| 摘要 |
PROBLEM TO BE SOLVED: To always perform a satisfactory focusing control and a satisfactory tracking control even when the kind of an optical disk is changed in an optical disk device capable of coping with plural kinds of optical disks by using one set of an optical head. SOLUTION: The arrangement intervals in a disk direction of three converged spots (100-102) to be formed on an optical disk are made so as to become half a track pitch with respect to a first optical disk 9a and so as to become the odd numbered multiple of one-fourth a track pitch and more than three-fourth the track pitch with respect to a second optical disk 9b, respectively. Concretely, the focal length of an objective lens and the grating constant of a diffraction grating in an optical head are set so as to satisfy a prescribed relational expression. Moreover, a differential push-pull system or a three beam system is used as a tracking control system and the systems are properly changed over in accordance with kinds of disks. |
