| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an objective lens for an optical information recording and reproducing device, which is compatible with various kinds of optical disks, forms a desirable spot while suppressing the spherical aberration especially when using an optical disk of a relatively low recording density and improving the light utilization efficiency, corrects the axial chromatic aberration especially when using an optical disk of high recording density, and suppresses the focusing function degradation even when the disk has a multilayered structure. <P>SOLUTION: This objective lens for an optical information recording and reproducing device has an objective lens including a phase shift structure having level difference groups defined by light path difference functions and applies the light path lengths different from one another to the incident light flux, and is configured so that the light path length differences ΔOPD1, ΔOPD2 set by each level difference group for the first light flux satisfy the predetermined conditions, and the secondary coefficient of each light path difference function has a predetermined relation, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT |
