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CICIORA’S CORNER: Display dynamics

Fri, 11/30/2007 - 7:10pm
Walter S. Ciciora, Ph.D., Recognized Industry Expert on Cable and Consumer Electronics Issues

When the National Television Systems Committee (NTSC) standard was set in 1941, it defined a picture quality level way beyond what could be produced. When color was added in 1953, the display devices lagged the theoretical capability by Walter S. Cicioraa substantial margin. There were big deficiencies in brightness, resolution, color fidelity and reliability. And the first cathode ray tubes (CRTs) were round. When introduced, those color sets cost as much as a small car and helped pay for the local TV repairman’s new car.

It took decades for display technology in the form of CRTs to be able to provide the full promise of the NTSC standard. First came rectangular tubes with rounded corners. Next came square corners. A brightness “horsepower race” evolved. Finally, the face plate flattened out from its early nearly spherical shape. Then very quickly, CRTs became inexpensive.

When the Advanced Television Systems Committee (ATSC) was creating the High-Definition Television (HDTV) standard, it was hoped that HDTV would provide a high hurdle for display technology and last a long time. This would breathe new life into the consumer electronics business. Astonishingly, that was not to be. Even before HDTV reached significant consumer penetration, the display technology met and surpassed the new standard. And now we are in a period of rapidly falling prices.

A few years ago, a good cable friend treated himself to the ultimate HDTV display (1080 lines, 1920 pixels per line, and progressive scanning) as a retirement gift. At that time, he spent around $20,000. While retirement is indeed something major to celebrate, maybe he should have bought a fancy car instead. It would have held its value better, even with the rapid depreciation cars experience. Now, a similar display costs around $2,000. If you go to a major consumer electronics retailer, you will find that the 1080p models are not as rare as they were a couple of years ago. They dominate the shelves! And some of the prices for smaller models approach $1,000. The dynamic here appears to be price “free fall.”

When I worked for Zenith in the 1970s and early 1980s, the only production color display was the picture tube. There was a lot of work going on in the research lab on alternatives, but they were always “10 years away.” And it was a sliding 10 years - the number never got shorter. There was work in the lab on flat panels based on liquid crystal displays (LCDs) and on plasma. There was also work on laser projection systems. The laser projection system seemed to have the most dramatic displays. They were big and they were full motion television. The laser display had a significant advantage in its driving electronics. It was a scanned display, just like the CRT, and so the signal processing remained the same. It was analog. But lasers can be dangerous if the scanning quits. There was a sign in the lab: “Do not look into laser with remaining good eye.” This bit of sick humor provides one of the reasons why that display technology stayed in the lab.

Back then, the LCD and plasma displays had a serious non-display problem. Since they are not scanned, they needed a whole new kind of signal processing. Each pixel had to be addressed discretely. And of course, there were really three pixels in each location: a red, green and blue spot. The digital electronics to do all of this were not anywhere near affordable. Moore’s law had not yet worked sufficient amounts of its magic. So, while the displays had a lot of technological evolution ahead of them, so did the drive electronics. Neither area was evolving quickly. There was no dynamism.

Now, everything has become more dynamic. There are color displays everywhere. Monochrome just isn’t good enough. Cell phones commonly come with two color displays, a small one visible without opening the phone and a bigger one inside. A number of start-ups have announced interesting display developments. Light Blue Optics Inc. has developed a miniature color projector, the size of a match box, which can be included in a cell phone. (The biggest concern seems to be battery life.) The projector will paint a color TV picture to be shared with others on any surface.

The micro-mirror display operates in a different way. An integrated circuit has a hinged aluminum micro-mirror in each of the pixel locations. A bright light is reflected off of the plane of mirrors and then focused with optics onto a screen. Electrostatic forces deflect the mirror so it does not contribute light to the image. The percentage of time the mirror is deflected determines the brightness of the pixel. It’s digital, not analog. These mirrors are operated at least three times the speed necessary to make a picture because they sequentially make the red, blue and green components of the picture. A rotating filter color wheel makes the color.

Our job is to provide the programming for this dynamic world of displays.

wciciora@ieee.org

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