Birefringence measuring apparatus for optical disc substrate

Details Birefringence measuring apparatus for optical disc substrate Birefringence measuring apparatus for optical disc substrate

1998-01-28

1999-09-21

Font, Frank G.

Optics: measuring and testing

By polarized light examination

With birefringent element

356376, G01J 400

Patent

active

059561467

ABSTRACT:
A birefringence measuring apparatus 30 measures a birefringence of a transparent substrate D1 of an optical disc D having a reflective layer D2 thereon by detecting a reflected light beam L2, which is a reflection of a light beam L1 from the disc. The light beam irradiates the disc at an incident angle of ".alpha.", penetrates the transparent substrate, and reflected by the reflective layer. The light beam emitted from a light source 1 has a coherence length shorter than an optical path length P which is a sum of optical paths P1 and P2. The optical path P1 is a distance from the surface of the transparent substrate to the reflective layer, and the optical path P2 is a distance from the reflective layer to the surface of the transparent substrate.

REFERENCES:
patent: 4655589 (1987-04-01), Cestaro et al.
patent: 5305090 (1994-04-01), Kowalski
patent: 5341205 (1994-08-01), McLandrich et al.
patent: 5517022 (1996-05-01), Bock et al.
Goodman et al, "Temperature Dependence of the Birefringence of Optical-disk Substrates", Applied Optics, vol. 35, No. 16, Jun. 1996, pp. 3031-3038, XP000594923.
Shribak, "Autocollimating Detectors of Birefringence", SPIE, vol. 2782, 1996, pp. 805-813, XP002065162.

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