In the study of a flexible fluid prism, it was noticed that the coherence of a collimated beam arising from a filtered Hg lamp (Δν ≤ 100 Å) was greatly reduced, even for prism angles of only a few degrees (7° or less). A mathematical description for the effect of thin prisms on the coherence was accordingly developed and used as a guide to further study of the effect. This description, as well as the confirming experimental results, is presented in this paper.
GEORGE B. PARRENT, JR. and ROBERT E. WHITNEY, "Relation between Bandwidth and Spatial Coherence in Experiments Involving Dispersion," J. Opt. Soc. Am. 55, 1116-1120 (1965)