Acquiring a best focus using a focus signal offset

Details Acquiring a best focus using a focus signal offset Acquiring a best focus using a focus signal offset

1990-09-28

1992-11-17

Envall, Jr., Roy N.

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

369 4427, 369 4432, G11B 700

Patent

active

051649322

ABSTRACT:
A focus acquisition system includes providing a focus offset and changing the offset symmetrically for each measurement cycle. The amplitudes of the readback or tracking error signal are sensed and compared. When the amplitudes of the tracking error or readback signal is different at each of the offsets, then a new measurment cycle is performed after calculating a new offset value. The process is repeated until the temporary measurement offsets result in readback amplitudes that are substantially equal. A best focus is then indicated as being a position in which small defocussing will not substantially degrade the quality of the readback signal.

REFERENCES:
patent: 4607157 (1986-08-01), Millar et al.
patent: 4733066 (1988-03-01), Konno et al.
patent: 5050151 (1991-09-01), Kurz
patent: 5077719 (1991-12-01), Yanagi et al.

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