| 摘要 |
PURPOSE:To provide changeability freely only with low density without changing the density of the total copying by furnishing a screen means which can change the area ratio of the photo-transmissive region to photo-shield region continuously formed alternately in the exposure light path leading from document to a photo-sensitive body. CONSTITUTION:A full-color copying machine includes a clear document table 1 on the oversurface and an exposing optical system 2 which makes photo-scan over the document 11 placed on the table 1 and exposes a photosensitive body 3. A screen device 18 as screening means to enhance the gradation of the copying image is installed in the exposure light path in proximity to the sensitive body 3 situated below this exposure optical system 2. Because the photo-quantity of a light source is variable and the area ratio of the photo-transmissive region to shield region of the screening means is changeable, only the density of the copying image corresponding to the low density part of the document image can be changed without canging the density of the total copying image. |
