| 摘要 |
An optical recording and reproducing method is able to record and reproduce information by using an optical system using recording and reproducing light with a wavelength selected in a range of from 780 nm +/- 10 nm and an objective lens with a numerical aperture NA selected in a range of from 0.45 +/- 0.01 and records and reproduces first and second optical recording mediums having different recording capacities. The first optical recording medium is constructed by using a substrate with a track pitch Tp1 being selected in a range of from 1.5 mu m to 1.7 mu m and a groove depth d1 being selected in a range of from 70 nm to 90 nm, and the second optical recording medium is constructed by using a substrate 11 with a track pitch Tp2 being selected in a range of from 1.2 mu m to 1.3 mu m and a groove depth d2 of the groove 12 being selected in a range of from 150 nm to 180 nm. This, the optical recording medium has compatibility with existing optical discs and has a recording density high enough to record a moving picture. <IMAGE>
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