Patent ID: 8320026

Claim:
An image reading apparatus comprising: an image sensor unit comprising a light source configured to irradiate illumination light onto an original document transferred to a predetermined image reading position, and a light receiving element configured to receive reflected light of said illumination light; a white reference member configured to perform shading correction, and provided so as to oppose said image sensor unit across a transferring path for said original document; an actuator configured to adjust a position of said white reference member in a direction of transferring said original document or to adjust an angle of said white reference member; and a control device configured to set a first position and a second position of said white reference member and to control said actuator so as to adjust said white reference member to said first position in which light reflected from said white reference member of said illumination light is received on said light receiving element when correcting shading, and configured to control said actuator so as to adjust said white reference member to said second position in which light reflected from said white reference member is not received on said light receiving element when reading an image, wherein said white reference member is a cylinder-shaped roller that transfers said original document; and said control device controls said actuator so as to adjust a position of said cylinder-shaped roller by displacing said roller from the first position to the second position along the direction of transferring said original document.