© naftemporiki.gr As the Harvard Gazette notes, the metalens controls at the same time three of the biggest “blurring” factors: focusing, astigmatism and image shifting.
Inspired by the human eye, Harvard researchers John A. Paulson School of Engineering and Applied Sciences (SEAS) developed an adaptive metalens, which is essentially a flat, electronically controlled artificial eye.
As the Harvard Gazette notes, the metalens controls at the same time three of the biggest “blurring” factors: focusing, astigmatism and image shifting.
“This research combines achievements in artificial muscle technology with metalens technology to create a metalens that can change its focus in real time just like the human eye”,
Alan Shi, senior SEAS and first author of the paper, says.
“We go a step further to develop the potential for correction of aberrations such as astigmatism and image shifting that the human eye can make from its natural”.
“This demonstrates the feasibility of built-in optical zoom and autofocus for a wide range of applications, including mobile phones, glasses and virtual and augmented reality equipment”,
says Federico Capaso, professor of Applied Physics and senior author of the paper.
“It also demonstrates the possibility of future optical microscopes, which operate fully electronically and can simultaneously correct many aberrations.”
To make the artificial eye, researchers first needed to increase the scale of the metalens. The metalenses focus on light and eliminate spherical aberrations through a dense nano-sequence; each smaller than a wavelength of light. The first metalenses were about the size of a single glitter piece.
“Because nanostructures are so small, the density of information on each lens is extremely large”,
“If you go from a 100 microns lens to a centimeter lens, you will have increased the information required to describe the lens by 10,000. Whenever we tried to increase the scale of the lens, the project file size alone was projected into gigabytes or even terabytes. “
To solve this problem, researchers have developed a new algorithm to reduce file size to make metalens compatible with the technology used to build embedded circuits.
Then the researchers needed to adapt the large metalens to an artificial muscle without diminishing its lens focusing capability.
For this reason, they chose a thin, transparent elastomer in which the light could travel without spreading too much, and adapted it to the lens.
The elastomer is controlled by the application of voltage. As it stretches, the position of the nanosets on the surface of the lens changes. The metalens can be adjusted by controlling the position of the columns with respect to the adjacent but also the overall displacement of the structures. Researchers also showed that the lens can simultaneously focus, control aberrations caused by astigmatism and cause image shifting. Together, the lens and the muscle are only 30 microns thick.
The next step for researchers is to improve lens performance and reduce the voltage needed to control it.
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