| 摘要 |
An objective lens used for recording data to and/or reproducing data from a plurality of types of optical discs having different thicknesses of cover layers. The objective lens satisfies a condition 0.02<M2-M1<0.15, WHERE M1 represents a magnification of the objective lens when recording/reproducing for a first optical disc is performed using the first light beam, and M2 represents a magnification of the objective lens when the recording/reproducing for a second optical disc is performed using the second light beam. Further, at least one of lens surfaces of the objective lens is provided with a diffracting structure having a plurality of annular zones configured to correct spherical aberrations for both of the first and second optical discs.
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