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A new miniature camera could find a place in the vision systems of autonomous vehicles, onboard planes or satellites to study atmospheric chemistry, or be used to detect camouflaged objects.
Polarization, a situation in which light vibrates in one direction, is invisible to the human eye but provides a great deal of information about the objects with which it interacts. Cameras that see polarized light are currently used to detect material stress, enhance contrast for object detection, and analyze surface quality for dents or scratches.
However, current-generation polarization-sensitive cameras are bulky, they often rely on moving parts and are costly.
Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a highly compact, portable camera that can image polarization in a single shot.
Atmospheric science, remote sensing, facial recognition, machine vision are just a few of the fields in which the development could be applied.
Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering at SEAS and senior author of the paper said: “Most cameras can typically only detect the intensity and color of light but can’t see polarization. This camera is a new eye on reality, allowing us to reveal how light is reflected and transmitted by the world around us.”
“Polarization is a feature of light that is changed upon reflection off a surface,” said Paul Chevalier, a postdoctoral fellow at SEAS and co-author of the study. “Based on that change, polarization can help us in the 3-D reconstruction of an object, to estimate its depth, texture and shape, and to distinguish man-made objects from natural ones, even if they’re the same shape and color.”
To unlock that powerful world of polarization, Capasso and his team harnessed the potential of metasurfaces, nanoscale structures that interact with light at wavelength size-scales. Using a new understanding how polarized light interacts with objects, the researchers designed a metasurface that uses an array of subwavelength spaced nanopillars to direct light based on its polarization. The light then forms four images, each one showing a different aspect of the polarization. Taken together, these give a full snapshot of polarization at every pixel.
The device is about two centimeters in length and no more complicated than a camera on a smartphone.
The technology could be integrated into existing imaging systems, such as the one in your cell phone or car, enabling the widespread adoption of polarization imaging and new applications previously unforeseen, according to phys.org.