Patent ID: 8238768

Claim:
An image forming apparatus comprising: a latent image carrier that holds a latent image; an image information obtaining unit that obtains image information; a latent image forming unit that forms a latent image on the latent image carrier based on the image information; a developing unit that conveys developer-containing toner and carrier along a predetermined circulation channel to a developing area that is an area where a developer holding body faces the latent image carrier by holding the developer on a moving surface of the developer holding body in a supply area that is an area of the circulation channel facing the developer holding body, that develops a latent image on the latent image carrier by attaching the toner in the developer thereto in the developing area, and returns the developer contributed to the development in the developing area to the supply area of the circulation channel along with the movement of the surface of the developer holding body; a toner supplying unit that supplies toner to a non-supply area that is not the supply area in the circulation channel through a toner supplying opening arranged at a predetermined position in the non-supply area; and a controlling unit that determines a driving amount of the toner supplying unit based on the image information, wherein a toner concentration detecting unit is provided at a position downstream of the toner supplying opening in the non-supply area and upstream of the supply area to detect toner concentration in the developer, and the controlling unit is structured to recognize an excess or a shortage in an amount of supplied toner correspondingly to a detection result of the toner concentration detecting unit, and to correct a determined value of the driving amount determined based on the image information correspondingly to the excess or the shortage that has been recognized.