Communications: directive radio wave systems and devices (e.g. – Clutter elimination
Reexamination Certificate
2000-04-06
2002-04-23
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Clutter elimination
C342S175000, C342S176000, C342S179000, C342S195000, C342S196000
Reexamination Certificate
active
06377206
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a method for attenuating stochastic effects in a digital image, and in particular, to a method for rejecting clutter in a digital image, such that structures in the digital image formerly obscured by such stochastic effects or clutter are more readily recognizable or detectable.
BACKGROUND OF THE INVENTION
Various methodologies have been utilized over the years to achieve detection of structures or targets (e.g., man-made structures, such as roads, buildings, vehicles, etc.) from space and/or airborne platforms. One such methodology is known as automatic data screening, which is a critical capability for imagery collection systems operating in a wide area search mode. Such automatic data screening is particularly useful for timely processing image data, especially in tactical situation and in view of the diminishing number of imagery analysts available to exploit the collected imagery. However, automatic data screening is, at times, problematic due to difficulties in maintaining a tolerable false alarm rate (e.g., false detection of objects/targets). Other methodologies for detection of structures have involved local methods such as small kernel convolvers or morphological filters. Unfortunately, these particular methodologies can produce unexpected results. And finally, still other methodologies depend upon repetitive target structure or convolved clutter, which is not typically present.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method for detecting objects of interest (e.g., man-made structures, such as vehicles, buildings, roads, etc.) from digital imagery.
It is another object of the present invention to provide a method for attenuating clutter or stochastic effects in digital imagery to enhance recognition or detection of objects of interest.
It is a further object of the present invention to provide a method for timely decorrelating stochastic effects in a digital image while preserving the structure(s) in the digital image, such that the structure(s) are recognizable (e.g., through conventional automatic target recognition methodologies) and a tolerable false alarm rate is maintained.
It is yet another object of the present invention to provide a method for rejecting clutter to enable detection/recognition of structures/objects/targets utilizing a single digital image (e.g., a digital image from an optical, infrared, or synthetic aperture radar imaging system).
The method of the present invention achieves one or more of these objectives by applying several (i.e., two or more) transforms to a single digital input image. Applying selected transforms, each of which is designed to reveal obscured objects of interest, to the single digital input image tends to preserve the structure(s) in the image while acting on the clutter (i.e., stochastic effects) in distinctly different ways, such that the clutter is decorrelated across the several transformed images. Such transformed images may be combined to produce a filtered image, whereby objects of interest are more readily detectable/recognizable than with any one of the transforms alone. Advantageously, only a single digital image of an area of interest is required by the method of the present invention. As such, the method of the present invention is particularly useful due to limited imaging resources, and the fact that multiple looks at the same area of interest may not be possible within a given required time frame.
Generally, the method of the present invention is particularly suited for filtering clutter from a first digital input image, such that at least a first object, target or structure in the first digital input image, formerly obscured by the clutter, is detectable/recognizable. In one aspect of the present invention, such filtering may be accomplished in a timely manner by applying or performing at least first and second transforms to first digital image data corresponding to the first digital input image, the first digital image data being in the image intensity domain, performing an appropriate filtering operation to retain, in first and second transform domains, at least a portion of transform indication(s) corresponding or at least correlatable to the structure, applying to the remaining transform indications inverse first and second transforms, and processing the filtered first digital image data to produce a single filtered image and/or image data.
More specifically, in one embodiment, the method of the present invention includes the steps of applying or performing a first transform to transform first digital image data corresponding to a first digital input image from one of an optical, infrared and synthetic aperture radar imaging system into first transformed digital image data in the first transform domain, applying or performing a second transform to transform the first digital image data into a second transform domain, the first and second transformed digital image data in the first and second transform domains each having first and second transform indications corresponding or at least correlatable to at least the first object and the clutter, respectively, filtering the transformed digital image data by retaining at least a portion of the first transform indications corresponding to the first object in the first and second transform domain, applying or performing an inverse first transform to transform at least a portion of the first transform indication in the first transform domain into at least a first filtered indication from the first transform domain, in the image intensity domain, and applying or performing an inverse second transform to transform at least a portion of the first transform indication in the second transform domain into at least a first filtered indication from the second transform domain, in the image intensity domain. In this embodiment, the first and second transform domains are different. For example, the first transform domain may be the Karhunen-Loeve or Eigen space domain and the second transform domain may be the wavelet coefficient domain. For purposes of further enhancing attenuation of clutter, such that the structure(s) of the image is/are detectable/recognizable, the method may further include the steps of applying or performing a third transform to transform the first digital image data into a third transform domain, the third transformed digital image data in the third transform domain having first and second transform indications corresponding or at least correlatable to at least the first object and clutter, respectively, filtering the third transformed digital image data to alter and/or modify the spatial frequency of the clutter/stochastic effects and to increase the contrast of the structure(s)
on-stochastic feature(s) relative to the clutter/stochastic effects in the third transform domain, and applying or performing an inverse third transform to transform the modified/altered third transformed digital image data into modified image data in the image intensity domain. The method may further include the step of combining two or more of the first filtered indications in the image intensity domain to produce a first filtered image, or, alternatively, the step of processing two or more of the first filtered indications in the image intensity domain using a principal component analysis, the result of which is that at least the first object may be recognizable or detectable now that the clutter or stochastic effects have been decorrelated.
In another aspect, the method of the present invention is directed to enhancing the recognizability/detectability of structures in a digital image in a timely manner, the structures being initially obscured by clutter or stochastic effects. In this aspect of the present invention, the method generally includes the step of prescreening first digital image data corresponding to a first digital image for candidate objects or structures of interest, such that at least a first digital sub-image may be selected, the fi
Gregory Bernarr E.
Lockheed Martin Corporation
Marsh & Fischmann & Breyfogle LLP
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