Electrically Tunable-Focusing Liquid Crystal Microlens Array with Simple Electrode

An electrically tunable-focusing liquid crystal (LC) microlens array exhibiting a wide-range tunable focal length is proposed. The lower substrate has strip indium tin oxide (ITO) electrodes, the upper substrate has periodic ITO electrodes with a certain gap coated on the inner surface., and an LC microlens is generated between the two strip electrodes. For each LC microlens, the gap between the top planar electrodes is directly above the center of the microlens. Unlike the conventional LC lens, the individual LC microlens is not coated with ITO electrodes on the central part of its upper and lower substrates, which helps to maintain the LC's horizontal orientation. In the voltage-off state, the focal length of the microlens array is infinity because of the homogeneous LC alignment. At a given operating voltage, an ideal gradient refractive index distribution is induced over the homogeneous LC layer, which leads to the focusing effect. The simulation result shows that the focal length of the LC microlens could be gradually drawn to 0.381 mm with a change of voltage.