Patent ID: 7876660
Filing Date: 2011-01-25
Classification: G11B

Abstract:
1. An optical pickup apparatus for recording and/or reproducing information on a first optical information recording medium comprising a protective layer with a thickness t 1 , the optical pickup apparatus comprising: a first light source for emitting a first light flux with a wavelength of λ1; a light-converging optical system for converging the first light flux onto an information recording surface of the first optical information recording medium, the light-converging optical system comprising an objective lens and an optical surface comprising a diffractive structure which, when the first light flux reflected from the information recording surface of the first optical information recording medium enters into the diffractive structure, emits a main light flux which is a diffracted light flux with a predetermined diffraction order and a secondary light flux which is a diffracted light flux with a diffraction order being different from the predetermined diffraction order; a first optical element comprising a first optical area and a second optical area which are arranged on both sides of an optical axis; a second optical element comprising a third optical area and a fourth optical area which are arranged on both sides of the optical axis; a light-converging element for converging the main light flux at a position between the first optical element and the second optical element; a polarization splitting optical member for splitting the main light flux and the secondary light flux each emitted from the first optical element and the second optical element; and a photodetector for receiving the main light flux, wherein the optical pickup apparatus records and/or reproduces information by converging the first light flux on an information recording surface of the first optical information recording medium through the light-converging optical system, wherein the first optical area and the fourth optical area provide a first polarization direction with the main light flux passing through the first optical area and the fourth optical area, the second optical area and the third optical area provide a first polarization direction with the main light flux passing through the second optical area and the third optical area, the first optical area and the third optical area provide a second polarization direction with the secondary light flux passing through the first optical area and the third optical area, and the second optical area and the fourth optical area provide a second polarization direction with the secondary light flux passing through the second optical area and the fourth optical area, wherein the main light flux passes through the first optical element and is converged between the first optical element and the second optical element by the light-converging element, and the main light flux passes through the second optical element and enters into the photodetector through the polarization splitting optical member, and wherein the secondary light flux passes through the first optical element and is not converged between the first optical element and the second optical element by the light-converging element, and the secondary light flux passes through the second optical element and does not enter into the photodetector by being branched by the polarization splitting optical member.