Photoelastic Methods for Measuring Anisotropy Effects

This chapter describes known and novel photoelastic measurement methods that can be used to analyze anisotropy effects created from stress differences in the glass. Depending on the method, different physical values can be visualized and measured. They are appropriate either locally for detecting the 3D stress state or for the 2D full-field analysis of optical retardations from stress differences. The author has also published the methods described herein in his publication: Dix et al. (2022b). At the end of the chapter, a device is introduced that can measure skylight polarization which bases on phase-shifting methods.