Medical vision : measurement of skin absolute spectral-reflectance image and the application to component analysis

Mapping the oxygen saturation of blood and melanin in skin is expected to give useful information for skin diagnosis. We have already proposed a technique to estimate the map of skin components from absolute spectral reflectance image obtained by multi-channel visible spectrum images based on the inverse optical scattering analysis. The spectral reflectance image is a result of dividing the spectral radiance image of object by the spectral radiance image of absolute white reference plane. However, the shape of skin is not 2 dimensional plane, so that the required absolute spectral reflectance is not obtained in the wide region of skin by the conventional method. In this paper, the absolute spectral reflectance and normal vector of the surface are obtained by using the photometric stereo technique. In the photometric stereo technique, four illuminants are used, and an image is taken by each illuminant. The pixel values in the obtained several images are used to calculate the absolute spectral reflectance and normal vector of the surface on the corresponding pixel. The index finger where the second joint was bind by a string was captured and analyzed by the proposed technique. The results show that the components are extracted in the wide range of the finger.