IMAGE READING APPARATUS

摘要

Provided is an image reading apparatus that can inhibit occurrence of a bright spot line image due to microstructures of a light guide. An image reading apparatus satisfies: 45−φ≦θ≦φ−ω/n (0≦ω≦ωmax); and 45−φ≦θ≦φ(−ωmax≦ω≦0), where θ is an angle (deg.) between a surface of original and a reflecting surface of a microstructure reflection surface of a light guide, ω is a half angle of view (deg.) of an imaging forming lens, ωmax (ωmax>0) is a maximum value (deg.) of the half angle of view of the imaging forming lens on an LED light source side with respect to a reading optical axis of the imaging lens, −ωmax is a maximum value (deg.) of the half angle of view of the imaging lens on a side opposite to the LED light source with respect to the reading optical axis, n is a refractive index of the light guide, and φ=sin−1(1/n).

主权项

1. An image reading apparatus, comprising:
an illumination unit comprising a light source and a light guide for guiding a light flux from the light source to a surface of original, the light guide being elongated in a first direction; and an imaging unit for collecting a light flux from the surface of original, wherein the light guide comprises:
an incident surface provided on an end surface in the first direction, the light flux from the light source entering the incident surface;an exit surface from which a light flux from the incident surface exits, the exit surface being elongated in the first direction; anda light guide surface opposed to the exit surface, for guiding the light flux from the incident surface to the exit surface, wherein the light guide surface comprises a plurality of prisms each having a reflecting surface opposed to the incident surface, and wherein the following conditions are satisfied:
45−φ≦θ≦φ−ω/n (0≦ω≦ωmax); and45−φ≦θ≦φ (−ωmax≦ω≦0)where, within a section perpendicular to the first direction, θ is an angle (deg.) between the original surface and the reflecting surface, w is a half angle of view (deg.) of the imaging unit, ωmax (ωmax>0) is a maximum value (deg.) of the half angle of view of the imaging unit on the light source side with respect to a reading optical axis of the imaging unit, −ωmax is a maximum value (deg.) of the half angle of view of the imaging unit on a side opposite to the light source with respect to the reading optical axis, n is a refractive index of the light guide, and φ=sin−1(1/n).