Design of liquid crystal Fresnel lens by uneven electric field

Abstract

We propose a liquid crystal Fresnel lens that consists of a liquid crystal layer sandwitched between two substrates, one of which a Fresnel lens-like structure is formed. Simulations on the liquid crystal orientations show that the retardation distribution of such a lens can mimic that of a spherical lens. The radius of the equivalent spherical lens can be varied by the bias across the liquid crystal layer. This may open a way to a thin variable-focus lens. As a preparation for building such a device, we have conducted preliminary experiments that involves modulated polymerization of polymer-network liquid crystal material by UV light exposure through a phase mask. A liquid crystal phase grating has been created by exposure through a prism sheet.