Liquid crystal lens with focal length variable from negative to positive values

A liquid crystal (LC) lens with focal length variable from negative to positive is reported. There are three electrodes in the LC cell. One electrode has a circular hole in the center. The lens is driven by two voltages that produce a spatially nonuniform and symmetrical electric field in the LC layer. By adjusting the voltages, a wide range of lens power is covered. The LC lens preserves its optical quality over the entire focus range.