Patent ID: 7710848
Filing Date: 2010-05-04
Classification: G02B,G11B

Abstract:
1. An optical pickup apparatus comprising: a first light source for emitting a first light flux with a wavelength λ a second light source for emitting a second light flux with a wavelength λ a light-converging optical system comprising the light-converging optical system being adopted to converge the first light flux onto an information recording surface of a first optical information recording medium through a protective layer with a thickness t wherein the coupling lens comprises a first diffractive structure arranged on an area on the coupling lens where the first light flux and the second light flux respectively used for recording or reproducing information on the first information recording medium and the second optical information recording medium, pass through, and the first diffractive structure includes a plurality of ring-shaped zones which are concentrically arranged around the optical axis and which have steps extending along the optical axis, and wherein the optical pickup apparatus satisfies following expressions: where ΔfB f ΔfB f νd νd