Document registration system

Abstract

In a document feeder for a copier which transports a document sheet onto and over the platen of the copier and which places the document in a desired registration position on the platen for copying by stopping the document platen transport of the document feeder, and thereby stopping the document being fed thereby at the desired position, without the document hitting a mechanical registration stop, the improvement comprising a variable registration control system for controlling the document platen transport to stop at a desired calculated stopping position, including a sensor adjacent by a known fixed distance the upstream, entrance, side of the platen for sensing the trail edge of an individual document sheet being transported onto the platen by the document platen transport, providing a first signal indicative of the selected size of the copy sheet onto which that document sheet is to be copied, providing a second signal indicative of the optical magnification or reduction ratio with which that document is being copied onto that copy sheet, and wherein the variable registration control system calculates a particular registration stopping position on the platen for that document which is controlled by the trail edge sensor and the first and second signals to provide appropriate document registration for the selected copy sheet size and copying magnification or reduction ratio.