TFT, LCD or wait for SED flat panel display ?

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Μέχρι τώρα είχαμε το debate μεταξύ TFT or LCD επίπεδη οθόνη πλέον θα έχουμε και το καινούργιο παιδί... το όνομα αυτού SED…
Evolution never ends…τουλάχιστον στα χαρτιά φαίνεται να σκίζει...

FPD Supplement: Canon, Toshiba Reveal SED with Contrast Ratio of 8,600:1
"It took us a little while to develop it, but we knew it was solid technology and we were prepared to spend the time needed. After all, the longer it takes to perfect the technology, the less likely it is that competitors will be able to match it," noted Fujio Mitarai, president and CEO of Canon Inc of Japan.

Canon, in a joint effort with Toshiba Corp of Japan, recently revealed a 36-inch surface conduction emitter display (SED) panel, a type of field-emission display (FED) panel being developed for use in television. The two companies plan to establish a joint venture named SED Inc of Japan in October 2004 to develop, manufacture and sell the panels, and hope to volume-produce a 50-inch panel in August 2005. While the initial monthly production will be a relatively low 3,000 units, they plan to boost this to 75,000 by the end of 2007, 150,000 by the end of 2008 and 250,000 by 2010.

There has been considerable anticipation shown for SED panels. Consumers are said to have held off purchasing plasma display panel (PDP) or liquid crystal display (LCD) televisions because of the low power consumption and excellent image definition of SED. The prototype shown at the joint press conference announcing the new venture strongly appealed performance that met these expectations. In the dim hall, the instant the cloth was whisked off the waiting SED panel, the audience was struck by the sheer beauty of the imagery. Unlike the usual prototype, the sheer maturity of the display was staggering.

Of the specifications given for the prototype, the contrast ratio for a dark environment was especially intriguing (see Fig). The prototype boasts a ratio of 8,600:1, as opposed to about 3,000:1 tops for PDP and 1,000:1 for an LCD. In PDPs, discharge light leaks cause the low contrast, while in LCDs light leaks from the backlight cause blacks to show faint cloudiness. Neither of these problems occurs with the SED. As one LCD panel engineer puts it, "The expression of black is a crucial index. The image looks entirely different."

Boosting Contrast Ratio

Most of the specifications provided by the two companies were superior to specs for the same items on PDPs or LCDs, such as power consumption. The only one that wasn $B!G (Bt too impressive was the contrast ratio (see Fig). A Canon employee agreed: "We are fully aware that it has a weak point when it comes to image appearance in a bright environment. Any improvements will start there."

An engineer at a PDP manufacturer pointed out, "For dark environments, a contrast ratio of about 2,000:1 is ample. It will be used for television instead of home theater then the contrast in bright environments will be the key spec. PDP offers a slightly better contrast at high ambient light levels." With FED panels, the usual way of boosting brightness (which is the key to improving the contrast ratio in bright environments) is to increase voltage or current input to the cathode, which emits the electrons. If voltage or current are too high, however, the phosphors will deteriorate, shortening service life. The above-mentioned PDP engineer explained that a good balance between brightness and life is essential.

SED panels are likely to make best use of the high contrast in dark environments to first develop the home theater market, but their performance in the television market will depend on how much improvement they can offer in bright environments.

by Takuya Otani

(December 2004 Issue, Nikkei Electronics Asia)

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