Modulation of laser power in accordance with a linear velocity by pulse division schemes

摘要

An optical recording process for recording data on a recording medium of phase-change type employs laser power modulation scheme for mark-length modulation recording. The process selects one of pulse division schemes for modulating the laser power in accordance with a linear velocity on the disc. The recording laser includes m pulses for nT mark having a power level Pw and a duration of alpha iT, with m intervals beta iT sandwiched therebetween, wherein on condition that m=n-k and SIGMA alpha i+ SIGMA beta i=n-j, alpha i or bias power Pbi is changed in accordance with the linear velocity, Pbi being a bias power level for modulation, k and j being an integer and a real number, respectively, both selected between 0 and 2. A large range of the linear velocity margin can be obtained for the disc without changing either the composition of the phase-change material or multi layer structure on the disc.