| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a compact objective lens for holographic recording/reproducing of optical information in which a wavelength being different from a wavelength performing recording/reproducing of information can be image-formed at the desired focal point and converging capability is excellent, and an optical pickup apparatus using the same. <P>SOLUTION: Resolution can be improved to near diaphragm in a luminous flux used for recording/reproducing information by using lenses of three groups or more. Also, since a light source side optical plane of a first lens group LG1 is convex for the light source side and the luminous flux is converged at this plane, the plane becomes the largest effective diameter plane, the optical system becomes more compact than the case being a concave plane. Also, luminous flux for a different wavelength can be focused at the desired position by using lens materials of different Abbe number for a positive lens and a negative lens constituting the lens group, and spherical aberration changed caused by different wavelength can be made smaller than Marechal's criterion. <P>COPYRIGHT: (C)2008,JPO&INPIT |
