Optical properties of the human skin / Optičke osobine ljudske kože

Abstract

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.

Diversification and convergence of aposematic phenotypes: truncated receptors and cellular arrangements mediate rapid evolution of coloration in harlequin poison frogs

“…Upon entering the deeper layer of the dermis, the transmitted light may be scattered by the collagen fibers (Gajinov et al. ). The interaction of the scattered light with the melanosomes and carotenoids of the xanthophores may result in brown hues.…”

An Overview of the Sensors for Heart Rate Monitoring Used in Extramural Applications

“…This principle is illustrated in Figure 4. The absorption of the emitted light depends on the wavelength used due to the different absorption coefficients of the tissue for various wavelengths [65], in accordance with the Beer-Lambert law [66]. Indeed, absorption of longer wavelengths (e.g., red and near-infrared light) is lower, meaning they will penetrate the tissue deeper, up to the larger arterioles and possibly arteries in the deep dermis [67].…”

Investigating the optical clearing effects of 50% glycerol in ex vivo human skin by harmonic generation microscopy

“…Glycerol is with a higher refractive index (1.47) than extracellular and intracellular fluids (1.34–1.36). After immersion the skin tissues into anhydrous glycerol, glycerol diffused inside and filled all of the skin tissues to create a higher refractive index matching environment for the scattering particles (such as organelles, protein fibrils, membranes, protein globules, with refractive index 1.39–1.47 55 , 56 ). Therefore, the light scattering was reduced and the image depth increased.…”