Communications: directive radio wave systems and devices (e.g. – Return signal controls radar system – Receiver
Reexamination Certificate
1999-08-26
2001-07-10
Gregory, Bernarr E. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Return signal controls radar system
Receiver
C342S02500R, C342S089000, C342S091000, C342S093000, C342S175000, C342S176000, C342S179000, C342S190000, C342S191000, C342S195000
Reexamination Certificate
active
06259396
ABSTRACT:
BACKGROUND
The present invention relates generally to imaging systems, and more particularly, to a Radon transform based method for target azimuth aspect estimation for use with imaging systems and a target acquisition system using the method.
In prior art radar systems and signal processing methods used therewith, target azimuth aspect estimations place a target-sized rectangular template on an image and then slide and rotate the template until the energy within the template is maximized. For example, an approach developed at Massachusetts Institute of Technology Lincoln Laboratory (MIT/LL) operates in such a manner. This is disclosed in a paper by L. Novak et al. entitled “Performance of a high-resolution polarimetric SAR automatic target recognition system,” Lincoln Laboratory Journal, vol. 6, no. 1, pp. 11-24, Spring 1993.
As with the MIT/LL discriminator, the Army Research Laboratory (ARL) false alarm mitigation stage also uses a binary correlation algorithm. The algorithm uses two series of masks. This is disclosed in a paper by G. Stolovy et al. entitled “An overview of the ARL end to end software based synthetic aperture radar automatic target recognition workstation,” presented at the Sensors and Electron Devices Symposium, U.S. Army Research Laboratory, January 1997. In this technique, a bright mask corresponds to the brightness areas in the target and a surrounding mask corresponds to dark areas or clutter surrounding the target. Each template has associated offset and threshold parameters. The shape of the template change considerably with target azimuth. Forty templates are used to span a full 360 degrees in azimuth.
There are problems with these two methods. A major problem is that these estimations are computationally intensive. For M targets, they require M different templates. The M templates are translated and rotated to cover the entire image over a full 360 degrees. Another problem is that the estimation performance is degraded if the target size is not provided.
Accordingly, it is an objective of the present invention to provide for an improved method for target azimuth aspect estimation for use with imaging systems such as synthetic aperture radar, forward looking infrared, and laser radar systems, and the like, and a target acquisition system using the improved method.
SUMMARY OF THE INVENTION
To accomplish the above and other objectives, the present invention provides for a Radon transform based method for target azimuth aspect estimation. The present invention uses a Radon transform-based technique for target azimuth aspect angle estimation and target shape measurement. A Radon transform is applied to a binary (N×N pixels) target chip to extract target features that are then used to measure length, width, and diagonal features of the target. In parallel, these features are used to estimate the azimuth aspect angle, or size, of the target. The Radon transform-based method is effective in discriminating targets from clutter. Furthermore, the method is also very time efficient and highly flexible in its operation because the features can automatically account for any target rotation or shift. The present invention also provides for a target acquisition system that employs the Radon transform based method for target azimuth aspect estimation.
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Q.H. Pham, et al, “Efficient end-to-end feature-based systems for SAR ATR,” XP000956141 Proc. of SPIE, 1998, vol. 3370, pp. 519-529, ISSN: 0277-786X.
C. Nilubol, et al. “Translational and rotational-invariant Markov model for automatic target recognition,” XP000956142 SPIE Proceedings, vol. 3374, pp. 179-185, ISSN: 0177-786X, 1998.
D.P. Kottke, et al, “A Design for HMM-Based SAR ATR,” SPIE vol. 3370, pp. 541-551, ISSN: 0177-786x.
Pham, Quoc H., Brosnan, Timothy M., Smith, Mark J.T., Mersereau, Russell M., “An Efficient End-To-End Feature Based System for SAR ATR,”SPIE vol. 3370 (Apr. 1998).
Nilubol, Chanin, Pham, Quoc H., Mersereau, Russell M., Smith, Mark J.T., Clements, Mark A, “Translational and Rotational Invariant Hidden Markov Model for Automatic Target Recognition,” SPIE vol. 3374 (Apr. 1998).
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Ezekiel Albert
Pham Quoc H.
Alkov Leonard A.
Gregory Bernarr E.
Lenzen, Jr. Glenn H.
Raytheon Company
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