| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical pickup optical system which is used for recording, reproducing, and erasing information to and from an optical recording medium, with a simple constitution. <P>SOLUTION: The optical pickup optical system is constituted of a collimator lens system 23, a beam expander 33, and an objective lens system 34 including an S-SIL element 34b. The beam expander 33 is composed of three lens elements 33a to 33c. The focusing position of a spot formed inside an optical recording medium 28 is adjusted by moving one or both of the lens elements 33a and 33b included in the beam expander 33 in the optical axis direction, while spherical aberration caused by depth difference of a recording layer is corrected. <P>COPYRIGHT: (C)2009,JPO&INPIT |
