Image reading apparatus

An image reading apparatus for reading an image on an original document by irradiating the original document with light and photoelectrically converting reflected light from the original document by a contact type image pickup unit, comprising:

• an original document guide member that is positionable at a position opposite to the image pickup unit, with a conveyance position of the original document therebetween, and is used when the original document is conveyed;
• a white reference member that is positionable at the position opposite to the image pickup unit, with the conveyance position of the original document therebetween, the white reference member having a reference white color on a surface;
• an achromatic constant-density reference member that is positionable at the position opposite to the image pickup unit, with the conveyance position of the original document therebetween, the achromatic constant-density reference member having a reference achromatic constant-density on a surface;
• a drive unit that moves one of the original document guide member, the white reference member, and the achromatic constant-density reference member so as to be positioned at the position opposite to the image pickup unit;
• and
• a control unit that controls execution of a first detection processing for dust detection from data obtained by moving the achromatic constant-density reference member to the position opposite to the image pickup unit by the drive unit and by reading the achromatic constant-density reference member, and execution of a second detection processing for dust detection from data obtained by moving the white reference member to the position opposite to the image pickup unit by the drive unit and by reading the white reference member.