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Proceedings Paper

Gain fixed-pattern-noise correction via optical flow
Author(s): SukHwan Lim; Abbas El Gamal
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Paper Abstract

Fixed pattern noise (FPN) or nonuniformity caused by device and interconnect parameter variations across an image sensor is a major source of image quality degradation especially in CMOS image sensors. In a CMOS image sensor, pixels are read out through different chains of amplifiers each with different gain and offset. Whereas offset variations can be significantly reduced using correlated double sampling (CDS), no widely used method exists for reducing gain FPN. In this paper, we propose to use a video sequence and its optical flow to estimate gain FPN for each pixel. This scheme can be used in a digital video or still camera by taking any video sequence with motion prior to capture and using it to estimate gain FPN. Our method assumes that brightness along the motion trajectory is constant over time. The pixels are grouped in blocks and each block's pixel gains are estimated by iteratively minimizing the sum of the squared brightness variations along the motion trajectories. We tested this method on synthetically generated sequences with gain FPN and obtained results that demonstrate significant reduction in gain FPN with modest computations.

Paper Details

Date Published: 24 April 2002
PDF: 8 pages
Proc. SPIE 4669, Sensors and Camera Systems for Scientific, Industrial, and Digital Photography Applications III, (24 April 2002); doi: 10.1117/12.463443
Show Author Affiliations
SukHwan Lim, Stanford Univ. (United States)
Abbas El Gamal, Stanford Univ. (United States)

Published in SPIE Proceedings Vol. 4669:
Sensors and Camera Systems for Scientific, Industrial, and Digital Photography Applications III
Nitin Sampat; Morley M. Blouke; John Canosa; John Canosa; Nitin Sampat, Editor(s)

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