OPTICAL DISC AND OPTICAL DISC DEVICE

摘要

PURPOSE:To attain track access by the detection of pre-format part by deviating sequentially the position of the pre-format at each track in the lengthwise direction so as to allow a laser spot cross the pre-format part at the sector boundary without fail at track access. CONSTITUTION:The pre-format part 2 is not arranged linearly in the radial direction of an optical disc 1 among tracks but deviated in the track lengthwise direction sequentially at each track 6. Thus,the pre-format part 2 belonging to the same sector 5 is arranged in spiral. Thus, the laser spots crosses the pre-format part in the rate of once per a predetermined number of tracks and the number of crossings is corrected so as to count the crossed number of tracks.