| 摘要 |
PURPOSE:To always automatically adjust the optimum density of an image irrespective of overshooting of a lighting source and the soiling of an illumination system by irradiating an original and a member having uniform density (reference) with light and controlling an exposure means by using the ratio of the reflection light quantity. CONSTITUTION:When a copying command is generated, a halogen lamp 3 is turned on, and also, the original 1 is preliminarily scanned. The light beams reflected at the original 1 and the member 6 having the uniform prescribed density are detected by a photodetector 4 in a short time (measurement interval between two <1 second), and the ratio of both outputs is detected, and then, the lighting voltage for the halogen lamp 3 is adjusted by a control part 5 in accordance with the value of the ratio. For example, in the case that the image density of the original is high, the lighting voltage for the halogen lamp 3 is set higher so as to increase the exposure quantity. And in the case of main scanning succeeding to the preliminary scanning, the halogen lamp 3 is turned on by the lighting voltage which is set in accordance with the image density, and the original 1 is exposed and a copied image is formed on the sheet in accordance with the original image. |
