Systems and methods of for measuring birefringence and stress in a sample made of ion-exchanged glass or a ceramic are disclosed, wherein the method includes digitally capturing TE and TM angular spectra of intensity versus pixel number for the sample. The TE and TM angular spectra are processed to minimize differences between respective regions of the TE and TM angular spectra. The amount of shift in pixels that best overlaps the processed TE and TM spectra is determined. The birefringence B is calculated by multiplying the pixel shift by the index resolution. The stress is calculated by multiplying the birefringence by the stress-optic coefficient.