OPTICAL DISK, RECORDING AND ERASING SYSTEM AND METHOD THEREFOR

摘要

PURPOSE:To allow the utilization of a reproducing device for a reproduction- only optical disk by specifying the reflectivity in the state of applying tracking to the grooves of a phase change optical disk to a specific value and regulating the mechanical size thereof to the standard size of the reproduction-only optical disk. CONSTITUTION:The structure of the phase change optical disk is so set as to attain >=60% and <=85% reflectivity in the state of applying the tracking to the grooves for tracking. Namely, the varying magnitudes of the reflectivity are the principle of reproduction with the reproduction-only optical disk, while the change in the reflectivity in the case in which a recording film is a crystal and the case in which the recording film is amorphous is utilized with the phase change optical disk. The reproduction of the recording signals by the reproducing device of the reproduction-only optical disk is executed in this way if the reflectivity is matched in the case of utilization of the phase change optical disk.