Measuring birefringence properties using a wave plate and an analyzer

The method of measuring birefringence properties using a quarterwave plate and an analyzer is examined, and explicit equations are derived for the case of a linear retarder and for a retarder–rotator system. These equations have been tested empirically by characterizing some previously known birefringent elements. In the case of a pure retarder agreement is generally better than 1°, while for retarder–rotator systems errors were typically 2° for retardation and between 1° and 2° for rotation. Possible sources of these errors are discussed.