This paper presents an analysis of the para-elliptic reflector together with its possible applications when used as a searchlight mirror. The horizontal sections of a para-elliptic mirror are portions of ellipses and the vertical sections are parabolas. The mirror is so designed that each parabola lies in a vertical plane through the secondary focus of the horizontal ellipse which passes through the vertex of the mirror and each elliptical section lies in a plane parallel to that of the ellipse through the vertex of the mirror. A beam of light projected from such a reflector converges in the horizontal planes to a line common to the intersection of the vertical planes and then diverges as a spread beam horizontally with minimum spread vertically.
BENJAMIN GOLDBERG and NELS C. BENSON, "Analysis of Para-Elliptic Reflector," J. Opt. Soc. Am. 39, 497-497 (1949)