Image-sensing fabrics may lead to cameras you wear

Image-sensing fabrics may lead to cameras you wear

Researchers create flexible, lensless imagerfrom a web of light-detecting fibers

Researchers at the Massachusetts Institute of Technology in Cambridge, MA, have developed light-detecting fibers that, when woven into a web, act as a flexible camera. The researchers, led by Associate Professor Yoel Fink of MIT’s Department of Materials Science and Engineering, say that work is rapidly progressing on developing fabrics capable of capturing images and have reported using such a fiber web to take a rudimentary picture of a smiley face.

“This is the first time that anybody has demonstrated that a single plane of fibers, or ‘fabric,’ can collect images just like a camera but without a lens,” said Fink. While lenses have a limited field of view and are susceptible to damage, optical fiber webs provide a distributed imaging capability by using the entire surface of a fabric, which is in principle much more robust if one area is damaged, other fibers can still function, extracting the image.

Drawn sensing fibers

Less than a millimeter in diameter, the imaging fibers are composed of layers of light-detecting materials nested one within another (see figure ). The layers include two rings of a semiconductor glass that are light sensitive. Four metal electrodes contact each rings along the length of the fiber, and each ring with its attached electrodes is encased in a polymer insulator with a diameter of 25 mm, controlling the sensor’s spacing and angle within the fiber.

MIT’s imaging fibers are made of two rings of semiconductor sensors that encircle a preform core. The components are encapsulated in a polymer insulator.

Once the sensors are in position, the polymer cylinder is heated and stretched using a process that is identical to the way in which commercial fiber is made for telecommunication applications. The resultant fiber has a diameter of hundreds of micrometers while retaining the orientation of the sensors. The process can produce many meters of fiber.

The individual fibers measure the intensity of the light illuminating them and convert it to a proportional electrical signal. The fibers are also sensitive to light at different wavelengths, and so can distinguish color. A mesh of fibers is then deployed to measure light intensity distribution at different wavelengths across a large area.

Happy days

The researchers demonstrated their approach’s imaging capability by placing an object — a smiley face — between a light source and a small swatch of fabric composed of the fibers. The electrodes from the fibers were then connected to an external amplifier and a computer. The smiley face was illuminated with light at two separate wavelengths. This generated a distinct pattern on the fabric mesh that was then fed into a computer. An algorithm processes the data to create a black-and-white image of the object on a computer screen.

According to researcher Fabien Sorin, as the individual fibers become more sophisticated, it is possible to envision fabrics with more intriguing and complex functionalities, such as ones capable of producing crisper images in color. Although applications aren’t yet well defined, Fink suggests that such a fiber-based camera could be used in a large foldable telescope or integrated into soldiers’ uniforms uniforms made of such a fabric would allow soldiers to look in all directions and identify threats that are off to their side or even behind them.

The work was supported by the Army Research Office through the Institute for Soldier Nanotechnologies, the National Science Foundation through the Materials Research Science and Engineering Center Program, the Defense Advanced Research Projects Agency, and the Department of Energy. For further information, contact Yoel Fink by e-mail at yoel@mit.edu.

Richard Comerford