Patent ID: 7672212
Filing Date: 2010-03-02
Classification: G02B,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 at least two areas which are a central area and a peripheral area surrounding the central area, the central area comprises a first optical path difference providing structure, 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, and wherein the first optical path difference providing structure is a ring-shaped structure including a plurality of ring-shaped zones which are concentrically arranged and have respective steps, and the steps in the first optical path difference providing structure have at least two kinds of step amounts selected from dA, dB, dC, and dD represented by following expressions: where λB is a design wavelength (μm), λB′ is an arbitral value which is 0.390 μm or more, and is 0.410 μm or less, n is a refractive index of the objective optical element for the design wavelength λB, and n′ is a refractive index of the objective optical element for a wavelength λB′.