An image reading apparatus includes a gray reference member, a reading unit, an adjusting unit, a calibration unit, a storage unit, and a control unit. The control unit is configured to execute a first preprocessing and a second preprocessing. The first preprocessing includes: acquiring first black data from one line worth of image data; acquiring white data; calculating white-black difference data; acquiring first light gray data; and calculating first light gray-black difference data. The second processing includes: acquiring second black data from the one line worth of the image data; acquiring second light gray data; calculating second light gray-black difference data; calculating a change ratio by dividing the second light gray-black difference data by the first light gray-black difference data; and calculating calibration data by multiplying the white-black difference data by the change ratio. Shading of the image data is calibrated in response to the calibration data.

An image scanner includes a transparent plate, a scanning device, a driving device, a positioning member, a light absorbing portion and a white reference portion. The transparent plate has an original placing surface. The scanning device irradiates an original with light by means of a light source and scans reflected light from the original. The driving device reciprocates the scanning device along the transparent plate. The positioning member positions the original placed on the original placing surface of the transparent plate. The light absorbing portion, which is disposed on the original placing surface side of the positioning member and at substantially a central portion of the positioning member in moving directions of the scanning device, absorbs ambient light entering to the original placing surface side of the positioning member through the transparent plate. The white reference portion is provided to the original placing surface side of the positioning member.

A printer includes a discharge unit, a first printing unit disposed along a sheet conveying path extending from the discharge unit and configured to print an image on a first sheet while the first sheet is conveyed from the discharge unit to the first printing unit and then to the discharge unit, a second printing unit disposed farther from the discharge unit than the first printing unit along the sheet conveyance path and configured to print an image on a second sheet while the second sheet is conveyed towards the discharge unit therethrough, a scanning unit disposed along the sheet conveying path between the discharge unit and the first printing unit, and configured to scan a surface of the first sheet, and a control unit configured to perform a shading correction of the scanning unit using the second sheet as a white reference.

An optical apparatus includes a reader having a contact optical system including an image sensor configured to read light condensed by lenses after passing along light shields each disposed between the lenses, and a fixed member fixed to a position where the fixed member faces the reader and partially or entirely having a white part. The reader is configured to perform reading by adjusting a focus onto an image on a document passing across a position closer to the reader than is the fixed member, and perform reading by adjusting the focus onto the white part of the fixed member.