CD's as parabolic mirrors? - test-drb@ccmp.vtda.org

8 Dec 2000

...
  I just noticed that sunlight reflecting off the top
side of a CD focuses
 somewhat, maybe with a focal length of about 20 feet. Off of the data side, it
...
  spreads. I've tried it with several different
types, and so far they all show
...
  the same effect. Would anyone care to explain why?

I remeber reading that a hologram of a lens would refract light in the
same was as a real lens would. This concept has formed the basis for
the flight-of-fancy holodeck/holosuite concept from Star Trek.

My guess is that (unintentionally) the spiral pattern sets up the
same interference pattern as a hologram of a parabolic mirror.

Regards,
-dq