| 摘要 |
An illumination device illuminates an original document by propagating an illuminating light beam output from each of a plurality of light emitting diodes (21) from a first end surface of a light guide to a second end surface of the light guide (22). Assuming that A is a dimension from the first end surface of the light guide (22) to the second end surface of the light guide (22), B is an interval between adjoining light emitting diodes (21), the light emitting diodes being arranged in an array format in a main scanning direction, ß is the angle of the direction where the light intensity of an LED is half of the maximum light intensity with respect to the direction of the optical axis of the LED, n1 is a refractive index of atmosphere outside of the light guide (22), and n2 is a refractive index of the light guide (22), a condition of tan -1 (B/2A)‰¤²‰¤À/2-{sin -1 (n1/n2)} is satisfied. |
