| 摘要 |
PURPOSE:To detect the concentration of a developer with always high accuracy and to control the concentration to a fixed value by providing the title device with an electrode arranged oppositely to a conductive transparent window, a developer concentration photodetecting means arranged on the opposite side to the electrode through the conductive transparent window and a means for forming an electric field between the conductive transparent window and the electrode. CONSTITUTION:The conductive transparent window 109a is formed on a developer carrying thickness regulating member 109 having a face in a direction crossing the outer periphery of a developer carrier 103, a developer concentration detector 111 consisting of a light emitting element and a light receiving element is formed on one face of the window 109a, a conductive counter electrode plate 113 is formed oppositely to the other face and an electric field is formed on a gap between the window 109a and the counter electrode plate 113 to allow the developer D to pass the gap. Thereby a trouble such as the adhesion of the developer D to the window 109a is not generated and the concentration of the developer D can be always accurately and stable detected. Consequently, the concentration of the developer D can be controlled always to a fixed value. |
