24 Apr
2010
24 Apr
'10
9:33 p.m.
On Sat, Apr 24, 2010 at 03:52:16PM -0700, Ken Restivo wrote:
Makes sense: at slower speeds, the laser could burn a
hole
in the media. So at slowest possible speed, I should get
the deepest possible pits, and thus the most reliable-to-read CD,
I guess.
No that's not how it works. Simplifying things as bit, on a
real 'stamped' CD the pits should be 1/4 wavelength deep,
so that the reflection of the bottom is in antiphase with
the one from the surface, this provides the best 'contrast'.
Writeable CDs don't have pits, either the color or the
reflectivity of the surface is modified by heating it.
Both require the laser power to be controlled in function
of write speed.
So the slowest allowed speed is not necessarily the best
one.
Ciao,
--
FA
O tu, che porte, correndo si ?
E guerra e morte !