Optical head device for reading two optical disks

Details Optical head device for reading two optical disks Optical head device for reading two optical disks

1997-02-06

1999-04-06

Swann, Tod R.

Dynamic information storage or retrieval

Specific detail of information handling portion of system

Radiation beam modification of or by storage medium

369 4414, 369 4437, 369 94, 369110, G11B 7135

Patent

active

058927492

ABSTRACT:
An optical head reader includes a laser light source; a polarization beam splitter for dividing first and second linearly polarized beams having first and second polarization directions which are perpendicular to each other; an optical transmission system for transmitting the first and second beams along first and second optical paths which are parallel to each other; a quarter wavelength plate for converting the first and second beams into first and second circularly polarized beams having polarization planes rotated in first and second directions opposite to each other; and a pair of first and second objective lenses provided having first and second focal lengths which are different from each other, so that one of the first and second circularly polarized beams is focused on an optical disk surface. The first and second circularly polarized beams are reflected by the optical disk surface and subsequently transmitted through the first and second objective lenses to the quarter wavelength plate, whereby the first and second circularly polarized beams are converted into third and fourth linearly polarized beams having the second and first polarization directions. The third and fourth beams are transmitted through the optical transmission system to the polarization beam splitter, whereby the third and fourth beams are transmitted along a common optical path to a single optical detecting system.

REFERENCES:
patent: 5144617 (1992-09-01), Gotoh et al.
patent: 5526338 (1996-06-01), Hasman et al.
patent: 5673247 (1997-09-01), Sekimoto et al.
patent: 5682373 (1997-10-01), Kim
patent: 5784354 (1998-07-01), Lee

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