This new metalens can focus and make adjustments for blurriness in real-time. This new lens has similar behavior as the human eye. (Image credit: SEAS)


Researchers at Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) may have just hit a breakthrough in artificial eye technology. The team has developed an adaptive metalens that acts similarly to the human eye. The lens has the ability to focus in real-time and even adjust for astigmatism and image shift, which often leads to blurry vision.


The design of the new flat lens takes full advantage of a metalens, which uses tiny nanostructures to focus light and eliminate spherical aberrations. For comparison, traditional lenses use various elements to achieve the same results, which is why they’re often bulky. During development, the team ran into issues when trying to scale up the lens – the file size would often be big enough to eat up gigabytes and terabytes.


“Because the nanostructures are so small, the density of information in each lens is incredibly high,” said Alan She, an SEAS graduated student at the Graduate School of Arts and Sciences and one of the authors of the paper. “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.”


So how did they solve this problem? They had to develop a new algorithm to reduce the file size in order to make the metalens work with the current technology used to create integrated circuits. After this, they were able to create a metalens that measures up to one centimeter in diameter, which makes it more ideal to be used in different applications.


The next step involved the metalens being applied to an artificial muscle without affecting its ability to focus light. In order to replicate the human eye’s ciliary muscles, which stretches or compresses the lens, the team chose a thin, transparent dielectric elastomer with low loss to attach to the lens. Applying voltage let them control the elastomer. 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. The researchers also showed how the lens can simultaneously focus, control aberrations caused by astigmatisms, and perform image shift.


“All-optical systems with multiple components — from cameras to microscopes and telescopes — have slight misalignments or mechanical stresses on their components, depending on the way they were built and their current environment, that will always cause small amounts of astigmatism and other aberrations, which could be corrected by an adaptive optical element,” said She. “Because the adaptive metalens is flat, you can correct those aberrations and integrate different optical capabilities onto a single plane of control.”


The new lens is showing great promise, but won’t make its way to consumer gadgets any time soon. Still, there’s no denying its potential. The researchers believe features like the embedded optical zoom and the autofocus could easily be applied to cellphone cameras, eyeglasses, and even virtual and augmented reality hardware. Researchers plan on further improving the functionality of the lens and decrease the voltage needed to control it.


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