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SED TV Technology

SED TV - New Flatscreen Technology
Andrew Carruthers, October 26, 2005
HDTV Solutions

Plasma and LCD HDTVs may soon be sharing shelf space at your local electronics store with a new flat panel technology called SED TV. Developed jointly by Canon and Toshiba; SED stands for Surface-conduction Electron-emitter Display.

Canon started development on this imaging technique back in the mid 1980s and joined up with Toshiba for the project in 1999. Both formed a dedicated company for the technology called SED Inc. in 2004. Neither of these companies is a notable player in the flat screen arena, but they are looking to make a big splash with SED TV. Test production runs are already underway with limited product availability expected by spring 2006. At present, it looks as if Toshiba will start manufacturing HDTV panels in earnest in 2007 barring any production problems.

How it Works
SED technology works much like a traditional CRT except instead of one large electron gun firing at all the screen phosphors that light up to create the image you see, SED has thousands of tiny electron guns known as "emitters" for each phosphor sub-pixel. Remember, a sub-pixel is just one of the three colors (red, green, blue) that make up a pixel. So it takes three emitters to create one pixel on the screen and over 6 million SED emitters to produce a true high definition (HDTV) image! It's sort of like an electron Gatling gun with a barrel for every target positioned at point-blank range. An army of electron guns, if you will.

This may bode well for video purists who feel that CRTs offer the best picture quality, bar none. One prototype has even attained a contrast ratio of 100,000:1. Its brightness of 400cd/m2 is a tad on the low side for an LCD TV and nowhere close to a plasma. This is expected to increase in the future, but still works out to about 116 ftL (foot Lamberts) or more than twice a regular TV. To put this in perspective, a movie theater shows a film at about 15 ftL.

Life Expectancy
It does look like SED TVs will last a good while as it has been reported that the electron emitters have been shown to only drop 10% after 60,000 hours, simulated by an "accelerated" test. This means that it is likely the unit will keep working as long as the phosphors continue to emit light. That can be a while. Maybe yours will even show up on the Antiques Roadshow in working condition in the far distant future. Time will tell but "accelerated" testing results should always be taken with a grain of salt as it only imitates wear and tear over time.

SED TV Compared to CRT
SED is flat. A traditional CRT has one electron gun that scans side to side and from top to bottom by being deflected by an electromagnet or "yoke". This has meant that the gun has had to be set back far enough to target the complete screen area and, well, it starts to get ridiculously large and heavy around 36". CRTs are typically as wide as they are deep. They need to be built like this or else the screen would need to be curved too severely for viewing. Not so with SED, where you supposedly get all the advantages of a CRT display but need only a few inches of thickness to do it in. Screen size can be made as large as the manufacturer dares. Also, CRTs can have image challenges around the far edges of the picture tube, which is a non-issue for SED.

SED TV Compared to Plasma TV
Compared to plasma the future looks black indeed. As in someone wearing a black suit and you actually being able to tell it's a black suit with all those tricky, close to black, gray levels actually showing up. This has been a major source of distraction for this writer for most display technologies other than CRT. Watching the all-pervasive low-key (dark) lighting in movies, it can be hard to tell what you're actually looking at without the shadow detail being viewable. Think Blade Runner or Alien. SED's black detail should be better, as plasma cells must be left partially on in order to reduce latency. This means they are actually dark gray - not black. Plasma has been getting better in this regard but still has a way to go to match a CRT. Hopefully, SED will solve this and it's likely to. Also, SED is expected to use only half the power that a plasma does at a given screen size although this will vary depending on screen content.

SED TV Compared to LCD
LCDs have had a couple of challenges in creating great pictures but they are getting better. Firstly, latency has been a problem with television pictures with an actual 16ms speed needed in order to keep up with a 60Hz screen update. That needs to happen all the way through the grayscale, not just where the manufacturers decide to test. Also, due to LCD's highly directional light, it has a limited angle of view and tends to become too dim to view off axis, which can limit seating arrangements. This will not be an issue for SED's self illuminated phosphors. However, LCD does have the advantage of not being susceptible to burn-in which any device using phosphors will, including SED. SED is likely to use about two-thirds the power of a similarly sized LCD. Finally, LCD generally suffers from the same black level issues and solarization, otherwise known as false contouring, that plasma does. SED does not.

SED TV Compared to RPTV
SED is flat and RPTVs aren't. RPTV also has limitations as to where it can be viewed from, particularly being vertically challenged with regard to viewing angles. A particular RPTV's image quality is driven by its imaging technology such as DLP, LCoS, 3LCD or, more rarely recently, CRT. With the exception of CRT, these units need to have their lamps changed at various times but usually at around 6,000 hours, costing an average of $250.

The cost of flat panels is largely dependent on production yields of saleable product. Nobody really knows for sure what this will be until real production starts, but new technology is always expensive in early production. If it works, the use of inkjet technology to make SED displays rather than the more expensive photolithography process used in LCD panels should help cost management. The first product release will be a 55" version at full HD resolution (1920x1080) priced comparably to today's plasma display panel (PDP) of similar size. That could be a big dollar difference by early 2007, as the price of plasma displays is expected to continue to drop.

New technology usually has its fits and starts, but on paper SED should be a strong contender. We will give you updates as the technology gets closer to market and we get a chance to see the first units at the next technology conference. For now, all that can be SED, has been said.

Update March 8, 2006 - Toshiba Corporation and Canon Inc. today announced that they will start the first stage of mass production of SED panels in July 2007 and launch SED TVs in the 4Q of calendar year 2007. Press Release

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(10/27/21 - 01:05 PM PST)
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