| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an objective lens and an optical pickup device, for reproducing/recording data to/from two types of optical disks having transparent substrates different in thickness by light sources of two wavelengths different from each other, simultaneously reducing color aberrations for the optical disk of a thin transparent substrate, and halving residual aberrations for the optical disk of a thick transparent substrate. <P>SOLUTION: In the optical pickup device, light fluxes from first and second light sources 111 and 112 are converged on an information recording surface 22 by an objective lens 16 including a diffraction pattern via the transparent substrate 21 of a first or second optical disk 20 to record/reproduce information. The tertiary spherical aberration component of a wavefront aberration of a light flux via the transparent substrate of the second optical disk is over-corrected, the light flux coming from the second light source through the objective lens, where the numerical aperture on the optical disk side is equal to or less than NA2 necessary for reproducing/recording of the second optical disk having a thick transparent substrate. When the absolute value thereof is WSA2λ3rms, 0.02λ2rms≤WSA2≤0.06λ2rms is satisfied. <P>COPYRIGHT: (C)2009,JPO&INPIT |
