An endoscope the thickness of a human hair: using adaptive transmission matrices to create a scanning spot at the output of a multimode fibre

We have developed a compact imaging system based on a single multimode, graded-index optical fibre approximately 120µm in diameter. Key to its operation is dynamically shaping the incoming laser beam, based on a fibre calibration, so the output forms a raster scanning spot interrogating a scene, the backscattered light from which gives the intensity of each pixel. Here we report two advances. Firstly, the dynamic switching between calibrations and secondly, the use of time-correlated, single-photon counting to give imaging in 3D.