| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an objective lens capable of satisfactorily reproducing both a CD and a DVD. <P>SOLUTION: The objective lens has its fundamental shape satisfactorily correcting the axial aberration and the off-axis aberration of the DVD and the off-axis aberration of the CD and a phase shifter having steps so selected that the generation of the aberration of light having a first wavelength is suppressed as much as possible and the aberration of light having a second wavelength can be reduced is provided on one surface thereof. The phase shifter having an annular step around an optical axis as a center is provided on one surface of the objective lens and the phase shifter is constituted of steps in a range of 1.01 to 1.13 λ<SB>1</SB>to light having the first wavelength when an absolute value of the phase difference is expressed in terms of a distance and when the first wavelength is defined as λ<SB>1</SB>. <P>COPYRIGHT: (C)2009,JPO&INPIT |
