Patent ID: 7463571
Filing Date: 2008-12-09
Classification: G11B

Abstract:
1. An optical element disposed on an optical path of first laser light and a plurality of laser lights, in order to share an objective lens for focusing light on a first recording medium, which comprises a recording layer which receives the first laser light through a transmission protection layer with a thickness of D 1 , in the plurality of laser lights whose wavelengths are different from that of the first laser light and in a plurality of recording media corresponding to the respective plurality of laser lights, the plurality of laser lights including second laser light which corresponds to a second recording medium having a transmission protection layer with a thickness of D an effective diameter of a luminous flux required when the first laser light enters the objective lens being R an effective diameter of a luminous flux required when the second laser light enters the objective lens being R an effective diameter of a luminous flux required when the third laser light enters the objective lens being R said optical element comprising: a first aberration correcting device for correcting aberration caused by a difference between the thickness D a second aberration correcting device for correcting aberration caused by the difference between the thickness D