Object lens for an optical pickup device

摘要

An object lens (100), having a numerical aperture of 0.75 or greater, is provided with a diffractive optical element (125) on one of its incident and exit surfaces (120, 140) and has a refractivity of f D /f<5, f D being a focus distance of the diffractive optical element and f being a focal distance of the object lens. The object lens (100) may be used in an optical pickup device (300) for recording/reproducing information to/from a high capacity recording medium (200), such as a Blu-ray disk or High-Definition DVD.