Optical disk

Details Optical disk Optical disk

1995-09-01

1997-03-25

Levy, Stuart S.

Dynamic information storage or retrieval

Storage medium structure

Layered

G11B 370

Patent

active

056152060

ABSTRACT:
Disclosed is an optical disk having rows of pits, corresponding to information signals, formed on a transparent substrate, and a reflective film formed on this substrate. The reflective film is formed of amorphous silicon (a-Si) or indium antimonide (InSb), which exhibits a third-order non-linear optical effect. Thus, the reflectance of the reflective film formed of this material increases nearly in proportion to the intensity of the irradiated beam spot. The beam spot irradiated on the optical disk has the highest intensity at the center portion and this intensity becomes weaker as a point in the spot approaches the edge. Therefore, the effective spot size of the beam spot can be reduced, making it possible to reproduce from the reflection type optical disk information signals with a spatial frequency above the cutoff spatial frequency defined by the reproducing optical system. In other words, a row of pits recorded at a high density can be reproduced. As a change in the reflectance of the reflective film does not alter the structure of the material, the reflective film has a fast response to the reflectance change and is hardly deteriorated by the repetitive change in reflectance.

REFERENCES:
patent: 4782477 (1988-11-01), Ichihara et al.
patent: 4984231 (1991-01-01), Yasuoka et al.
patent: 5157249 (1992-10-01), Hashimoto et al.

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