| 摘要 |
<p>A magnetic disk (501) has a normal servo area and a double servo area on both of which a servo pattern for control the positioning of a magnetic head (171) is recorded. The interrupt period T2 is half the period T1 of when only a normal servo area is provided. For each servo interrupt period, the level of a position signal of a sample point is measured. The difference between the levels of the position signals of two adjacent sample points are determined, and the differences are summed a predetermined times while changing the sample points one by one. According to the result of the summing, a high-frequency vibration observing unit (60) observes the high-frequency vibration component the period of which is the same as the servo interrupt period of when only a normal servo area is provided. With such a structure, the high-frequency vibration component of period T1 caused by the vibration of a magnetic head can be observed.</p> |
