| 摘要 |
PURPOSE:To prevent completely illumination light from being reflected by a slit and incident and to obtain image of high quality by employing a plane surface opposite the slit of the 1st Fresnel lens of a copying machine with a function which forms a white frame at the end part of a projection image, and then forming plural small lenses which have a specific Fresnel lens on the opposite surface from the plane surface. CONSTITUTION:The 1st Fresnel lens F1 is so formed that plural small lens surfaces (c) and (d) which have different Fresnel angles and make projection light incident in parallel to the axis of a photosensitive drum consist of a top- side half surface 12 and a reverse-side half surface 13 symmetrical about an optical axis 11 set at the center part of the Fresnel lens body 10. Therefore, reverse surfaces (e) and (f) of a surface where the small lens surfaces (c) and (d) of the Fresnel lens body 10 are arrayed annularly along the lengthwise direction of the photosensitive drum are formed in a plane shape. Consequently, the illumination light l which is irradiated by an original illumination lamp 9 and strikes on the small surface (c) of the reverse half surface 12 is reflected regularly in direction deviating from the direction of the slit S as shown by an arrow A.
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