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Scientists see the light, then capture it
Move over digital cameras. Imaging with special light-detecting fibres may be on its way.
Researchers from the Massachusetts Institute of Technology (MIT) have developed a crisscrossing web of transparent fibres that senses the direction, intensity and phase of light in 3D.
It does this without lenses, filters or detector arrays typically used for the task.
The lightweight fibres could be used to make space telescopes that unfurl sail-like imagers, say the scientists.
Alternatively, interactive computer screens made with the fibres could respond to light instead of mouse clicks.
And fibres in electronic clothing could one-day sense the environment better than the wearer.
"We have shown already that these very simple fibre arrays can extract images without a lens," says Yoel Fink, an associate professor of materials science at MIT.
Fink, with postdoctoral associate Ayman Abouraddy and colleagues, publish the results in the latest issue of the journal Nature Materials.
In conventional imaging systems, the lens is a crucial component, as it focuses the light onto the detector surface, whether that is a light-sensitive film or computer chip.
But in Fink's system, a software algorithm does the work of the lens after light hits the photo-detecting fibres.
"It's a completely new way of doing things," says Eli Yablonovitch, professor of electrical engineering at University of California, Los Angeles.
Fibres have three elements
The fibres are 1 millimetre in diameter and have three elements: a semiconducting core flanked by metal conductors, all encircled in an insulating shell of a polymer.
Weaving the fibres together produces a screen-like product with unique coordinates for each location where two fibres intersect.
With this method, scientists can pinpoint where on the grid light is shining.
Placing one screen in front of another, or forming one screen into a sphere as the team did in laboratory tests, provides even more detail.
Light passes through a coordinate on the facing screen and through another coordinate behind. So the scientists determine where the light came from by drawing an imaginary line through the two coordinates.
At the same time, the fibre is collecting information about the light, including its intensity and the frequency of the light waves.
A software algorithm then calculates how the light would change if it passed through a lens and uses the answer to generate a picture of the light's source.
Light from all directions
Whereas conventional imaging systems have a limited field of view, Fink's system can sense light coming from all directions.
"The beauty of this is that they are able to make this three-dimensional detection and to do so with an object that is essentially transparent," says Malvin Teisch, professor of physics and electrical and computing engineering at Boston University.
Fink's team is working on fibres that can sense a wider range of light wavelengths, to produce colour images, as well as ones that can read heat and sound.
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