High Density Phase-change Optical Disk System Having Write And Read Compatibility With 90mm MO Disk

An optical disk system has been widely used, especially after the introduction of a 90mm magneto-optical (MO) disk meeting the Is0 standardization. Optical disk shall play the leading role in multi-media applications. On multi-media applications overwrite capability is indispensable. Phase-change (PC) optical recording technology has a feature to realize overwrite function only by the optical means, such as a write-once optical head. A 130mm 1 GB PC rewritable multifunction optical disk system was introduced in the market in early 1992. (1) This paper presents the high density recording characteristics of a PC optical disk and a 256MB 90mm overwritable PC optical disk system with full compatibility with a conventional MO disk.