Simple method for spherical aberration correction in direct laser writing.

The relation is established which shows the focussing depths with compensated spherical aberrations under the high aperture focussing through the planar surface in materials with different refractive indices and the same pre-compensation settings in focussing optics. Typically, the focussing objective possesses the correction ring calibrated for single specific material. The developed relation allows calculation of depth at which correct pre-compensation is applied for any material.