Patent ID: 8136904
Filing Date: 2012-03-20
Classification: G03G,H04N

Abstract:
1. An image forming apparatus comprising: a belt member movable in a cross-scan direction; a plurality of organic photoconductive (OPC) drums; a control unit to form toner images respectively representing a first set of registration marks and a second set of registration marks on the belt member as the belt member moves in the cross-scan direction, wherein the first set of registration marks and the second set of registration marks are separated from each other in a scan direction, the control unit being further configured to form toner image representing a first image density mark on the belt member, each of the first and second sets of registration marks including plurality of registration marks corresponding to a first color, plurality of registration marks corresponding to a second color, a plurality of registration marks corresponding to a third color and plurality of registration marks corresponding to a fourth color, wherein the first set of registration marks and the first image density mark are arranged on the belt member in a first single cross-scan direction line, and the second set of registration marks belt member in a second single cross-scan direction line; a first optical module to detect the toner images representing the first set of registration marks and the first image density mark formed on the belt member as the belt member moves in the cross-scan direction, the first optical module including a first light emitter disposed to radiate a beam onto the belt member at a location which is downstream of a last one of the OPC drums and upstream of where an inner surface of the belt member disengages contact with one of belt rollers that is closest to the last one of the OPC drums in relation to a rotational direction of the belt member, the first optical module further including a first light receiver to receive beams reflected from the first set of registration marks and the first image density mark formed on the belt member and to generate detection signals in accordance with the received beams; and a second optical module to detect the toner images representing the second set of registration marks formed on the belt member as the belt member moves in the cross-scan direction, the second optical module including a second light emitter disposed to radiate a beam onto the belt member at a location which is downstream of the last one of the OPC drums and upstream of where the inner surface of the belt member disengages contact with the one of belt rollers that is closest to the last one of the OPC drums in relation to the rotational direction of the belt member, the second optical module further including a second light receiver to receive beams reflected from the second set of registration marks formed on the belt member and to generate detection signals in accordance with the received beams, wherein, during execution of subsequent printing operations, a color registration error and an image density error are capable of being compensated based on information obtained via the first set of registration marks, the second set of registration marks and the first image density mark formed on the belt member.