Polarization preservation in diffusive scattering from in vivo turbid biological media: effects of tissue optical absorption in the exact backscattering direction
Ia. Vitkin et Rcn. Studinski, Polarization preservation in diffusive scattering from in vivo turbid biological media: effects of tissue optical absorption in the exact backscattering direction, OPT COMMUN, 190(1-6), 2001, pp. 37-43
There is considerable recent interest in using polarized light to investiga
te turbid biological media. Although tissue multiple scattering randomizes
incident polarization states, there are circumstances when appreciable degr
ee of polarization can be observed in diffusive scattering. Tn this study,
we use polarization modulation and synchronous detection to examine in the
exact backscattering direction the polarization properties of diffusely ref
lected visible light from hands of human volunteers of varying pigmentation
levels. The surviving polarization fraction increases with increasing pigm
entation, likely due to preferential loss of highly scattered, long-pathlen
gth photons: this mechanism lowers the average pathlength traversed by the
detected light and hence increases the measured polarization preservation.
This behavior is contrasted with the overall diffuse reflectance intensity,
whose magnitude decreases with increasing absorption. These experiments de
monstrate the important influences of medium optical properties on the pola
rization characteristics of multiply scattered light, which must be further
investigated to enable quantitative polarization evaluation of turbid medi
a such as biological tissues. (C) 2001 Elsevier Science B.V. All rights res
erved.