Importance

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Abstract

An optical disk for optical recording and reproducing data has a spiral track and further includes a single index field and a plurality of sectors. The index field includes an index mark that indicates the position at which an optical head of the optical recording and reproducing apparatus retraces a spiral track by jumping a specific portion of the guide track. Each of the sectors has a sector header, which comprises a sector mark located at the start of the sector and an address field including a track address, sector address, and an error detecting and correcting code. The index mark in the field is detected, and the optical head is made to perform a jumping operation in response to the resulting signal, whereby the jumping operation is rendered certain. When there is a failure to read the address fields, the signal produced by detecting the index mark starts a counter which counts the signal produced by detecting a sector mark, for recovering the sector address.

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First Claim