Patent ID: 7282684
Filing Date: 2007-10-16
Classification: G11B

Abstract:
1. An optical pickup apparatus, comprising: (1) a light source device to emit selectively an ordinary polarized light ray and an extraordinary polarized light ray by controlling a polarization condition of a light flux having a wavelength of λ1; (2) a light converging optical system having an objective lens and for converging a light flux having the wavelength of λ1 onto an information recording surface of a first optical information recording medium through a protective layer having a thickness of t (3) an optical detector for receiving a reflected light from the information recording surface of the first optical information recording medium and the second information recording medium and for outputting a signal; wherein the objective lens has a phase structure on one of optical surfaces through which a parallel light flux is transmitted, the phase structure is made of a doubly refracting medium in which an ordinary ray refractive index n