Phase-shifting birefringent scatterplate interferometer. 
We realized what we believe is a new phase-shifting scatterplate interferometer by exploiting the polarization characteristics of a birefringent scatterplate.  The common-path design of the interferometer reduces its sensitivity to environmental effects, and phase shifting allows quick and accurate quantitative measurements of the test surface.  A major feature of the birefringent scatterplate approach for phase shifting is that no high-quality optical components are required in the test setup.  The theory of the interferometer is presented, the procedure for the fabrication of the birefringent scatterplate is described, and experimental results are shown.