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EDN.COMMENT: Get the picture?

One day in January this year I noticed, in the London Times, the following bit of technology reporting by its television reviewer—programme reviewer, that is, not technology reviewer. On one level it’s interesting because it’s fairly rare for a journalist in a mass-circulation paper to take an interest in technology, unless it is his or her specific subject. Here’s what the piece said: “I was talking to a television engineer over the weekend—I won’t say from which company—and he confirmed to me what I long suspected: the picture quality on LCD flat screens is a joke within the industry. The future, apparently, is not even plasma but something called SED (surface-conduction electron-emitter display), which uses a combination of flat panel and CRT (cathode-ray tube) to deliver better quality than either LCD or plasma. Expect to see the first sets this spring.”

One thing the display industry has never been short of is candidate technologies to be the perfect display of the future. And, all too often, they stay exactly that—some way off in the future. SED sits—in my mental filing cabinet, at any rate—alongside other technologies such as FED; if the file has a label, it says something like, “Might mature into a real product. Maybe. One day.” Not that anything of what the TV reviewer says is wrong—except, perhaps, the bit about “this spring”—I hope he’s not holding his breath, waiting.

SED, if you can’t call to mind the details, is a pixel-driven CRT technology. Rather than the single steered-beam electron gun of a conventional CRT, each pixel—which has CRT-type phosphors— has a corresponding individual electron emitter: a voltage accelerates the electrons across a small—in vacuo—gap, and they do the usual excitation thing. The result is CRT-like colour rendition and brightness from flat-panel geometry. FED (field-emissive display) differs from SED mainly in the mechanism the developers used to generate the free electrons. In the case of FED, a potential causes the discharge of electrons from a very fine point or collection of points. Recent developments efforts use carbon nanotubes as the points, and of course anything that involves carbon nanotubes is ultra-cool in technology terms.

So why are there no SED TV sets out there in the market (yet)? For one thing, the industry has done what it does so well—having invented a promising technology, it got itself embroiled in a damaging legal dispute over IP that the participants in that wrangle—which include Canon and Toshiba—have only recently resolved (if you want that bit of the story, Google will provide). Which is part of the reason that the sets our TV reviewer has been told to expect, have been similarly promised as “just around the corner” for at least the last two years.

Also, companies working in this field have spread their resources around— the same companies that might bring SED to market are also making sure they have all options covered by working on OLED TV. Is that technology ready? Yes, in a manner of speaking— if you are willing to pay enough for one of a limited supply of an 11-inch model by Sony.

I would not decry any of these technologies: they are probably all capable of producing beautiful results. I also don’t know anyone in the business who would not acknowledge the limitations of LCD (though calling it a “joke” is a bit excessive): less-than-ideal colour gamut, poor energy efficiency, limited contrast and, as it is a subtractive technology, an enduring problem with black levels. But the question is not where it falls short, but: Is it good enough? And for the purpose of television, the answer appears to be “yes”. It’s only television after all, it doesn’t have to do a precision-colour reproduction of the Sistine Chapel. TV is only an illusion to begin with—given a decentresolution image with no disastrous artefacts, in approximately the right colours, our own, very clever, eye-brain combination will readily complete the illusion for us.

The real problem for any new technology in the sector is the internalcombustion- engine effect. While new technologies struggle to get to market, LCD becomes more entrenched as the high-volume standard, its manufacturing costs decline even further, and it becomes even more difficult for any new arrival to compete with. (Just as with vehicle engines: Are there better ways of powering a car than with reciprocating pistons burning volatile hydrocarbons?— Of course there are, but the incumbent technology has a century’s head start in development.)

You reach the point where the question is not, “Is this technology—SED, FED, OLED, or whatever—better than LCD?” but, “Is this technology better by a sufficient margin, given the—inevitably— higher price point at which it will enter the market, to displace LCD?” That’s not a display phenomenon, it’s true of any innovation in any market: but it’s particularly acute in this one because the key attributes are all— well… on display.