Patent ID: 6714230
Filing Date: 2004-03-30
Classification: G11B

Abstract:
A method for optically recording information on an optically re-writable information medium having at least one track, said method comprising the steps of:focusing a laser light to a laser spot to form a mark on said optically re-writable information medium; and modulating a size of said mark according to a level of a multi-level signal that corresponds to said information to be recorded, and wherein a strength of said laser light for recording each mark is modulated according to a waveform comprising a first rectangular erasing pulse signal, a rectangular recording pulse signal, an off-pulse signal and a second rectangular erasing pulse signal, said laser light having a strength set to a value indicated by said first rectangular erasing pulse signal can erase a recorded mark, said laser light having a strength set to a value indicated by said rectangular recording pulse signal can record a mark, a strength of said laser light set to a value indicated by said off-pulse signal is less than a strength of said laser light used in reproduction of said recorded marks, said laser light having a strength set to a value indicated by said second rectangular erasing pulse signal can erase said recorded mark, and a product of the time interval of said rectangular recording pulse signal and a relative linear velocity between said laser spot and said optically re-writable information medium is shorter than a length of said recorded mark, and wherein a length of said rectangular recording pulse signal is set to a predetermined constant value and a length of said off-pulse signal is adjusted according to said multi-level signal.