Patent ID: 7233749

Claim:
An image forming device, comprising: an image carrier on which a latent image is formed; a development device to which a plurality of development units for containing developer with the same color are detachably installed; and a control unit for forming a latent image on said image carrier based on a control parameter corresponding to said development unit and for developing said latent image by attaching the developer of said development unit thereto, wherein said control unit includes a calibration control unit for forming a latent image of a predetermined patch pattern on said image carrier at a predetermined calibration timing, developing said latent image by the developer of said development unit, detecting said developed patch pattern, and deciding said control parameter, wherein said calibration control unit stores a relationship of control parameters for said plurality of development units in a memory, wherein at said predetermined calibration timing, which comprises a timing when power is turned ON or a timing when said image carrier is replaced, said calibration control unit executes a first calibration by using only one arbitrary or one specific development unit out of said plurality of development units, and determines the control parameter for each unit based on said first calibration result and said relationship of the control parameters stored in said memory, and wherein, when said development unit is replaced or when the residual amount of developer of said development unit becomes a predetermined amount or less, said calibration control unit executes a second calibration by using said replaced development unit or by using said development unit of which the residual amount becomes said predetermined amount or less, and updates the relationship of the control parameters stored in said memory according to said second calibration result.