Patent ID: 7962057

Claim:
An image forming apparatus, comprising: a developing apparatus for developing an electrostatic latent image formed on an image bearing member with a developer, the developing apparatus including a developer carrying member for carrying the developer to develop the electrostatic latent image with the developer and a developer supplying member having a foam layer into which the developer can enter for supplying the developer to the developer carrying member, the developer carrying member having a core electrode for rotatably supporting the developer carrying member, and the developer supplying member having a core electrode for rotatably supporting the developer supplying member; a developing apparatus moving device for moving the developing apparatus between a first position in which the developer carrying member is in contact with the image bearing member to perform a developing operation and a second position in which the developer carrying member is separated from the image bearing member to not perform the developing operation; and a detector for detecting information relating to capacitance between the core electrode of the developer carrying member and the core electrode of the developer supplying member when applying an alternating bias to the core electrode of the developer carrying member or the core electrode of the developer supplying member, wherein the detector detects the information relating to capacitance when the developing apparatus is in the second position.