Eyeglasses with adaptive focus
from Health and Wellbeing (357 articles)
Eyeglasses with adaptive focus
Image Gallery ( 2 images )April 15, 2006 The end is nigh for bifocals, and not a moment too soon. Optical scientists at the University of Arizona have developed new switchable, flat, liquid crystal diffractive eyeglass lenses that can adaptively change their focusing power. The new technology will open the way for a new generation of "smart" eyeglasses with built-in automatic focus. In the foreseeable future, with this technology, you won't change prescription eyeglasses but will have your eyes tested and the optician will dial in a new prescription into the specs you already own. Indeed, we can even see the possibility of geeks doing their own eye tests and creating superglasses designed to focus perfectly depending on what you’re looking at.
"Right now, in our prototype, you switch the lenses on or off to change focus," said Nasser Peyghambarian, chair of photonics and lasers in UA's College of Optical Sciences and professor of optical sciences, materials science and engineering. "But ultimately this will act just like your automatic camera: Eyeglass lenses will know where to focus just like your auto-focusing camera does."
Peyghambarian is part of the team that began developing the focus-changing lenses in 2001 under an agreement between the university and private industry. The UA licensed three patents from the work to the Johnson and Johnson Development Corp., which sponsored the research. A firm called Pixel Optics has since purchased the patent licenses from Johnson and Johnson to commercialize the innovative technology.
Ten UA scientists and two colleagues now at the Georgia Institute of Technology are publishing their first science paper about the switchable-focus lenses in an article online at the Proceedings of the National Academy of Sciences website.
The novel lenses focus electroactively, said Guoqiang Li, UA optical sciences assistant research professor and lead author on the scientific paper.
They are basically two pieces of flat glass spaced five microns apart. Five microns is an incredibly small space -- roughly one-twentieth the diameter of a human hair. The space is filled with liquid crystal -- the same kind of stuff in your laptop's liquid crystal display.
The flat glass is coated with an even thinner layer (one-tenth micron) of indium tin oxide, or ITO, which is a transparent electrode. Unlike electrodes made of aluminum or gold, ITO transmits most of the light that hits it.
The transparent electrodes are patterned in a circular array over the area of the lens. The circular pattern is created through photolithography, an extremely precise technique that processes with light and chemicals.
Applying less than two volts to the circuit changes the orientation of the liquid crystal molecules, and that changes the optical path length through the lens. It takes only about 1.8 volts to change the index of refraction so that light refocuses, Peyghambarian and Li explained. The result is a flat piece of glass that acts like a lens.
