Two general theorems in the theory of mirrors are presented. The first one asserts that a mirror that reflects a parallel beam into a beam with zero mean curvature must be harmonic. The second one provides a universal characterization of the spot diagram of rays from a reflected parallel beam as they intersect a plane orthogonal to their direction of propagation.
© 2002 Optical Society of America
J. Rubinstein and G. Wolansky, "Two theorems in catoptrics," J. Opt. Soc. Am. A 19, 129-131 (2002)