| 摘要 |
<P>PROBLEM TO BE SOLVED: To enable an objective lens compatible with a BD and an HD by the same wavelength to cope with the change of environmental temperature. <P>SOLUTION: An objective optical element has at least a first region and a second region provided on the periphery of the first region. A first optical path difference imparting structure is formed in the first region, m-th order diffraction light and n-th order diffraction light are generated more as compared with other order diffraction light when a first luminous flux passes through the structure, diffraction orders m and n satisfy (1)¾m-n¾=1 and (2) m=-n, the m-th order diffraction light is condensed so that recording and playback of information can be performed on a first optical disk, the n-th order diffraction light is condensed so that recording and playback of a second optical disk can be performed, the first luminous flux passing through the second region is condensed so that recording and playback can be performed on the information recording surface of the first optical disk, the first luminous flux passing through the second region is not condensed so that recording and playback can be performed on the information recording surface of the second optical disk and a second optical path difference imparting structure correcting spherical aberration generated by the change of environmental temperature is formed in at least the second region. <P>COPYRIGHT: (C)2010,JPO&INPIT |
