| 摘要 |
PURPOSE:To lower redundancy and to improve reliability in track detection by providing track groups each consisting of plural tracks in a band, and an identification area between the track groups for identifying the track groups. CONSTITUTION:The track 4 each is composed of a 1-bit start bit 20 and a stop bit 21, a 3-bit track number area 30 and a data area 31. Eight of such tracks 4 are assembled together to form the track group 32. When an optical head 11 reaches the band 3 to which the targeted track to be read, belongs scanning is performed sequentially track by rack and the head is moved relatively in the direction A and the track identification is performed between the track groups by the combination of the count number of the times of appearance of the identification areas 33 and the number of the track number area 30 in the track group 30. When the total area of the identification area 33 is the same information, the track group may be identified without being influenced by the dirt or injury. In such a way, the track number area of each track may be reduced to reduce the redundancy.
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