Polarimetry using liquid-crystal variable retarders: theory and calibration

A Mueller-matrix polarimeter in transmission mode using two electronically controlled liquid-crystal variable retarders has been developed. Its design , theory and calibration are described. Although liquid crystals have been proposed earlier, this paper is focused on the process of the calculation o f the Mueller matrix by a matrix-inversion method, oriented to static syste ms and in vitro samples. By driving the retarders with appropriate voltages , nine independent pairs of polarization states can be produced (incomplete polarimetry), while the other additional seven pairs are obtained by placi ng two quarter-wave plates tin the input and output optical paths respectiv ely). This configuration allows extraction of 16 independent measurements o f intensity. The Mueller matrix of the sample is calculated from them. The results of Mueller matrices for air, a linear polarizer and a quarter-wave plate are presented. Additional polarization parameters such as retardation , ellipticity or degree of polarization were also computed and some applica tions of the system are proposed.