Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1990-09-07
1994-07-05
Psitos, Aristotelis
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
3692753, G11B 700
Patent
active
053274083
ABSTRACT:
An optical disk has groups of features (such as depressed areas) arranged in a preselected position sensing servo pattern, and a flat, non-grooved surface between a plurality of circumferentially spaced sectors. A single photodetector senses the change in amplitude of reflected light as a spot from a laser passes over one of the features and generates position sensing signals corresponding to the pattern. At least three phases of the position sensing signal are generated for each sector. Each phase is determined by edges on the disk offset circumferentially with respect to each other and separated radially from each other by a preselected critical distance that is independent of the pitch of the recording tracks on the disk to provide a track error signal that is substantially linear within a desired range to either side of a zero-crossing point.
Each even sector includes a plurality of features formed in an arrangement which is the complement and/or reversal in order circumferentially of their arrangement in the intervening odd sectors to cancel simultaneously, by averaging the position sensing signals from adjacent sectors, errors caused by variations in pattern size and/or radial velocity of an optical head as it moves generally radially of the disk.
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International Business Machines - Corporation
Otto, Jr. Henry E.
Psitos Aristotelis
Tran Thang V.
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