Position demodulation apparatus and position demodulation method

A position demodulation apparatus comprising:

• a demodulator configured to demodulate a first demodulation signal and a second demodulation signal having a phase difference of 90 degrees to the first demodulation signal based on a read-out signal obtained by reading out a servo pattern recorded on a medium by the head for positioning of a head with respect to the medium;
• a correcting module configured to perform, on the first demodulation signal and the second demodulation signal, a correction on an axis tilted by 45 degrees from respective coordinate axes on a plane representing the first demodulation signal as values on one of the coordinate axes and the second demodulation signal as values on the other of the coordinate axes;
• and
• a position demodulator configured to demodulate a positional signal for determining a position of the head based on the first demodulation signal and the second demodulation signal after being corrected by the correcting module.

A position demodulation method of a position demodulation apparatus comprising:

• demodulating, by a demodulator, a first demodulation signal and a second demodulation signal having a phase difference of 90 degrees to the first demodulation signal based on a read-out signal obtained by reading out a servo pattern recorded on a medium by the head for positioning of a head with respect to the medium;
• correcting, by a correcting module, the first demodulation signal and the second demodulation signal in which, when a trace of a Lissajous figure is drawn representing the first demodulation signal and the second demodulation signal as values on coordinate axes different from each other on a plane, a ratio of respective lengths between intersections of the trace intersecting with two axes orthogonal at an origin of the plane and different from the coordinate axes is kept constant;
• and
• demodulating, by a position demodulator, a positional signal for determining a position of the head based on the first demodulation signal and the second demodulation signal after being corrected at the correcting.