This sphere of optical fibers, 30 centimeters in diameter, senses light from all directions; software then builds a 3-D image. (Courtesy of Greg Hren)

What would it be like to have eyes in the back, sides, and top of your head? Researchers at MIT have built a spherical optical system that can record images from all directions. Photons strike the sphere's network of 900-micrometer­wide polymer and glass composite fibers and penetrate a transparent cladding to a photosensitive semiconductor material at the fiber's core. An algorithm analyzes the resulting signal and constructs an omnidirectional image; it can also pinpoint the direction of a light beam based on where it entered and exited the sphere. For now, the prototype is used mainly to test materials that can at least crudely discern surrounding objects and thus might be useful in soldiers' uniforms. The researchers are working on algorithms that build clear images even if the sensors take unusual shapes, as they would when integrated into clothing. Future applications could include surveillance, with a sphere replacing multiple cameras. Ayman Abouraddy of MIT's Research Lab of Electronics says his team, directed by materials scientist Yoel Fink, expects to have a prototype of an optical-fiber mesh--using fibers 200 micrometers wide--next year.

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