Focal-field distribution of the solid immersion lens system with an annular filter

The focal field of the solid immersion lens (SIL) system with an annular filter is calculated by using vector method. Polarization of the transmitted field, size and shape of spot are analyzed. Numerical results show that, as the increase of the obstruction ratio of annular filter for low-NA (numerical aperture) SIL systems, the shape of spot is almost invariant and the size of spot decreases. But both the axial component of the transmitted field and the depth of focus increase with the obstruction ratio. For high-NA SIL systems, an annular-amplitude filter couldn't produce superresolving effects. It is especially noted that, when the obstruction angle is near the critical angle, the shape of spot of the SIL with high-NA becomes fairly bad due to the stronger axial component.