Polarization-insensitive liquid crystal microlens array with dual focal modes.

We demonstrate a liquid crystal (LC) microlens array (MLA) fabricated by LCs possessing negative dielectric anisotropy, in conjunction with a cell with a three-electrode structure. The presented LC MLA is polarization-insensitive and can be operated in both concave and convex modes. The shortest focal length of the LC MLA is -2.54 and 2.22 mm in concave and convex mode, respectively. Disclination lines that are usually observed in conventional hole-patterned LC lens can also be avoided because of the vertical alignment treatment of LCs.