| 摘要 |
PURPOSE:To detect the density of originals even if a space between an exposure start position and a lens position in a magnification mode is narrow by moving a light source to an image forming lens in a maximum magnification mode before exposure starts and permitting a density detecting element to detect an original range B where an upstream original 8 is exposed and scanned. CONSTITUTION:An optical system before exposure start is in a status shown by full lines. When automatic exposure is selected, a lighting unit including a lamp 9 and a mirror 1 moves up to a broken line position, that is, the position of the image forming lens 12 in a maximum magnification mode. The density detecting element 13 detects the quantity of light reflected from the original 8 which lies within the original range B where the upstream original 8 is exposed and scanned, and based on the detected result the lighting voltage of the lamp 9 or a development bias voltage is controlled. After the density of the original is detected, the lamp 9, etc., return to their original exposure start positions, and images of the original 8 are exposed on a photosensitive drum. |
