The problem with all sound recording/playback systems prior to the advent of
Compact Disc-style technology can be summed up with one word: friction.
A phonograph needle wears minuscule amounts of the vinyl from the surface
of the record it is playing. Worse, nearly any hard, sharp object can cause a record to skip. The oxide on recording tape is not only
physically deteriorated by its rubbing across a tape recorder's playback
head, but the signal contained as magnetic impulses on the oxide also
diminishes in intensity and quality if it comes into contact with parts of the
tape recorder which are magnetized. A music-box's chimes slowly abrade
the notches in the box's cam, and could conceivably wear them completely away
given time. Even a paper player piano roll is stressed and weakens after
repeated playings.
A Compact Disc is read by a beam of light, shed upon the myriad dents
contained in a thin film layer, by the compact disc player's high-tolerance
servo mechanism and bounced off of the surface of the film layer, back to a photosensor
which detects the pattern of dents and converts it into digital information.
Not only is this sublime metallic film of very high tolerance of more than
sufficient capacity to hold the music from an entire record album; it is
completely enclosed in a plastic not unlike LexanTM (G.E. Corp.),
rendering it safe from dust, dirt, scratches, stale beer, etc. for eternity.
"Alright," you say, "so you've got some dented tinfoil that's been covered
with polycarbonate. That's all well and good, but what if one should
obscure the view of the laser by scratching it, rubbing it with dirt, or
spilling last night's cheap Chianti upon the coating? How then will
our laser "see" the data on the tinfoil?"
"Your eyeglasses are filthy," I respond.
"What?!" You're nonplussed.
Now let's learn from our soiled eyeglasses. They can sure be coated
with an awful lot of gook, yet one can still see relatively clearly out of them.
That's because our eyes focus on the objects we're seeing and do not
focus upon the surface of the lens nor the filth thereupon. Of course, a
face-full of wedding cake, or some mud splashed up by a taxi crossing a pothole,
will obscure your view completely. These phenomena (the wedding cake, the
mud) will also serve to obscure the view of the CD from the laser, too!
Simply put, the plastic on the outside of a Compact Disc has to be in pretty bad
shape to be "un-playable."
Expensive kits are manufactured for cleaning CDs. These devices slather
your precious discs with a solvent and gently caress it with velvet brushes.
(The frugal audiophile, however, will have long dispensed of his/her expensive
CD-cleaning potions and opt for liquid hand dish soap in tepid water, applied
with a sponge, to remove even the most stubborn party-soil from discs.)
There are also just a few tid-bits to add to the already-bountiful factoids
offered herein about CDs:
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As early as 1978, the Magnavox Corporation's "Magnavision" was utilizing a
laser reading a plastic-coated disc to play movies through one's television set.
The concept was an expensive flop. (The discs were over 12" in
diameter, and available movie titles were rather limited. But the system sure
was a great status symbol!)
-
James T. Russell, an American physicist, was the first to patent Compact Disc
technology, in 1970, on behalf of the Battelle Memorial Institute. Russell
had worked on the project for the better part of a decade prior to its practical
application. It was
called a "digital-to-optical recording and playback system." The
unit was received coolly by potential corporate investors. It was finally
funded by a venture capitalist, Eli Jacobs, who started the Optical Recording
Corporation in 1971, hiring Russell and a number of his colleagues.
Philips' disc was an analog device, which emerged at the same time as
Russell's. In fact, Philips announced their own digital "Laserdisc" device
two months after Optical Recording Corporation demonstrated its own
color-capable digital laser video recording and playback system at an
industry trade show.
-
Optical Recording Corporation was the winner of a
patent infringement lawsuit in 1992, finally confirming that it alone could
claim ownership of the patents for the Compact Disc. Although the award
was about $30 million, Russell didn't see a penny of it as he was merely an
employee of Optical Recording.
Sources:
Interview, Eli Jacobs, 1998, Greenwich, Connecticut
http://web.reed.edu/reed_magazine/Nov2000/a_the_discoverer/3.html
http://www.intelligentmd.com/about_us/directors.htm
http://web.mit.edu/invent/iow/russell.html