| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical pickup which can record or reproduce information appropriately on different optical information recording media by using two or more light sources of different wavelengths, and an objective lens used in this optical pickup. SOLUTION: Phase shifts are not made by the level differences in the flux of light from the light source of wavelength λ1, if the step amount of those level differences PS1 is made the integer multiple of the wavelength λ1 on the optical surface of an objective lens in the direction of an optical axis. On the other hand, a phase shift is made by the level differences PS1 for the light flux from the light source of wavelength λ2 different from the wavelength λ1. Information can be appropriately recorded or reproduced on the medium having transparent substrates different in thickness, by suppressing the spherical aberration in the light flux from the light source of wavelength λ2 using this effect. |
