Flexible Sheet Cameras

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The researchers say that their new sheet camera can be wrapped around everyday objects, allowing capture of images that cannot be taken with one or more conventional cameras. [Credit: Columbia Computer Vision Laboratory]

Shree Nayar, Daniel Sims and Yonghao Yue of Colombia University, N.Y., USA, will present what they describe as a novel flexible lens array design for a sheet camera next month at the International Conference on Computational Photography at Northwestern University, Ill., USA. According to the team, the array passively adapts to bending, correcting the lens optics and allowing for the capture of sharp images from varying fields of view. Although the researchers must still create the image sensors for the proposed sheet camera, their work on the optical system needed to form images on such sensors is, they report, moving the concept closer to reality. 

Intrinsic optical adaptation

The sheet camera concept, dubbed “flex-cam,” requires two optics technologies: a thin optical system that projects sharp images onto a flexible image sensor array. Nayar’s team chose to tackle the design of the optical system first, saving the sensor array for later.

The engineers’ biggest challenge was designing an optical system with a lens array that could optically adapt to the thin, flexible camera format. An array made out of small, hard lenses would have gaps between the lenses when the flex-cam is bent, resulting in incomplete scene sampling and aliasing artifacts. To overcome this challenge, they used silicone rubber to fabricate a 33 x 33 prototype array of plano-convex lenses.

The stretchy silicone allows the focal length of each lens in the array to change independently whenever the flex-cam bends. And because the focal-length adaptation happens automatically, there is no need for additional mechanisms that would spoil the sleek flex-cam design. After calculating the lenses’ optical axes for different flex-cam deformations, the engineers were able to demonstrate that the array could produce high-quality images free from aliasing artifacts and with different fields of view.

Next steps

Nayar says: “The adaptive lens array we have developed is an important step towards making the concept of flexible sheet cameras viable. The next step will be to develop large-format detector arrays to go with the deformable lens array.”

The researchers suggest that if flex-cams can be made at a low cost, they could be used to image the world in ways not achievable with conventional cameras and could enable any surface to capture visual information.

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