Patent ID: 7619847

Claim:
A head controller that controls using thermal expansion due to a heater, a position of a tip of a head that faces a storage medium and that at least reads signals from the storage medium, the head controller comprising: a heater controller that increases a heater power of the heater till reaching a first threshold; an acquiring unit that acquires a sample of a combination of the heater power and a signal level of signals that are read from the storage medium during an increase in the heater power till a second threshold smaller than the first threshold is reached; a determining unit that determines an approximation function that approximates a relation of the sample acquired by the acquiring unit; a peak acquiring unit that acquires a peak of the signal level during an increase in the heater power till reaching the first threshold; and a calculating unit that calculates an upper limit of the heater power based on the approximation function determined by the determining unit and the peak acquired by the peak acquiring unit.