Patent ID: 7680425

Claim:
An image forming apparatus comprising: a latent image carrier that carries an electrostatic latent image on its surface; a toner carrier rotated in a predetermined direction as carrying a toner on its surface, thereby transporting the toner to an opposing position with respect to the latent image carrier; and a controller operative to visualize the electrostatic latent image with the toner by transferring the toner carried on the toner carrier to the latent image carrier, thereby forming a toner image, and to control tone correction characteristics of the apparatus based on a detected density of the toner image formed as a patch image, wherein the patch image includes: a gradation image portion progressively varied in tone level thereof along a moving direction of a surface of the toner carrier at the opposing position; and a header image portion formed prior to formation of the gradation image portion and having a length along the moving direction that is a length corresponding to a circumferential length of the toner carrier or more, and wherein the header image portion is a solid image having a single tone level, the controller determines image densities of plural points in the header image portion, and corrects each of the detected densities of the gradation image portion based on the density of the corresponding point as to the circumferential length of the toner carrier, thereby removing periodical density variations from the detected densities of the gradation image portion, and the gradation image portion is an image varied in the tone level thereof from a maximum level to a minimum level along the moving direction.