Age‐related changes in surface reflection, diffuse reflection, and subsurface scattering light of facial skin: Luminance value measured by the system for the optical properties of facial skin

Abstract We have developed a system that separates and measures the optical properties of skin that determine its visual quality, that is, the surface reflection, diffuse reflection, and subsurface scattering components of the skin. This system includes two polarization filters that separate light from the skin into a surface reflection component image and a diffuse reflection component image. Furthermore, by using a projector as a light source and irradiating the skin using a high‐frequency binary illumination pattern, the subsurface scattering component image alone can be separated and generated. Application of an algorithm that calculates the luminance value Y for each component image not only makes it possible to analyze each light signal from the skin quantitatively, but also enables understanding of how each light signal is related to the skin's overall appearance. Using the proposed system, we performed a survey of 154 Japanese women aged from their 20s to their 70s and analyzed age‐related changes in the optical properties of their skin. The results revealed the following. First, the luminance value Y of the surface reflection from the cheek and its standard deviation within the analysis area increase with age. Second, the Y value of diffuse reflection from the skin decreases with age. Third, the amount of light in the subsurface scattering components also decreases with age. The proposed system is expected to be suitable for a wide range of applications, including color science, and various studies of the appearance of human skin.