OBJECTIVE LENS, LIGHT CONVERGING OPTICAL SYSTEM, OPTICAL PICKUP APPARATUS, AND RECORDING/REPRODUCING APPARATUS

摘要

An objective lens for recording information on and/or reproducing information form an optical information recording medium, 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 data side numerical aperture necessary for recording on and/or reproducing from an optical information recording medium.