Telecentric, flat-field, anastigmatic, four-mirror optical system for lighographic camera

A telecentric flat field and anastigmatic four mirror optical camera system is developed for lithographic application. We have Obtained initially the analytic solutions of the four spherical mirror system free from four Seidel aberrations with reduction magnification (5x). However the systems obtained after corrections have still sizable amount of residual aberrations and small field. To overcome these shortcomings aspherization of the three mirrors is performed and it is found that it gives more improved performances.