Freeform surface selection based on parametric fitness function using modal wavefront fitting.

We present an analytic methodology to guide the selection of a surface within an optical design to apply freeform optimization. The methodology is discussed in the context of other means currently available, such as human intuition, aberration theory, and other direct surface construction methods. We describe the selection criteria for our proposed method and provide the form of the parametric fitness function used to combine the criterion. Finally, a case study comparing a design optimization procedure guided by the proposed methodology to human intuition is presented based on a real instrument designed for a millimeter-wave astronomy application. The methodology is shown to be effective even in the case of an optical system with a large number of freeform/optical surfaces. The proposed approach provides an objective and scalable solution to guide freeform optical system design by aiding a human's design intuition.