A. Joets et R. Ribotta, CAUSTICS AND SYMMETRIES IN OPTICAL IMAGING - THE EXAMPLE OF CONVECTIVE FLOW VISUALIZATION, Journal de physique. I, 4(7), 1994, pp. 1013-1026
It is shown that qualitative and quantitative information can be colle
cted from the study of the full caustic formed by light rays deflected
by some medium. The study necessitates the calculation of the ray tra
jectories along with a detailed balance of the symmetries of the whole
set-up. As an example we consider the case of the caustic produced by
parallel rays interacting with a periodic convective flow in a liquid
crystal. The amplitude of the flow and all its essential features can
be deduced, indicating that a caustic carries more information than a
simple image.