Steven L. Jacques, Ph.D., Department of Electrical and Computer Engineering
Oregon Graduate Institute, Portland, Oregon, USA. email:,

The basic idea.

Illuminate the skin with linearly polarized light, oriented "parallel" to the scattering plane defined by the source-tissue-observer plane. As light enters the skin, about 5% is reflected from the surface as glare. About 2% is reflected from the subsurface superficial tissues and is still polarized. About 40% penetrates deeply and is backscattered to the surface after multiple scatterings which randomize the orientation of polarization, hence 20% is parallel and 20% is perpendicular. About 53% of the incident light is absorbed by the skin and does not escape.


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