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Mannequin head: A 3D rendering of a mannequin head recorded through the endoscope, and observed from different angles.

Revolutionising 3D imaging with an endoscope the width of a human hair

Scientists have developed a new form of endoscope, just a hair’s width in diameter, that could transform 3D imaging for a wide range of applications from industrial inspection to environmental monitoring, and eventually make medical imaging less uncomfortable for patients.  

The pioneering new system was developed by an international team of scientists including Professor David Phillips from the University of Exeter, and led from the University of Glasgow’s Optics Group. 

The researchers have developed a new technique to record 3D video through a single multimode optical fibre, just a tenth of a millimetre in diameter, using a process known as time-of-flight 3D imaging.  

Normally, when light shines through a single optical fibre, crosstalk between modes scrambles the light to make the image unrecognisable. To resolve this, the team use advanced beam shaping techniques to pattern the input laser light to the fibre to create a single spot at the output. That spot of light then scans over the scene and the system measures the intensity of the backscattered light into another fibre - giving the brightness of each pixel in the image.  

By using a pulsed laser, they also measure the time of flight of the light and hence the range of every pixel in the image.  

These 3D images can be recorded at distances from a few tens of millimetres to several metres away from the fibre end with millimetric distance resolution and frame rates high enough to perceive motion at close to video quality. 

The study, titled ‘Time-of-flight 3D imaging through multimode optical fibres’, is published in the journal Science, on Friday, December 10th 2021. 

Professor Phillips, from Exeter’s Physics department said: “Our work delivers 3D imaging capabilities through an exceedingly narrow optical fibre, opening a window into a variety of new environments that were previously inaccessible. Future iterations of our prototype may enable the internal chambers of systems such as jet engines or nuclear reactors to be mapped and inspected in intricate detail – rendering a 3D model of their insides without even having to open them.” 

The prototype system currently delivers images through a 40 cm long optical fibre at 5 Hz, each frame containing up to approximately 4000 independently resolvable features, with a depth resolution of ∼5 mm. Currently the MMF must remain in a fixed position after calibration.  

Future research will look at reducing the calibration time and managing the dynamic nature of bending fibres – aspects that Prof. Phillips’ research group at Exeter is already focussing on: 

The team aim to work with industry to develop this world-changing research into functional technology within the next ten years. 

Professor Miles Padgett, Royal Society Research Professor at the University of Glasgow, and Principal Investigator for QuantIC the UK Hub for Quantum Enhanced Imaging, said: “Traditional endoscopes use a bundle of optical fibres, one fibre for every pixel in the image, resulting in a device as thick as a finger. As an alternative, we are developing a new type of endoscope based on a single optical fibre the width of a human hair. 

 “Our ambition is to create a new generation of single-fibre endoscopes that can produce 3D images of remote scenes. Such systems will have applications relevant to industrial and environmental inspection, and medical imaging.” 

The project is a collaboration between physicists at the University of Glasgow, University of Exeter, Fraunhofer Centre for Applied Photonics Glasgow, Leibniz Institute of Photonic Technology Germany and the Institute of Scientific Instruments of the CAS Czech Republic.  

The research was supported by funding from Engineering and Physical Sciences Research Council (EPSRC), European Research Council (ERC), The Royal Academy of Engineering, UK National Quantum Technology Programme (NQTP) and The Royal Society.  

Date: 10 December 2021

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