Patent ID: 7528851

Claim:
An image forming apparatus comprising: a plurality of photoconductive members arranged in parallel, each corresponding to one of a plurality of color components that form a target image data; a memory device configured to prestore control information and registration pattern data; an optical writing device configured to form a latent image of each one of the plurality of color components on a corresponding one of the photoconductive members by controlling a laser beam based on the control information; a traveling member configured to travel in a direction perpendicular to a direction in which the plurality of photoconductive members are arranged; a toner pattern forming device configured to form a toner pattern, which includes a plurality of marks of the plurality of color components, on the traveling member according to the registration pattern data; a position detecting device configured to detect each of the plurality of marks in the toner pattern formed on the traveling member by the toner pattern forming device; a control information correcting device configured to correct the control information according to a difference among positions of the plurality of marks detected by the position detecting device; a main-scan registration correcting device configured to adjust, based on the corrected control information, a start-of-write timing in the main scanning direction in a unit of a pixel, clock cycle and to adjust a writing timing in the main scanning direction in a unit smaller than the pixel clock cycle by controlling a phase of the pixel clock cycle; a sub-scan registration correcting device configured to independently control a rotational speed of each of the plurality of photoconductive members of a corresponding one of the plurality of color components; and an image range correcting device configured to allocate a fraction generated by a calculation of a valid image range, calculated for each of the plurality of color components as a number of pixels based on a size of a recording medium within a main scanning range of a laser beam, to some of the pixels out of the valid image range by controlling a phase of pixel clock cycles corresponding to the pixels so as to correct dimensions of each valid image range in the main-scanning direction.