| 摘要 |
PROBLEM TO BE SOLVED: To make reducible the effects of high density recording/reproducing and the tilt of an optical information medium by providing an optical means attenuating partial light intensity or adding a phase difference to a part of parallel luminous flux emitted from a light source and forming a small-sized spot of a diffraction limit value or below by the optical super-resolution effect. SOLUTION: An emission beam from a semiconductor laser 11 is made into a parallel beam by a collimate lens 12, and a luminous flux cross section is shaped into nearly a circle by a beam shaping prism. The beam passing through an optical element 14 inserted in the vicinity of the optical axial center of the parallel beam is focused on the information recording surface 170 of the optical information medium 17 through a beam splitter 15 by an objective lens 16. Since the part of the beam made incident on the rectangular part 14a of the optical element 14 is attenuated in the light intensity, the part is converged to the diffraction limit value or below through the objective lens 16 by the super-resolution effect, and the small-sized spot is formed. Thus, the information can be high density recorded/reproduced, and a track offset amount due to the tilt of the optical information medium is reduced. |
