Any two rectilinear light vibrations A and B whose angle is given by u always have a time-average direction. They are thus able to induce an anisotropy in a silver-silver chloride photographic emulsion H. Here we show that when they are incoherent, their linear combination may be retrieved by observation of H between crossed polarizers after exposure. In the case they are coherent, H exhibits an interferogram whose black fringes characterize the value of angle u.
J. M. C. Jonathan,
"Application Of The Weigert Effect To Optical Processing In Partially Coherent Light," Optical Engineering 19(6), 196828 (1 December 1980). https://doi.org/10.1117/12.7972619