| 摘要 |
The present invention pertains to a book scanner that reads the image of an document such as a book or magazine while it is placed open and face up, and more particularly, to an image reader that detects the height distribution of the document prior to performing a pre-scanning to detect the size of the document and the background luminance of the document. Thus, a focal length adjustment is performed in response to the detected height distribution while the pre-scanning takes place in order to prevent defocusing caused by the curvature of the document consisting of an open book or magazine. The book reader also reads the book in at least two spectral regions to detect and eliminate image anomalies.
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