Patent ID: 9264570
Filing Date: 2016-02-16
CPC Classification: H04N

Claim Text:
1. An image forming apparatus, comprising: an automatic document feeder (ADF) configured to feed a document automatically; a light source configured in a horizontal scanning direction to irradiate the document conveyed by the ADF with light; a control circuit configured to switch, when reading the document, a glass member arranged between the light source and the ADF to a first mode in which the light from the light source is transmitted and to a second mode in which the light from the light source is reflected; a signal processing circuit configured to include an image sensor for receiving the reflected light of the document and the reflected light of the glass member, read an image of the document in the first mode and generate a signal of a white reference value based on the reflected light of the glass member in the second mode; a shading correction circuit configured to correct, based on the signal of the white reference value, image data of the document read by the image sensor such that the brightness in the horizontal scanning direction is uniform; a printer section configured to process the image data corrected by the shading correction circuit to form an image on an image receiving medium; a carriage capable of moving the light source in a vertical scanning direction of the document; a white reference board configured at a position deviated from the glass member in the vertical scanning direction; and a driving control circuit configured to control in such a manner that the carriage is driven to enable the light from the light source to enter the white reference board, and the reflected light of the white reference board is input to the image sensor, wherein the signal processing circuit generates a signal of a first white reference value based on the reflected light from the white reference board, and meanwhile, generates a signal of a second white reference value based on the reflected light from the glass member, and the shading correction circuit calculates a correction coefficient corresponding to the ratio of the first white reference value to the second white reference value, and then multiplies the correction coefficient by the second white reference value to carry out the shading correction.