Japanese beauty giant Shiseido has taken the wraps off its research into the behaviour of light on the skin, including how emissions decrease with age.
Working with the Muroran Institute of Technology and Norwegian University of Science and Technology, Shiseido has developed the world's first optical measurement system capable of non-invasive measurement and analysis of three-dimensional facial shape and optical conditions.
In pursuit of achieving skin translucency, Shiseido’s optical research focused on how light incident on the skin penetrates the stratum corneum, reaches the dermis, and again exits the skin's surface (subsurface scattering light).
Measurement and analysis results revealed that short-wavelength light reaches the epidermis, mid-wavelength light reaches the area from the epidermis—centred around the basement membrane—to near the upper dermis, and long-wavelength light reaches the collagen layer of the dermis before it is re-emitted from the skin's surface.
Furthermore, as short-wavelength light reaches the epidermal layer, non-invasive measurement and analysis of the relationship between melanin level and light reaching and emitted from the epidermal layer revealed that melanin is significantly involved in light absorption.
Melanin blocks light, making it difficult to penetrate the skin, thereby reducing the amount of light emitted from the skin's surface.
Additionally, as long-wavelength light penetrates the dermal collagen layer, Shiseido applied the internal and external skin elasticity 3D imaging system that visualizes both inside and outside the skin and enables non-invasive observation of collagen status in living human skin, to evaluate collagen fibre density and analyse correlation.
The results revealed that reduced collagen density decreases the amount of light reaching the dermis and emitted from the skin's surface.
These findings demonstrate that melanin levels in the stratum corneum and the epidermis, along with dermal collagen density, are essential for achieving skin translucency.
Furthermore, using the optical measurement system, Shiseido applied a newly developed evaluation technique to approximately 150 women aged 20s to 70s, while simultaneously acquiring vast amounts of data through its proprietary non-invasive skin measurement technology.
Examination of the parameters influencing light emission at different penetration depths demonstrated that light reaching the epidermis and re-emitted from the skin’s surface is most strongly influenced by absorption by epidermal melanin.
Furthermore, light reaching the dermis and re-emitted from the skin’s surface is associated with multiple factors, among which the influence of collagen fibre density is also significant.
Previous studies have shown that light emitted from within the skin tends to decrease with age, but the characteristics of light at different penetration depths remain unknown.
By measuring and analysing light at different penetration depths, researchers discovered that light reaching the epidermis and re-emitted from the skin’s surface tends to gradually decrease with age.
Conversely, light reaching the dermis and re-emitted from the skin’s surface shows relatively small changes in younger age groups, but exhibits a greater tendency to decrease in older age groups.
