The effects of absorptive layers on light reflectance

-A physical model representing the optical properties of layered biological tissue was constructed for the s tudy of light reflectance. Reflectance was measured for a spot light source incident on a medium that contained diffusive and absorptive layers. Results were analyzed by means of an index defined as the natural log ratio of reflectance intensities from a uniform and a test medium. The index was determined as a function of source-detector separation distance. The study reveals that the shape of the index curves for diffusive and absorptive layers a t depth within the medium are similar, but differ in the separation a t which a test medium begins to diverge from a uniform medium. These results demonstrate that absorptive layers must be considered separately from diffusive layers within a biological material.