Bundles of the fibres could be fed through pipes and immersed in fluids, to image oil fields, aquifers, or plumbing, without risking damage to watertight housings. And tight bundles of the fibres could yield endoscopes with narrower diameters, since they would require no additional electronics.
The researchers say that the positions of the fibres’ free ends don’t need to correspond to the positions of the photodetectors in the array. By measuring time of flight the device can determine the fibres’ relative locations.
Barmak Heshmat, from the Camera Culture group at the Media Lab, said: “Previous works have used time of flight to extract depth information. But in this work, I was proposing to use time of flight to enable a new interface for imaging.”
In their experiments, the researchers used a bundle of 1100 fibres positioned opposite a screen on which symbols were projected. The other end of the bundle was attached to a beam splitter, which was in turn connected to both an ordinary camera and a high-speed camera that can distinguish the optical pulses’ times of arrival.
Perpendicular to the tips of the fibres at the bundle’s loose end, and to each other, were two ultrafast lasers. The lasers fired short bursts of light, and the high-speed camera recorded their time of arrival along each fibre.
Because the bursts of light came from two different directions, the software used the differences in arrival time to produce a two-dimensional map of the positions of the fibres’ tips. It then used that information to unscramble the jumbled image captured by the conventional camera.
The resolution of the system is limited by the number of fibres; the 1100-fiber prototype produces an image that’s roughly 33 x 33 pixels. Because there’s also some ambiguity in the image reconstruction process, the images produced in the researchers’ experiments are blurry.
For their prototype, the researchers used off-the-shelf optical fibres that were 300µm in diameter. Fibres a few micrometers in diameter have been commercially manufactured, the scientists claim that the resolution could increase without increasing the bundle size for industrial applications.