Patent ID: 8045874

Claim:
An image forming apparatus, comprising a latent image carrier; a charge device configured to charge the latent image carrier with a prescribed potential; a latent image forming device configured to form a latent image on the surface of the latent image carrier; a developing device having a developer-carrying member configured to carry developer at least including toner, said developing device applying a development bias to the developer carrying member and transferring the toner on the developer-carrying member to the latent image on the latent image carrier and developing the latent image; a transfer device configured to transfer a toner image from the latent image-carrying member to a transfer member; an optical detection device configured to detect a light reflected from the toner image on one of the latent image carrier and the transfer member; a control device configured to periodically form a gradation sequence pattern having at least two toner patches formed based on a different image formation condition attracting a different amount of toner with each other, said control device adjusting the image formation condition using a detection value detected by the optical detection device; wherein, said control device controls image formation such that at least one toner patch of the at least two toner patches included in the gradation sequence pattern is formed based on a prescribed fixed image formation condition so that a toner attraction amount attracting to the at least one toner patch enters a prescribed range detectable for the optical detection device within a variable range of development gamma defined by a relation between a toner attraction amount and a development potential, while forming the rest of the at least one toner patch based on a previously adjusted prescribed image formation condition so that data of a toner attraction amount attracting to the rest of the at least one toner patch enter the prescribed range dispersing substantially at the same interval.