Patent ID: 8599672

Claim:
An objective lens comprising a diffraction portion provided on a laser beam incident plane or a laser beam output plane of the objective lens, wherein the diffraction portion includes a first diffraction region that is circular in shape and is provided on an innermost circumferential portion, a second diffraction region that is annular in shape and is provided outside the first diffraction region, and a third diffraction region that is annular in shape and is provided outside the second diffraction region, wherein first laser beams corresponding to a first optical disc having a first transmissive layer are condensed on a data recording portion of the first optical disc, second laser beams corresponding to a second optical disc having a second transmissive layer thicker than the first transmissive layer are condensed on a data recording portion of the second optical disc, and third laser beams corresponding to a third optical disc having a third transmissive layer thicker than the second transmissive layer are condensed on a data recording portion of the third optical disc, and wherein the objective lens is configured such that an evaluation parameter, which is calculated on the basis of an in-plane efficiency distribution function that indicates a proportion of, among the first laser beams incident on the diffraction portion, the first laser beams condensed on the data recording portion of the first optical disc in association with a distance from an optical axis of the incident plane in a radial direction and which has a correlation with a symbol error rate corresponding to the first optical disc, has a value corresponding to the symbol error rate that is less than a predetermined value.