| 摘要 |
An optical pickup for at least reproducing and/or recording information from/on two kinds of optical information recording medium having different protection substrate thicknesses comprising a first light source emitting a first light beam of wavelength U1, a first objective lens used for focusing the first light beam from the first light source onto the information recording surface of a first optical information recording medium when information is reproduced or recorded from/on the first optical information recording medium having a protection substrate thickness t1, and a second objective lens used for focusing the first light beam from the first light source onto the information recording surface of a second optical information recording medium when information is reproduced or recorded from/on the second optical information recording medium having a protection substrate thickness t2, wherein the effective diameter of the first objective lens on the light source side is approximately equal to the effective diameter of the second objective lens on the light source side.
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