Yoshiyuki Miyabata

High-density mark edge recording on a phase-change rewritable disk by a 680-nm laser diode

This paper reports a study of mark edge recording on the phase change rewritable disk. With the optical head using 680-nm laser diode and lens NA 0.6, 55 dB or higher carrier-to-noise ratio is obtained for signals whose recording mark length is 0.53 micrometers . In mark edge recording it is important to record all marks in their proper lengths. Hence, we first study shift behavior of the beginning and ending edges with regard to all marks, and then propose a new writing compensation method to make up for shifts. In the new compensation method the laser power modulation pattern consists of the first pulse, the multi-pulse chain and the last pulse. Adjusting the first and last pulse positions so that all marks are recorded in their proper lengths makes it possible to accomplish mark edge recording of the RLL (1,7) code with the linear density 0.4 micrometers /bit, jitter (sigma) /T(omega) to 6.5%. For the linear density of 0.35 micrometers /bit as well, a clear eye-pattern is obtained.

Optimization of mark edge recording waveform for a phase change rewritable optical disk using a 680 nm laser diode

A high density mark edge recording method on a phase change rewritable disk is reported. A carrier-to-noise ratio of 55 dB for a mark length of 0.55,μm is obtained by using a 680 nm, NA 0.6 head and a phase change rewritable disk. In mark edge recording, it is necessary to record each mark in correct length. A new laser power modulation pattern is proposed. This pattern consists of a first-pulse, a multi-pulse chain and a last-pulse. Both positions of the first-ptilse and the last-pulse are movable. By adjusting these positions, a jitter, σ/Tw (Tw is window margin), is improved to 6.5% in high density EFM (Eight to Fourteen Modulation) recording of 0.4 μm/bit.