| 摘要 |
PURPOSE:To measure toner density for a long time with high accuracy and with stability, by projecting light from a light source to an upstanding tuft part of developing agents through a transparent plate and receiving reflecting light with photoelectric conversion elements. CONSTITUTION:A dry type magnetic two-component developing agent 20 consisting of magnetic powder and toner powder is held and transported while forming an upstanding tuft part with a function of a magnetic roll 17, and electrostatic latent images which are formed in a photosensitive drum 11 are toner-developed as the upstanding tufts act on the drum 11. The upstanding tuft part of the agent 20 opposing to a transparent plate 25 is arranged in a shape matching to a magnetic line of force and at the same time is regulated at a certain height with the plate 25, which causes a gap. The light from a light source 33 reaches the agents 20 through the plate 25 and the upstanding tuft gap, and reflects irregularly, a part of it reaches photoelectric conversion elements through the plate 25, and then the reflectivity of the agents 20 is measured. |
