| 摘要 |
PURPOSE:To detect an optical system being dirty and to obtain an adequate picture while the optical system is invariably clean, by detecting and comparing the potential of one of potential parts formed based upon the exposure of a reference original with the reference potential of the potential part. CONSTITUTION:On a photoreceptor 15, the reference potential part consisting of a high potential part corresponding to a black part 3, a low potential part corresponding to a white part 4, and a fine streak part 6 with a little bit lower potential than the high potential part is formed separately from a picture part of an original 7. When the amount of exposure is deficient, the potential of the whole part rises and when the amount of charging is deficient, the potential drops, but in such a state, a comparison with a referece signal corresponding to prescribed initial condition is made by a control circuit 21 to supply a necessary control signal from a control circuit 21 according to the result of the comparison. According to whether the thin streak part 6 uses black or white, the reference potential is determined and the dirtying of the optical system 14 is detected by variation in the potential of a corresponding part of the thin streak part 6. Consequently, whether the optical system 14 is cleaned or not is displayed automatically. |
