Autofocusing glasses do away with swapping eyewear
Image credit: Dan Hixson/University of Utah College of Engineering
Innovative glasses that can automatically focus on what a wearer is looking at have been developed by American researchers, promising to offer an all-in-one solution for near and far-sightedness.
Until today, people with worsening eyesight had to accept the hassle of having to carry around two sets of eyeglasses – one for reading and the other for seeing objects at longer distances. Bifocal glasses incorporating both types of lenses into one frame are common but, in many users, these glasses can cause headaches and dizziness. The comfort of using bifocals for reading or working on a computer is also limited as the field of view is rather small.
The new adaptive glasses by a team from the University of Utah rely on liquid-based lenses that can adjust their curvature in response to what the wearer is focusing at.
“Most people who get reading glasses have to put them on and take them off all the time,” said Utah electrical and computer engineering professor Carlos Mastrangelo who developed the technology together with his doctoral student Nazmul Hasan. “You don't have to do that anymore. You put these on, and it’s always clear.”
The lenses are made of glycerine enclosed in a flexible rubber container. The rear membrane of the container in each lens is connected to a system of three mechanical actuators that push the membrane back and forth like a transparent piston, adjusting the focal length between the lens and the eye by changing the curvature of the lens.
The lens essentially mimics the natural functioning of the human eye, which tends to deteriorate with age.
“The focal length of the glasses depends on the shape of the lens, so to change the optical power we actually have to change the membrane shape,” Mastrangelo explained.
The lenses are fitted into rather unfashionable frames. The thick frames contain electronic systems and a battery that can power the actuators for up to 24 hours. A distance meter is placed in the bridge of the frames measuring the distance from the glasses to an object via pulses of infrared light. When the wearer looks at an object, the meter instantly measures the distance and tells the actuators how to curve the lenses. If the user then sees another object that is closer, the distance meter readjusts and tells the actuators to reshape the lens for far-sightedness.
The refocusing happens within 14 milliseconds.
The researchers hope to eventually make the frames lighter and subtler. The technology, described in the latest issue of the journal Optics Express, could hit the market within three years. The researchers established a start-up called Sharpeyes LLC to commercialise the invention.
The glasses come paired with a smartphone app, which allows the user to adjust the glasses to their personal prescription. The researchers say that as the glasses can be readjusted whenever the prescription changes, the users could use the same glasses their whole lives.