is that the combined array of red, green, and blue LEDs has no inherent color bias, unlike fluorescent lamps. By controlling the mixture and on-off cycles of LEDs, it should be possible to achieve a high degree of accuracy when referencing standard red, green, and blue color coordinates. LumiLEDs claims their LED backlight system can achieve 105% of the NTSC (SMPTE-C) color space, which would certainly make any LCD display a lot more attractive for critical video displays. The company also claims that their system can help to minimize LCD motion smear (caused by a lag in the liquid crystals transitioning from one state to another) by rapid on/off switching, much the same way that a shutter works in a motion picture projector. I can say that the Samsung demonstration of this technology, which used a live feed from an HD-resolution camera to show a series of Lava lamps in different colors, was very impressive. Amber, gold, hunter green, and turquoise are problematic colors to render with fluorescent backlights, but the images shown on the LN-460D TV were very close to the real thing.
Figure 1. Samsung’s LED-powered
46-inch LCD TV
Sony, who is a partner with Samsung in SLCD, a new joint venture 7th-generation TFT LCD fabrication line in Tangjung, Korea, also showed their version of this 46-inch TV, branded as the Qualia 005. Their demonstration at CES didn’t have any live subjects nearby for comparison, but the quality of flesh tones and shades of subtle pastel colors in their video demo was equally impressive. The construction of the LED stripes is also clever, and takes into account the sensitivity (or insensitivity) of the eye to the color blue. 7 rows of LEDs are arranged in a configuration with 26 red LEDs, 26 green, and 13 blue for a total of 455 individual LEDs. The nominal light output of this array? A tad under 500 nits.
Figure 2a-b. A compact matrix of
red, green, and blue LEDs (left)
You’re probably wondering just how reliable an LED backlight would be in the long run. The industry-accepted life cycle for LEDs is between 50,000 and 100,000 hours, so it’s not unreasonable to assume you’d get rid of an LED-equipped LCD TV long before it reached half brightness. Incidentally, LumiLEDs also figured into other demonstrations of ‘pocket’ projectors at CES in the InFocus and BenQ booths. No one could say for sure just how much light you’d get out of one of these tiny boxes (best guess was 30-40 lumens), but the concept was certainly an eye-opener. THE WORLD OF TOMORROW Over in the far reaches of the South Hall of the Las Vegas Convention Center, Toshiba held some private demonstrations of the SED, and believe me, it was difficult to gain access to this demo. Once inside, though, the experience was well worth it. The prototype SED shown was a 36-inch model with 1280x768 resolution, and mounted alongside it were a 40-inch LCD TV and a 42-inch plasma monitor. Trust me, it wasn’t a fair fight, although the Toshiba people admitted they made no attempt to calibrate the plasma and LCD monitors for this shoot out. The SED won hands down – it had no discernable motion artifacts, exhibited deep, rich colors, a super-dark level of black, and plenty of image detail and contrast. Plus, it used much less power in doing all this, if you could believe the large green LED display of real-time power consumption that was included in the demo. The concept behind the SED is similar to that of a CRT. Electrodes along the backplane of the display emit electrons when they are switched into a conductive state. These electrons are attracted to the front of the SED (which you could consider to be the functional equivalent of an anode) by a high voltage potential, somewhere around 10 kV.
Figure 3a. The Canon – Toshiba
SED display had the best color
Figure 3b. The SED principle uses
low-voltage electron emitter activation and
The front glass is coated with tiny red, green, and blue phosphors just like a CRT. The electrons are accelerated to very high speeds and strike each individual phosphor, causing it to glow brightly. Since the emitters (or cathodes, for you old-timers) are aligned precisely with the phosphors, there’s no need for any deflection yokes.
Figure 4. SEDs can be made considerably smaller and lighter than CRTs.
That makes for a much more compact and lighter display. It’s pretty bright, too. Toshiba claims the SED can achieve 10,000:1 contrast in a darkened room, but at that number I’ll bet the grayscale images would be bloomed out and crushed. Still, this technology has lots of potential, if it can be brought to market quickly enough at competitive prices and in multiple screen sizes. (Toshiba representatives talked about a 50-inch design with 1920x1080 resolution as the most likely first-generation commercial product.) If not, then SED may get lost in the crush of lower-priced “dime a dozen” LCD and plasma TVs and monitors that are descending on us like another tsunami. And that wouldn’t be the first time that a superior technology lost the race (remember Betamax and VHS?). THE GROOVE TUBE Fujitsu chose, as they usually do, to avoid the hubbub of the convention center and instead opted for a comfortable suite at the Venetian, in which they managed to tuck numerous plasma monitors, their brand-new 1920x1080 HTSP LCD front projector, and a small exhibit on the plasma tube. The plasma tube concept is pretty revolutionary. Individual tubes, measuring 1 meter long and 1 millimeter in diameter, contain individual red, green, and blue phosphors. These tubes are then sandwiched between electrode plates, which are manufactured separately (and less expensively, too!).
Figure 5. The plasma tube concept
is ingeniously simple.
The chief advantage to this process is a substantial reduction in weight of the finished plasma monitor, which could allow for much larger sizes to be manufactured. But there’s another aspect to consider, and that is the flexibility of the plasma tubes. They can be bent to allow the construction of a curved display, something that’s just not possible with conventional plasma architecture. The luminous efficiency of plasma tubes is supposed to be far greater than that of conventional rib and deep pixel structures, and Fujitsu’s target is to achieve 5 lumens per watt of energy used. That means it would be possible to build a 100-inch plasma display that would consumer less power than today’s 42-inch panels.
Figure 6. Fujitsu had samples of plasma tubes out for inspection at CES.
According to Fujitsu, the costs and complexity of plasma manufacturing would both come down as no clean room is required. The tubes would be manufactured in long sections and simply mated to the electrode-bonded motherglass in whatever screen size is desired (can you say ‘tiled display’?). Given the reduced power consumption of the tube design, it’s possible that the current king of large emissive displays – the LED – could be knocked off its throne in the not-too-distant future. The big question is; does Fujitsu’s retrenchment from the plasma manufacturing business (http://www.hdtvexpert.com/pages/strangesan.htm) mean this technology is stillborn, or will manufacturing partner Hitachi pick up the baton and run with it, given that they have purchased all of Fujitsu’s patents and IP related to plasma technology? |
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