2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/108815We review the complex differential geometry of the space of oriented affine lines in ${\Bbb{R}}^3$ and give a description of Hamilton's characteristic functions for reflection in an oriented C$^1$ surface in terms of this geometry.10 pages AMS-LATEX, 3 figuresDifferential Geometry51M30, 78A05text