Patent ID: 8822908

Claim:
An image scanner comprising: a plate-shaped transparent member for placing a document thereon; a light source for irradiating a document with light through the transparent member; an image scanning section for scanning an image of the document irradiated with light from the light source; a dew-condensation determination member provided on the transparent member; a dew-condensation determination data acquisition section operable to cause the image scanning section to scan an image of the dew-condensation determination member to thereby acquire the scanned image as dew-condensation determination data; a black reference data acquisition section operable to cause the image scanning section to scan an image without the light irradiation by the light source, to thereby acquire the scanned image as black reference data; and a dew-condensation determination section operable, when a difference between image brightness represented by the dew-condensation determination data and image brightness represented by the black reference data is greater than a difference in brightness represented by a predetermined dew-condensation determination threshold value, to determine that dew condensation occurs on the transparent member.