| 摘要 |
PROBLEM TO BE SOLVED: To provide a high density information storage medium in which excellent noise properties are furnished while keeping required high density storage capacity and a wide servo margin is securable. SOLUTION: The medium includes a center hole, a clamping area and a data area wherein user data are written. The ratio of λ/NA to the track pitch TP is <=1.45, where λ stands for the wavelength of irradiation light for writing and/or reading the information, and NA stands for the numerical aperture of an objective lens converging the light and forming a light spot with a specified size on a writing surface. |
