Patent ID: 6724708
Filing Date: 2004-04-20
Classification: G11B

Abstract:
A method for reading address information from an optical disk medium which comprises 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 sub-block mark is provided within each said sub-block and used to identify the sub-block, and wherein a part of the track groove has a sawtooth-like wobble shape that is defined by a combination of a steep displacement pattern and a gentle displacement pattern to represent address information of the block unit, the method comprising: generating a first sync signal and multiplying the first sync signal and a read signal together to obtain a first product, the read signal having been detected in accordance with the wobble of the track groove and having a basic frequency, the first sync signal being synchronized with the read signal and having a frequency that is equal to the basic frequency of the read signal; generating a second sync signal and multiplying the second sync signal and the read signal together to obtain a second product, the second sync signal being synchronized with the read signal and having a frequency that is twice as high as the basic frequency of the read signal; integrating the first and second products to obtain an integral; and comparing the integral with a predetermined threshold value, thereby defining the address information.