| 摘要 |
<P>PROBLEM TO BE SOLVED: To change a detected signal even if an objective lens having a large numerical aperture NA, and to reduce aberration. <P>SOLUTION: An optical pickup 20 uses an objective lens 30 having a numerical aperture NAr larger than a seaming numerical aperture NAa of the objective lens 30 when being irradiated by an object optical beam 40a. The optical pickup 20 receives a sub-optical area AR±1 at the peripheral edge of the objective lens 30 where no object optical beam 40a enters with respect to a reflected object optical beam 41 so that no overlapped area Wa is formed when a diffraction angle θ of the sub-optical area AR±1 is larger than that of a main optical area AR0 because of a small track pitch TP, and the reflected object optical beam 41 is received by the objective lens 30. The optical pickup 20 superposes a reference optical beam 40b on the sub-optical area AR±1 to form an interference area Wb. <P>COPYRIGHT: (C)2009,JPO&INPIT |
