| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an optical pickup device which can properly record/reproduce information to/from an optical disk having a plurality of information recording layers, and to provide an objective lens unit. <P>SOLUTION: An opening limiting element AP is arranged more on an optical disk side than the surface vertex P of an objective lens OL. Then, NA1≈NA0≈NA2 is attained, so that a change in a numerical aperture can be suppressed, when the numerical aperture is defined as NA0 when a parallel luminous flux indicated by a solid line is made incident on the object lens OL, the numerical aperture as NA1 when diverging light indicated by a dotted line is made incident, and the numerical aperture as NA2 when converging light indicated by a chain line is made incident. <P>COPYRIGHT: (C)2011,JPO&INPIT |
