Flat Lens capable beyond human vision

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A group of scientists developed an electronic flat lens that has capabilities better than the human eye. This breakthrough could revolutionize optical technologies like cameras, eyeglasses, and telescopes, and aid human vision conditions like astigmatism.

Researchers from Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) harnessed the capabilities of recent developments in artificial muscle and flat lens technologies to develop the electronic lens that functions closely like the human eye.

This electronic lens has the capability of elastomer muscle, which allows the lens to focus in almost real-time. And, it also does some things the human eye can’t, including adjusting for astigmatism and image shift.

Photo: The Harvard Gazette

“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 SEAS graduate student at the Graduate School of Arts and Sciences, and first author of the paper.

“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 added.

Researchers believe that the new breakthrough ushers a wide range of applications in optical technology.

“This 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,” said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior author of the paper.

“It also shows the possibility of future optical microscopes, which operate fully electronically and can correct many aberrations simultaneously.”

One primary feature of the newly developed lenses is its flatness, which relied on the earlier breakthrough made by some members of the current team.

The flat lens design used in this new breakthrough was earlier developed by the same team called the “metalens.” It uses tiny nanostructures to focus light.

In this way, it’s able to focus the entire visible light spectrum at a single point. Traditional lenses that are available in the market right now use multiple elements to achieve this kind of capability, making them bulky rather than flat.

Photo: The Harvard Gazette

Metalenses, focus light and eliminate spherical aberrations through a dense pattern of nanostructures, each smaller than a wavelength of light.

In the past, the SEAS scientists said that they were only able to manufacture metalenses in “the size of a piece of glitter.” However, with their new development, they were able to find a way to make their lenses bigger and larger at approximately one centimeter in diameter. The researchers said that in this context, “bigger is better” because they can now apply the lense in other technologies like cameras, telescopes, and other optics-based equipment. In cameras, for example, the lenses need to be big enough to cover the entire sensor to prevent vignetting.

“Because the nanostructures are so small, the density of information in each lens is incredibly high,” said She. “If you go from a 100 micron-size lens to a centimeter sized 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.”

In order to resolve the gap in the science behind the technology, the researchers developed a new algorithm to shrink the file size to make the metalens 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 Capasso.

Because of the new algorithm and a series of other processes developed by the researchers, the lens and muscle are only 30 microns thick.

Nonetheless, this is not the end of the development for the team as they have hopes to improve the lenses in the future. Much like any other new breakthroughs, it will take a considerable amount of time before the new lenses become available commercially. For now, the researchers hope to improve the functionality of the lens further and decrease the voltage required to control it.

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