"josephkook"


Actually there is. It has to do with the optics works. At nominal
wavelength the phase difference between "pits" and "spaces" is about 1/4
wavelength. If you change the laser wavelength from 700 to 400 there is
no longer an unambiguous flying height solution.


** Care to flesh that last one out a bit ?

A "blue ray" laser would see the pits on a CD reflecting light back
essentially in-phase with the rest of the surface.

The focus height does not come into it.


.... Phil