Abstract
A novel method based on a polarized optical heterodyne interferometer with a common path feature was proposed and set up. This interferometer was used to measure the phase difference δ f of the fast wave of the elliptical polarized eigenstate in the directions of the P and S waves in an elliptical birefringence wave plate. The values of δ f are calculated on the basis of the phase difference and the ratio of the amplitude of input polarized light with the accuracy up to 10-3. The measurement results provide evidence of the existence of elliptical birefringence in both λ/4 and λ/2 quartz wave plates.