Artificial eye can simultaneously control focus, astigmatism, and image shift

March 06, 2018 // By Rich Pell
Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (Cambridge, MA) have developed what they say is essentially a flat, electronically controlled artificial eye that can perform focal length tuning, as well as on-the-fly astigmatism and image shift corrections, which until now were only possible in electron optics.

To create the artificial eye, the researchers combined a metalens - a lens made from an engineered material not found in nature - and artificial muscle technology. The result is an adaptive, tunable metalens that can change its focus in real time - just like the human eye, say the researchers.

However, says Alan She, an SEAS graduate student at the Graduate School of Arts and Sciences, and first author of a paper on the research, "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.” The resulting adaptive metalens can simultaneously control for three of the major contributors to blurry images: focus, astigmatism, and image shift.

This, say the researchers, demonstrates the feasibility of embedded optical zoom and autofocus for a wide range of applications, including cell phone cameras, eyeglasses, and virtual and augmented reality hardware. In addition it shows the possibility of future optical microscopes that fully operate electronically, and compact optical systems that use the principles of adaptive optics to correct many orders of aberrations simultaneously.

Metalenses focus light and eliminate spherical aberrations through a dense pattern of nanostructures, each smaller than a wavelength of light. Earlier metalenses were about the size of a single piece of glitter, and to create their adaptive metalens, the researchers needed to find a way to scale up the metalens.

"Because the nanostructures are so small, the density of information in each lens is incredibly high," says She. "If you go from a 100 micron-size lens to a centimeter-size lens, you will have increased the information required to describe the lens by 10,000. Whenever we tried to scale up the lens, the file size of the design alone would balloon up to gigabytes or even terabytes."

Ultimately the researchers developed a new algorithm to shrink the file size to make the metalens compatible with