| 摘要 |
PURPOSE:To detect toner or carrier deposited on a transparent detection window in an optical toner density detection method. CONSTITUTION:Two-component developer constrained with magnetic field is caused to periodically come in contact with a transparent detection window 54. In addition, the developer is exposed to light through the window 54 and toner density is detected on the basis of a light quantity reflected from the developer (i.e., output from a light receiving element 53). On the other hand, when the variation range VD of the reflected light quantity is equal to or less than the predetermined reference value, the occurrence of an abnormal condition due to toner or carrier deposition on the window 54 is confirmed and annunciated. According to this system, toner or carrier deposition on the window 54 can be detected at an early stage. |
