HIGH-DENSITY RECORDING CHARACTERISTICS OF A 90 MM PHASE-CHANGE OPTICAL DISK

A fairly reliable capacity of 300 Mbytes has been achieved on a single side of a 90 mm high-density phase-change optical disk, using a 0.6-m m-thick disk and an optical head which had a 690 nm laser diode and a 0.6 numerical aperture objective lens. The carrier-to-noise ratio (CNR ), erasability, and the bit error rate (BER) of the optical disk were investigated. It has been confirmed that these parameters have a wide laser power tolerance for most inner and outer tracks.