Optical coherence tomography speckle reduction by a partially spatially coherent source

Speckle in optical coherence tomography ( OCT ) images originates in the high spatial coherence of incident light that enables interference of light backscattered from spatially heterogenous tissue specimens. We report results of a numerical simulation and an experiment to test speckle reduction using a partially spatially coherent source. A Gaussian- Schell model for a partially spatially coherent source is used in the OCT simulation. For the experiment, such a source was generated by a spatially coherent boardband light source and a multimode fiber. The advantage of using a multimode fiber in combination with a broadband source is the large number of photons per coherence volume. To illustrate speckle reduction with a partially spatially coherent source, we record low- coherence interferograms of a scattering surface using single- mode and multimode source fibers. Interferograms recorded using a single- mode source fiber are indicative of those observed using conventional OCT. Speckle in OCT images recorded using a multimode source fiber is substantially reduced. (C) 2005 Society of Photo- Optical Instrumentation Engineers.