Image Reading Apparatus

An image reading apparatus that reads an image of a sheet under one of a plurality of reading conditions, the image reading apparatus comprising:

• a reference member;
• a light source unit that emits light to the sheet or the reference member;
• a reading unit that outputs an output value based on reflection light from the sheet or the reference member;
• a light intensity adjusting unit that adjusts at least one of luminosity and lighting time of the light source unit such that the output value from the reading unit reaches a predetermined value;
• a white reference value generating unit that generates a group of white reference values based on the output value from the reading unit under one of the plurality of reading conditions in a state where the light source unit is turned on with the luminosity and lighting time adjusted by the light intensity adjusting unit;
• a white reference value storing unit that stores the group of white reference values generated by the white reference value generating unit and the luminosity and lighting time adjusted by the light intensity adjusting unit;
• a white reference value converting unit that converts the group of white reference values stored in the white reference value storing unit into a group of white reference values of a different reading condition based on a correlation between the reading condition under which the group of white reference values is generated by the white reference value generating unit and the different reading condition;
• a sheet reading control unit that controls the reading unit to read the sheet while turning the light source unit on with the luminosity and lighting time stored in the white reference value storing unit when the image of the sheet is read under the one of the plurality of reading conditions;
• and
• a shading correcting unit that performs a shading correction for the output value output from the reading unit,
• wherein, if the one reading condition is the reading condition with which the group of white reference values is generated, the shading correcting unit performs the shading correction by using the group of white reference values that are stored in the white reference value storing unit, and
• wherein, if the one reading condition is a reading condition other than the reading condition with which the group of white reference values is generated, the shading correcting unit performs the shading correction by using the group of white reference values that are converted by the white reference value converting unit.