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Optical design may be thought of as an exercise in the solution of sets of simultaneous, nonlinear, algebraic equations with prescribed boundary conditions. Several methods for solving such sets of equations are discussed, and numerical examples are given for some of them. These methods are believed suitable for use with automatic computing machinery.In the optical problem there are usually many more equations than variables, so that an exact solution is seldom possible. If, however, the quality of a system is specified by a merit function φ, then a set of parameters which make φ a minimum can be interpreted as a solution of the equations.
Donald P. Feder (Tue,) studied this question.