Image analysis – Applications – Target tracking or detecting
Reexamination Certificate
1999-06-07
2001-07-10
Buczinski, Stephen C. (Department: 3662)
Image analysis
Applications
Target tracking or detecting
C382S199000, C701S223000, C356S004010
Reexamination Certificate
active
06259803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The field to which this invention applies is image correlation, in particular, correlation using only data that represents spatial parameters. A specific application is correlation of digitally processed data obtained from a scanning laser such as a LADAR.
2. Background
It is known to use multispectral image correlation systems in air-to-ground target detection and acquisition. Such systems include means for image-processing, which automatically register images produced by airborne platform-mounted sensors operating in different wavelengths and from different points of view.
It is further known that an effective technique for registering images from different sensor types is that of edge matching, that is, matching pronounced target scene edges appearing in one sensor image with similar target scene edges appearing in one or more other sensor images. However, conventional image processing techniques for edge extraction rely upon detection of discontinuities in the light intensity of adjacent pixels, which often produces unsatisfactory results because of reflected laser energy which exhibits large random fluctuations from pixel to pixel, because of atmospheric effects, surface texture, and receiver noise. Such random fluctuations can overwhelm systematic variations caused by the reflectance of the target.
Accordingly, there is a need for a method and system for target detection acquisition, and terminal guidance, utilizing edge extraction from laser-radar (ladar) images relying solely on spatial information, rather than light intensity data.
SUMMARY OF THE INVENTION
It is, therefore, an object of the invention to provide a method for enhancing air-to-ground target detection, acquisition and terminal guidance, utilizing only spatial parameters of data for edge extraction from laser-radar images.
A further object of the invention is to provide an image correlation system for correlating edge information from a recorded and stored template of a target scene with current real-time images from laser-radar sensors mounted on an airborne platform, the system operating to provide edge information from the sensor images based upon a comparison of the range of a pixel with each of its neighboring.
With the above and other objects in view, as will hereinafter appear, a feature of the invention is the provision of a method for enhancing air-to-ground target detection, acquisition, and terminal guidance, the method comprising the steps of
(1) providing a reference image of a target scene with a designated selected target therein,
(2) detecting contract boundaries and orientation thereof in the reference image,
(3) identifying maxima edge pixels in the reference image determined by contract boundaries and tracing edges along the maxima edge pixels, to provide a reference image template,
(4) translating points in the reference image to points in three-dimensional space, and compressing the reference image by fitting straight line segments to the reference image edges, and storing in a computer memory only end points of the straight line segments, the compressed data represented by end points of the line segments thus constituting a reference image in a library of reference images,
(5) providing video image of the target scene from a sensor, such as a LADAR, mounted on an airborne platform,
(6) determining a range value for each pixel in the video image and computing a gradient based edge strength value for each pixel based only upon the range value thereof,
(7) transforming the range values from the video image and scaling them to that of the reference image having the same perspective, range, and scale to that of the reference image template,
(8) correlating the transformed and scaled edges of the video image with the above reference image, and
(9) overlaying the above reference image upon the video image, thus providing an enhanced video image of a pre-specified target as part of the video image.
In accordance with a further feature of the invention, there is provided a multispectral image correlation system, a library of reference images containing compressed data defining the pertinent edges within a three-dimensional space containing a pre-specified target, the target defined by a tracing along the most pronounced of the target's edges, a laser-radar (LADAR) sensor mounted on an airborne platform for providing real-time LADAR imagery of the target scene, means for determining a range value for each pixel comprising the LADAR imagery and for computing gradient based edge-strength values for each based only upon a range value thereof, and for thereby identifying the presence of a structural 90° corner. The system further includes means for resetting all edge-strength values greater than a first value resultant from a reflection off the 90° corner to that the first value, means for resetting to zero the range value of any pixel adjacent another pixel having a shorter range value to identify a structural edge traced by the range values of those pixels exhibiting the first value, means for correlating the structural edge traced by the range values of those pixels exhibiting the first value, means for correlating the structural edge identified by the LADAR imagery with the appropriate reference imagery, and means for overlaying the pre-selected target from the appropriate reference image upon the LADAR imagery, to provide enhanced LADAR imagery to identify the pre-selected target therein.
The above and other features of the invention, including various novel details of method steps, arrangements, and combinations of parts will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular method steps and devices embodying the invention are shown by way of illustration only and not as limitations of the invention. The principles and features of this invention may be employed in various and numerous embodiments without departing from the scope of the invention.
REFERENCES:
patent: 4835532 (1989-05-01), Fant
patent: 5640468 (1997-06-01), Hsu
Ditzler William R.
Wirtz Michael M.
Baugher Jr. Earl H.
Buczinski Stephen C.
The United States of America as represented by the Secretary of
LandOfFree
Simplified image correlation method using off-the-shelf... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Simplified image correlation method using off-the-shelf..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Simplified image correlation method using off-the-shelf... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2502967