Abstract: An image reading apparatus acquires first image data of a background portion stored in advance and read by a reading unit, acquires second image data by reading the background portion, generates third image data by increasing resolution of the first image data and fourth image data by increasing resolution of the second image data, detects an amount of shift of an image sensor relative to a lens array in a predetermined direction by shifting a specific pixel range of the fourth image data relative to the third image data and comparing the specific pixel range with the third image data, and compares fifth image data obtained by shifting the fourth image data in accordance with the shift amount with the third image data, so as to determine whether each of pixels included in the fifth image data is a defective pixel having an abnormal value.

Abstract: An image reading apparatus acquires first image data of a background portion stored in advance and read by a reading unit, acquires second image data by reading the background portion, generates third image data by increasing resolution of the first image data and fourth image data by increasing resolution of the second image data, detects an amount of shift of an image sensor relative to a lens array in a predetermined direction by shifting a specific pixel range of the fourth image data relative to the third image data and comparing the specific pixel range with the third image data, and compares fifth image data obtained by shifting the fourth image data in accordance with the shift amount with the third image data, so as to determine whether each of pixels included in the fifth image data is a defective pixel having an abnormal value.

Abstract: The controller of the image reading apparatus acquires second reference data indicating a reading value of a background plate by causing the reading unit to read the background plate during a non-document-reading period between a document-reading period and a document-reading period, calculates a first difference indicating a difference between a value in a first pixel range corresponding to an element group, among the plurality of photoelectric conversion elements, in a range under temperature influence by a given heat generation source and a value in a second pixel range, that is, part of a pixel range which does not fall under the first pixel range with respect to the second reference data, and updates, when the first difference exceeds a first allowable value, the first reference data by correcting a value in the first pixel range of the first reference data based on the first difference.

Abstract: The controller of the image reading apparatus acquires second reference data indicating a reading value of a background plate by causing the reading unit to read the background plate during a non-document-reading period between a document-reading period and a document-reading period, calculates a first difference indicating a difference between a value in a first pixel range corresponding to an element group, among the plurality of photoelectric conversion elements, in a range under temperature influence by a given heat generation source and a value in a second pixel range, that is, part of a pixel range which does not fall under the first pixel range with respect to the second reference data, and updates, when the first difference exceeds a first allowable value, the first reference data by correcting a value in the first pixel range of the first reference data based on the first difference.