| 摘要 |
PURPOSE:To change the cutoff amount of exposure luminous flux and to uniformize exposure amount distribution in a longitudinal direction by providing lens edge surface parts with light shielding plates and displacing the light shielding plate perpendicular to a lens optical axis and in a direction corresponding to the longitudinal direction of a slit-shaped exposure part. CONSTITUTION:The two light shielding plates 10 and 11 are provided on the lens edge surface parts 3A and 3B. The light shielding plates 10 and 11 are provided on a lens holding member 3-1 holding an image-formation lens system 3 and displaced integrally with the system 3. That is, when the system 3 is displaced, the light shielding plates 10 and 11 are also displaced. Every time a copying magnification is changed, the light shielding plate 10 is displaced perpendicular to the lens optical axis in the direction in response to the longitudinal direction of the slit-shaped exposure part. Therefore, the cutoff amount of the exposure luminous flux is changed based on the displacement of the light shielding plates 10 and 11 so as to uniformize the exposure amount distribution. Thus, irrespective of the changing of the copying magnification, slit exposure can be achieved always with the appropriate exposure amount distribution. |
