With fibers roughly the width of a human hair, researchers created a 3D imaging system that holds many potential applications, they say, ranging from remote inspection of small or dangerous machines to a miniaturized and minimally invasive endoscopic tool. Their report provides a proof-of-concept prototype for a 3D imaging system that uses multimode optic fibers (MMFs) instead of the traditional bulk optics. MMFs are extremely efficient at transporting light and are designed to carry thousands of light rays, or modes, each of which can act as independent information channels within a very small area. Because of these characteristics, there is a great deal of interest in using MMFs in new, high-resolution 3D imaging systems, as previous techniques often require a collection of optics at least several centimeters in diameter. One way to reconstruct a 3D scene – a process known as time-of-flight 3D imaging – is through lasers. Pulses of light are sent out and the distance or depth to a point in space can be determined by how long it takes for the pulse to be reflected. Many fixed points can be used to recreate a 3D scene. However, creating such systems using MMFs has been challenging as optical signals are subject to scrambling, which distorts resulting images. In their new study, Daan Stellinga et al. overcame these limitations. After characterizing the transmission matrix of an MMF, the authors developed a 3D imaging system capable of scanning a scene at nearly 23,000 points per second with depths as far as several meters beyond the end of a ~40-centimeter-long fiber. The system also was able to record near-real-time 3D video at a frame rate of nearly 5 hertz.
Time of flight 3D imaging through multimode optical fibres
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