Patent ID: 8194294

Claim:
An image reading device comprising: an illumination portion, which irradiates light onto an original, including a plurality of luminescence portions disposed at predetermined intervals in a main scanning direction, a diffuser plate that is disposed between the original and the plurality of luminescence portions and causes the light emitted by the plurality of luminescence portions to diffuse, and a reflective portion that reflects light, which is a portion of the light diffused by the diffuser plate and not directly irradiated onto the original, so as to irradiate the light onto the original; at least one mirror that forms a light path by reflecting a luminous flux from the original; an imaging lens that forms an image from the luminous flux reflected by the at least one mirror; and a reading portion that is disposed in an imaging position of the imaging lens, and reads an image of the original based on image formation by the imaging lens, wherein the illumination portion further comprises a light splitting portion that is disposed between the diffusion plate and the original, and splits the light diffused by the diffusion plate into first diffused light that is directly irradiated onto the original and second diffused light that is irradiated onto the reflective portion.