Optical system for catadioptric reduction projection - has two lens groups, one positive and another one negative, and polarisation beam splitter

摘要

The first lens group of positive refraction converts a light beam from the object plane into a collimated light beam. The first group light beam is split into a reflected portion and a passed portion by a polarisation beam splitter. The second lens group of negative refraction is fitted in one split beam for widening the light beam from the polarisation beam splitter. A concave reflection mirror focusses the light beam of the second lens group and reflects it to the polarisation beam splitter via the second lens group. A third lens group of positive refraction focusses the reflected beam, passed by the beam splitter, to reduce the object image from the first plane and for its imaging on a second plane. Between the beam splitter and the concave mirror is a quarter-wavelength platelet. USE/ADVANTAGE - Semiconductor circuit mfr. with improved focussing based on catadioptic system.