Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1994-09-20
1997-06-24
Tran, Thang V.
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 4437, G11B 709
Patent
active
056423411
ABSTRACT:
A compact disc (CD) read sensor apparatus for reading data from a CD track uses multiple laser beams for performing both tracking and reading data. In one embodiment, two laser beams are used to track by controlling the radial position of the two beams that are nominally radially disposed towards opposite edges of the recorded track. A differential signal is used to obtain tracking information and a sum signal is used to produce a read signal. In another embodiment, three laser beams are used corresponding to prior art three beam systems using two beams nominally disposed towards opposite edges for tracking and a center beam for reading. The three beams are combined to form an enhanced read signal with an improved signal-to-noise ratio over that obtained by any one beam. The combining operation includes adjusting for any relative delays between the multiple beam signals detected by the photocells to produce synchronous laser beam signals followed by a summing operation that may optionally include optimal combining operations such as weighted summing, filtering, and neural network processing.
REFERENCES:
patent: 5272723 (1993-12-01), Kimoto et al.
patent: 5400312 (1995-03-01), Haraguchi
Donald G. Fink et al., Electronics Engineers' Handbook, Second Edition, McGraw-Hill Book Company, New York, pp. 20-67 through 20-69 (1982).
Erik S. Schetina, The Compact Disc, Prentice Hall, New Jersey, pp. 166-175.
Ricoh & Company, Ltd.
Ricoh Corporation
Tran Thang V.
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