Relationship of the Optical Density Parameters of a Sample and its Absorptivity

The relationship of the optical density parameters of a sample and the absorptivity of the sample material is studied; this is important when analyzing and differentiating the results of measurements by filtering of the luminous flux and spectral devices (densitometers and spectrophotometers). To clarify the analytical relationship between the values of the optical density of a sample and the absorptivity of the sample material, a formula is derived for calculating the diffuse optical transmittance density for the case in which the detected light contains directed and diffuse components. The first term in this formula characterizes the absorptivity of the sample material and the second is a correction owing to the diffuse component of the radiation and is a function of the ratio of the coefficients of diffuse and directed transmission. Expressions are obtained for functionally and quantitatively determining the ratio of the absorbance of the sample material and its optical transmittance density. The results of a calculation of the absorbance of a sample material, the diffuse radiation component, the diffuse optical transmittance density, and corrections to these are presented.