Image reading apparatus with function of correcting for variation of light distribution

An image reading apparatus comprising:

• a transparent member having transparency;
• a light irradiation unit that irradiates light toward the transparent member;
• an image reading unit that has reading elements aligned in a main scanning direction, which is a direction orthogonal to a conveying direction of an original, and that reads an image of the original that is conveyed over the transparent member;
• a reference member that is provided such that the transparent member is provided between the light irradiation unit and the reference member;
• a correction value determination unit that, in a case of continuous reading of a plurality of originals, determines a light quantity correction value for each main scanning position of each original based on a reading value obtained by the image reading unit reading the reference member between when a trailing edge of a preceding original passes through an image reading position of the image reading unit and when a leading edge of a succeeding original reaches the image reading position;
• an anomaly detection unit that detects, based on the reading value obtained from the reference member with respect to the preceding original and the reading value obtained from the reference member with respect to the succeeding original, an anomaly in the reading value with respect to the succeeding original, and specifies a main scanning position at which the anomaly occurs;
• and
• a modification unit that, upon detection of an anomaly by the anomaly detection unit, modifies a reading value at the main scanning position at which the anomaly occurs, out of reading values obtained from the reference member with respect to the succeeding original, or a correction value for the main scanning position at which the anomaly occurs, out of light quantity correction values with respect to the succeeding original,
• wherein in the case where the anomaly has been detected, the correction value determination unit determines the correction value using the reading value modified by the modification unit.