High quality adaptive liquid crystal microlenses

An adaptive microlens was built with planar aligned liquid crystal and circ ular electrode structure on one side Of a sandwiched liquid crystal cell. T he fringing effects at the edges of the electrodes produce a spatial distri bution of the electric field. Applying a voltage deforms the liquid crystal director field. This produces an axial asymmetric profile of the extraordi nary refractive index. The liquid crystal cell becomes a convex (converging ) lens. A dual frequency liquid crystal mixture was used to study the influ ence of material parameters on the lens quality. Ale found that the quality of the lens is best if the lens diameter is approximately one and a half t he cell thickness. For such microlenses diffraction limited lens properties with Strehl intensities of 0.9 are measured. The lenses show off-axis prop erties. In the diffraction limited regime, a focal length change of approxi mately 18% is obtained for different electric control parameters.