| 摘要 |
PURPOSE:To insert and remove easily a dot or halftone screen to and from the optical path in accordance with an original by providing a mark to be detected on a belt-shaped sheet correspondingly to each screen and providing a copying machine body with a means which detects said mark. CONSTITUTION:A belt-shaped sheet 101 which is brought into contact with the upper face of a contact glass 2 and carries the dot or halftone screen right and left movably is provided and is wound around a core 102. The belt-shaped sheet 101 is provided with marks 101c and 101d to be detected in positions corresponding to a dot screen 101a and a transparent screen 101b, and a sensor 104 is provided in one end of an original platen 2 in such position that it can detect said marks 101c and 101d. The sensor 104 is a transmission type sensor consisting of a light emitting element and a photodetector provided above and under the original platen, and each of said marks 101c and 101d consists of one or two lines which intercept the light, and these marks are detected to discriminate ends of the dot screen 101a and the transparent screen 101b. |
