Patent ID: 7953334

Claim:
An image-forming apparatus comprising: a plurality of rotatable rollers; 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 a plurality of toner patch images; an optical sensor disposed opposite a first roller of the plurality of rotatable rollers, wherein the optical sensor detects reflected light when the plurality of toner patch images are irradiated with light; a storing unit that stores detection results detected by the optical sensor in no toner areas of the endless belt where no toner images are formed; and a correcting unit that corrects the detection results detected by the optical sensor when the plurality of toner patch images are irradiated with light based on the stored detection results of the no toner areas detected at a plurality of positions of the first roller, wherein each of the positions synchronizes with a position of the first roller, the position when the detection result of the patch to be corrected is detected, wherein a length of the no toner areas in a direction in which the endless belt is moved is approximately equal to or equal to a circumference of the first roller.