SEATTLE, Sept. 16, 2025 — Ultra-flat optics have immense potential for imaging technologies, but chromatic aberration has hindered the technology’s ability to produce high-quality color images when the optic has a large aperture. According to researchers, the limitation has been seen by many as an impassable barrier.

A team at the University of Washington, working with Princeton University’s computer science department, showed that a camera containing a large aperture, ultra-flat optic can record high-quality color images and video comparable to what can be captured using a conventional camera lens. The work challenges a commonly held belief that sharp, full-color imaging would be impossible using a single, large-aperture metalens.

The lens developed by the team is just one micron thick. Affixed to its supporting substrate, it is still only 300 μm thick — about the width of four human hairs laid side by side. Altogether, it’s hundreds of times smaller and thinner than a standard refractive lens, meaning substantial savings in volume, weight, and battery life.

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An illustrative comparison of a standard refractive lens next to an ultra-flat optic developed by the research team. The ultra-flat optic is hundreds of times smaller and thinner. When this metalens replaces a conventional camera lens or stack of lenses, the savings in volume, weight, and device battery life can be substantial. Courtesy of Princeton University/Liz Sabol.

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“Previously, it was assumed that the larger the metalens is, the fewer the colors there are that can be focused,” said Johannes Fröch, an assistant professor at the University of Washington. “But we went beyond that and beat the limit.”

“We treated this as a holistic system,” said Praneeth Chakravarthula, an assistant professor of computer science at the University of North Carolina. “That allowed us to leverage the complementary strengths of optics and computation, where we didn't design these different parts of the imaging system sequentially, but instead, we jointly optimized them to maximize performance.”

Most earlier efforts with metalenses were working with camera apertures that were less than one millimeter in size. In comparison, the aperture in the camera the research team engineered is one centimeter in size, significantly larger. The team demonstrated that with a strong computational backend co-designed with the optical hardware, even larger apertures are possible.

“People have tried purely physics-based or heuristic, handcrafted optical designs to address this issue, but in our work, we treat it as a computational problem,” Chakravarthula said. “We used AI tools to figure out what should be the shape of these lens structures and what should be the corresponding computation.”

The computational backend of the team's optical system incorporated a probabilistic diffusion-based neural network. This AI-powered backend takes in the data received from the ultra-flat optic and outputs images with lower haze, better color accuracy, more vivid hues, and better noise reduction. This all results in high-quality color images that are almost indistinguishable from what can be captured with a conventional camera.

“Previously, I was always considering problems from the optical side of the system,” Fröch said. “But this project really showed me that if you consider the whole system and then try to leverage the strength of each part — the optics and the computational backend — they can work synergistically to produce this really good image quality that we've shown here.”

Next steps for the research team include further refining and improving image quality produced by their ultra-flat optic. Team members are also planning to explore different modalities for the optical system they developed that could be useful for augmenting human vision. These modalities involve capturing and working with information from light that is beyond what is visible to the human eye.

Commercialization of this ultra-flat optic is also a distinct possibility in the near future. Metalenses are suitable for mass manufacturing in foundries using nanoimprint lithography, which makes the optics affordable and scalable. The team is currently talking with a University of Washington professor in the ophthalmology department, who is interested in creating small, lightweight, hand-held devices that would be easier to use for eye inspections.

Fröch also said there are startups that might be interested in commercializing this technology. He noted as well that the team's research could open new avenues for others in the field of optics to explore.

The research was published in Nature Communications (www.doi.org/10.1038/s41467-025-58208-4).

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