| 摘要 |
PURPOSE:To access an optional position of a track directly and to easily obtain high-track density by reading a servo pattern through a head and calculating the position, and tracking the head to a servo track and forming a spiral data track on a recording medium. CONSTITUTION:A signal reproduced from a disk 1 through the head 2 is passed through an AGC circuit 11, a sector detecting circuit 12, and an index detecting circuit 13 to detect an index mark, thereby detecting whether a servo sector is an index zone as a position reference or not. A sample generating circuit 14 sends a timing signal to the circuit 11 to control a playback signal to a constant value. The playback signal is inputted to sample holding circuits 15a-15r and extracted according to a timing signal and substracters 16a and 16b generate a difference signal, which is inputted to a CPU through an AD converter 17; and signals extracted by the circuits 15p-15r are inputted to the CPU18 to position the head 2, thereby forming the spiral data track.
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