The applications of liquid crystal variable retarders in the productio
n of spin-polarized electrons and in the determination of the polariza
tion of optical radiation from atoms excited by polarized electrons ar
e discussed. The advantages of using liquid crystal variable retarders
in the measurement of Stokes parameters are insensitivity to the inci
dent photon direction, large transmission diameter, variable retardati
on over large wavelength range without mechanical movement, and in sit
u calibration. (C) 1996 American Institute of Physics.