One problem with every type of eyeglasses, contact lenses, and even the plastic lenses implanted after cataract removal is that they all have a fixed focal length. Auto-focus cameras don't, but they operate on a principle that wouldn't work for a pair of spectacles. Until now.
At the University of Arizona and Georgia Tech, optical scientists have demonstrated flat, liquid crystal diffractive lenses capable of changing their focal distance. According to researcher Nasser Peyghambarian, the prototype requires manual switching to change focal distance; the commercial version will do that task electroactively.
The lenses consist of two pieces of flat glass spaced five microns apart. The space between the panes is filled with liquid crystal. The glass is coated with a 0.1 micron thick layer of indium tin oxide, which functions as a transparent electrode and transmits most of the impinging light. Photolithography is used to arrange the electrodes in a circular pattern on the lens. The application of ~1.8 V to the circuit rapidly changes the orientation of the liquid crystal molecules and thus the optical path through the lens.
Prototype spectacles were shown not to affect distance vision when the glasses were inactive and enabled close-up vision when activated. The commercial models will probably be available first for those who require the use of bi- or tri-focals. Dentists are also expected to embrace the new technology because they must quickly switch from extreme close-ups of a patient's mouth to views of more distant equipment trays.
UA licensed three patents from the work to the Johnson and Johnson Development Corp., which sponsored the research. Pixel Optics has since purchased the patent licenses to commercialize the technology.
Dr. Bernard Kippelen, School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA; 404-385-5163, [email protected]