Illuminating device

摘要

A illuminating device used for an document reading apparatus that has two rod shape light guides and light emitting elements where each of the light guides has a light emitting face and two flat light reflection faces, which may have a group of minute prisms that are formed along the longitudinal direction of the faces, and where light from each light emitting element is guided in the longitudinal direction by the light guide and reflected by that faces, such that the light is emitted from the light emitting face of each light guide and a virtual plane that is vertical to a longitudinal direction of each of the two light guides has two light intensity peaks.

主权项

1. An illuminating device that illuminates a document disposed on a document surface plane of a platen, the document extending in a main scanning direction defined as to and between one side edge of the document and an opposing side edge of the document extending parallel to the one side edge and a subscanning direction defined as to and between a top edge of the document and an opposing bottom edge of the document extending parallel to the top edge, the subscanning direction being perpendicular to the main scanning direction, the document having a document reading axis extending thereacross to and between the one side edge and the opposing side edge in the main scanning direction and positioned between and extending parallel to the top edge and the opposing bottom edge with a reference plane extending through the document reading axis and perpendicularly to the main scanning direction and the subscanning direction, the illuminating device comprising:
a first rod shaped light guide extending in the main scanning direction and a second rod shaped light guide disposed apart from the first rod shaped light guide in a facially opposing manner and extending parallel thereto, the first and second rod shaped light guides disposed on opposing sides of the reference plane and equidistantly therefrom, each one of the first and second rod shaped light guides includes a first light reflection face and a second light reflection face extending thereacross, the first and second light reflection faces being oriented angularly relative to each other as viewed in cross-section at an angle being either greater than 180 degrees or less than 180 degrees, wherein light is reflected by the first and second flat light reflection faces of each one of the first and second rod shaped light guides such that the light is emitted therefrom onto a document surface of the document to form first and second light intensity peak positions thereon from the first rod shaped light guide and third and fourth light intensity peak positions thereon from the second rod shaped light guide, wherein the first and second light intensity peak positions are disposed on opposite sides of the document reading axis and the third and fourth light intensity peak positions are disposed on opposite sides of the document reading axis with the first and third light intensity peak positions being on a top edge side of the document reading axis while the second and fourth peak positions are disposed on a bottom edge side of the document reading axis, wherein the second light intensity peak position is disposed closer to the document reading axis than the first light intensity peak position and wherein the fourth light intensity peak position is disposed closer to the document reading axis than the third light intensity peak position.