Optical disc apparatus switching focus point between layers

Details Optical disc apparatus switching focus point between layers Optical disc apparatus switching focus point between layers

2005-03-08

2005-03-08

Nguyen, Hoa T. (Department: 2652)

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

C369S053280

Reexamination Certificate

active

06865141

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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