Imaging polarimeter for testing single crystals and phase retardation plates

Spatial inhomogeneity of the phase difference in the birefringent plates of YAlO3 and LiNbO3 crystals with the dimensions ranging from 7x8 to 20x20 mm(2) are measured. A considerable eigenwave ellipticity k similar to 0.001 is revealed in the samples doped with neodymium, which can be explained by lowering symmetry of those crystals. The studies for the spatial optical inhomogeneities are performed with the imaging polarimeter which utilizes computer registration and processing of images. The apparatus have been used for the measurements of spatial distribution of the optical anisotropy parameters characterizing several single crystals. The results obtained agree well with the data derived with the automated polarimeter which works according to a single-ray scheme and utilizes usual single-element photodetector.