| 摘要 |
PURPOSE:To attain wide recording power margin without deteriorating an optical disk by widening a recording/reproduction beam at recording and narrowering the beam at reproduction. CONSTITUTION:A recording/reproduction collimator lens is moved in the optical axis direction at recording to apply defocusing and an elliptic erasure beam 18 is radiated to erase a recording bit 17 and the recording beam 19 modulated by the signal is used for recording. At reproduction, said collimator lens is focused at the reproduction and the stopped reproduction beam 20 is used to sense the difference in reflectance. Thus, the size of the recording bit is over the erased beam width thereby preventing unerased recording or eliminating the need for a large erasure for the erased power. As a result, the recording power margin is increased without deteriorating the optical disk. |
