| 摘要 |
An illumination device that illuminates an original document by propagating an illuminating light beam output from each of a plurality of light emitting diodes from a first end surface of a light guide to a second end surface of the light guide. Assuming that A is a dimension from the first end surface of the light guide to the second end surface of the light guide, B is an interval between adjoining light emitting diodes, the light emitting diodes being arranged in an array format in a main scanning direction, n 1 is a refractive index of atmosphere outside of the light guide, and n 2 is a refractive index of the light guide, a condition of tan<SUP>-1</SUP>(B/2A)<=beta<=pi/2-{sin<SUP>-1</SUP>(n 1 /n 2 )} is satisfied.
|
