Patent ID: 8154977
Filing Date: 2012-04-10
Classification: G11B

Abstract:
1. An optical pickup used for performing recording, reproduction, or deletion of information with respect to three types of optical recording media A, B, and C having different used wavelengths, the optical pickup comprising: a light source A that emits light having a wavelength of λ a light source B that emits light having a wavelength of λ a light source C that emits light having a wavelength of λ a converging unit A that converges the light emitted from the light source A onto a recording surface as an accessed object of the optical recording medium; a converging unit BC that converges the light emitted from the light source B and the light emitted from the light source C onto recording surfaces as accessed objects of the optical recording media; a branch unit A that is arranged on a light path between the converging unit A and the light source A and branches a return light flux through the converging unit A; a branch unit BC that is arranged on a light path between the converging unit BC and the light sources B and C and branches a return light flux through the converging unit BC; a light receiving unit A that receives the return light flux branched by the branch unit A at a predetermined light receiving position; a light receiving unit BC that receives the return light flux branched by the branch unit BC at a predetermined light receiving position; a reflecting wavelength plate BC that is arranged on the light path between the converging unit BC and the branch unit BC; and a reflecting mirror A′ that is arranged on a light path between the converging unit A and the reflecting wavelength plate BC; wherein the reflecting wavelength plate BC includes a substrate, a reflecting film laminated on the substrate, and a sub-wavelength concavo-convex structure the reflecting wavelength plate BC is configured so that a filling factor and a groove depth of the sub-wavelength concavo-convex structure are determined so as to add a phase difference obtained by (kπ)/8, where k is an integer, to the light emitted from the light source B and the light emitted from the light source C and the reflecting film reflects the light having a wavelength of λ the reflecting wavelength plate BC includes a sub-wavelength concavo-convex structure the reflecting wavelength plate BC is configured so that a filling factor and a groove depth of the sub-wavelength concavo-convex structure