Patent ID: 7952977

Claim:
An optical pickup apparatus for irradiating an optical recording medium having a plurality of recording layers with light and recording information on a recording layer of the optical recording medium or reproducing information from the recording layer of the optical recording medium, the optical pickup apparatus comprising: a light source for emitting light; a lens system for collecting light emitted from the light source onto the recording layer of the optical recording medium and transmitting reflected light from the recording layer of the optical recording medium; a light receiving portion for receiving the reflected light from the recording layer of the optical recording medium; a diffracting portion for diffracting the reflected light from the recording layer of the optical recording medium toward the light receiving portion, the diffracting portion being disposed in an optical path between the light source and the optical recording medium; and a light splitting portion for splitting the light emitted from the light source into a main light beam and a sub light beam, wherein the diffracting portion includes: a first diffraction region having a first diffraction efficiency; and a second diffraction region having a second diffraction efficiency lower than the first diffraction efficiency, the second diffraction region being disposed so that first-order diffraction light from a non-light-collecting recording layer enters thereon, the non-light-collecting recording layer being another layer than a light-collecting recording layer which is currently involved in collection of the light emitted from the light source, wherein the second diffraction region is disposed so that the first-order diffraction light of the main light beam from the non-light-collecting recording layer enters thereon while a part of the first-order diffraction light of the sub light beam from the non-light-collecting recording layer does not enter thereon, and wherein the first diffraction region is disposed so that the part of the first-order diffraction light of the sub light beam from the non-light-collecting recording layer enters thereon.