Data reproduction apparatus and data reproduction method

摘要

A data reproduction apparatus of an optical disk having a maximum likelihood detection system for compensating a stationary edge shift and an edge shift depending on record pattern at the time of reproduction. The edge shift that has not completely been compensated at the time of recording in an optical disk is compensated by controlling an expected value in branch metric calculation of maximum likelihood detection while recognizing the pattern of record data at the time of reproduction. The edge shift amount is measured on the basis of the reproduction signal relative to the VFO area of the optical disk, and an expected value compensation table for showing an optimum expected value in branch metric calculation is selected preliminarily according to the measured amount. Thereby, the pattern of record data in the data area of the optical disk is recognized, the optimum expected value according to the recognized pattern of record data is determined by referring to the selected expected value compensation table, and the branch metric calculation is operated by using the optimum expected value.