Patent ID: 8233813

Claim:
An image forming apparatus comprising: an image forming unit including at least one image carrier that carries a latent image; at least one charging unit that charges a surface of the image carrier; a latent-image forming unit that forms a latent image on the surface of the image carrier charged by the charging unit; and a plurality of developing units that have developer carrying units containing toners of different colors, respectively, and apply developing biases to the developer carrying units to transfer the toner onto the latent image on the surface of the image carrier, so that a toner image is formed on the image carrier; a transferring unit that transfers the toner image onto an endless rotating member or on a recording medium carried by the endless rotating member; an optical detecting unit that detects a reflected light from the toner image on the endless rotating member; and a control unit that causes the image forming unit to form a plurality of tone patterns with the toners of different colors, respectively, on the image carrier and causes the transferring unit to transfer the tone patterns from the image carrier to the endless rotating member, each of the tone patterns containing a plurality of toner patches having different toner densities, calculates index values of developing performances of the developing units, respectively, based on a result of detection of the toner patches by the optical detecting unit, and controls image forming conditions for the different colors based on the index values, respectively, wherein when forming the tone patterns the control unit provides control such that some of the toner patches in each of the tone patterns are formed under a predetermined fixed image forming condition, rest of the toner patches in each of the tone patterns are formed under previous image forming conditions, respectively, the previous image forming conditions being image forming conditions set based on the previous image forming conditions obtained by the control unit through a previous control process, and a target toner density of a largest toner density of the rest of the toner patches in each of the tone patterns is determined based on a magnitude relation of previous index values calculated by the control unit through the previous control process.