When an isotropically polarized light beam is passed through a linear polarizer followed by a quarter-wave compensator, the polarization of the emergent light can be made to assume all possible states (represented by the points in the complex plane) by rotating the polarizer and compensator around the beam axis. With regard to this arrangement the complex polarization variable

is a function of

and

,

, where

and

represent the azimuths of the transmission axis of the polarizer and the fast axis of the compensator, respectively, measured from the

axis (counterclockwise, looking into the beam) of the

space-fixed Cartesian coordinate system whose

axis is along the direction of propagation of the incident light beam.
The figure shows a collective view of the constant-

, variable-

contours for the special case when the polarizer is set at a fixed azimuth and the quarter-wave compensator is rotated.