| 摘要 |
PURPOSE:To correct an off-track state with a simple mechanism by using a data surface containing a correcting servo track to which the correcting servo data is written to position a servo head at a position where the variance degree is added to the servo data. CONSTITUTION:A disk 1 contains a servo surface 3, a data surface 4 and a data surface 4' including a data track and a correcting servo track 20. When an off-track state occurs, a data head 6' is positioned in the D-D' direction with some variance although a servo head 5 is positioned. Then a davit waveform (d) is read out and sent to a variance detecting circuit 23 from a waveform amplifier. Then an output difference (dd) of the peak value is detected and sent to a variance calculating circuit 23 via an A/D converter 24 for calculation of a correction amount. Then the correction value is sent to a signal adder 21 via a D/A converter 26. The adder 21 adds said correction value with the output of a signal producing circuit 8. This added value is sent to a position control circuit 27, and each head is shifted for correction of an off-track state of a working data head 6. |
