| 摘要 |
PROBLEM TO BE SOLVED: To provide the optical pickup device capable of reproducing two kinds of disks which are different in density by forming double-beam foci having different size from each other. SOLUTION: A beam generated from a laser light source is reflected by a beam splitter 160 and is progressed to an optical disk 180. This laser beam is transmitted through a selective light-transmission part 150 installed in front of an objective lens, and is then focused on the optical disk 180 by the objective lens. The light beam is totally transmitted through a circular part on the inner side of the selective light-transmission part 150, while the light beam is partially transmitted through a surrounding part of this circular part. A beam transmitted through the inner side circular part is formed into a large beam spot on the disk 180, while a beam transmitted through the surrounding part a small beam spot respectively. Consequently, since spherical aberration attending upon a thickness change of the disk 180 can be minimized by utilizing the beam transmitted through the inner side circular part of the selective light-transmission part 150 having a small numerical aperture, the disk 180 having different density from each other can be reproduced by one optical pickup device respectively. |
