Focus point switching

Details Focus point switching Focus point switching

2007-05-01

2007-05-01

Miller, Brian E. (Department: 2627)

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

C369S094000, C369S053280

Reexamination Certificate

active

10988536

ABSTRACT:
A focus jump technique enables focus control on recording layers of a disc in such a manner that its effect is not absorbed by disturbance or a variation in the movement speed of an objective lens. The technique involves monitoring level of a focus error signal and rejecting noise from the error signal. A speed sensor detects movement speed of an objective lens; and a speed control circuit generates a voltage for controlling the objective lens, based on the detected movement speed. Movement speed of the objective lens is detected during focus jump, a corresponding lens drive signal is generated, and an end position is determined from behavior of the error signal immediately before the end of the jump. A focus control is pulled, from a focus point corresponding to one recording layer, into a focus point corresponding to another recording layer forcibly in a stable manner.

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