Importance

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Abstract

A system for aligning data with corresponding sector marks in an optical disk storage system. In an optical disk storage system, data is written into a number of concentric bands, each of which contains a servo track and a number of data tracks. Each band is divided circumferentially into a series of sectors which are defined by marks in the servo track. The beginning of a sector is detected by identifying one of the marks in the servo track, and the beginning of a data record must coincide with the beginning of a sector. Recorded during the manufacture of the storage disk of the present invention, are pairs of special tracks wherein the first sector mark on a track is identified by an index mark, and the adjacent data track has a beginning of data mark recorded at a fixed location relative to the index mark. The disk read/write head is moved over one of these pairs and the difference in time between the occurrence of the index and occurrence of the beginning of data mark is measured. This difference in time is then fed to a delay circuit that electrically delays the sector pulse to coincide with the actual beginning of data. Because the beginning of data and the occurrence of a sector mark is measured with time, and because the relative velocity between the disk and the head is different if the head is located over an inner diameter of the disk as opposed to the head being located over an outer diameter of the disk, two measurements are made: one on an inner diameter and one on an outer diameter index track. The difference between these two measurements is used to extrapolate a sector mark to data time difference for each data band that occurs between the inner and outer diameter bands.

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First Claim