IEEE S.F. Bay Area Council e-GRID's
BayAreaTech

TUESDAY November 4, 2014
SCV Photonics Chapter
– multi-mode, resolvable features, optimization, methods …
Speaker: Prof. Joseph M. Kahn, Stanford University
Time: Networking/Light Dinner at 6:00 PM; Presentation at 7:00 PM
Cost: none
Place: INTEL Building SC-12 Auditorium, 3600 Juliette Lane, Santa Clara
RSVP: from website
Web: ewh.ieee.org/r6/scv/leos

Image transmission through multi-mode fibers (MMFs) has long been of fundamental interest and is now being pursued vigorously for applications such as endoscopic in vivo imaging.  An endoscope using one MMF would be potentially much more compact than endoscopes employing a bundle of fibers or one fiber with a scanning head.  We experimentally demonstrate endoscopic imaging through a MMF in which the number of resolvable image features approaches four times the number of spatial modes per polarization propagating in the fiber. In our method, a sequence of random field patterns is input to the fiber, generating a sequence of random intensity patterns at the output, which are used to sample an object.  Reflected power values are returned through the fiber and linear optimization is used to reconstruct an image.  The factor-of-four resolution enhancement is due to mixing of modes by the squaring inherent in field-to-intensity conversion.  The incoherent point-spread function (PSF) at the center of the fiber output plane is an Airy disk equivalent to the coherent PSF of a conventional diffraction-limited imaging system having a numerical aperture twice that of the fiber.  All previous methods for imaging through MMF can only resolve a number of features equal to the number of modes.  Most of these methods use localized intensity patterns for sampling the object and use local image reconstruction.