| 摘要 |
PURPOSE:To perform a retrieval to form an index in a short time by moving a head continuously so that the output of a signal read head becomes maximum when the signal read head scans the arranging position of a control data in the circumference direction of a disk. CONSTITUTION:Assuming that a track pitch on the disk is set as Pt, the rotation cycle of the disk as Td, the number of control data on the same track of the disk as (n), and N is a positive integer, the signal read head is moved continuously so that the output of the signal read head becomes maximum at a speed of Vh=n.Pt/N.Td, when the signal read head scans the arranging position of the control data in the circumference direction of the disk. In other words, by selecting the N as small as possible, the signal read head crosses either of plural recording positions of the control data having the same intervals in each circumference direction, against the track on which the control data having an index data is recorded, on the disk spirally, and a scanning is performed in a state that the output of the signal read head becomes maximum at the crossing point.
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