Researchers at the University of Central Florida in Orlando have reported the development of a liquid crystal lens with a focal length that can be tuned continuously from infinity to 0.6 m. They describe the device in the June 7 issue of Applied Physics Letters. To fabricate the lens, the scientists sandwiched a custom-made high-birefringence liquid crystal mixture between two planar substrates. The bottom substrate was glass, whose concave surface was coated with indium tin oxide to serve as a spherical electrode and the cavity filled with a UV-cured polymer. The top substrate also was made of glass and featured a planar electrode.The application of a voltage induced a centrosymmetric gradient refractive index distribution in the liquid crystal that enables tunable focusing. The researchers note that the method may be used to fabricate a negative lens by reversing the shape of the spherical electrode.