A solution to the Schwarzschild two-reflector optical system is presented in a simple parametric form of particular use in antenna design. Examples are shown and a connection with the Zeiss-Cardioid system is revealed.
G. E. ROBERTS, "Parametric Solution of the Equations of the Schwarzschild Two-Reflector Optical System," J. Opt. Soc. Am. 54, 1111-1112 (1964)