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Elk River, MN, United States

Great River Energy is an electric transmission and generation cooperative in the U.S. state of Minnesota; it is the state's second largest electric utility, based on generating capacity, and the fifth largest generation and transmission cooperative in the U.S. in terms of assets. Great River Energy was formed in 1999 when Cooperative Power Association and United Power Association merged.Great River Energy owns or co-owns more than 100 energy transmission substations in the region. The company's system also includes more than 500 distribution substations. Great River Energy is a not-for-profit cooperative that provides wholesale electricity to more than 1.7 million people through 28 member distribution cooperatives in Minnesota, covering roughly 60 percent of the state. The company also owns transmission lines in North Dakota and Wisconsin. Wikipedia.

Li Y.,Great River Energy
Journal of the Optical Society of America A: Optics and Image Science, and Vision

Rectilinear propagation of light rays in homogeneous isotropic media makes it possible for optical generation of ruled surfaces as the ray is deflected by a rotatable mirror. Scan patterns on a plane or curved surface are merely curves on the ruled surface. Based on this understanding, structures of the scan fields produced by mirrorscanning devices of different configurations are investigated in terms of differential geometry. Expressions of the first and second fundamental coefficients and the first and second Gauss differential forms are given for an investigation of the intrinsic properties of the optically generated ruled surfaces. The Plücker ruled conoid is then generalized for mathematical modeling of the scan fields produced by single-mirror scanning devices of different configurations. Part II will be devoted to a study of multi-mirror scanning systems for optical generation of well-known ruled surfaces such as helicoids and hyperbolic paraboloids. © 2011 Optical Society of America. Source

Nonparaxial ray tracing is performed to investigate the field scanned out by a single beam through two rotatable thick prisms with different parameters, and a general solution is obtained and then expanded into a power series to establish the third-order theory for Risley prisms that paves the way to investigate topics of interest such as optical distortions in the scan pattern and an analytical solution of the inverse problem of a Risley-prism-based laser beam steering system; i.e., the problem is concerned with how to direct a laser beam to any specified direction within the angular range of the system. © 2011 Optical Society of America. Source

Nonparaxial ray tracing through Risley prisms of four different configurations is performed to give the exact solution of the inverse problem arisen from applications of Risley prisms to free space communications. Predictions of the exact solution and the third-order theory [Appl. Opt. 50, 679 (2011)] are compared and results are shown by curves for systems using prisms of different materials. The exact solution for the problem of precision pointing is generalized to investigate the synthesis of the scan pattern, i.e., to create a desirable scan pattern on some plane perpendicular to the optical axis of the system by controlling the circular motion of the two prisms. © 2011 Optical Society of America. Source

Horng J.-S.,National United University | Li Y.,Great River Energy
Applied Optics

This paper presents analytical and numerical results that elucidate the impact of error sources on the performance of dual-wedge beam steering systems. Different types of error sources are considered. Specifically, we investigate optical distortions in the pattern scanned out by a single ray through a pair of rotatable wedge elements with slightly different parameters. Case examples are given to reveal the difference between the distorted patterns and the patterns produced by a pair of perfectly equal wedge elements. Furthermore, nonparaxial ray tracing is performed to investigate the impact of assembly errors on the accuracy of steering a laser beam to a remote target. We found that a misalignment in a bearing axis of rotation with respect to the system optical axis will result in a change of beam deflection off-axis that gives rise to a severe decrease of pointing accuracy to a level well below the level that a tilted wedge prism may attain. © 2012 Optical Society of America. Source

Recent researches about the vector theory of the Hanbury Brown-Twiss effect at optical frequencies have shown that a new statistical quantity, called the degree of cross-polarization, is needed to predict the correlations between intensity fluctuations in stochastic electromagnetic beams. This note is devoted to an investigation of the variations of the degree of cross-polarization and then to a comparison of the distributions of degree of coherence and the correlations between intensity fluctuations across the cross-section of stochastic electromagnetic Gaussian Schell-model (GSM) beams. Analysis leads to a generalization of scalar theory of the degree of global coherence that describes the GSM sources that generate the electromagnetic GSM beams of either spatially very coherent or spatially very incoherent in the global sense. © 2013 Elsevier B.V. Source

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