Rotating birefringent ellipsometer and its application to photoelasticimetry

摘要

An ellipsometer for measuring the polarization parameters &agr; and . lambda. of an elliptically polarized light wave. The light wave passes successively through an orientable quarter-wave plate, a birefringent plate rotatable at a constant speed &ohgr; and a polarizer and then impinges upon a photodetector. Reference signals having angular frequencies of 2&ohgr; and 4&ohgr; are generated, one of these signals being employed to synchronously detect the signal at the output of the photodetector by adjusting the quarter-wave plate until the synchronously detected signal component is zero, the orientation of the quarter-wave plate then corresponding to the polarization parameter &agr;. The parameter &lgr; is obtained by measuring the phase of the component at the output of the photodetector having an angular frequency of 4&ohgr;. PPThe invention applies in particular to photoelasticimetry.