Image sensor chip and image reading device provided with it

An image reading apparatus comprising:

• a plurality of image sensor chips carrying a plurality of light receiving elements for photoelectric conversion, the plurality of light receiving elements having light receiving surfaces serving as a plurality of image reading picture elements, the plurality of image reading picture elements being arranged in a row at a constant pitch on the chip;
• a substrate carrying thereon the plurality of image sensor chips arranged in an array;
• a light source for irradiating a reading line area of a document image with light;
• a lens for focusing the light, which is irradiated by the light source and reflected from the document, at the plurality of image reading picture elements;
• wherein the number N of the image reading picture elements is defined as N=n·k (other than an integer multiple of 16);
• wherein n represents the number of image signals processed as a group when the image signals from the light receiving elements are subjected to level correction on a group-by-group basis;
• wherein k is a minimum integer satisfying =b 0<(n·k−γ·p)<n;
• wherein γ is a resolution defined as the number of image reading picture elements per predetermined unit length;
• wherein p is a minimum difference between required reading widths as calculated on the basis of said unit length.