The optical design space of some simple lenses is investigated systematically. Typical space topographies are visualized with 3-D graphics, where the complete set of available solutions is clearly identified. The space characteristics are then studied and compared through the use of several merit functions with differing degrees of complexity. A two-phase search algorithm, based on global optimization techniques, is proposed here. In the first phase, using a coarse sampling approach, the program finds the favorable regions that correspond to potentially promising configurations. In the second phase, conventional optimization routines are used to find the best solutions in each region. Then an optimum solution
is determined according to the application at hand. The proposed algorithm is analyzed and compared to more conventional design approaches. A further refinement of the algorithm excludes from the systematic search some unfavorable configuration regions through the use of a simple expert system. Search times are further reduced through parallel-processing methods. The algorithm provides overall information about a given design space and offers a selection of "best" solutions to choose from. As an example, it is applied to a triplet objective.