Light guiding unit, and light illuminating device and image reading apparatus using the same

摘要

Provided is a light guiding unit including: a light guiding member including an incident surface, an exit surface elongated in a first direction, and a light guiding surface opposed to exit surface; and a diffusion member opposed to light guiding surface, in which: light entering the light guiding member from incident surface is guided via light guiding surface and diffusion member to exit surface, and exits from exit surface to illuminate the original; the light guiding member further includes a plurality of prisms arrayed in first direction on light guiding surface on a side opposed to diffusion member; each of prisms has a rectangular shape in a first section; and each of prisms satisfies the following condition: W tan(sin−1(1/n))≦H≦2W, where W and H represent a width and a height of each of prisms in the first section, respectively, and n represents a refractive index of the light guiding member.

主权项

1. A light guiding unit, which is to be used in an image reading apparatus configured to read an original, the light guiding unit comprising:
a light guiding member comprising an incident surface, an exit surface that is elongated in a first direction, and a light guiding surface opposed to the exit surface; and a diffusion member opposed to the light guiding surface, wherein light entering the light guiding member from the incident surface is guided via the light guiding surface and the diffusion member to the exit surface, and exits from the exit surface to illuminate the original, wherein the light guiding member further comprises a plurality of prisms arrayed in the first direction on the light guiding surface on a side opposed to the diffusion member, wherein each of the plurality of prisms has a rectangular shape in a first section including the first direction and being perpendicular to the light guiding surface, and wherein each of the plurality of prisms satisfies the following condition:
W tan(sin−1(1/n))≦H≦2W, where W represents a width of the each of the plurality of prisms in the first section, H represents a height of the each of the plurality of prisms, and n represents a refractive index of the light guiding member.