Abstract: A drive system for an optical imaging head assembly of a scanner includes a rack having a first side and a second side opposite the first side, the first side including a toothed surface and the second side including a guide surface, a pinion engaged with the toothed surface of the rack, and at least one guide member contacting the guide surface of the rack.

Abstract: A drive system for an optical imaging head assembly of a scanner includes a rack having a toothed surface and a guide surface, a pinion engaged with the toothed surface of the rack, and at least one guide member contacting the guide surface of the rack.

Abstract: An automatic document feeder for moving a stack of individual sheets from a stack loaded position to a single sheet separator in a document processing apparatus uses a gate comprised of a rotatable stack stop having a finger movable between a stack blocking position and a stack transmitting position. The stack stop is driven through a drag clutch from a single source of rotary power which also drives the conventional single sheet separator and other movable parts of the document processing apparatus. Presentation of the stack to the single sheet separator is thus automated since the operator of the document processing apparatus loads the document stack against the gate comprised of the automated stack stop to avoid operator loading of a stack directly to the nip of the single sheet separator and resultant mispicks and multipicks of sheets from the stack.