Enhanced signal coupling in wide-field fiber-coupled imagers.

Some high-performance imaging systems, including wide angle "monocentric" lenses made of concentric spherical shells, form a deeply curved image surface coupled to focal plane sensors by optical fiber bundles with a curved input and flat output face. However, refraction at the angled input facet limits the range of input angles, even for fiber bundles with numerical aperture 1. Here we investigate using a curved beam deflector near the focal surface to increase the field of view and improve spatial resolution at the edges of the field of view. We show the field of view of such an imager can be increased from approximately 60° (full width at half maximum intensity) to over 90° using an embossed refractive microprism array, where the prism angle varies across the aperture to maintain coupling. We describe a proof-of-principle experiment using a f = 17.8mm fiber-coupled monocentric singlet lens, and show that a local region of microprisms embossed into a thin layer of SU-8 photopolymer can increase the field of view by 50%.