OVERVIEW

A typical problem with most electro-optical sensors is that backgrounds can be complex and can include influences that reduce the chances of discerning targets that are superimposed on such backgrounds. The backgrounds against which targets are viewed are often as bright as, and sometimes brighter than, the targets themselves. This complicates and sometimes prevents the task of detection. To detect targets, the sensed background noise (or clutter) levels must be different from the sensed target levels and able to be processed so as to provide acceptable false detection rates. In addition, the background may include spatial variation that includes a size distribution that matches that of the target. However, spatial variation in the background at all spatial frequencies will have a negative impact on the ability of a sensor/human to find the target, as we shall illustrate below. In general, it is desirable for any sensor to possess the capability of detecting targets in a variety of environments and backgrounds.

Borrowing from the radar community, the spatial and temporal amplitude variation in the background is usually referred to as clutter. Clutter is a structured background phenomenon that is not spatially or temporally constant. It is not a process that allows the signals to be combined in a root-sum-squared (RSS) fashion; rather, the signals must be simply added to other noise sources. From elementary statistics, we know that adding noise sources creates a total that is larger than would be the case if the terms were added in an...