| 摘要 |
PROBLEM TO BE SOLVED: To obtain the high resolution uniform over the entire direction of a disk by arranging a quarter-wave plate between electro-optic elements and an objective lens of a high numerical aperture NA to form a condensed light spot to a circular shape and changing the relative position between the condensing light spot and a recording medium by a scanning means. SOLUTION: The parallel light beams from a light source 1 are polarized to linearly polarized light by a polarizing element 2. This linearly polarized light is made incident on the first and second electro-optic elements 3 for modulating optical intensity and the electro-optic element 4 for controlling polarization direction, by which the linearly polarized light within the plane perpendicular to the plane of Fig. and inclusive of the optical axis is formed. This light is transmitted through the quarter-wave plate 5 arranged in such a manner that that the crystal axis attains 45 deg. with the polarization direction by which the light is converted to the circularly polarized light. The luminous flux made into the circularly polarized light is made incident on the objective lens 6 of NA >=0.8 and is condensed onto the recording medium 7. As a result, the uniform resolution which does not depend on the direction of the disk and the shape and groove direction of plotting marks is obtd. without making the spot shape asymmetrical even if the high-NA objective lens is used. The formation of the stable and high-density optical disk raw plate is made possible. |
