Abstract: A developing apparatus is provided in which the concentration of a toner in a developer material and the amount of developer material is kept constant by the use of simple mechanical parts so as not to deteriorate the electrification performance of the developer material. In the image forming apparatus of the present invention, a pocket 25 of a discharged developer material weighing part 20 receives a discharged developer material discharged from a developer material discharge port 14. Each time the accumulated weight thereof reaches a prescribed weight, the discharged developer material thus received is discharged into a discharged developer material receiving part 30, and this discharge is detected by a sensor 27. An unillustrated control unit counts this detection and calculates an amount of carrier decreased. Based on this result, a carrier supply roller 13 of the replenishment device is driven to replenish the carrier.

Abstract: The present invention employs a thickness detecting mechanism including a system for emitting polarized light and a reception system for receiving reflected light and generating electric signals. By use of this thickness detecting mechanism, the thickness of a toner layer attached to a latent image is measured. Developing conditions are controlled in relation to the measured thickness.

Abstract: A developing apparatus of the present invention has a mechanism capable of reducing the conductivity of a toner liquid. When the conductivity of the toner liquid is increased as a result of the replenishment of the toner liquid, the conductivity of the toner liquid to a control initial value by a mechanism that can reduce the conductivity of the toner liquid, thereby a stabilized image can be obtained.