| 摘要 |
PROBLEM TO BE SOLVED: To commonly use both a DPD method and a push-pull method by providing the interference film being made of the surface of the recording film to be irradiated with laser beams so that the phase differences and the reflectivities of the laser beams reflected by a mark and a non-mark are varied by providing a prescribed thickness. SOLUTION: In the case of the push-pull method, the optical depth of a groove 9 is set to λ/8, the phase difference between a land 8 and the groove 9 is made 90 deg. and a maximum signal sensitivity is obtained. On the other hand, in the case of the DPD method, an interference film 3d is provided to cover a recording film 3c, the thickness of the film 3d is set to make the phase difference between a mark and a non-mark to be within the range of 90 to 120 degrees and the phase difference caused by the entire reflected light beams becomes in the range of 180 to 210 degrees. Thus, the phase differences and the reflectivities of he reflected light beams from a mark and a non-mark are made optimum against the disk having a groove. Therefore, a recording and a reproducing are conducted under a best condition employing the DPD method and the push-pull method for a DVD-RAM. |
