Focusing problem in OCT: comparison of Monte-Carlo simulations, the extended Huygens-Fresnel principle, and experiments

Andreas Tycho; Thomas Martini Joergensen; Lars Thrane

doi:10.1117/12.384168

28 April 2000 Focusing problem in OCT: comparison of Monte-Carlo simulations, the extended Huygens-Fresnel principle, and experiments

Andreas Tycho, Thomas Martini Joergensen, Lars Thrane

Author Affiliations +

Proceedings Volume 3915, Coherence Domain Optical Methods in Biomedical Science and Clinical Applications IV; (2000) https://doi.org/10.1117/12.384168
Event: BiOS 2000 The International Symposium on Biomedical Optics, 2000, San Jose, CA, United States

Abstract

In the later years, a great effort has ben put into simulation of the geometry of an optical coherence tomography (OCT) system. Recently, a new analytical model of the OCT geometry has been developed based on the extended Huygens-Fresnel (EHF) principle. Although advanced, the result of the model are surprisingly simple and easy to handle for e.g. system optimization. To validate this model, new features have been added to the Monte Carlo (MC) simulation program MCML, which is widely used and recognized for its credibility. We have incorporated the true shape of a focused Gaussian beam including the finite size of the beam waist, which previously has been approximated by a point. This enables us to do high-resolution comparison of the intensity distribution in the focus plane and excellent agreement is found between the EHF model and the MC simulations. Results are also compared with previously published modeling result and it is shown that there are substantial differences. We emphasize the importance of the so-called shower curtain effect (SCE), which is an inherent - but often overlooked - effect in light propagation through random media. Finally, we calculate the OCT signal using MC simulation. This is done by keeping track of the path length traveled by each photon packet and restricting its access back into the OCT system from the sample using the antenna theorem. The degradation of the detected signal due to scattering is determined, and compared with the EHF model and experiments. The comparison of MC simulations with EHF allows us to show that the SCE is an inherent effect in MC simulation, and that for common tissue parameters, the EHF model yields the same results as the MC simulation but with faster computation time and with field and phase information available.

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Andreas Tycho, Thomas Martini Joergensen, and Lars Thrane "Focusing problem in OCT: comparison of Monte-Carlo simulations, the extended Huygens-Fresnel principle, and experiments", Proc. SPIE 3915, Coherence Domain Optical Methods in Biomedical Science and Clinical Applications IV, (28 April 2000); https://doi.org/10.1117/12.384168

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