Patent ID: 7808878
Filing Date: 2010-10-05
Classification: G11B

Abstract:
1. An optical pickup apparatus for performing at least one of information recording, information reproduction, and information erasing with respect to an optical recording medium having an information recording layer for recording information and a light transmitting layer, comprising: a light source; an objective lens for condensing a beam of light emitted from the light source on the information recording layer of the optical recording medium; a coupling lens disposed between the light source and the objective lens; a diffraction element disposed between the light source and the coupling lens, for diffractively branching reflection light from the optical recording medium to a zero-order diffraction light beam and ±first-order diffraction light beams; a light detecting section including a first light-receiving element for receiving the zero-order diffraction light beam and a second light-receiving element and a third light-receiving element for receiving the ±first-order diffraction light beams; a light branching section for directing the diffraction light beams from the diffraction element to the first light-receiving element, the second light-receiving element, and the third light-receiving element; and a calculating section for generating a reproduced signal and a push-pull signal on the basis of an output signal from the first light-receiving element, generating a focus error signal on the basis of an output signal from the second light-receiving element, and generating an objective lens shift signal on the basis of an output signal from the third light-receiving element, wherein, the third light-receiving element is disposed outwardly of a circular region having an optical axis of the zero-order diffraction light beam on the light detecting section as its center, a radius of which is expressed by (2×t/n)×(f