MULTIPULSE RECORDING METHOD FOR PULSE-WIDTH MODULATION RECORDING ON AN ERASABLE PHASE-CHANGE OPTICAL DISK

A laser irradiation scheme "multipulse (MP) recording method" was examined on an erasable phase change optical disk having a chalcogenide alloy film. Each recording mark in the amorphous state is formed on the precrystallized disk by irradiation of successive multiple short pulses, the widths or periods of which gradually change. This markedly reduces the teardrop-shaped distortion of the mark. For the recording examination of 345 kHz single-frequency signals at 1.4 m/s of linear velocity, CNR > 50 dB and SHD < -40 dB were obtained by the MP method, while the SHD by the conventional method remained -30 dB. The simple electrical device prepared, which produces 9 kinds of multiple pulses according to the signal lengths, 3T to 11T, successfully recorded the eight to fourteen modulation (EFM) signals of the audio compact disk format with small jitter at 1.25 m/s.