CS Colloquium, co-sponsored with Biomedical Engineering
Steven L. Jacques
Title: The optics of skin: why skin looks pink instead of orange
Host: Alex Doronin
The skin is an optically turbid medium with embedded absorbers (blood, melanin, water) and scatterers (collagen, lipid membranes). The scattering greatly affects the observed color of the skin. A homogeneous mixture of scatterers and blood will yield an orange color, since absorption by blood scales as blue > green > red. But the architecture of the skin has a superficial layer of relatively low blood content: the epidermis and superficial papillary dermis. Hence, blue light can reflect from this superficial layer before seeing any blood while green and red light penetrate more deeply and see the deeper blood. This moves the skin color from orange to pink. Of course, melanin offers an additional absorption filter that strongly attenuates blue light, but subsurface melanin yields the blue coloring of Nevus of Ota. IN SUMMARY, skin architecture plays a key role in the appearance of skin color.