Patent ID: 8643921

Claim:
An image reader comprising: a reading unit configured to read an image on a document sheet while moving relative to the document sheet in an auxiliary scanning direction, wherein the reading unit comprises: a plurality of light sources each of which is configured to emit light of a wavelength different from wavelengths of the other light sources; a light introducing unit configured to introduce the light emitted by each light source so as to be incident onto the document sheet; and a light receiving unit comprising light receiving elements disposed linearly along a main scanning direction perpendicular to the auxiliary scanning direction, the light receiving unit being configured to receive light reflected from the document sheet and output a reading signal corresponding to a light intensity of the received light; a driving current supplying unit configured to supply a predetermined driving current to each light source; a light-emitting-time determining unit configured to determine a light-emitting time separately for each light source and a non-light-emitting time, in a predetermined reading period, wherein the light-emitting time is a period of time during which one of light sources is required to emit the light such that the light receiving unit receives the reflected light of a light intensity necessary for reading the image on the document sheet in the predetermined reading period under the driving current supplied to the light source from the driving current supplying unit, and wherein the non-light-emitting time is a period of time during which none of the light sources is required to emit the light in the predetermined reading period; a light-emitting-timing setting unit configured to divide the non-light-emitting time into a plurality of segmental non-light-emitting times and set a light-emitting moment separately for each light source as a moment to emit the light in the predetermined reading period, such that the segmental non-light-emitting times are arranged in a dispersed manner in the predetermined reading period; and a controller configured to control each light source to emit the light during the light-emitting time determined by the light-emitting-time determining unit at the light-emitting moment set by the light-emitting-timing setting unit.