The next generation of imaging technology could be right around the corner … led by a single optical fiber that is about the width of a human hair.
An international team led by the University of Glasgow (Scotland) has developed a new imaging technique that can create video images via a single multimode optical fiber. It also employs time-of-flight 3D imaging, which touts applications such as environmental monitoring and motion tracking—according to the study, published in Science, “depth is recovered by measuring the round-trip flight time of laser pulses, typically using collection optics several centimeters in diameter.”
“Our ambition is to create a new generation of single-fiber imaging devices that can produce 3D images of remote scenes,” says Miles Padgett, a Royal Society research professor at the University of Glasgow and principal investigator for QuantIC, the UK Hub for Quantum Enhanced Imaging.
Communication exchanges between light modes typically scramble any light shining through a single optical fiber when imaging, rendering the image unrecognizable. The Glasgow-led team—which includes physicists from the University of Exeter, Fraunhofer Centre for Applied Photonics (Glasgow), Leibniz Institute of Photonic Technology (Germany), and Brno University of Technology (Czech Republic)—has been able to resolve this, thanks to advanced beam shaping techniques. According to the researchers, it allowed them to “pattern the input laser light to the fiber to create a single spot at the output.” That spot of light, in turn, can scan the scene as the system measures the intensity of the backscattered light into another fiber; this provides brightness for each pixel in the image.
“In applications like endoscopy and boroscopy, imaging is traditionally achieved by using a bundle of optical fibers—one fiber for every pixel in the image, resulting in devices the thickness of a finger,” Padgett says. In their study, he and fellow researchers essentially demonstrated “near-video-rate 3D imaging through multimode fibers with a total aperture of several hundred micrometers.”
The researchers used a pulsed laser in part of their work, allowing them to measure the light’s time of flight as well as the range of every pixel in the image. They also implemented aberration correction via wavefront shaping synchronized with a pulsed source to scan the scene at ~23,000 points per second. They note in the study that they were able to image “moving objects several meters beyond the end of a ~40-cm-long fiber of 50-µm core diameter at frame rates of ~5 Hz.” In their prototype system, each frame contains up to “approximately 4000 independently resolvable features, with a depth resolution of ~5 mm.”
Specifically, the team recorded the 3D images at distances ranging from “a few tens of millimeters to several meters away from the fiber end with millimetric distance resolution and frame rates high enough to perceive motion at close-to-video quality.”
The researchers will next aim to reduce the calibration time and manage “the dynamic nature of bending fibers.”
