| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical pickup device by which information is recorded and/or reproduced properly in/from an optical information recording medium by carrying out proper spherical aberration processing. <P>SOLUTION: An expander optical system EXP corrects mainly three-order spherical aberration caused by the error of the thickness of a protection layer, and a liquid crystal device LC gives a prescribed phase pattern to a luminous flux passing through itself to correct at least fifth-order spherical aberration characteristic to the optical pickup device, so that the information is recorded and/or reproduced properly in/from any optical disk having the protection layer of different thicknesses. <P>COPYRIGHT: (C)2007,JPO&INPIT |
