Novel approach to assess the emissivity of the human skin

Abstract

To study the radiation emitted by the human skin, the emissivity of its surface must be known. We present a new approach to measure the emissivity of the human skin in vivo. Our method is based on the calculation of the difference of two infrared images: one acquired before projecting a CO(2) laser beam on the surface of the skin and the other after such projection. The difference image contains the radiation reflected by the skin, which is used to calculate the emissivity, making use of Kirchhoff's law and the Helmholtz reciprocity relation. With our method, noncontact measurements are achieved, and the determination of the skin temperature is not needed, which has been an inconvenience for other methods. We show that it is possible to make determinations of the emissivity at specific wavelengths. Last, our results confirm that the human skin obeys Lambert's law of diffuse reflection and that it behaves almost like a blackbody at a wavelength of 10.6 microm.

Thermographic imaging in sports and exercise medicine: A Delphi study and consensus statement on the measurement of human skin temperature

“…While controversy in the literature regarding emissivity exists (Sanchez-Marin et al, 2009;Steketee, 1973), 96% of experts strongly agreed that an emissivity of 0.98 (ε) should be used for clean dry skin. Due to circadian rhythm (Costa et al, 2015;Marins et al, 2015), tsk is likely to change during the course of the day, therefore, when individuals are assessed over multiple days or when comparisons between participants are made at different time of the day, the time of day at which the images were recorded should be reported.…”

Effect of perspiration on skin temperature measurements by infrared thermography and contact thermometry during aerobic cycling

“…Besides, to get a correct value of skin temperature by quantifying the emitted radiation, the emissivity of the measured surface has to be known (31).…”

Infrared camera assessment of skin surface temperature – Effect of emissivity

“…On the other hand, Sanchez et al mention the various criteria for emissivity measured with infrared thermography. They were aware of the important fact that the skin is not to be covered by any kind of substance that could affect actual measurement [33].…”