| 摘要 |
PURPOSE:To prevent deterioration of S/N by reproducing a servo pattern in which magnetized information of three frequencies is recored successvely and repeatedly in order of tracks by a head for servo having track width twice the track pitch, and extracting differential signal of two signals in each freeuqncy component. CONSTITUTION:When moving a magnetic head from 0 track to n track, the head is moved in speed mode to (n-1) track, and changed to a positional mode at a position moved by 1/2 track from the (n-1) track. When moving in a speed mode, pulse is made from a positional error signal PES according to tne level and inputted to a subtraction counter and subtracted from the value of objective track. A mode is changed to a positional mode at a position where the head is moved by 1/2 track from (n-1) track, and a voice coil motor is controlled by PES signal in the track. Thus, track width of the head for servo can be doubled when three frequencies are used, and the S/N of the servo signal can be improved accordingly, and the accuracy of head positioning can be improved. |
