Specific features of diffuse reflection of human face skin for laser and non-laser sources of visible and near-IR light

摘要

The Specific features of diffuse reflection from different areas of human face skin for laser and non-laser sources of visible and near-IR light have been investigated to localise the closed-eye (eyelid) region. In the visible spectral range the reflection from the eyelid skin surface can be differentiated by measuring the slope of the spectral depend- ence of the effective optical density of skin in the wavelength range from 650 to 700 nm. In the near-IR spectral range the reflectances of the skin surface at certain wavelengths, normalised to the forehead skin reflectance, can be used as a criterion for differentiating the eyelid skin. In this case, a maximum discrimination is obtained when measuring the skin reflectances at laser wavelengths of 1310 and 1470 nm, which correspond to the spectral ranges of maximum and minimum water absorption.