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Crofton, MD, United States

Kanaev A.V.,GTEC Inc. | Murray-Krezan J.,U.S. Navy
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2010

Hyperspectral anomaly detection algorithms are well developed however their ability to account for illumination conditions is limited only to mild variations. We propose an approach specifically designed to handle shadows and poorly illuminated regions present in otherwise well-illuminated imagery without making any assumptions about shaded backgrounds or object signature evolution. The algorithm, Segmentation Adaptive RX (SARX), relies on panchromatic segmentation of the data into dark and bright clusters based on the illumination level. Bright cluster detection employs standard subspace RX and dark cluster detection subspace is limited by only few higher variance spectral dimensions to reflect diminished signal-to-noise ratio in shadows. Anomaly detection near the geographical border between the clusters utilizes Stochastic Mixing Model. We demonstrate experimentally superior ability of SARX to detect anomalous objects in variety of illumination conditions. © 2010 SPIE. Source

Gordon W.B.,GTEC Inc.
IEEE Transactions on Antennas and Propagation | Year: 2010

An algorithm is presented for calculating the positions of the specular points that appear when a collection of reflecting surfaces is illuminated by an external source. The set of specular points is represented as the fixed point of a certain mapping, and this fixed point is calculated by the method of successive approximations (MSA). The MSA is an iterative technique which is essentially different from a search or shooting and bouncing ray technique. The latter require much larger numbers of functional evaluations, especially when the number N of reflecting surfaces is greater than unity. A search technique requires a number of function evaluations that varies exponentially with N, whereas the number of function evaluations required by the MSA varies linearly with N. © 2010 IEEE. Source

Florea C.,GTEC Inc. | Sanghera J.,United States Naval Research Laboratory | Aggarwal I.,United States Naval Research Laboratory
Optical Engineering | Year: 2011

In this paper, we propose using chalcogenide glasses for improved, large-angle, beam steering of infrared radiation, with minimal spectral dispersion and improved thermal performance over wavelength intervals covering the 2 to 12-μm range. For example, we evaluate that full-angle dispersion in the 2 to 5μm region for LiFAs2S3 combination should be three times smaller than in the case of LiFZnS combination. We also evaluate that using the ZnSeAs2Se3 combination will provide twice as small thermal walk-off than a similar ZnSGe system in the 8 to 12-m region. © 2011 Society of Photo-Optical Instrumentation Engineers (SPIE). Source

Florea C.,GTEC Inc. | Sanghera J.,U.S. Navy | Busse L.,U.S. Navy | Shaw B.,U.S. Navy | Aggarwal I.,U.S. Navy
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2011

We demonstrate improved laser damage threshold of chalcogenide glasses with microstructured surfaces as compared to chalcogenide glasses provided with traditional antireflection coatings. The surface microstructuring is used to reduce Fresnel losses over large bandwidths in As2S3 glasses and fibers. The treated surfaces show almost a factor of two of improvement in the laser damage threshold when compared with untreated surfaces. © 2011 SPIE. Source

Currie M.,U.S. Navy | Olson C.,U.S. Navy | Olson C.,GTEC Inc.
Optics Express | Year: 2011

Optical pulse propagation in water is experimentally investigated using an evolutionary algorithm (EA) to control the shape of an optical pulse. The transmission efficiency (ratio of output to input optical power) is maximized by searching the combined amplitude and phase space governing an optical pulse shaper. The transmission efficiency of each tested pulse is physically determined by experiment during the course of the optimization. Combining the EA with an experiment in this manner is a powerful means of improving some figure of merit because no analytical or computational model is required-we optimize directly given the physics of the experiment. In addition, the EA is capable of efficiently searching a large parameter space. Here, we demonstrate improved linear optical pulse propagation near 800nm. Our results demonstrate a pulse with a dramatically narrower bandwidth that coincides with a local absorption minimum (near 800 nm) implying that the transmission efficiency is dominated by water's absorption spectrum. Source

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