I find this line of research into lenses quite interesting because it promises to one day replace the thick bulky curved lenses we use today with light-weight flat ones.
https://phys.org/news/2021-01-millimeter-size-flat-lens-vr-ar.html
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Despite all the advances in consumer technology over the past decades, one component has remained frustratingly stagnant: the optical lens. Unlike electronic devices, which have gotten smaller and more efficient over the years, the design and underlying physics of today's optical lenses haven't changed much in about 3,000 years.
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a team of researchers ... has been developing the next generation of lenses that promise to open that bottleneck by replacing bulky curved lenses with a simple, flat surface that uses nanostructures to focus light.
In 2018, the Capasso's team developed achromatic, aberration-free metalenses that work across the entire visible spectrum of light. But these lenses were only tens of microns in diameter, too small for practical use in VR and augmented reality systems.
Now, the researchers have developed a two-millimeter achromatic metalenses that can focus RGB (red, blue, green) colors without aberrations
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