CD Technology

[Jonathan Schattke <wizwom@ripco.com>]

Rubywand wrote:

>      CD's do not depend upon magnetic storage; so, there does not seem to any
> need for them to contain magnetic materials. CD's are read by laser beams.
> The aluminum or whatever inside the plastic probably has little tiny blips
> created by a laser during recording which are detected during playback.

CD's bear a lot of resemblance to a phonograph record.  There are divots in the
surface which are read by the laser.  The originals (and current music and
CD-ROMS) are made by a one-time mastering process which blasts the aluminum with
a laser, abating material; then a micro-accurate cast is made of the original,
and it is cast in aluminum as many times as the producer wishes.

Writeable CDs use a magneto-optic or dual-level process to heat a special
material disk.  They are much more expensive to manufacture, thus the higher
price.  If they must be writable multiple times, then the process must also be
reversible, adding further expense.

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