| 摘要 |
<p>An objective lens (2) is described, which is switchable between a far-field mode and a near-field mode. The objective lens (2) comprises a lens (4), an optical element (8) having a variable refractive index and a solid immersion lens (6), which are disposed on a common optical axis (A), wherein the optical element (8) is arranged at a convex side (9) of the solid immersion lens (6) and has a top and a bottom surface (5,7) arranged adjacent to each other in a direction of the optical axis (A), the bottom surface (7) having a concave shape that is adapted to the shape of the convex side (9) of the solid immersion lens (6) and the top surface (5) having a curvature that is lower than a curvature of the convex side (9) of the solid immersion lens (6), and wherein a difference between a refractive index of said optical element (8) and the solid immersion lens (6) is small in the far-field mode so that the solid immersion lens (6) and the optical element (8) act substantially as a single optical element in the far-field mode, whereas said difference is large in the near-field mode so that the optical effect of the solid immersion lens (6) is significant in the near-field mode.</p> |
