Abstract

Lithographic lenses provide a phenomenal amount of image pixels in combination with amazingly small amounts of distortion and departure from field flatness. These difficult achievements require about twenty lens elements in today’s state-of-the-art designs. Their evolution from simpler versions is as haphazard as the birth of Topsey—they just grew. What is needed today is a more rational approach to lens design that would allow a controlled attack on the design of such systems. This should involve two efforts. The first is the settling, through theoretical research and experimentation, of several questions about what is the optimum way to achieve certain design goals, for example, what is the best balance between relaxation and strain in a design. Controlled amounts of the latter may be required for correction of seventh-order distortion and field curvature, but this limits field coverage due to bad ninth- and higher-orders. The other effort required is the further development of the design technique described elsewhere¹ that allows one to build a design from scratch with the correction of the most difficult higher-order aberrations being built in from the beginning. This needs to be expanded to give seventh-order control early in the design evolution.

© 1991 Optical Society of America