* "James S. Lee" <[EMAIL PROTECTED]> on Wed, 23 Aug 2000
| Are you saying that the depth of the burn is proportional to the
| intensity of the laser that burned it?
CD is not burned by a laser. Neither is LD.
| Well, that is true. Are you then implying that the strength of the
| reflected light (on playback) is also proportional to the depth of the
| stamped pits on the surface of the disc? Just trying to get clear.
More a matter of angles. If you shine a laser at a reflective surface at a
fixed angle, the focal point of the beam (I think that is the correct term)
will vary depending on the distance of the surface from the emitter.
For example, the angle of incidence is 45 degrees, the distance from
emitter to land is 1cm and the depth of a pit is 0.5cm. When the laser
shines on a land spot, the beam is reflected to a point 1.414cm away from
the emitter (assuming a nice right triangle). When the laser shines on a
pit, the beam is reflected to a point 2.121cm away from the emitter.
To use this hypothetical medium for digital storage I could say that any
pit from 0.0cm to 0.25cm deep is "1" and any pit deeper than that is "0".
To use this medium for analog storage, such as a video stream, I say that
0.0cm is pure white, 0.5cm is pure black, and anything in between is a
proportional color value.
That is not exactly how CD and LD work, but it should give you an idea of
how "digital" media is often really analog media used in an interesting
manner.
--
Rat <[EMAIL PROTECTED]> \ Ingredients of Happy Fun Ball include an
Minion of Nathan - Nathan says Hi! \ unknown glowing substance which fell to
PGP Key: at a key server near you! \ Earth, presumably from outer space.
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