Patent ID: 7817317

Claim:
An image reading apparatus comprising: an image reading unit including a light source for illuminating an original and an image sensor adapted to read images of the original at a predetermined original reading position; a first reference member arranged at a first position having a first optical distance between the first position and the image sensor that is different from a second optical distance between the original reading position and the image sensor; a reference data acquiring unit adapted to acquire first reference data based on data read from the first reference member by the image reading unit, and adapted to acquire second reference data based on data read from a second reference member positioned at the original reading position or a position substantially identical to the original reading position by the image reading unit; a correction data generating unit adapted to generate first correction data based on the first reference data and adapted to generate second correction data based on the second reference data; a shading correction data generating unit adapted to generate shading correction data referring to the first reference member, and based on the first correction data and the second correction data; and a shading correction unit adapted to perform a shading correction of the images of the original read by the image reading unit based on the shading correction data generated by the shading correction data generating unit, wherein the shading correction data generating unit performs shading correction data generation processing in which a compensation is applied to data which is based on data read from the first reference member using the first and second correction data generated from the first and second reference members, and wherein the compensation is applied in consideration of a difference of light intensity distribution resulting from a difference between the original reading position and the first position of the first reference member.