Distribution of exit angles of diffuse-reflected photons


Aksel E., Akin A.

Conference on Optical Tomography and Spectroscopy of Tissue VI, California, United States Of America, 23 - 26 January 2005, vol.5693, pp.102-110 identifier identifier

  • Publication Type: Conference Paper / Full Text
  • Volume: 5693
  • Doi Number: 10.1117/12.590369
  • City: California
  • Country: United States Of America
  • Page Numbers: pp.102-110

Abstract

In this work, 2D and 3D distribution of exit angles of diffuse-reflected photons from a semi-infinite, homogeneous slab are obtained by Monte-Carlo simulations. During simulations, a single point source emits incident photons normally onto the slab. For the calculation of exit angles, we consider the exit angles from a hemisphere with a varying radius. Hemispheres are distributed on the upper side of the slab for reflectance geometry. In both 2D and 3D cases, only photons exiting the slab through bases of hemispheres are considered. As a photon intersects the hemisphere surface, exit angles of the photon with respect to a spherical coordinate system whose origin is on the center of base of the hemisphere are recorded. In the 2D case, projection of the direction of exit of a photon onto upper surface of the slab is tallied hence only a single exit angle (polar angle) with respect to a polar coordinate system is considered. In the 3D case however, two exit angles, namely polar and azimuth angles, are recorded. Our results show that, in both 2D and 3D distribution of exit angles of diffuse-reflected photons have similar patterns for all hemispheres. The distributions of exit angles are observed to aggregate on angles away from the source. This property is preserved independent of the hemisphere position with respect to the point source.