Patent ID: 7542177
Filing Date: 2009-06-02
Classification: H04N

Abstract:
1. An image reading device for optically scanning a document surface, generating, when reading a plurality of lines from a reference white plate with a one-dimensional image sensor, shading correction data on the basis of input data, and correcting, when reading a document image with said one-dimensional image sensor, input data with said shading correction data, said image reading device comprising: first white sum data storing means for storing white sum data representative of a sum of white data of pixels derived from the reference white plate; first white data storing means for storing white data of each pixel; decision value calculating means for calculating an input data decision value for each pixel on the basis of white data of a previous line stored in said first white data storing means; input data determining means for comparing the input data decision value and the input data to thereby determine whether or not said input data is normal; weighted averaging means for selecting, in accordance with a result of a decision made by said input data determining means, either one of white data stored and input data and performing weighted averaging with said data stored or said input data and white data stored; second white data storing means for storing a result of weighted averaging output from said weighted averaging means; sum data selecting means for selecting either one of white data stored and input data in accordance with the result of the decision made by said input data determining means; sum data calculating means for adding the data stored or the input data selected by said sum data selecting means to the first sum data stored in said first white sum data storing means; second white sum data storing means for storing a result of an addition output from said sum data calculating means; mean calculating means for dividing the white sum data stored by a number of lines added to thereby produce a mean value; shading correction data storing means for storing the mean value output from said mean calculating means; and shading correcting means for correcting shading of the input data in accordance with the shading correction data stored; wherein the shading correction data is generated by storing white data and white sum data, making, based on said white data, a decision on whether or not the input data is abnormal, selecting the data to be added in accordance with a result of said decision to thereby generate white sum data, and dividing, when the reference white plate is fully read, white sum data by a number of lines added.