Reflective objects such as plumbing fixtures, electronics, automobile parts, and travel mugs all offer a strange representation of the world. The mirror in figure 1 offers a view that is strange in its own way. The surfaces of all these objects are not often built to function as optical components, and they generally lack the rotational symmetry possessed by optical devices. The irregular surfaces are called freeform.
The ability to machine freeform surfaces of optical quality has been available for only about a decade, and is largely due to the Defense Advanced Research Projects Agency conformal optics program. The relative complexity of freeform surfaces means that designing a surface for a particular end is trickier than for rotationally symmetric optical elements, and traditional design approaches can be problematic. New design techniques, however, have emerged in concert with the improved machining capability, as have applications for optical systems containing freeform surfaces....
