Flat fisheye metalens produces 180-degree panoramic images

September 21, 2020 //By Nick Flaherty
Flat fisheye metalens produces 180-degree panoramic images
Researchers at MIT have used a metamaterial to produce an ultra-wide angle fisheye lens that is completely flat, allowing 180º panoramic images.

For the fisheye lens, the team at MIT and the University of Massachusetts at Lowell used a thin glass sheet etched with nanostructures that scatter incoming light to produce panoramic images. The lens works in the infrared part of the spectrum, but the researchers say it could be modified to capture images using visible light as well.

The design could be used in smartphones and laptops as well as medical imaging devices such as endoscopes, as well as in virtual reality glasses, wearable electronics, and other computer vision devices.

“This design comes as somewhat of a surprise, because some have thought it would be impossible to make a metalens with an ultra-wide-field view,” said Juejun Hu, associate professor in MIT’s Department of Materials Science and Engineering. “The fact that this can actually realize fisheye images is completely outside expectation.”

The metalens is a single transparent piece made from calcium fluoride with a thin film of lead telluride deposited on one side. The team then used lithographic techniques to etch the optical structures into the film that operate with 5.2micron IR light.

Each structure is shaped into one of several nanoscale geometries, such as a rectangular or a bone-shaped configuration, to produce a phase delay.

In conventional fisheye lenses, the curvature of the glass naturally creates a distribution of phase delays that ultimately produces a panoramic image. The team determined the corresponding pattern of meta-atoms and carved this pattern into the back side of the flat glass.

‘We’ve designed the back side structures in such a way that each part can produce a perfect focus,” said Hu.

To make a similar flat fisheye lens for visible light the optical features may have to be made smaller than they are now, to better refract that particular range of wavelengths. The lens material would also have to change. But the general architecture that the team has designed would remain the same.

The researchers are

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