An apparatus in which an original document is housed. The support on which the original document is positioned becomes selectively opaque so as to mask portions of the original document disposed thereon....http://www.google.es/patents/US3936172?utm_source=gb-gplus-sharePatente US3936172 - Liquid crystalline platen for an electrophotographic printing machine
Liquid crystalline platen for an electrophotographic printing machine
