| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical pickup suppressing the influence of a shift of an objective lens unit in its radial direction. <P>SOLUTION: The optical pickup includes an objective lens 12 which focuses first, second and third light beams of respective wavelength λ1, λ2, λ3 (λ1<λ2<λ3) on the respective information recording surfaces of first, second and third recording media, and a diffraction optical element 11 which diffracts and refracts the respective light beams and makes the respective light beams incident on the objective lens 12. The diffraction optical element 11 makes the first, second and third light beams incident on the objective lens 12 as divergent light and the convergence/divergence degrees incident on the diffraction optical element 11 for the first, second and third light beams, are respectively defined as Φinr and ΦinIr, and the divergent degrees incident on the objective lens 12 as Φoutr and ΦoutIr, diffraction optical element 11 satisfies ¾Φinr¾<¾Φoutr¾ and ¾ΦinIr¾<¾ΦoutIr¾. <P>COPYRIGHT: (C)2008,JPO&INPIT |
