Harvard researchers have developed a flat, electronically controlled artificial eye that can simultaneously controls for three of the major contributors to blurry images: focus, astigmatism, and image shift.
The study, published on Friday in the journal Science Advances, was partially inspired by how the human eye works, and has demonstrated the feasibility of embedded optical zoom and autofocus for cell phone cameras, eyeglasses and virtual and augmented reality hardware.
"This research combines breakthroughs in artificial muscle technology with metalens technology to create a tunable metalens that can change its focus in real time, just like the human eye," said Alan She, a Harvard graduate student and the paper's first author.
"We go one step further to build the capability of dynamically correcting for aberrations such as astigmatism and image shift, which the human eye cannot naturally do," She said.
Metalens is a new type of lens that can focus light and eliminate spherical aberrations through a dense pattern of nanostructures, each smaller than a wavelength of light.
Researchers have scaled up the metalenses up to centimeters or more in diameter. Also, they developed a new algorithm to cope with the massive data created by larger metalens, making it compatible with the technology currently used to fabricate integrated circuits.
"This research provides the possibility of unifying two industries: semiconductor manufacturing and lens-making, whereby the same technology used to make computer chips will be used to make metasurface-based optical components, such as lenses," said Harvard professor Federico Capasso, the senior author of the paper.
Then, researchers managed to adhere metalens to an artificial muscle without compromising its ability to focus light.
In the human eye, the lens is surrounded by ciliary muscle, which stretches or compresses the lens, changing its shape to adjust its focal length. Capasso and his team chose a thin, transparent elastomer with low loss, meaning light travels through the material with little scattering.
The elastomer is controlled by applying voltage. As it stretches, the position of nanopillars on the surface of the lens shift.
The metalens can be tuned by controlling both the position of the pillars in relation to their neighbors and the total displacement of the structures. Together, the lens and muscle are only 30 microns thick.
"Because the adaptive metalens is flat, you can correct aberrations and integrate different optical capabilities onto a single plane of control," She said.