| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an objective optical system for an optical information recording/reproducing device which has compatibility with multiple types of optical discs having specifications different from each other and which is capable of effectively correcting a longitudinal chromatic aberration caused when an optical disc having a high recording density is used, while achieving a simple configuration. <P>SOLUTION: The objective optical system for the optical information recording/reproducing device which has compatibility with multiple types of optical discs is provided, and the objective optical system includes a longitudinal chromatic aberration correction element having a negative power first lens and a positive power second lens made of materials different from each other and cemented together to correct a longitudinal chromatic aberration, at least one phase shift surface having a prescribed phase shift structure to give a predetermined optical path length difference of nearly three wavelengths to a first light beam, and an objective lens. The longitudinal chromatic aberration correction element is located along an optical path common to the first and second light beams on a light source side with respect to the objective lens and the longitudinal chromatic aberration correction element satisfies a prescribed condition in the relation with the phase shift structure. <P>COPYRIGHT: (C)2009,JPO&INPIT |
