Patent ID: 8873979

Claim:
A development device comprising: a developer container for containing two-component developer; a developer bearer to carry by rotation the developer contained in the developer container to a development range facing a latent image bearer; a partition dividing at least partly the developer container into an upper compartment and a lower compartment arranged vertically; an upper developer conveyance member disposed in the upper compartment to transport the developer inside the upper compartment; a lower developer conveyance member disposed in the lower compartment to transport the developer inside the lower compartment; a communication portion through which the developer moves from the lower compartment to the upper compartment, the communication portion disposed in a downstream end portion of the lower compartment in a direction in which the lower developer conveyance member transports the developer; and a toner concentration detector to detect a concentration of toner in the developer beneath the communication portion inside the lower compartment, the toner concentration detector being positioned directly beneath the communication portion with respect to a vertical direction and a longitudinal direction, and the toner concentration detector being positioned beneath the lower developer conveyance member.