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How laser video disks work

technofile  by al fasoldt

Columns and commentaries in a life-long dance with technology
 

Simple gray rule



How laser video disks work 


By Al Fasoldt

Copyright © 1988, The Syracuse Newspapers

Video is surprisingly low-tech compared with audio and computers.

At a time when record stores are overflowing with digital compact discs and computers around the world use the latest high-speed digital processors, video is stuck in a time warp. The picture you watch uses the same technology as the pictures your parents saw 40 years ago.

Even the video recorders we enjoy in these days of high-tech excitement are little more than kissing cousins of the VCRs from a dozen years ago.

But video's super-tech future is sneaking up on us fast. The first wave is here already.

In fact, it arrived while most of us weren't looking -- 15 years ago.

This decade-and-a-half-old technology is the laser video disc, which was developed by Philips of The Netherlands in the late ‘60s and early ‘70s.

Philips, which had invented the common audio cassette a decade earlier, worked with the idea of using a tiny beam of light to decipher video signals engraved on a plastic disc.

Only a special kind of light would do. It had to be able to focus down on very tiny grooves running around the disc—so minuscule, in fact, that 1,000 of them would fit in one regular record groove.

Lasers, which were becoming cheaper and smaller by the late ‘60s, were the perfect source of light for such a video player. Unlike regular light beams, which scatter like a mob of rabble-rousers at daybreak, laser beams are like an army of photons all marching in step, in the same direction.

This means they also bounce off a smooth groove in the same direction, too—right back up to a little window in the disc player. But no army, photons or otherwise, can handle bumpy obstacles without scattering to each side. So when the laser beam shines on one of the bumps in the groove, the beam is scattered and the window goes dark.

The next step was a genius idea: Make two kinds of bumps: long ones, like upside-down canoes, for one type of signal, and short ones, like overturned wheelbarrows, for another. With these long-and-short bumps spaced out in a video equivalent of Morse code, you could encode TV pictures in the grooves of a laser disc.

When these shiny discs and their players first arrived in North America in the ‘70s, they caught the imagination of videophiles and sold out literally overnight. But within a short time the sales curve of laser video discs and players looked more like a winter temperature chart. They almost died out.

One culprit was the bad rap all video discs got from a competing system, sold mostly by RCA. The RCA system, which is remembered these days as perhaps one of the worst inventions of all time, used a phonograph-type needle to play a vinyl disc. The discs wore out almost as fast as the patience of those who tried to get their money back after they took the players back to the store.

But something else was to blame for the troubled times of the laser video disc. The discs themselves were expensive, which was bad enough, but worse yet, you couldn't record on them.

At a time when video cassette recorders were just becoming popular, there weren't many consumers who wanted a non-recording video machine.

Nowadays, VCRs are found in just as many homes as toasters are. Videophiles and ordinary TV watchers alike are looking for a second source of programs, and they don't care whether it can record or not.

As a result, laser video is coming into its second age, and this time it's likely to stay. In fact, some industry experts are predicting that laser video players—especially the newest kind, which can play audio compact discs as well as video discs—might be one of the hottest selling items of the coming year.


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