1. An image input apparatus comprising: feed means for feeding an object in a constant direction; illumination means having a light source for applying light rays toward the object fed by the feed means in the constant direction and a filter for cutting heat rays from the light source while allowing visible light rays to pass through; monochromatic and color pickup means for picking up the object illuminated by the light rays with a linear field of view intersecting the feed direction; and cooling means for forced cooling by generating an air flow between the light source of the illumination means and the filter, wherein the monochromatic pickup means has a high resolution appropriate for a character recognition and the color pickup means has a low resolution appropriate for a character area detection.