Image forming apparatus and method for correcting color misregistration by the same

An image forming apparatus capable of forming color images using different colors of toner, comprising:

• a plurality of imaging units each containing a different color of a photoconductor, and forming a visible image with toner on the photoconductor;
• a transfer member that rotates unidirectionally and onto which the visible toner images formed by the respective imaging units are transferred;
• and
• an image correcting unit that corrects the visible toner images, which are formed on the transfer member by the imaging units, at predetermined timings,
• wherein the image correcting unit includes
• a toner amount sensor that detects amounts of toner of the visible toner images formed on the transfer member,
• a toner density adjustment patch image forming section that forms toner density adjustment patch images on the transfer member, the toner density adjustment patch images being used to adjust toner densities of each color,
• a toner-density adjusting section that measures amounts of toner of the toner density adjustment patch images of each color, which are formed by the toner density adjustment patch image forming section, by using the toner amount sensor, and adjusts the toner densities of each color,
• a toner density adjustment patch image misalignment measuring section that measures amounts of misalignment of the toner density adjustment patch images formed by the toner density adjustment patch image forming section,
• a color-misregistration correction patch image forming section that forms color-misregistration correction patch images on the transfer member after the toner density adjustment patch image forming section forms the toner density adjustment patch images, the color-misregistration correction patch images being used to correct color misregistration of the visible toner images of each color,
• a color-misregistration correcting section that measures amounts of misalignment of the color-misregistration correction patch images formed by the color-misregistration correction patch image forming section to correct the color misregistration, and
• a control unit that controls the color-misregistration correction patch image forming section to change the color-misregistration correction patch images to be formed in accordance with the amounts of misalignment of the toner density adjustment patch images of each color measured by the toner density adjustment patch image misalignment measuring section.