Patent ID: 7505057

Claim:
A color image forming apparatus, comprising: an image forming unit configured to form a latent image for each of a plurality of colors by scanning a corresponding photoconductor with a light beam based on an input image, and to develop the latent image into a color toner image in the corresponding color; a transfer mechanism configured to transfer the color toner image in turn onto a transfer medium to form a color image in the plurality of colors; a pattern forming mechanism configured to control the image forming unit to form a first pattern for color registration adjustment, and to form a second pattern for color registration adjustment when requested, wherein each of the first and second patterns includes at least a set of marks each corresponding to one of the plurality of colors, arranged in parallel to each other, and the marks in the first and second patterns are formed at a predetermined interval and at a longer interval than the predetermined interval, respectively, as the pattern forming mechanism forms the marks in different time intervals between the first and second patterns; a detection mechanism configured to detect the marks in the first and second patterns; a displacement calculation mechanism configured to obtain a predetermined value and preset reference values, to calculate an amount of displacement of each of the detected marks in the first and second patterns based on the corresponding preset reference values, to determine whether or not the amount of the displacement is equal to or less than the predetermined value when the amount of the displacement is measured by using the first pattern, wherein the displacement calculation mechanism requests the pattern forming mechanism to form the second pattern when the amount of the displacement is larger than the predetermined value, and a displacement correction mechanism configured to control the image forming unit to correct the displacement based on the amount of the displacement by forming a latent image so as to offset the amount of the displacement.