Patent ID: 6041146
Filing Date: 2000-03-21
Classification: H04N

Abstract:
An image reader for reading a book document placed on a document platen in a face upward condition, said image reader comprising:a shading reference panel provided beside the document platen,an image reading device for reading the book document and the shading reference panel, and for outputting image data,first detecting means for detecting a height distribution of the book document, said height distribution comprising a plurality of vertical height measurements of a document surface above the platen and substantially distributed across said document surface,second detecting means for detecting an illuminance irregularity in accordance with the image data corresponding to the shading reference panel,calculating means for calculating shading correction data based on analysis of both the detected height distribution across said document surface and the illuminance irregularity corresponding to the shading reference panel, andshading correction means for correcting an illuminance irregularity of the image data corresponding to the book document in accordance with the shading correction data.