Patent ID: 7348529

Claim:
An optical device for an optical pickup apparatus for recording or reproducing information with respect to an information recording medium, comprising: a hologram element divided into first and second regions having different diffraction axes and configured to diffract incident light of first and second wavelengths that are different from each other; and a light receiving element configured to receive the diffracted incident beams from the hologram element, the light receiving element comprising: first light receiving regions configured to commonly receive diffracted beams from the first and second regions of the hologram element without regard to the wavelengths of the diffracted beams, the diffracted beams originating from main beams that are emitted toward the information recording medium to detect information from the information recording medium, are reflected by the information recording medium, and are diffracted by the first and second regions of the hologram element; and second light receiving regions each including a pair of sections to separately receive diffracted sub-beams depending on the wavelengths of the diffracted sub-beams, the diffracted sub-beams originating from first and second sub-beams that are emitted toward the information recording medium, are reflected by the information recording medium, are diffracted through the first and second regions of the hologram element, and are used to conduct a tracking operation along a track of the information recording medium, diffracted beams from the first region of the hologram element originating from incident light of the first wavelength being detected by the second light receiving regions and combined into a common output, diffracted beams from the second region of the hologram element originating from the incident light of the first wavelength being detected by the second light receiving regions and combined into a common output, diffracted beams from the first and second regions of the hologram element originating from the first sub-beam of the second wavelength being detected by the second light receiving regions and combined into a common output, diffracted beams from the first and second regions of the hologram element originating from the second sub-beam of the second wavelength being detected by the second light receiving regions and combined into a common output.