126 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Figure lB can be seen within the skin folds over the joints of the fingers. These same areas have the appearance of dryness in Figure 1A and must originate from regions of surface scatter and depolarization of reflected light. A similar effect can be found on the palmar surface near to the base of the fingers and the hypothenar eminence. The reference metallic surface in each photograph demonstrates clearly the near extinc- tion of the polarized light with a crossed polaroid filter. Depolarized light from the reference white standard shows little change with the orientation of the polaroid filter on the camera, and therefore any observed changes in detail or color must originate from preferential interaction with the skin. POLARIZED REFLECTION SPECTROSCOPY OF HUMAN SKIN Figure 2 shows the reflection spectra from the hypothenar eminence of the hand ob- tained using an integrating sphere with the Perkin-Elmer Lambda 7 spectrophotom-

OPTICAL DISCRIMINATION OF SKIN 127 Figure 1C eter. Contour A is a diffuse reflection spectrum typical of those published in the litera- ture (14). Reflection is highest in the near infrared and red, i.e., 700 nm to 600 nm. The rapid fall between 600 nm and 400 nm is characteristic of absorption by hemo- globin with a doublet between 600 nm and 500 nm and the Soret band near 420 nm. Contour B, the polarized reflection spectrum, shows a completely different wavelength dependence, with very little contribution from hemoglobin and no appreciable change in the level of reflection from the far red (70%) to the violet (60%). The inflections near 570 nm and at 425 nm are probably hemoglobin, but the bands at 500 nm and 460 nm are new. The latter may, however, be present as a slight inflection in contour A. Figure 3 is representative of the polarized reflection spectra from the hand using the Jobin-Yvon spectrofluorimeter in synchronous scan mode. Contour A was obtained with polarizer and analyser perpendicular and is the depolarized reflection spectrum. The major attenuations of the reflected light are again attributable to hemoglobin. In the polarized reflection spectrum (contour B), the overall level of reflected light inten-