Now, 'smart glasses' that automatically focus on what you see

The days of wearing bifocals or constantly swapping reading glasses may soon be over, thanks to new 'smart glasses' developed by scientists, including one of Indian origin, that can automatically adjust the focus on what a person is seeing, whether it is far away or close.
The glasses developed by researchers at University of Utah in the US contain lenses made of glycerin, a thick colourless liquid enclosed by flexible rubber-like membranes in the front and back.
The rear membrane in each lens is connected to a series of three mechanical actuators that push the membrane back and forth like a transparent piston, changing the curvature of the liquid lens and the focal length between the lens and the eye.

"Most people who get reading glasses have to put them on and take them off all the time. You don't have to do that anymore. You put these on, and it's always clear," said Carlos Mastrangelo, computer engineering professor at Utah.
The human eye has a lens inside that adjusts the focal depth depending on what you look at.
However, as people age, the lens loses its ability to change focus, which is why many people ultimately require reading glasses or bifocals to see objects up close and regular eyeglasses to see far away.

"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 said.

The lenses are placed in special eyeglass frames also invented by the group, including graduate researcher Aishwaryadev Banerjee, with electronics and a battery to control and power the actuators.
In the bridge of the glasses is a distance meter that measures 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, researchers said.
If the user then sees another object that is closer, the distance meter readjusts and tells the actuators to reshape the lens for farsightedness.

The lenses can change focus from one object to another in 14 milliseconds. A rechargeable battery in the frames could last more than 24 hours per charge, Mastrangelo said.
Before putting them on for the first time, all users have to do is input their eyeglasses prescription into an accompanying smartphone app, which then calibrates the lenses automatically via a Bluetooth connection.
Users only need to do that once except for when their prescription changes over time, and theoretically, eyeglass wearers will never have to buy another pair again since these glasses would constantly adjust to their eyesight.
Currently the team has constructed a bulky working prototype, but expect to constantly improve the design to make them smaller and lighter which could hit the marketplace in as early as three years, researchers said.

The study was published in the journal Optics Express.