The Crossed Polarizer System

This simple arrangement was previously discussed in secdon 2.6 and consists of two crossed polarizers that bracket the sample. In that section the sample was taken to be both birefringent and dichroic. These anisotropies were also taken to be coaxial and oriented at an angle 0. Using the notadon describing the PSGs and PSAs in table 8.2 and table 8.2, 

The angle a defines the orientation of the pair of orthogonal polarizers relative to a laboratory frame. 

The last limitation can be simply overcome by performing two separate measurements at different values of the angle a. This procedure was first used by Osaki and coworkers [26]. They performed separate measurements of intensity for a = 0° and 

Equations (8.5) bring out an additional problem that is inherent in any birefringence experiment, and that is that the measured intensity is a sinusoidal function of the retardance. This means that there can be ambiguity regarding the absolute magnitude of the retardance, since it will not have a unique value for a given measurement of the intensity. The intensity will oscillate and pass through a maximum whenever S = wtc, where n = 1, 3,. .. and will be zero when n = 0, 2, This problem represents a serious lim- 

Operation of the experiment requires making two separate measurements, one with the second polarizer crossed with respect to the first, and another with the second polarizer oriented parallel to the first. These two intensity measurements arc identified as Ix 

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