Patent ID: 7684091

Claim:
An image reading apparatus, comprising: a transportation section for transporting a document on a predetermined transportation path; a first image reading section for reading out image from a first surface of the document transported on the predetermined transportation path; a second image reading section for reading out an image from a second surface of the document, at a position lower in a document transportation direction, relative to an image readout position where the image is read out by the first-image reading section; a speed detection section connected to the first and second image reading sections that detects a first document transportation speed when the first image reading section reads out the image, and a second document transportation speed when the second image reading section reads out the image; a reading cycle setting section connected to the speed detection section that sets a reading cycle, in the document transportation direction, of the first image reading section and/or the second image reading section, in accordance with a result of detection by the speed detection section; and a reference readout image acquisition section that acquires: (i) a first reference readout image which is read out by the first image reading section; and (ii) a second reference readout image which is read out by the second image reading section, from a reference document which is being transported on the transportation path and which has surfaces on which reference images are formed, respectively, wherein each of the reference images having have an image property that periodically or serially changes in a sub-scanning direction in parallel to the document transportation direction, in accordance with the image properties of the first and second reference readout images acquired by the reference readout image acquisition section; and the speed detection section detecting the document transportation speed when the first image reading section reads out the image and the document transportation speed when the second image reading section reads out the image.