Abstract: Apparatus for duplex printing comprising: a first impression roller (24) on which a first side of a sheet (22) having a leading edge and a trailing edge is printed referenced to the leading edge; a second impression roller (26) on which a second side of the sheet is printed; and a transport system (20) that removes a printed sheet from the first impression roller (24) and transports it to the second impression roller (26), the transport system comprising a perfector (32) that receives the sheet and grips it along both the leading and trailing edges of the sheet, which perfector turns the sheet over and transfers the sheet trailing edge first towards the second impression roller.

Abstract: A tandem printer with a mechanism for fine substrate-position correction, comprising: a first printing station; a second printing station; a rotatable element, rotating at a given rotation rate, that receives the substrate after printing thereon by the first printing station and transfer the substrate toward the second printing station; a sensor which measure the position of an edge of the substrate during its transfer from the first printing station to the second printing station; and a controller, which applies a corrective step change in angular position of the rotatable element responsive to the measurements of the sensor, without changing the general rotation rate of the rotatable element.

Abstract: A method for registration of print separations in a printer comprising: (a) printing a first pattern, for which at least one image characteristic varies relatively weakly with misregistration, using at least one of first and second separations; (b) printing a second pattern, for which said at least one image characteristic varies relatively strongly with misregistration, using said at least one first and second separations; (c) determining said at least one image characteristic for the first and second patterns; and (d) correcting the mutual registration of said at least one first and second separations responsive to a difference in the determined at least one image characteristic for the first and second patterns.