Researchers from MIT and the University of Massachusetts Lowell created a flat fish eye lens. Traditional fish eye lenses have a spherical and multipiece design, which makes them bulky and expensive to produce.
The team’s new wide-angle lens can produce a crisp 180 degree image. The design is a metalens, a wafer-thin material patterned with microscopic features that work together to manipulate light. The new lens is made of a single, flat, millimeter thin piece of glass. One side of the glass is covered with tiny structures that scatter incoming light to create panoramic images.
3D artistic illustration of the wide-field-of-view metalens capturing a 180° panorama of MIT's Killian Court and producing a high-resolution monochromatic flat image. Source: Mikhail Shalaginov, Tian Gu, Christine Daniloff, Felice Hankel, Juejun Hu
The metalens is largely still in the experimental phase, but it has the potential to reshape the field of optics. Expanding a metalens field of view would typically need additional optical components to correct image issues, which adds bulk to the lens.
The team’s simple design doesn’t need additional components, eliminating the extra bulk. The new metalens is a single transparent piece of calcium fluoride with a thin film of lead telluride deposited on one side. The team used lithographic techniques to carve a pattern of optical structures into the film. The structures are shaped into one of several nanoscale geometries that reflect light in a specific way.
In a conventional fish-eye lens, the glass has a curve that naturally creates a distribution of phase delays and produces a panoramic image. The team found that etching a corresponding pattern of metatoms into the back of the flat glass created the same effect. The front of the glass has an optical aperture. Light comes through the surface of the lens, refracts onto the first surface and is angularly dispersed, creating new angles and producing a fish eye effect.
To demonstrate the new lens, the team tuned it to operate in the mid-infrared region of the light spectrum. They used an imaging set up equipped with a metalens to take pictures of a striped target. The pictures were compared to the same photos but taken with a conventional fisheye lens. Results of this proved that the new lens produced images that were crisp and clear, even at the edges.
The new lens works on the infrared spectrum, but the team says it could be modified to use visible light and other wavelengths. The general architecture of the lens would stay the same, but the lens material and optical features would be made larger or smaller, depending on the desired wavelength.
A paper on this technology was published in NanoLetters.
