CD's as parabolic mirrors?

From: Eric Smith <eric_at_brouhaha.com>
Date: Mon Dec 11 17:28:29 2000

> 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.

Some other specs:

  disc:
    substrate thickness: 1.2 +- 0.1 mm
    refractive index 1.55 +- 0.1
    limits for the angular deviation of
      reflected beam: +- 1.6 degrees
    birefringence of substrate: 100 nm max
    limits for reflectivity variation
      in program area: 3% for f < 100 Hz

  pickup:
    wavelength: 780 +- 10 nm
    polarization: circular
    numerical aperture (NA): 0.45 +- 0.01
Received on Mon Dec 11 2000 - 17:28:29 GMT