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Proceedings Paper

The uncertainty of scanner illumination
Author(s): Chengwu Cui
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Paper Abstract

Since typical document scanners are based on the principle of comparing the amount of light reflected from point of interest with that of a known surface, the reflectance of point of interest on the document measured by a scanner is therefore impacted by the reflectance of its neighboring region via multiple light reflections. The effect was referred to as the "integrating cavity effect". We investigate the effect by establishing an optical model with optical ray tracing. We demonstrated the effect by examining the illumination profile after accounting for multiple reflections off the document. The simulation shows that the impact is less significant for the slow scan direction as opposed to the fast scan direction. We identified that the platen glass can contribute just as much as the illumination assembly to the effect but the impact is much more localized. Further we demonstrated that the impact of the illumination assembly and the platen glass is independent from each other to a great degree and the impact of the illumination assembly to the illumination profile is equivalent to a convolution of the original document content with a Gaussian kernel of a considerable band width.

Paper Details

Date Published: 18 January 2010
PDF: 8 pages
Proc. SPIE 7529, Image Quality and System Performance VII, 75290J (18 January 2010); doi: 10.1117/12.839613
Show Author Affiliations
Chengwu Cui, Lexmark International, Inc. (United States)

Published in SPIE Proceedings Vol. 7529:
Image Quality and System Performance VII
Susan P. Farnand; Frans Gaykema, Editor(s)

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