| 摘要 |
PROBLEM TO BE SOLVED: To provide a thin surface light source device which can obtain nearly surface-uniform luminance, on a light emission surface of a diffusion plate. SOLUTION: The image reader is provided with a light source 38, the diffusion plate 50, which increases in thickness from one end part to the other end part and a reflection member 52 which reflects the irradiation light from the light source 38 to the diffusion plate 50. The light source 38 is arranged at nearby the other end part of the diffusion plate 50. The luminance on the light- emitting surface 66 of the diffusion plate 50 is nearly uniform, over the surface and the light emitted by the light emitting surface 66 is made to uniformly irradiate the surface to be irradiated.
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