The images below are visualizations of the average path taken by photons as they move from the source to the detector. The sample is a homogeneous slab 0.5 cm thick, irradiated by an infinitely thin laser in the center. The material has an absorption coefficient of 10 cm-1 and a scattering coefficient of 90 cm-1. The anisotropy factor "g" = 0.75, so this material scatters light predominately in the forward direction. ( g = average of the cosine of the scattering angle )
The images are not exactly cross-sections through the slab, rather, they are plots of the log of photon intensity versus radius (horizontal) and depth (vertical). The laser hits the sample at the upper left corner, and the intensity is maximum at this point. The 0-60 numbers are an artifact of the contouring program; the actual scale is 0 to 5 mm in both directions. The contour lines span 8 decades; each pair of lines spans a factor of 10 in intensity.
Click on each picture for a larger version.
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| Total detected photons, photons that escaped between 0-1 mm , and photons that escaped between 1-2 mm (0-12 and 12-24 on the horizontal scale). | ||
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| Photons that escaped between 2-3 mm, 3-4 mm, and 4-5 mm (24-36, 36-48, and 48-60 on the horizontal scale). | ||