Hyperspectral Modeling of Skin Appearance

Abstract

Exploration of the hyperspectral domain offers a host of new research and application possibilities involving material appearance modeling. In this article, we address these prospects with respect to human skin, one of the most ubiquitous materials portrayed in synthetic imaging. We present the first hyperspectral model designed for the predictive rendering of skin appearance attributes in the ultraviolet, visible, and infrared domains. The proposed model incorporates the intrinsic bio-optical properties of human skin affecting light transport in these spectral regions, including the particle nature and distribution patterns of the main light attenuation agents found within the cutaneous tissues. Accordingly, it accounts for phenomena that significantly affect skin spectral signatures, both within and outside the visible domain, such as detour and sieve effects, that are overlooked by existing skin appearance models. Using a first-principles approach, the proposed model computes the surface and subsurface scattering components of skin reflectance taking into account not only the wavelength and the illumination geometry, but also the positional dependence of the reflected light. Hence, the spectral and spatial distributions of light interacting with human skin can be comprehensively represented in terms of hyperspectral reflectance and BSSRDF, respectively.

Assessing the sensitivity of human skin hyperspectral responses to increasing anemia severity levels

“…3), eumelamin and pheomelanin, albeit in small amounts, have a dominant attenuation role in this spectral region. 25,37 In the NIR region, on the other hand, not only the Hb absorption profile is relatively low, but light attenuation is also affected by the presence of water and lipids. 25,37 For the DP specimen, the impact is minor across all selected spectral regions with respect to the mild and moderate levels.…”

“…25,37 In the NIR region, on the other hand, not only the Hb absorption profile is relatively low, but light attenuation is also affected by the presence of water and lipids. 25,37 For the DP specimen, the impact is minor across all selected spectral regions with respect to the mild and moderate levels. It becomes somewhat significant, notably in the visible-G (500 to 600 nm) range (Fig.…”

“…These are performed using a recently developed hyperspectral light transport model for human skin, henceforth referred to as Hyperspectral Light Impingement on Skin (HyLIoS). 25 This model, capable of predictively simulating both the spectral and spatial distributions of light interacting with the skin tissues, takes into account the detailed layered structure of these tissues and the particle nature of their main light attenuation agents, namely the melanosomes, the organelles encapsulating melanin in an aggregated form. 26 In fact, it employs a first principles simulation approach that incorporates all main light absorbers (keratin, DNA, uranic acid, melanins, hemoglobins, beta-carotene, bilirubin, lipids, and water) and scatterers (cells, collagen fibers, melanosomes, and melanosome complexes) acting within the skin tissues in the ultraviolet (UV) (250 to 400 nm), visible (400 to 700 nm), and near-infrared (NIR) (700 to 2500 nm) domains.…”

“…1 The web interface for the Hyperspectral Light Impingement on Skin (HyLIoS) model 25 available through the Natural Phenomena Simulation Group Distributed framework. 30 Through this web interface, 29 researchers can configure physical parameters and execute light transport simulations involving different skin specimens.…”

“…Both sets of in silico experiments were performed with respect to UV, visible, and NIR regions of the light spectrum where skin spectral responses to variations in Hb concentration have a higher probability to be detected, more specifically, in the 250 to 850 nm range. 25,37 Unless otherwise stated, the resulting reflectance data were obtained considering an angle of incidence of 10 deg. The specific parameters employed in the characterization of the skin tissues considered in the first and second sets of in silico experiments are provided in Tables 1 and 2, respectively, while characterization parameters employed in both sets of experiments are provided in Table 3.…”