Color recipe prediction for facial epithesis materials

The computer aided design of epitheses, i. e. artificial substitutes for body parts, involves the construction of a suitable shape and the reproduction of the colors of the replaced or surrounding skin surface. The latter is a crucial point especially for facial epitheses. Color reproduction is based on a precise measurement of the color defining remission spectrum. Furthermore, it requires a method of color recipe prediction, i. e. the calculation of concentrations of given colorants, necessary to reproduce a certain color. An adequate model describing the radiative transfer within translucent materials is the two-stream approximation given by Kubelka and Munk. As this theory excludes a refractive index change at the surface, an additional surface correction is applied in order to convert the measured overall remission of a color specimen into the internal remission caused only by absorption and scattering within the medium. On the basis of color specimens of epithesis material mounted on white and black coated substrates, the constants of absorption and scattering of the involved colorants are determined. Examples of color recipe prediction based on these data are presented.