Posted by JoeBloe on 10/01/06 19:24

On 1 Oct 2006 09:40:54 -0700, "gerry" <gerrytwo@hotmail.com> Gave us:

>By the way, what exactly is a data pit?

On a pressed disc, the laser cuts a master in glass, so the pits are
hard, sharp pits which then stamp the plastic gobs to become a disc
ready for metallization.

A recordable disc merely gets "impinged" upon by the laser's heat
(especially the RW types). The pits are more like hills and valleys
and there are no hard cliffs like with the glass masters for pressed
discs. This is why earlier, single power level laser diodes caused
read problems when the discs were burned at too high a speed, as the
contrast ratio gets reduced as the "laser on pit" time decreases. No,
they have multiple power level lasers to make the faster turning
record sessions receive more light energy to maintain a valid contrast
ratio.

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