A 1X projection optical system for deep ultra-violet (DUV) photolithography
is disclosed. The optical system is a modified Dyson system capable of
imaging a relatively large field at high numerical apertures at DUV
wavelengths. The optical system includes a lens group having first and
second prisms and four lenses having a positive-negative-positive negative
arrangement as arranged in order from the prisms toward the mirror. A
projection photolithography system that employs the projection optical
system of the invention is also disclosed.
