Patent ID: 7379408

Claim:
A disk apparatus, comprising: a reading unit which reads reflection light from a disk and outputs a read signal; an equalizing unit which carries out partial response (PR) equalization for the read signal based on a plurality of tap coefficients; a decoding unit which carries out a decoding process for the read signal equalized by the equalizing unit; a calculating unit which obtains an ideal signal of the decoded read signal, and compares the ideal signal and the decoded read signal with each other, thereby calculating an error signal; and a control unit configured to: group the tap coefficients into at least a first coefficient group and a second coefficient group which are groups of tap coefficients at symmetrical locations each, determine tap coefficients of the first coefficient group at least in a range of a first limit value according to the calculated error signal, and determine tap coefficients of the second coefficient group in a range of a second limit value which is different from the first limit value, and supplies the determined tap coefficients to the equalizing unit, so as to control an equalizing process, wherein, if at least the first coefficient group is more outward than the second coefficient group with respect to a central tap coefficient, the first limit value for restricting update of a tap coefficient is not less than the second limit value.