Optical head including ring-shaped light blocking or light non-c

Details Optical head including ring-shaped light blocking or light non-c Optical head including ring-shaped light blocking or light non-c

1997-03-31

1998-12-01

Swann, Tod R.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369112, 369 94, 369 4423, G11B 7125, G11B 7135, G11B 1512

Patent

active

058448799

ABSTRACT:
A masking member is provided so as to move in an interlocked manner with a shift of an objective lens designed for a high-density disk. Since the masking member reduces an effective numerical aperture (NA) of the objective lens, and greatly reduces affection of aberration, the objective lens allows a CD whose substrate is thicker than that of the high-density disk to be stably reproduced. Also, for example, even when the objective lens moves in a track direction of the high-density disk or CD, the masking member follows that movement. Therefore, a suitably sized light spot is formed on a signal surface of the high-density disk or CD. Especially, a light flux having passed inside the masking member with relatively small aberration is used to form a suitably sized light spot on the signal surface of the CD.

REFERENCES:
patent: 5523338 (1996-06-01), Hasman et al.
patent: 5638353 (1997-06-01), Takahashi
patent: 5708641 (1998-01-01), Choi et al.

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