Two Half-shade Devices for Optical Polarizing Instruments

Abstract

THE development of interference microscopes of the double-refracting type has stimulated a renewed interest in eyepieces having at their focal planes sensitive birefringent devices for increasing the accuracy with which forms of polarization can be determined. These devices usually employ a boundary or boundaries formed by one or more birefringent plate elements viewed through an analyser, and the difficulty arises of making boundaries sufficiently precise for the maximum sensitivity to be achieved. The present communication is a brief account of two rather promising solutions to this problem which have recently been investigated here.