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Optical Engineering

Methods for efficient correction of complex noise in outdoor video rate passive millimeter wavelength imagery
Author(s): Terrell Nathan Mundhenk; Josh Baron; Roy M. Matic
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Paper Abstract

Passive millimeter wavelength (PMMW) video holds great promise, given its ability to see targets and obstacles through fog, smoke, and rain. However, current imagers produce undesirable complex noise. This can come as a mixture of fast shot (snowlike) noise and a slower-forming circular fixed pattern. Shot noise can be removed by a simple gain style filter. However, this can produce blurring of objects in the scene. To alleviate this, we measure the amount of Bayesian surprise in videos. Bayesian surprise measures feature change in time that is abrupt but cannot be accounted for as shot noise. Surprise is used to attenuate the shot noise filter in locations of high surprise. Since high Bayesian surprise in videos is very salient to observers, this reduces blurring, particularly in places where people visually attend. Fixed pattern noise is removed after the shot noise using a combination of non-uniformity correction and mean image wavelet transformation. The combination allows for online removal of time-varying fixed pattern noise, even when background motion may be absent. It also allows for online adaptation to differing intensities of fixed pattern noise. We also discuss a method for sharpening frames using deconvolution. The fixed pattern and shot noise filters are all efficient, which allows real time video processing of PMMW video. We show several examples of PMMW video with complex noise that is much cleaner as a result of the noise removal. Processed video clearly shows cars, houses, trees, and utility poles at 20 frames per second.

Paper Details

Date Published: 11 June 2012
PDF: 10 pages
Opt. Eng. 51(9) 091608 doi: 10.1117/1.OE.51.9.091608
Published in: Optical Engineering Volume 51, Issue 9
Show Author Affiliations
Terrell Nathan Mundhenk, HRL Labs., LLC (United States)
Josh Baron, HRL Labs., LLC (United States)
Roy M. Matic, HRL Labs., LLC (United States)

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