By Anne Eisenberg
NEW YORK Reading glasses are the lot of most people over 45, but lenses that magnify fine print blur objects more than an arm's length away.
Now a company in Roanoke, Virginia, is developing electronic glasses that it says are smart enough to know where people are looking and adjust the focus automatically.
Such glasses might eliminate the need to switch from reading glasses to driving glasses, or to tilt the head to read through the lower part of bifocals. The glasses would change their refractive power to let users focus on nearby objects like the page of a book or faraway ones like a sign on a highway.
"We have a prototype," said Ron Blum, an optometrist who is president and chief executive of e-Vision, the company that is developing the variable focus glasses. "The prototype is crude, but it works." E-vision is a subsidiary of the Egg Factory, a company also headed by Mr. Blum that develops promising technology to sell or license to larger companies. Mr. Blum said that tests of the prototype should be completed within two years.
If the glasses live up to their promise, they might banish lorgnettes and bifocals. And a change in prescription would mean a change not in the glasses but in the computer program that runs the glasses. The variable focus glasses bend light not by the shape of their lenses, as traditional glasses do, but with the help of software, microchips and a thin layer of a material whose refractive index changes when a voltage is applied.
To do the job, the glasses first emit an infrared beam that bounces off the object at which the person is looking, for instance, a book. Then software calculates the focusing power needed to read the words on the page.
Then the workload shifts to the lenses, which, unlike traditional glass or plastic lenses, have an embedded material, either a polymer or a liquid crystal, that can respond to an electric field. The area of the lens is broken up into many small pixels, and a different voltage is applied to each pixel. This voltage changes the refractive index of the materials in the lens, providing a focus that is appropriate either for a near object or one far away.
Many challenges must be overcome before the glasses can become a reality, said Larry Thibos, a professor of optometry at Indiana University in Bloomington who is evaluating the electronic lenses for the developers.
One problem involves light transmission. To function properly, reading spectacles must transmit as much light as possible, but these lenses are not like glass or plastic ones: they have within them a thin layer of electroactive materials that absorb light. They also have electrodes on either side of those materials that apply the voltages to change the index of refraction. These electrical contacts also absorb light.
"We have to make sure we introduce the chemicals and electrical contacts in such a way that doesn't cause a great deal of light absorption," said Dwight Duston, chief technology officer at the Egg Factory.
Mr. Duston said that teams of researchers were dealing with the engineering problems that need to be solved before the glasses will be ready for commercialization.
The appearance of the glasses, too, is a concern. "Even when we solve the technical problems," said Mr. Thibos, "there are still the mundane problems of how to package the glasses cosmetically at a price people can afford and not look like some computer geek."
