Using PLM to identify an unknown birefringent sample.

A: Sample will appear dark when its optic axis is parallel to the transmittance axis of the Polarizer.

B: At any other angle the sample will appear bright on a polarized dark background due to the interaction of the o- and e-rays at the Analyzer.

C: Irregularly shaped birefringent object creates o- and e-rays of varying optical path differences. When the rays are combined by the Analyzer wave interference can create varying amounts and levels of "rainbow" spectra.

D: A Full-Wave Retardation Plate placed 45° to the polarizer will produce a Magenta background by eliminating Green (550nm) from polarized white light. By orienting a birefringent sample with its slow axis parallel to the slow axis of the Compensator the sample will appear a characteristic color (via wave interference) representative of its Birefringence and Optical Path length. The Michel-Lévy Color Chart can be used to determine either the sample thickness or Birefringence.

E: If the sample is reoriented 90° so that the fast axis of the birefringent sample is parallel to the slow axis of the Compensator the resulting interference color will be the complement of that which is generated in the previous orientation (D).