| 摘要 |
PURPOSE:To decrease a light spot diameter substancially without degrading a regenerating signal S/N by forming a temperature dependency optical shutter layer absorbing a reproducing laser wavelength at normal temperature and transmitting it at high temperature on a recording medium. CONSTITUTION:A temperature dependency transmissivity variable medium 14 whose light transmissivity is raised at high temperature is formed to the objective lens side of an optical recording and reproducing layer 15. At the time of reproducing, when outgoing laser power is controlled and the medium temperature in the light spot 4 and in the vicinity of the spot is controlled, the temperature of the medium 14 in the vicinity of the light spot 4 is raised high at the rear side of the advancing direction of the light spot 4 when the optical disk is rotated. Thus, only the area 11 where the high temperature area 10 of the medium temperature and the light spot 4 are superposed us participated to reproducing and a substancial reproducing spot diameter is reduced than the light spot diameter 4. Further, since signal reflection from the recording and reproducing layer 15 is generated only at the area of the high medium temperature no S/N is degraded trough the substancial light spot is reduced. |
