  This study presents the morphological and biochemical findings on human downy
arm hairs using 3-D quantitative phase imaging techniques. 3-D refractive index
tomograms and high-resolution 2-D synthetic aperture images of individual downy
arm hairs were measured using a Mach-Zehnder laser interferometric microscopy
equipped with a two-axis galvanometer mirror. From the measured quantitative
images, the biochemical and morphological parameters of downy hairs were
non-invasively quantified including the mean refractive index, volume,
cylinder, and effective radius of individual hairs. In addition, the effects of
hydrogen peroxide on individual downy hairs were investigated.
