Importance

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Abstract

A defect detection unit (5), a disc position detection unit (9), and a disc rotation speed detection unit (1) are in a disc control device which includes a repetition control device to control storing to and reading from a memory unit (3) functioning as a learning memory and for varying the number of memory divisions of the memory unit (3) on the basis of detection by the detection units. Components having periodicity apparently due to partial surface runout or partial eccentricity are stored in memory unit (3) by increasing the resolution and microscopic noise components, and noise components having no periodicity are not stored in memory unit (3). This system carries out stable focus tracking control even when disturbances such as device vibration or scratches on a disc are mixed.

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First Claim