Patent ID: 7327662

Claim:
An optical pickup device comprising: a light source that irradiates light to an optical recording medium; a focusing unit configured to focus the light emitted from the light source on the optical recording medium; a recording area discrimination unit configured to detect a portion of the optical recording medium the light is focused on; a diffraction unit provided between the light source and focusing unit and configured to diffract the light emitted from the light source so that zero-order light resulted from the diffraction is focused by the focusing unit on the optical recording medium while other diffracted light than the zero-order light goes to a focus shifted in an optical-axial direction not to be focused on the optical recording medium, the diffraction unit configured to vary a diffraction efficiency of the light based on the portion of the optical recording medium detected by the recording area discrimination unit; and a light detecting unit configured to detect a portion reflected from the optical recording medium, of the zero-order light from the diffraction unit.