Image analysis – Applications – Target tracking or detecting
Reexamination Certificate
1998-05-08
2001-12-25
Patel, Jayanti K. (Department: 2723)
Image analysis
Applications
Target tracking or detecting
C250S330000, C342S02500R, C342S053000
Reexamination Certificate
active
06333986
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a homomorphic method and system for detecting and/or classifying objects, and in particular, relates to a cepstral method and system for detecting and/or classifying obscured cultural objects and/or replicated objects using image data from passive and/or active imaging systems, such as optical, infrared or synthetic aperture radar imaging systems.
BACKGROUND OF THE INVENTION
Generally, for purposes of obtaining images of a particular area of interest from an air-based or space-based platform, optical (e.g., visible), infrared and synthetic aperture radar systems have been utilized. However, the capability of current optical, infrared and synthetic aperture radar systems to detect and/or classify obscured objects of interest is limited. For example, in instances where one or more cultural objects are obscured by cloud cover, use of images from current optical and infrared systems to detect and/or classify the obscured cultural object is extremely limited, if not impossible. Of course, in such instances where the cultural object of interest is covered by clouds, a synthetic aperture radar system may be utilized to image the area of interest. However, such synthetic aperture radar systems may not be readily available for use to image the particular area or cultural object of interest. In addition, in instances where the cultural object of interest is obscured by foliage (e.g., trees) or soil, a synthetic aperture radar system may not have the capability to provide a suitable image of the cultural object or objects of interest.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method and system for utilizing an optical, infrared and/or synthetic aperture radar image to detect and/or classify one or more obscured objects.
It is a further object of the present invention to provide a homomorphic method and system for utilizing digital image data from an optical, infrared and/or synthetic aperture radar imaging system to detect and/or classify one or more obscured objects.
It is yet another object of the present invention to provide a cepstral method and system for processing image data from an optical, infrared and/or synthetic aperture radar system to attenuate corruption (e.g., due to clouds for optical and infrared images, and due to foliage or a thin layer of soil for synthetic aperture radar images) of one or more objects.
It is still another object of the present invention to provide a cepstral method and system for processing image data from a synthetic aperture radar system to amplify an obscured structure (e.g., a replicated structure comprising a plurality of cultural objects arranged in a pattern or an array), the structure being obscured by corruption, which can include noise from the imaging system, clutter, foliage (e.g., trees) or a thin layer of soil or water.
The present invention achieves one or more of these objectives by providing a method and system for detecting and/or classifying objects obscured by clutter (e.g., cloud cover) in optical and infrared imagery, and objects obscured by clutter (e.g., foliage or a thin layer of soil or water) in synthetic aperture radar imagery. Generally, the method and system of the present invention is directed to performing or conducting a homomorphic (e.g., cepstral) analysis on at least first image data corresponding to a first image from at least one of an optical, infrared and synthetic aperture radar (“SAR”) imaging system and displaying an output of the homomorphic analysis in at least one of the spatial quefrency domain and the pixel domain to detect at least one of an obscured first cultural object (e.g., man-made structures or effects, such as buildings, air-based, sea-based or land-based vehicles, heat trails, such as plumes, or shadows attributable thereto, etc.) and an obscured first replicated object or structure (e.g., an array or pattern of objects, such as mines, etc.). More specifically, two-dimensional spatial image data (e.g., digital or, in some instances, analog) in the pixel domain comprising signals or signatures corresponding to at least the obscured first cultural object and/or the obscured first replicated object may be analyzed using a cepstral analysis to attenuate signals corresponding to corruption relative to the first cultural object signal and/or the first replicated object signature, and/or to enhance the first cultural object signal and/or the first replicated object signature. As a result, obscuration of at least the first cultural object and/or the first replicated object may be reduced or attenuated, such that the first cultural object and/or the first replicated object is detectable and/or classifiable.
Of importance, the method and system of the present invention is especially useful in low to very low signal-to-background ratio cases, with zero or lower decibels (dB) being not uncommon. It should be noted that this methodology for cloud cover attenuation in infrared imagery relies on the fact that cloud cover can be approximately modeled as a convolution of the cloud cover with the uncorrupted image. As such, the attenuation of cloud cover in infrared imagery is accomplished with the cepstral methodology described herein. In addition, any replicated signals will be amplified by virtue of this aspect of the cepstral methodology, which is not uncommon in cultural scenes.
In one aspect, the present invention is directed to a method for detecting and/or classifying at least a first cultural object using image data from one of an optical, infrared and SAR imaging system, the image data including at least signals corresponding to noise (e.g., system noise) and at least a first cultural object convolved with corruption. In one embodiment, the method includes the steps of processing the first image data from the pixel domain into the spatial quefrency domain, whereby the signals in the image data corresponding to at least the first cultural object and corruption correspond to separable cepstral coefficients in the spatial quefrency domain, processing in the spatial quefrency domain at least a first cepstral coefficient corresponding to the corruption signal to attenuate or reject at least a portion of the corruption signal, and processing at least a first cepstral coefficient corresponding to at least the first cultural object signal to obtain at least a portion thereof in the pixel domain, wherein at least a portion of the first cultural object is detectable in the spatial quefrency and/or pixel domain. Specifically, in order to deconvolve or separate signals corresponding to the first cultural object and corruption, the step of processing the first image data includes the steps of applying a two-dimensional Fourier transform (e.g., discrete or fast Fourier transform) to the first image data in the pixel domain to transform the first image data into a first discrete term in the spatial frequency domain, the first discrete term comprising a product of the spatial frequency of the first cultural object signal and the spatial frequency of the corruption signal in the spatial frequency domain, applying in the spatial frequency domain a complex logarithm to at least the first discrete term, the output of which comprises a discrete sum which includes a sum of the complex logarithms of the spatial frequencies of the first cultural object signal and the corruption signal, and applying an inverse two-dimensional Fourier transform to the discrete sum to transform the discrete sum into at least first cepstral coefficients corresponding to the first cultural object signal and the corruption signal in the spatial quefrency domain. In order to reject at least the portion of the corruption signal while retaining at least a portion of the first cultural object signal, the step of processing in the spatial quefrency domain at least a first cepstral coefficient corresponding to the corruption signal includes the step of modifying at least the first cepstral coefficient corresponding to the corruption sign
Lockheed Martin Corporation
Marsh & Fischmann & Breyfogle LLP
Patel Jayanti K.
LandOfFree
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