Data head offset detecting circuit in magnetic disk unit and magnetic disk unit using said data head offset detecting circuit

摘要

A data head offset detecting circuit in a magnetic disk unit includes a first offset detector that detects an offset beta based on servo information on a data surface read by the data head, a second offset detector that detects an offset gamma based on servo information on the servo surface read by the servo head, and an offset calculator for calculating a real offset alpha resulting from the subtracting of the offset gamma from the offset beta . By using the above circuit, an offset for a correction of an offtrack is detected accurately even when the heads are vibrating.