Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Patent
1999-03-24
2000-08-22
Cabeca, John W.
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
369 4422, 360103, 359819, G11B 700
Patent
active
061082929
ABSTRACT:
Apparatus for optically scanning an information plane of a disc-shaped optical record carrier having an underlying surface extending parallel to the information plane. A radiation source supplies a scanning beam, and an optical scanning unit has a lens system which focuses the scanning beam to a scanning spot on the information plane. The lens system has an optical axis, a first lens unit with a first lens having an entrance side (11) and an exit side (13), and a second lens unit with a second lens situated opposite the exit side of the first lens. The scanning unit also includes a drive motor for displacing the first lens along the optical axis and a rotation element for adjusting the position of the second lens with respect to the underlying surface of the record carrier. To inhibit spherical and/or comatic and astigmatism aberrations during scanning, the rotation element is rotatably driven and forms part of the second lens unit. It is journaled in a stationary element (17), and has a disc-shaped surface provided with a pattern of grooves therein. This results in increased air pressure in the gap between the underlying surface of the record carrier and the rotation element during scanning, thereby maintaining a correct gap spacing.
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Cabeca John W.
Chu Kim-Kwok
Eason Leroy
U.S. Philips Corporation
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