Systems and methods of performing a stress measurement of a chemically strengthened glass using a light-scattering polarimetry system include adjusting the intensity of a light beam from a light source in an illumination system using a rotatable half-wave plate and a first polarizer operably disposed between the light source and a rotating light diffuser that has a rotation time tR. The first polarizer is aligned with a second polarizer in a downstream optical compensator to have matching polarization directions by rotating the rotatable half-wave plate to a position where the exposure time tE falls within an exposure range tR≤tE. The method also includes performing an exposure using the exposure time tE to obtain the stress measurement. One or both of the half-wave plate and first polarizer can be tilted to avoid deleterious back-reflected light from entering the light source.