Image sensor and image reading apparatus

An image sensing unit comprising:

• an illumination section including a long light guide having a length adapted to illuminate across the width of a document and a light source provided at the end of said light guide;
• image sensing elements arranged along the length of said light guide adapted to convert an optical image of the document into an electrical signal;
• a plurality of cylindrical lenses arranged along the length of said light guide adapted to focus the optical image on said image sensing elements;
• and
• a frame adapted to integrally hold said illumination section, said image sensing elements, and said lenses,
• wherein a surface of said light guide on the document side, except an irradiation part, is inclined downwardly with respect to a lower surface of the light guide as a position of the surface recedes from said irradiation part in the direction perpendicular to the length direction so as to prevent light other than the light, irradiated from the irradiation part, from irradiating a reading position of the document to be read by said image sensing elements.