| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical pickup device and the objective lens and the optical device used in it by which the recording and reproduction of information to a information recording medium having a different thickness is attained even though a small number of optical devices or objective lenses are used. SOLUTION: The optical pickup device by which a comparatively large spot size is obtained without excessively converging a beam size even though an aperture restriction for a small numerical aperture NA is not used when the outside luminous flux of a specified numerical aperture is set a flare in a use state on a side at which a numerical aperture NA is small by using the objective lens provided with a diffraction ring band, and the recording and the reproduction of the information is performed for the plural kinds of the information recording media having the different thickness is provided. |
