Apparatus and method for reading address information from an optical disk

An apparatus for reading address information using an optical head from an optical disk medium which comprise a track groove thereon and on which information is recorded along the track groove on a block unit basis, the block unit having a predetermined length, wherein the block unit includes a number of sub-blocks that are arranged along the groove, wherein a part of the track groove has a wobble shape that is defined by a combination of a steep displacement pattern and a smooth displacement pattern to represent address information of the block unit, the apparatus comprising: a differential operating circuit for obtaining a wobble signal corresponding to the wobble shape; and a signal processor for measuring a phase polarity of a second harmonic of a fundamental wobble frequency of the wobble signal and for judging the measured phase polarity as information 0 or 1 for each sub-block; and a corresponding method and signal processing device