Multiple scattering in optical coherence tomography I Investigation and modeling

TLDR

Existing OCT models rely on the extended Huygens–Fresnel principle and assume partially coherent interfering fields. The study introduces a new OCT model that incorporates multiple scattering. The model represents the OCT signal as a sum of spatially coherent fields with random‑phase arguments constant over measurement time, and its mean is computed using statistical optics and Monte Carlo simulation. The model’s predictions match depth‑scan measurements, and analysis shows that backscattered fields stay spatially coherent, yielding a stationary interference signal even with multiple scattering.

Abstract

We present a new model of optical coherence tomography (OCT) taking into account multiple scattering. A theoretical analysis and experimental investigation reveals that in OCT, despite multiple scattering, the field backscattered from the sample is generally spatially coherent and that the resulting interference signal with the reference field is stationary relative to measurement time. On the basis of this result, we model 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 of such a random signal from classical results of statistical optics and a Monte Carlo simulation. OCT signals predicted by our model are in very good agreement with a depth scan measurement of a sample consisting of a mirror covered with an aqueous suspension of microspheres. We discuss other comprehensive OCT models based on the extended Huygens–Fresnel principle, which rest on the assumption of partially coherent interfering fields.