| 摘要 |
PURPOSE:To uniform the illuminance distribution on a photosensitive material surface by fixing a light shielding member between an original surface and a lens, and cutting off the end part of luminous flux incident to the lens according to magnification. CONSTITUTION:The lens 3 is moved closer to the original surface than a position B for unmagnification copying during enlargement and moved closer to a photosensitive surface 2 during reduction. The light shielding member 5 is set fixedly at a position O between the original 1 and lens 3 and the contour of the light transmission part of the light shielding member is so formed that luminous flux reflected by the circumferential part of the original 1 is cut at a specific rate as the magnification varies from enlargement to reduction. When an exposing means for providing original surface illuminance necessary for the maximum variable power, the reflected light from the original end part is cut by the light shielding member at a rate corresponding to the magnification to obtain uniform illuminance distribution on the photosensitive material surface 2. When the ratio of the necessary quantity of light of the circumferential part during the maximum variable power to the center quantity of light is amax and the ratio of the necessary quantity of the light of the circumferential part during magnification (x) to the center quantity of light is ax, the cutting rate l1 during the magnification (x) is represented by an equation 5x. |
