Fitzpatrick,Cella, Harper & Scinto
Image reading apparatus for obtaining a shading correction factor using two white reference members
 An image reading apparatus comprises a reader for photo-electrically reading an image, a first reference member to be used for the measurement of irregularity of an output signal from the reader, a second reference member having density data indicating a density thereof recorded thereon, a correction unit for correcting irregularity of an image signal derived by reading an image of a document sheet by the reader based on a first reference signal derived by reading the first reference member by the reader, and a compensation unit for compensating the irregular correction operation by the correction unit based on a second reference signal derived by reading the second reference member by the reader and the density of the second reference member derived by reading the density data. 
Canon Kabushiki Kaisha
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H04N H04N H04N
inventional inventional inventional
Yasumichi Masanori Eiji
Suzuki Yamada Ohta