Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1995-09-20
1998-01-13
Young, W. R.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 4442, 2502015, G11B 7095
Patent
active
057086346
ABSTRACT:
Focussing system methods and apparatus are provided for apparatus capable of simultaneously reading multiple tracks of an optical disk. Astigmatism introduced by a cylindrical lens disposed adjacent to the light source, or before the focus detectors arranged at the edge of a wide-area field of illumination, is used to compute an error signal corresponding to the degree of out-of-focus, which error signal is provided to a servo-system that moves the objective lens to correct the focus. An alternative embodiment employs a pair of focus detectors and a pair of micro-lenses having different focal lengths that directs the reflected light onto the focus detectors to generate a focus correction signal. Further alternative embodiments of employing the astigmatism method of focussing are described.
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The Compact Disk Handbook, K. Pohlmann, A-R Editions, Inc., Madison, Wisconsin (2d ed. 1992), pp. 111-117.
Alon Amir
Finkelstein Jacob
Katz Itzhak
Naor Michael
Shapira Shlomo
Pisano Nicola A.
Young W. R.
ZEN Research N.V.
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