| 摘要 |
A line-illuminating device 10, 20 having a light guide 11, 21 of which the cross-sectional shape is rectangular and its one comer is chamfered to form an emission plane 11a, 21a is provided, in which the light guide 11, 21 is housed in a light guide casing 12, 22, wherein the chamfer dimension of the emission plane 11a, 21a is more than 40% of a height dimension of the light guide 11, 21. By enlarging the chamfer dimension and broadening the width of the emission plane 11a, 21a, the directional characteristics of the emitted light is expanded. In this manner, it is possible to reduce the extent of decrease in the quantity of illuminating light on a document surface when the document surface is elevated.
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