Light guide, line-illuminating device, and image-scanning device

Abstract

A light guide, a line-illuminating device, and an image-scanning device are provided which are excellent in uniformity of the light amount. A light-reflecting portion comprised of tubular concave surfaces becomes a reflecting surface having tubular convex surfaces when seen from the inside of the light guide. With such structure, even when the incident angle of light from a light source unit slightly displaces, the reflection angle in the tubular convex surfaces significantly changes. In an irregular surface having a triangular shape, as in a conventional example, the incident angle becomes almost uniform in the area far from the light source unit, and thereby the reflection angle also becomes uniform. Consequently, it is difficult to achieve uniform reflection in the main-scanning direction. However, with the tubular concave surfaces, light is reflected uniformly toward the upper surface as a light-emitting surface.