Patent ID: 8005386

Claim:
An image forming apparatus comprising an image bearing member, a development device which develops an electrostatic image formed on the image bearing member, a developer bearing member which is provided in the development device so as to be opposed to the image bearing member, and which carries a developer, a density sensor which emits light to the developer bearing member on the surface that carries the developer, and which can detect developer density on the developer bearing member by a reflection output value of the developer, and a supply device which supplies a supply developer to the development device in accordance with a detection result of the density sensor, wherein if a reflection output value detected by the density sensor in a state where the developer is carried on the developer bearing member is defined as A and a reflection output value detected by the density sensor in a state where the developer is not carried on the developer bearing member is defined as B, a value of B/A is in a range of 0.3<B/A<2.