Patent ID: 7453786
Filing Date: 2008-11-18
Classification: G11B

Abstract:
1. An optical pickup apparatus for recording and/or reproducing information for an optical disk, the optical pickup apparatus comprising: a first light source for emitting a first light flux having a first wavelength λ a second light source for emitting a second light flux having a second wavelength λ a third light source for emitting a third light flux having a third wavelength λ an objective optical element wherein the optical pickup apparatus records and/or reproduces information by converging the first light flux onto the information recording surface of the first optical disk, by converging the second light flux onto the information recording surface of the second optical disk, and by converging the third light flux onto the information recording surface of the third optical disk, wherein the objective optical element comprises an optical surface comprising a central area and a peripheral area surrounding the central area, the central area comprises a first optical path difference providing structure, and the peripheral area comprises a second optical path difference providing structure, wherein the objective optical element converges the first light flux which passes through the central area of the objective optical element onto the information recording surface of the first optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the first optical disk, the objective optical element converges the second light flux which passes through the central area of the objective optical element onto the information recording surface of the second optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the second optical disk, the objective optical element converges the third light flux which passes through the central area of the objective optical element onto the information recording surface of the third optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the third optical disk, the objective optical element converges the first light flux which passes through the peripheral area of the objective optical element onto the information recording surface of the first optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the first optical disk, and the objective optical element converges the second light flux which passes through the peripheral area of the objective optical element onto the information recording surface of the second optical disk so that the optical pickup apparatus can record and/or reproduce information on the information recording surface of the second optical disk, wherein the third light flux which passes through the first optical path difference providing structure forms a first best focus in which the third light flux forms a spot having a smallest diameter, the third light flux which passes through the first optical path difference providing structure forms a second best focus in which the third light flux forms a spot having a second smallest diameter, and the first best focus and the second best focus satisfy a following expression: where f (mm) is a focal length of the objective optical element for the third light flux which passes through the first optical path difference structure and forms the first best focus, and L (mm) is a distance between the first best focus and the second best focus, wherein the third light flux which passes through the objective optical element forms a spot on the information recording surface of the third optical disk, and the spot comprises, in order from a center to an outside of the spot when viewing the spot from a direction of an optical axis of the objective optical element: wherein the central spot portion is used for recording and/or reproducing information for the third optical disk, and the intermediate spot portion and the peripheral spot portion are not used for recording and/or reproducing information for the third optical disk, and wherein the peripheral spot portion is formed on the information recording surface of the third optical disk by the third light flux which passes through the second optical path difference providing structure of the objective optical element.