Patent ID: 8090281

Claim:
A tandem-type color image forming apparatus that conveys a toner image or a recording sheet with use of a conveyor, comprising: a toner pattern former operable to form, on the conveyor, a toner pattern in which tone levels vary in a sub scanning direction; a toner marker former operable to form, on the conveyor, toner markers each opposing, in a main scanning direction, a different one of tone level portions in the toner pattern so as to indicate positions of the tone level portions, each tone level portion representing a different one of the tone levels, and the toner markers being a same color as the toner pattern; a position determiner operable to determine the positions in the sub scanning direction by reading the toner markers; a density detector operable to detect a density of each of the tone level portions corresponding to the determined positions; and a corrector operable to correct, in an image formation, tone of image data based on a relationship between the density and a tone level of the corresponding one of the tone level portions.