| 摘要 |
PROBLEM TO BE SOLVED: To specify a rotational position highly accurately even if a dropout state in which a signal is missing occurs. SOLUTION: The tracking direction of a magnetic head 23a is sequentially subjected to location control by a rotary positioner correspondingly to each track, and a servo track signal is written on a magnetic disk 22 for every track on the basis of the rotational position information of the magnetic disk 22 obtained from a signal processing logic circuit to process Doppler signals from an LDV optical head 24. Here, at the time of creating a rotational-position signal obtained by a Doppler signal from the LDV optical head 24, dropout sections corresponding to rotational positions are previously examined to optimize the timing of signal processing at the dropout sections. By this constitution, even if a dropout state occurs, it is possible to detect rotational position information highly accurately.
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