Projection optical system and projection exposure apparatus having the same

Abstract

A projection optical system includes a plurality of lenses that cause birefringence and at least one optical element for substantially eliminating the birefringence caused by the plurality of lenses. The at least one optical element is detachably mounted on the projection optical system.

What is claimed is:  
     
         1 - 10 . (Cancelled)  
     
     
         11 . A projection optical system comprising: 
 a plurality of lenses that cause birefringence; and    at least one optical element for substantially eliminating the birefringence caused by said plurality of lenses;    wherein said at least one optical element is detachably mounted on said projection optical system.    
     
     
         12 . A projection exposure apparatus comprising: 
 an illumination system for illuminating a reticle with light; and    a projection optical system for projecting a pattern of the reticle onto a wafer, said projection optical system including (i) a plurality of lenses that cause birefringence, and (ii) at least one optical element for substantially eliminating the birefringence caused by said plurality of lenses, wherein said at least one optical element is detachably mounted on said projection optical system.    
     
     
         13 . A device manufacturing method, comprising the steps of: 
 exposing a wafer with a device pattern by use of a projection exposure apparatus as recited in  claim 12;  and    developing the exposed wafer.