Patent ID: 7126888
Filing Date: 2006-10-24
Classification: G11B

Abstract:
1. An optical pickup apparatus for irradiating laser light onto an optical recording medium and for directing the light reflected from at least the optical recording medium to a light-receiving device section through a diffraction element to detect a focus-error signal by a spot size detection method using diffracted light caused by the diffraction element, wherein the position of the light-receiving device section is set to the position offset closer to the diffraction element from the focal position of the 0 order light passing through the diffraction element, and wherein the position of the light-receiving device section is offset closer to the diffraction element from the focal position of the 0 order light passing through the diffraction element as long as the following relation is satisfied: where NA[+1] indicates the numerical aperture of the +1 order light diffracted by the diffraction element; NA[−1] indicates the numerical aperture of the −1 order light diffracted by the diffraction element; D1 indicates the distance from the focal position of the +1 order light diffracted by the diffraction element to the light-receiving device section; and D2 indicates the distance from the focal position of the −1 order light diffracted by the diffraction element to the light-receiving device section.