diacaustic
  折光; 折射散焦線
  Di·a·caus·tic a.  Opt. Pertaining to, or possessing the properties of, a species of caustic curves formed by refraction. See Caustic surface, under Caustic.
  Di·a·caus·tic, n.
  1. Med. That which burns by refraction, as a double convex lens, or the sun's rays concentrated by such a lens, sometimes used as a cautery.
  2. Math. A curved formed by the consecutive intersections of rays of light refracted through a lens.
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