Glass Inhomogeneity Measurement Using the Shelyubskii Method

Inhomogeneity in glass can be measured in terms of the variance of the refractive index distribution by using the Shelyubskii method. In the method, the transmission of an optical cell containing glass particles immersed in a nearly matching refractive index liquid is measured. Transmission can be measured accurately and reproducibly as a function of wavelength with a conventional spectrophotometer. The primary source of errors, hitherto, has been the Raman‐Shelyubskii theory to relate the transmission to the refractive index variance by using interference optics principles. It is shown that a common Shelyubskii experiment can be described more cogently by a theory based on the principles of geometric optics. A Monte Carlo simulation of light ray tracing through the optical cell containing glass particles with a random distribution of refractive index was conducted. The fraction of intensity collected within the acceptance angle of the spectrophotometer, identified as the transmission, agrees well with the measured data. A glass inhomogeneity meter based on the simulation experiments is described.