Ricoh Company, Ltd.

Norimitsu Kikuchi

Kazunori Bannai

Noboru Sawayama

Takashi Bisaiji

Takayuki Maruta

Takeyoshi Sekine

Nobuhiro Nakayama

Kouji Hayashi

Kazunari Yamada

Tetsuro Miura

An image forming apparatus having a developing device of the type using a two-component type developer and developing an electrostatic latent image by a bias electric field having an alternating electric field. A predetermined reference latent image is electrostatically formed on an image carrier by a reference latent image forming device and then developed by the developing device to become a reference toner image. An irregularity detecting circuit determines the degree of difference between the density of the edge and the density of the central portion of the reference toner image. A bias electric field control circuit controls the bias electric field in matching relation to the output of the irregularity detecting circuit, thereby preventing the image quality from being degraded by a change in the resistance of the carrier.

Electrophotographic image forming apparatus which controls developer

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Yokohama, Japan

Norimitsu Kikuchi