OPTICAL DISK, METHOD FOR RECORDING AND REPRODUCING WRITE-ONCE INFORMATION ON AND FROM OPTICAL DISK, OPTICAL DISK REPRODUCING DEVICE, OPTICAL DISK RECORDING AND REPRODUCING DEVICE, DEVICE FOR RECORDING WRITE-ONCE INFORMATION ON OPTICAL DISK, AND OPTICAL DISK RECORDING DEVICE

摘要

An optical disk comprising a magnetic recording layer may be used to protect software copyright by preventing the duplication, unauthorised use, etc., of the software. Write-once information is formed on the optical disk by first recording areas and second recording areas in a predetermined portion of the recording layer. The recording layers have different magnetic anisotropies in a direction perpendicular to a surface of the magnetic layer. In a method and apparatus for reproducing write-once information from an optical disk, linearly polarised laser light is irradiated onto the predetermined portion of an optical disk and a change in polarisation orientation of light transmitted or reflected from the optical disk is detected in accordance with the recording signal on the optical disk, allowing write-once information to be reproduced from the optical disk.