Patent ID: 8411320

Claim:
An image forming apparatus, comprising: multiple image forming units respectively that forms images of different colors; a density correction image formation control unit that instructs the respective image forming unit to draw images for forming density correction images of the respective colors, transferring the formed density correction images of the respective colors onto an image carrier, and forming the density correction images of the respective colors on the image carrier; a density detecting unit that detects densities of the density correction images of the respective colors formed on the image carrier; a density correction control unit that corrects densities of images of the respective colors based on density detection outputs by the density detecting unit on the density correction images of the respective colors; a color shift correction execution check unit that detects positions of the density correction images of the respective colors based on first binary signals of the density detection outputs by the density detecting unit on the density correction images of the respective colors, and also checks, based on the detection by the color shift correction execution check unit, whether a color shift correction processing is required to be executed or not; a color shift correction image formation control unit that, when the color shift correction execution check unit determines that the color shift correction processing is required to be executed, that instructs the respective image forming units to draw images for forming color shift correction images of the respective colors, transferring the formed color shift correction images of the respective colors onto an image carrier, and forming the color shift correction images of the respective colors on the image carrier; and, a color shift correction control unit that detects positions of the color shift correction images of the respective colors based on second binary signals of density detection outputs by the density detecting unit on the color shift correction images of the respective colors, and also corrects color shifts based on the detection by the color shift correction control unit.