Patent ID: 7021541

Claim:
An original illuminating apparatus for use in an image reading apparatus to illuminate image information on an original, wherein the image information is imaged on reading means through a reading optical system, and wherein a sub-scanning direction in the image reading apparatus is a direction along which the reading means moves relative to the original, and a main scanning direction is a direction perpendicular to the sub-scanning direction and to a reading optical axis of the reading optical system, the apparatus comprising: a plurality of tubular light sources extending in the main scanning direction, wherein the plurality of tubular light sources are arranged in a direction of the reading optical axis such that, when viewed from a direction parallel to the reading optical axis, tube diameters of said tubular light sources overlap one another in a sub-scanning direction, and wherein when the tube diameter of the plurality of tubular light sources is D, and a quantity of overlapping between the adjacent two tubular light sources in the sub-scanning direction is N, the following relationship: 0.25 <N/D ≦1.0 is satisfied.