Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Patent
1997-08-15
1999-09-21
Hindi, Nabil
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
369 4441, 369 4428, G11B 700
Patent
active
059563044
ABSTRACT:
In an optical disk storage device, a differential phase detector is disclosed for generating a position error signal independent of the frequency content of the recorded data. A pair if diagonal signals S1 and S2 are generated by adding a pair of respective quadrants of a four-quadrant photodetector, where the phase offset between the diagonal signals represents the position error of the pit image as it passes over the photodetector. The position error is determined in the present invention by computing the difference between a positive and negative correlation of the diagonal signals S1 and S2, otherwise referred to as a dual arm correlation (DAC) ##EQU1## where .DELTA. is the correlation offset and L is the correlation length. In the preferred embodiment, the correlation offset .DELTA. is adaptively adjusted to maximize the correlation between S1 and S2. In this manner, the position error estimate is substantially insensitive to the frequency content of the recorded data. Furthermore, this method extends the position error over a range of plus or minus one-half a track, which facilitates generating a quadrature signal for use in counting track crossings during seek operations.
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Feyh German S.
King Larry D.
Romano Paul M.
Supino Louis
Cirrus Logic Inc.
Hindi Nabil
Sheerin Howard H.
Shifrin Dan A.
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