Image reading device, image forming apparatus, and image reading method

An image reading device comprising:

• a low resolution imaging portion including a plurality of light receiving elements arranged with a first pitch in a main scanning direction from a first reference position;
• a high resolution imaging portion including a plurality of light receiving elements arranged with a second pitch in the main scanning direction from a second reference position which is separated from the first reference position by a predetermined distance in a sub scanning direction, a resolution of the high resolution imaging portion being n times that of the low resolution imaging portion, where n is an integer;
• a data generating portion configured to generate image data of a document that is a reading target, using output data from the high resolution imaging portion and the low resolution imaging portion;
• a first reading portion configured to acquire, from the high resolution imaging portion, as the output data for one pixel, data acquired by n-number of the light receiving elements that are adjacent to each other in the main scanning direction in the high resolution imaging portion;
• a second reading portion configured to acquire the output data from the light receiving elements arranged in the main scanning direction from a start position which is a position displaced by a distance corresponding to m times the second pitch in the main scanning direction from the first reference position in the high resolution imaging portion, where m is an integer;
• and
• a reading control portion configured to execute a reading operation for a document by the low resolution imaging portion and the high resolution imaging portion, selecting the first reading portion or selecting both of the first reading portion and the second reading portion.