It is not essential that a designer understand all of the details of the process by which a design program carries out the optimization. Successful designers will, however, understand the principles and options that are available. Much time and effort has been expended by program developers to make the process as bulletproof and transparent to the user as possible. The past few years have seen an incredible improvement in the ability to control the modification of lenses by a program, and to explore new regions for solutions.

A basic comprehension of the important issues and procedures used is needed by any successful designer. This chapter provides enough insight to permit the designer to make the decisions necessary, but does not provide enough information to write design optimization programs. For detailed information the reader is referred to papers by Levenberg (1944), Wynne (1959), Rosen and Eldert (1954), Spencer (1963), and the summary by Kidger (1993). Discussion of newer techniques for optimization are found in papers by Kuper, Harris, and Hilbert (1994), Forbes and Jones (1993), and, of course, the various program manuals.

Optimization consists of adjusting the parameters of a lens to meet as closely as possible the requirements placed on the design. Current design programs have achieved a high degree of sophistication, and can rapidly search the design space for the closest approach to the design goals. The process of optimization requires the selection of a starting point and a set of variables.