| 摘要 |
PROBLEM TO BE SOLVED: To effectively reduce or eliminate the effect of ghost light by a transparent parallel flat plate for dust protection by arranging the transparent parallel flat plate for dust protection, arranged between a scanning image forming lens and a surface to be scanned, slantingly to a subscanning correspondent direction. SOLUTION: The transparent parallel flat plate 3 for dust protection is provided at a partition part which partitions an optical scanning device side and an image formation part side and prevents suspended dust from the image formation part side from entering the optical scanning device side. At this time, this plate is provided at a tilt angleθs to the subscanning corresponding direction. Thus, the tilt angleθs of the transparent parallel flat plate 3 is properly set to make reflected light from the parallel flat plate 3 not return to the scanning image forming lens 2 or reduce a part returning to the scanning image forming lens 2. Consequently, the generation of ghost light can effectively be prevented or reduced.
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