Lensless single-fiber ghost imaging.

We demonstrate lensless single-fiber ghost imaging, which allows illumination and collection using a single optical fiber without a transmission-type system. Speckle patterns with relative coincidence degrees of 0.14 were formed by image reconstruction using improved differential ghost imaging. Employing fiber with a diameter of 105 µm, we achieved a spatial resolution of 0.05 mm in an observing area of 9 , at a working distance of 10 mm. Compared to a conventional neuroendoscope at a power density of 94 / , our imaging could be realized by extremely weak illumination at a laser power density of 0.10 / . Using our lensless single-fiber ghost imaging, with 30,000 speckle patterns and implementing a diffuser, we attained an average coincidence degree of 0.45.