Method and apparatus for optical detection of information

摘要

Method and apparatus for optically detecting information from a recording medium in which pits are formed by thermal energy of a light spot to record the information. A reproduction spot is irradiated onto the recording medium to produce a detection signal. From a differential signal of the detection signal, a signal indicative of zero points of the differential signal and a signal indicative of the presence of the pits are detected, and both the signals are used to detect positions of the pits. For stable and accurate detection of the pit position, the relation between pit size W and reproduction spot size Ws is prescribed and the pit size and reproduction spot size are so set as to satisfy 0.45