Patent ID: 8270280
Filing Date: 2012-09-18
Classification: G11B

Abstract:
1. An optical pickup device for irradiating a recording medium having laminated recording layers and servo layers with laser light, the optical pickup device comprising: a first laser light source for emitting first laser light having a first wavelength; a second laser light source for emitting second laser light having a second wavelength different from the first wavelength; an objective lens for converting the first laser light emitted from the first laser light source, and the second laser light emitted from the second laser light source on the recording medium; a focus position adjuster for changing a focus position of the first laser light by the objective lens in an optical axis direction, an astigmatism element for imparting astigmatism to the first laser light and the second laser light reflected on the recording medium; a spectral element for imparting diffraction in such a manner that at least four light fluxes of the first laser light are separated from each other, when a light flux of the first laser light and a light flux of the second laser light reflected on the recording medium are divided into four by a first straight line in parallel to a converging direction by the astigmatism element, and a second straight line perpendicular to the first straight line, and that the four light fluxes of the first laser light propagate on an outer side than the light flux of the second laser light; and a photodetector including a first sensor group for receiving the separated four light fluxes of the first laser light to generate a reproduction signal, and a second sensor group for receiving the second laser light to generate a servo signal for use in controlling the objective lens.