| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a multilayer optical disk wherein the effect of measures taken against crosstalks between information layers in one optical disk is secured, equal to the effect of measures taken against crosstalks among information layers in the other optical disk, in an optical pickup device where measures taken against crosstalks among first and second information layers, to an optical disk having specifications for one optical disk of different optical disk specifications. <P>SOLUTION: In the multilayer optical disk, when a distance between first and second information layers 7 and 9 having a first optical disk specification and an NA (numerical aperture) of an objective lens of the optical pickup device are defined as L1 and NA1, respectively; and when a distance between first and second information layers 17 (27) and 19 (29), having a second optical disk specification and an NA of an objective lens of the optical pickup device, are defined as L2 and NA2, respectively, the distance L2 between the first and the second information layers, having the second optical disk specification satisfies the relation L2=L1×(NA1)<SP>2</SP>/(NA2)<SP>2</SP>. <P>COPYRIGHT: (C)2008,JPO&INPIT |
