Objective lens, light converging optical system, optical pickup apparatus, and recording/reproducing apparatus

摘要

An objective lens (160) for recording information on and/or reproducing information from an optical information recording medium (200), comprises a diffractive structure including ring-shaped diffractive zones on at least one surface thereof. The objective lens is a single lens made of plastic material, at least one surface thereof is an aspheric surface, and the following conditional formula is satisfied; NA ≥ 0.7
where NA represents an image side numerical aperture necessary for recording on and/or reproducing from an optical information recording medium.