Fabricating spherical microlens arrays with a two step laser beam writing technique

The fabrication process of refractive microlens arrays with a continuous surface relief is described. The elements are fabricated with a laser beam lithographic system and are directly written into photoresist. By this method the manufacturing of lenses with a broad range of numerical apertures N.A. is possible. Lenses with different diameters in the range from 25 to 100 mu m were written in photoresist. Furthermore a modified technique with two subsequent exposures is applied which simplifies the procedure for generating the data and writing the lens topography. First attempts to transfer the structures into the substrate by ion etching show positive results. A first suggested fabrication method of the spherical microlenses by an exposure technique using a z-stepped probe chuck is described.