Patent ID: 8036094

Claim:
An objective lens, which is switchable between a far-field mode and a near-field mode, comprising: a lens, an optical element having a variable refractive index and a solid immersion lens, which are disposed on a common optical axis, wherein the optical element is arranged at a convex side of the solid immersion lens and has a top and a bottom surface arranged adjacent to each other in a direction of the optical axis, the top surface having a curvature that is lower than a curvature of the convex side of the solid immersion lens, wherein the bottom surface of the optical element has a concave shape that is adapted to the shape of the convex side of the solid immersion lens, and wherein a difference between a refractive index of said optical element and the solid immersion lens is small in the far-field mode so that the solid immersion lens and the optical element 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 is significant in the near-field mode.