OPTICAL PICK-UP APPARATUS, OBJECTIVE LENS, DIFFRACTIVE OPTICAL ELEMENT, OPTICAL ELEMENT, AND RECORDING/REPRODUCING APPARATUS

摘要

PROBLEM TO BE SOLVED: To provide an optical pick-up apparatus capable of performing recording or reproduction of information to three kinds of optical information recording mediums having specifications different from each other.

SOLUTION: In the optical pick-up apparatus, reproduction and/or recording of information is performed to a first optical information recording medium having a first protective substrate having a thickness t1 using a luminous flux having a wavelength λ1 from a first light source 1 and reproduction and/or recording of information is performed to a second and a third optical information recording mediums having second and third protective substrates having thicknesses t2 and t3 (t3>t2>t1), respectively, using luminous fluxes having wavelengths λ2 and λ3 (λ1<λ2<λ3) from second and third light sources 2 and 3, respectively. The optical pick-up apparatus uses a common objective lens 8 constituted of one lens group for reproduction and/or recording of information to the first to the third optical information recording mediums and has a substrate thickness difference correcting means 7 for correcting spherical aberration changing caused by thickness difference of the first to the third protective substrates.

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