Abstract

The two-constant theory of diffuse reflection and transmission deduced by Kubelka and Munk is much used for the determination of the absorption coefficient of dyed materials. Although the theory is derived for diffuse illumination of the specimen, it is often applied to reflectance values measured with reflectometers for parallel incidence. If the diffusing material can be prepared in the form of a thin sheet, a means is given to control the validity of the theory with respect to the optical geometry of the reflectometer. Experiments made with the geometries R_D,0, R_6,D, R_0,45, and R_60,D, show that if the material is colored, only reflectance values obtained with diffuse incidence, as predicted by the theory, may be applied with great accuracy to the Kubelka-Munk theory. For white or light colored materials, the optical geometry of the reflectometer is of minor importance in this respect.

© 1955 Optical Society of America

An Integrating Sphere for Measuring Diffuse Reflectance in the Near Infrared

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Photodissociation and Photoionization of Oxygen (O₂) as Inferred from Measured Absorption Coefficients

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