A semi-analytical model accounting for multiple scattering in optical coherence tomography

We present a semi-analytical model of optical coherence tomography (OCT) taking into account multiple scattering. The model rests on the assumptions that the measured portion of the backscattered sample field is spatially coherent and that the sample is motionless relative to measurement time. This allows modeling an OCT signal as a sum of spatially coherent fields with random phase arguments-constant during measurement time-caused by multiple scattering. We calculate the mean OCT signal from classical results of statistical optics and a Monte Carlo simulation. Our model is shown to be in very good agreement with a whole range of experimental data gathered in a comprehensive study of cross-talk in wide-field OCT realized with spatially coherent illumination. The study consists of depth scan measurements of a mirror covered with an aqueous suspension of microspheres. We investigate the dependence of cross-talk on important optical system parameters, as well as on some relevant sample properties. We discuss the more complex OCT models based on the extended Huygens-Fresnel principle, which rest on different assumptions since they assume partially coherent interfering fields.