Scanner capable of compensating for distortion

A scanner comprising:

• an image read unit including an illumination unit to emit light onto a document, a linear image sensor having a length in a main scanning direction, and imaging optics to image light reflected from the document on the linear image sensor, wherein at least one of the illumination unit, the imaging optics, or the linear image sensor is movable in a sub-scanning direction;
• a compensation value calculation unit to:
• compare data read from a main scanning reference pattern including a plurality of main scanning sections arranged in the main scanning direction with data of the main scanning reference pattern that is previously stored, and
• calculate a plurality of main scanning scale compensation values respectively corresponding to the plurality of main scanning sections;
• and
• an image processing unit to compensate for distortion in the main scanning direction by dividing an image read from the document into a plurality of main scanning image areas respectively corresponding to the plurality of main scanning sections and applying the plurality of main scanning scale compensation values respectively to the plurality of main scanning image areas.