Disclosed is a projection exposure apparatus by a scan-exposure method. The apparatus includes an illuminating means for illuminating a mask transfer region with illumination light for an exposure through an aperture of a variable field stop disposed in a position substantially conjugate to the ...http://www.google.com/patents/US5854671?utm_source=gb-gplus-sharePatent US5854671 - Scanning exposure method and apparatus therefor and a projection exposure apparatus and method which selectively chooses between static exposure and scanning exposure 
