Friday, July 28, 2006

Light-Sensing Fibers for Transparent Cameras

Continued from page 1

By Kevin Bullis

A simple manufacturing process makes the fibers inexpensive, and thus it could be practical to cover large areas with them -- even the outside of buildings. The fibers begin as a "preform," a long cylinder about as thick as a spray-paint can that has the same structure (core, electrode, and polymer) as the finished product, only with a much larger diameter. The preform is then heated and pulled into kilometers-long fibers as thin as a tenth of a millimeter. In developing this method, the researchers had to find materials that could be drawn into thin fibers at the same temperature without coming apart. The metal electrodes actually melt during the process, but stay in place, contained by the polymer and glass.

The fiber grids are ready now for early single-point light detection applications, such as being woven into soldier's uniforms to detect laser sightings by snipers (see "Material Alert"). They can also be tuned to detect heat, helping medics locate wounds. "There's no more research that needs to go in for this to go into clothes," Abouraddy says. "A lot of things you see in papers, there's a distance between what you see in the paper and the application. With these fibers, there's no distance, this is how they would look." Another relatively early application could be incorporating the fibers into computer screens, allowing speakers giving presentations or video-game players to control their computers with a laser pointer.

But Abouraddy says work still needs to be done to make the scene-imaging capabilities practical. For example, the resolution of the images is limited by the need to space the fibers within the grid far enough apart that the first grid does not distort the image received by the second. The grids themselves also need to be separated, which could make the current system difficult to incorporate into some applications, such as on the skin of a car, where keeping the grids at a distance wouldn't be practical. But the researchers say work is currently being done that could overcome these limitations.