METHOD TO CONTROL FOCUS ON OPTICAL DISK, OPTICAL DISK DRIVE, AND OPTICAL DISK

摘要

PROBLEM TO BE SOLVED: To carry out stabilized focus control to realize high-density recording and reproducing in an optical disk drive which has a light condensing means of high numerical aperture on a flying object floating on the surface by the rotation of the disk. SOLUTION: An objective lens of high numerical aperture is disposed on the slider of the optical pickup 6 flying on the surface of an optical disk 1 by the rotation of the disk 1. Irradiation of light to an optical disk 1 and detection of the reflected light are performed through the objective lens. The focus is controlled by the floating height of the objective lens, i.e., linear velocity of the optical disk 1. The control section 8 controls the linear velocity of the optical disk 1 so that the floating height of the objective lens is controlled depending on the change of the thickness of the protective coat film 4 on the recording film 3.