A method is described that permits the quantitative measurement of light scattered by the bulk material and individual scattering centers in transparent crystals and photographic recording with an ultramicroscope. The bulk scattering observed in sodium chloride single crystals is proved to be Brillouin scattering. This suggests the use of Brillouin scattering as a reference for the measurement of the intensity of light scattered by individual centers.
Gerhard Heilmann, "Intensity Measurements in Ultramicroscopic Studies," Appl. Opt. 5, 1065-1068 (1966)