| 摘要 |
PURPOSE:To attain highly accurate head positioning in a small-sized device by arranging symmetrically each servo pattern having the arrangement in the outer direction and inner direction recorded on a servo area on a center line of a data track of a positioning object. CONSTITUTION:The servo pattern on a disc consists of a pattern PA having the arrangement in the outer direction and a pattern PB having the arrangement in the inner direction crossing the data track with shifted phase. The servo head 11 detects the servo signal of the patterns PA, PB, the detected voltage is used as a position error signal by a demodulator 22, stored in a shift register 18 and stored in an RAM 31 as a bit string of the patterns PA, PB. A CPU 30 compares each bit, decides the position of the track of the head 11, a signal representing the position shift of the head 11 and the shift direction drives a step motor 28 to adjust the position of the head 11. |
