ISSN : 1796-2048
Volume : 2    Issue : 1    Date : February 2007

Extreme Zoom Surveillance: System Design and Image Restoration
Yi Yao, Besma R. Abidi, and Mongi A. Abidi
Page(s): 20-31
Full Text:
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Applications of digital imaging with extreme zoom are traditionally found in astronomy and wild life
monitoring. More recently, the need for such capabilities has extended to long range surveillance
and wide area monitoring such as forest fires, harbors, and waterways. In this paper, we present a
number of sensor arrangements for such applications, focusing on optical setups, auto-focusing
mechanisms, and image deblurring techniques. Considering both the speed of convergence and
robustness to image degradations induced by high system magnifications and long observation
distances, we introduce an auto-focusing algorithm based on sequential search with a variable
step size. We derive the transition criteria following maximum likelihood (ML) estimation for the
selection of suitable step sizes. The efficiency of the proposed algorithm is illustrated in real-time
auto-focusing and tracking of faces from distances of 50m~300m. We also develop an image
restoration algorithm for high magnification imaging systems, where an adaptive sharpness
measure is employed as a cost function to guide the fine search for an optimal point spread
function (PSF) for image deblurring. Experimental results demonstrate a considerably enhanced
robustness to image noise and artifacts and ability to select the optimum PSF, producing superior
restored images.

Index Terms
surveillance, auto-focusing, long range, high magnification, image restoration, sharpness