1959 年 28 巻 4 号 p. 219-223
Diffuse reflectance spectra are generally used to estimate the spectral distribution of absorption coefficient of powdered samples. But, when the absorption is weak, it is obscured by strong scattered light and rendered undiscernible. In such cases, if the scattered light be made to fall on and reflect from the sample repeatedly, the absorption would be multiplied and become measurable. With this idea, the following method for the measurement is proposed.
A pair of small integrating spheres of the same size is prepared; the inside of one of the spheres is coated with standard powder such as magnesia and that of the other with the sample, both being illuminated by a monochromatic light. Intensities of reflected lights are compared.
A simple mathematical formulation is made for the calculation and experiment using neodymium filter and its results are described.