Patent ID: 8391736

Claim:
An image-forming apparatus comprising: a plurality of rotatable rollers including a sensor-opposite-roller; an endless belt suspended and moved by the rollers; an image forming unit that forms a toner image on the endless belt, wherein the image forming unit forms toner patch images of individual colors, the patch images being for density adjustment of the image-forming apparatus; an optical sensor disposed opposite the sensor-opposite-roller, and detecting reflected light when the toner patch images of individual colors are irradiated with light; a storing unit that stores detection results detected by the optical sensor in no toner area of the endless belt where no toner images are formed at each position of the sensor-opposite-roller, wherein a length of the no toner area in a direction in which the endless belt moved is shorter than a total length of the toner patch images of the individual colors; a correcting unit that corrects the detection results of toner patch images detected by the optical sensor based on the stored detection results of the no toner area, wherein the detection results of the no toner area, which are used for correcting the detection results of the toner patch images of the individual colors, are the detection results of the no toner area at a position corresponding to a detection position of each of the toner patch images; and a modifying unit that modifies the detection results when the optical sensor detects the toner patch images, based on a storing value stored in the storing unit corresponding to a position of the sensor-opposite-roller of the detection result, wherein the endless belt does not have a circumference equal to an integral multiple of that of the sensor-opposite-roller.