Visual perception of human skin is determined by the light that reflects off the skin surface to retina and interpretation of these information by visual centers in the brain cortex. Skin has a partly translucent and turbid structure and visual perceptions depend on interactions between the light and structures of the skin surface and below it, through absorption, reflection and scattering. Light absorption by the skin depends on the composition, absorption spectra and amount (volume fraction) of chromophores. Subsurface scattering occurs within the skin layers: Rayleigh scattering (subcellular structures sized up to 1/10 of incident wavelength) and Mie scattering (collagen, melanosomes). Due to fluctuations of the refractive index within tissue components and intense scattering, the spatial distribution of light within the skin is diffuse. Skin images are created by the light that reflects off the skin after being color-modified by absorption and being scattered on the skin surface and internal skin structures.
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