CHAPTER 4 - Bio-Optical Properties of Human Skin

Abstract

To accurately simulate the mechanisms of light propagation and absorption that determine visual attributes of the skin, it is necessary to carefully account for its biophysical and structural characteristics. This chapter examines these characteristics and how they affect skin optics and ultimately its appearance, which may vary considerably not only among different individuals, but also among different cutaneous regions belonging to the same individual. The appearance of human skin depends on spectral and spatial light distributions controlled by endogeneous and exogeneous factors. Endogeneous factors are associated with skin constituents (e.g., pigments, cells, and fibers), whereas the exogeneous factors are associated with environmental conditions (e.g., illumination and temperature) and the presence of external materials (e.g., hair, oil, sweat, and cosmetics). The variations of these factors among the human population result in different spectral signatures and scattering profiles. Such variations and their outcomes are also reviewed in this chapter. Several photobiological processes that affect the appearance and health of human skin are triggered by electromagnetic radiation outside the visible domain. This chapter concludes with an overview of these phenomena and their visual and medical implications.