Photoelectric Polarimeter using the Faraday Effect

Abstract

THE sugar industry is becoming increasingly interested in the possibility of replacing polarimeters of the visual type with photoelectric instruments. Of the various designs which have been suggested, a promising one is that in which the plane of polarization of the light emerging from the polarizer is made to oscillate through a suitable angle. When the analyser is perpendicular to the mean direction of the plane of polarization, the emergent light intensity, though it may be modulated at twice the frequency of oscillation, has a zero alternating component at the fundamental frequency. This condition is detected by means of a photocell and amplifier, the system thus combining the advantages of a.c. amplification and of the half-shadow principle used in visual polarimetry.