Patent ID: 6500598
Filing Date: 2002-12-31
Classification: G11B,Y10S

Abstract:
A method of recording and reproducing for a multilevel phase change optical recording medium comprising first to N-th (N&gE;2) phase change optical recording layers, wherein an i-th layer and a j-th layer, which are two recording layers arbitrarily selected from the first to N-th recording layers and located within the depth of focus of a plurality of laser beams having different power levels, meet the conditions of:Ti>Tmi and &tgr;wixi, and Tjmj or &tgr;wj>&tgr;xj, with respect to a particular recording laser beam selected from the plurality of recording laser beams, where T is the maximum temperature of the recording layer in a recording operation, Tm is the melting point of the recording layer, Tx is the crystallizing point of the recording layer, &tgr;w is a time required for the recording layer to be cooled down from Tm to Tx after the laser beam irradiation, and &tgr;x is the crystallizing time of the recording layer and wherein said method comprises:irradiating the multilevel phase change optical recording medium with recording beams having different power levels, thereby performing recording; and irradiating the recorded multilevel phase change optical recording medium with a reproducing beam to detect reproducing signals, followed by digitizing the reproducing signals, thereby performing reproducing wherein all of the beams come from the same side and have the same wavelength, wherein three recording beams each different in power level are used for recording the i-th layer and the j-th layer, and wherein a recording beam having a first power level is used for recording only in the i-th recording layer, a recording beam having a second power level is used for recording both the i-th and j-th recording layers, and a recording beam having a third power level is used for recording only the j-th recording layer.