| 摘要 |
<P>PROBLEM TO BE SOLVED: To sufficiently reduce the spherical aberration caused by the variance of thickness between disks, even though a numerical aperture NA is enlarged. <P>SOLUTION: A beam magnifying optical system 33 of a magnification factor (m) of 1.2≤m≤1.5, is arranged in a parallel optical path up to an objective lens 26 from a light branching element 23. The spherical aberration caused by the thickness tolerance of a covering glass 27 of an optical recording medium 28 is compensated. The beam magnifying optical system 33 includes a biconcave lens 24 which is a 1st lens, and a plano-convex lens 25 which is a 2nd lens. The mounting of the lens is simplified by expanding the lens mounting tolerance, then stabilization of a recording/reproducing signal at the spherical aberration correction is also attainable. <P>COPYRIGHT: (C)2004,JPO |
