READER OF INFORMATION MEDIUM HAVING PRE-RECORDING PATTERN

摘要

PROBLEM TO BE SOLVED: To reduce track pinch without causing any problem in the detection of tracking error by reversing the offset order of prerecord pattern every revolution or a part of revolution. SOLUTION: Centered ends 50 of adjacent data areas can be observed for respective scanning lines 58, 59, 60 comprising three continuous tracks while holding a specified region between them. The end 50 is defined by sectioning a prerecorded groove pattern with the specified region. Since the track element is narrower than the inter-track gap, the track appears darker than the inter- track gap when it is read out optically using a light spot 53. The track appears darker because it diffracts more light.