Patent ID: 7502041
Filing Date: 2009-03-10
Classification: G03G,H04N

Abstract:
1. An image forming apparatus which generates a sync clock signal and produces a color image by forming and superimposing first, second, third, and fourth elementary color toner images of a color image sequentially in this order in synchronism with the sync clock signal, the apparatus comprising: a first image forming mechanism configured to selectively form the first and third elementary color toner images of the color image; a second image forming mechanism configured to selectively form the second and fourth elementary color toner images of the color image; an intermediate transfer member including a reference marking and configured to perform two rotations per one cycle of producing a color image of the first, second, third, and fourth elementary color toner images sequentially superimposed; a mark detection mechanism configured to detect the reference marking on the intermediate transfer member; a measuring mechanism configured to measure a time that elapses after a detection of the reference marking by the mark detection mechanism; and a controller configured to instruct the first and second image forming mechanisms to start sequentially and alternately image writing for the first, second, third, and fourth elementary color toner images of the specific color image based on a value measured by the measuring mechanism, a number of image productions, and a number of rotations of the intermediate transfer member; wherein the reference marking includes a plurality of reference marks evenly spaced, and wherein a first image forming operation of the first elementary color toner image performed by the first image forming mechanism is started based on a proximate arbitrary reference mark and each one of subsequent image forming operations is started based on another proximate arbitrary reference mark distant from a preceding reference mark by a total length of a transfer sheet in a sheet conveyance direction applied and a spacing between a preceding transfer sheet and a following transfer sheet; and further comprising: a storage configured to store a first preset reference count, wherein the image writing starts in synchronism with the sync clock signal delayed by a number of counts indicated by the first reference count from the sync clock signal detected immediately after the detection of the reference marking, and the image writing stops in synchronism with the sync clock signal delayed by the number of counts indicated by the first reference count.