In optics, a caustic or caustic network[1] is the envelope of light rays which have been reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface.[2] The caustic is a curve or surface to which each of the light rays is tangent, defining a boundary of an envelope of rays as a curve of concentrated light.[2] In some cases caustics can be seen as patches of light or their bright edges, shapes which often have cusp singularities.
^Lynch, DK; Livingston, W (2001). "The caustic network". Color and Light in Nature. Cambridge University Press. ISBN978-0-521-77504-5.
^ abWeinstein, Lev Albertovich (1969). Open Resonators and Open Waveguides. Boulder, Colorado: The Golem Press.