[AV Media M atters] Increased BLER at OD of discs

[KIrelan@syda.o rg]

	The issue of BLE R increasing at the outer diameter of a disc
could be related to dye fo rmulation but that would likely only be
due to a complicated set of f actors including dye characteristics
which change from batch to batch, writ er laser power and servo
characteristics interacting with a particular dy e batch, write
speed, etc.

	However, increased BLER  at the OD of a disc is known to be
caused by birefringence.  Birefringence is optical distortion in the
polycarbonate layer of a disc caused by different indices of
refraction for different directions of polarization.  This is often
caused by stress produced during injection molding by uneven
cooling, uneven pressure during molding and flow lines and is most
often worst on the OD of a disc.

Kevin Irelan