11 Dec
2000
11 Dec
'00
11:17 a.m.
If anyone
knows the spiral spacing off-hand, I could tell you distance at
which a given wavelength focuses.
The specified track pitch is 1.6 +- 0.1 micron. from the disk, light from the outer portion (6 cm)
would focus at 18.2 cm
from the disk. Voilet (4000 angstrom) from the edges focuses at 23 cm.
Red (7000
angstroms) at 12 cm.
That matches pretty well with what I see when I look into a disk with a
strong light behind my back.
The focusing reported is definitely a refective surface geometric effect
and not a diffraction effect.
Eric