February 12, 2016

Imaging with an “optical brush”

The fibers of a new “optical brush” are connected to an array of photosensors
at one end and left to wave free at the other. Image: Barmak Heshmat

(February 12, 2016)  New imaging system uses an open-ended bundle of optical fibers — no lenses, protective housing needed.

Researchers at the MIT Media Lab have developed a new imaging device that consists of a loose bundle of optical fibers, with no need for lenses or a protective housing.

The fibers are connected to an array of photosensors at one end; the other ends can be left to wave free, so they could pass individually through micrometer-scale gaps in a porous membrane, to image whatever is on the other side.

Bundles of the fibers 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 fibers could yield endoscopes with narrower diameters, since they would require no additional electronics.

From left to right: patterns used to test the imaging system; the raw image from the
shuffled fibers; the reconstruction performed by the researchers’ algorithm;
and a comparison of the reconstruction with an ideal reconstruction. Image: Barmak Heshmat

The positions of the fibers’ free ends don’t need to correspond to the positions of the photodetectors in the array. By measuring the differing times at which short bursts of light reach the photodetectors — a technique known as “time of flight” — the device can determine the fibers’ relative locations.

In a commercial version of the device, the calibrating bursts of light would be delivered by the fibers themselves, but in experiments with their prototype system, the researchers used external lasers.

“Time of flight, which is a technique that is broadly used in our group, has never been used to do such things,” says Barmak Heshmat, a postdoc in the Camera Culture group at the Media Lab, who led the new work. “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.”

The researchers reported their results today in Nature Scientific Reports. Heshmat is first author on the paper, and he’s joined by associate professor of media arts and sciences Ramesh Raskar, who leads the Media Lab’s Camera Culture group, and by Ik Hyun Lee, a fellow postdoc.

Travel time

In their experiments, the researchers used a bundle of 1,100 fibers that were waving free at one end and 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 optical pulses’ times of arrival.

read entire press  release >>

journal reference (Open Access) >>