| 摘要 |
A light guide 3 has a cross-sectional shape substantially oval. An end of a major axis side of the oval is cut (chamfered) to include a focal point of the oval. Light scattering patterns 3P are provided on a plane 3d formed by cutting. The light guide 3 is housed in a light guide casing 4 to allow the emission plane 3a to be exposed, and a light-emitting source base plate is provided on an end surface of the light guide 3 in the longitudinal direction to form a line-illuminating device 10. This line-illuminating device 10 shows characteristics in which intensity distribution in a sub-scanning direction is not changed much relative to elevation of a document surface. Accordingly, if an optical axis of a rod lens 5 and a light-receiving surface of a line image sensor 6 are arranged in an area with less change of light intensity relative to elevation of the document surface, it is possible to reduce possible deterioration of a reading image even when the document surface is elevated
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