title: Determination of unit normal vectors of aspherical surfaces given unit directional vectors of incoming and outgoing rays: comment.
abstract: In a recent paper by Lin and Tsai [J. Opt. Soc. Am. A 29, 174 (2012)] there is presented a rather complicated method for derivation of the unit normal vectors of an aspherical surface given the knowledge of the unit directional vectors of the incoming and outgoing rays. In our comment we present a much simpler method that leads to compact equations suitable for practical implementation.
authors: Czech Technical University in Prague, Faculty of Civil Engineering, Department of Physics, Prague, Czech Republic.
authors: Antonín
authors: A
authors: Mikš
authors: Pavel
authors: P
authors: Novák