| 摘要 |
PURPOSE:To keep a surface density constant by comparing the ratio of the surface density and a standard pattern image density with a reference value, and controlling an exposing quantity with the value of the compared ratio. CONSTITUTION:Toner density control forms the standard black pattern image on a photosensitive body 121, reads the reflection input of the irradiating light of a P sensor PSN, and compares the fact with the reference value of a toner density to turn on/off the toner replenishing roller clutch of a developing unit. When it is judged that the density is light, the clutch is turned on at every sheet till the 10th sheet of the next detecting time, and tone replenishing is continued via the replenishing roller. When it is judged that the density is dark, the replenishing is not carried out till the next detecting time. In toner density detection, the drum 121 is rotated, a light emitting diode 404 is turned on when a P sensor pattern image reaches a P sensor position, the P pattern image is irradiated with light, and reflected light is received by a phototransistor 403 to detect the density of the P pattern image. Thus, the surface density of the image can be kept constant. |
