Liquid crystal lens with large-range electrically controllable variable focal length

A novel structure model with different disc-ring radii of liquid crystal lens is proposed, in which liquid crystal director could be controlled by changing the electric field intensity dependence. Then the theory of liquid crystal and the geometric optics are analyzed. By using the finite element method, under the same constant voltage, we obtain the distributions of the electric field intensity at different positions of the liquid crystal layer. Then, the simulation results provide a theoretical guideline for the experimental fabrication. Due to the fact that the electric field intensity at the electrode edges is stronger than that at the circular hole, a shorter focal convergence could be realized by controlling the voltage between the upper and the lower substrates. In this paper, the influences of the electrode size and spacer thickness on the focal length of liquid crystal lens are also discussed experimentally and theoretically. Through optimizing various parameters, a prototype liquid crystal lens with a large zoom range and simple structure is obtained. Its focal length can be controlled to be 75-230 mm in a range of 25 V_RMS-250 V_RMS.