thinking of all the possibilities, I know, the optics, X Y stage, UV (or other exposure method) controls, etc. that make up what looks very complex at first but inspecting the various elements I think, hmmm, a mask alignment system, either contact or projection, from bits gathered together could very well be assembled at much less than the cost of, say, a refurbished Karl Suss, Canon, etc. mask aligner.
all I could find though was this pdf link...
http://colossus.cs.rpi.edu/~azonenberg/papers/litho1.pdfRobert