| 摘要 |
PROBLEM TO BE SOLVED: To provide a multilayer optical recoding medium whose position- deviation of preformat area is small, which can perform stable recording and reproduction and can perform highly efficient rewriting. SOLUTION: At least a preformat area of a recording layer most distant from an objective lens which condenses an irradiating light beam among a plurality of recording layers has guard areas provided at both ends in a tracking direction and on which data are not recorded. When each length of the guard area is defined as GL, the maximum allowable value of the position-deviation in the tracking direction of the preformat areas of the most distant recording layer and the other recording layers is YL, the numerical aperture of the objective lens is NA, the interval between the most distant recording layer and the other recording layers is T, and the refractive index of the medium between recording layers is n. The length GL of the guard area is set so as to satisfy the equation of GL>=YL+T×(NA/n)/[1-(NA/n)2]1/2. |
