M.W. Hyde

Air Force Institute of Technology, Dayton, Ohio, United States

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Publications (32)33.08 Total impact

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    ABSTRACT: Optical wave propagation through long paths of extended turbulence presents unique challenges to adaptive optics (AO) systems. As scintillation and branch points develop in the beacon phase, challenges arise in accurately unwrapping the received wavefront and optimizing the reconstructed phase with respect to branch cut placement on a continuous facesheet deformable mirror. Several applications are currently restricted by these capability limits: laser communication, laser weapons, remote sensing, and ground-based astronomy. This paper presents a set of temporally evolving AO simulations comparing traditional least-squares reconstruction techniques to a complex-exponential reconstructor and several other reconstructors derived from the postprocessing congruence operation. The reconstructors' behavior in closed-loop operation is compared and discussed, providing several insights into the fundamental strengths and limitations of each reconstructor type. This research utilizes a self-referencing interferometer (SRI) as the high-order wavefront sensor, driving a traditional linear control law in conjunction with a cooperative point source beacon. The SRI model includes practical optical considerations and frame-by-frame fiber coupling effects to allow for realistic noise modeling. The "LSPV+7" reconstructor is shown to offer the best performance in terms of Strehl ratio and correction stability-outperforming the traditional least-squares reconstructed system by an average of 120% in the studied scenarios. Utilizing a continuous facesheet deformable mirror, these reconstructors offer significant AO performance improvements in strong turbulence applications without the need for segmented deformable mirrors.
    Applied Optics 06/2014; 53(18):3821-3831. · 1.69 Impact Factor
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    ABSTRACT: An investigation of the array-tilt aberration for hexagonal, optical phased arrays is presented. The investigation begins with theoretical derivations of the far-zone radiated field, the array factor, and the far-field radiated power for the seven-element hexagonal array with array tilt present. Physical insights gained from this analysis are discussed. An analytical treatment of correlation-based array-tilt estimators is also undertaken. Two novel array-tilt estimation techniques are developed from the analysis. The new techniques are shown to be significantly more efficient computationally than the traditional estimation approach. Simulation and experimental results are presented to validate the new array-tilt estimation methods.
    Applied Optics 04/2014; 53(11):2416-2424. · 1.69 Impact Factor
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    Applied Optics 03/2014; 53(11). · 1.69 Impact Factor
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    M.W. Hyde, M.J. Havrilla
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    ABSTRACT: A simple technique is presented which utilizes dual-ridged waveguide to rectangular waveguide transitions to provide broadband material characterization measurements. Compared to a recently published technique which used dual-ridged waveguides, the proposed method significantly simplifies specimen preparation while maintaining measurement bandwidth. The behavior of the fields in the dual-ridged waveguide to rectangular waveguide transitions is briefly discussed. In addition, a brief discussion on the derivation of the theoretical scattering parameters, required for the extraction of permittivity and permeability of the material under test, is provided. Experimental material characterization results of a magnetic absorbing material are presented and analyzed to validate the proposed technique.
    IEEE Transactions on Electromagnetic Compatibility 01/2014; 56(1):239-242. · 1.33 Impact Factor
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    ABSTRACT: The case of a partially-coherent wave scattered from a material circular cylinder is investigated. Expressions for the TMz and TEz scattered-field cross-spectral density functions are derived by utilizing the plane-wave spectrum representation of electromagnetic fields and cylindrical wave transformations. From the analytical scattered-field cross-spectral density functions, the mean scattering widths are derived and subsequently validated via comparison with those computed from Method of Moments Monte Carlo simulations. The analytical relations as well as the simulation results are discussed and physically interpreted. Key insights are noted and subsequently analyzed.
    Optics Express 12/2013; 21(26):32327-39. · 3.55 Impact Factor
  • Mark F. Spencer, Milo W. Hyde
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    ABSTRACT: The individual phases of a multi-beamlet laser source can be manipulated by exploiting high-bandwidth phase loops to correct for aberrations induced within the optical beamlet trains. With the current state of the art in phasing technology, this phasing of the beamlet trains is successfully accomplished up to a common aperture sharing element or on a pointsource target; however, in the presence of an extended target, rough surface scattering through laser-target interaction adds the additional constraints of speckle and depolarizing effects. In particular, speckle phenomena and atmospheric effects create unobservable modes in the beam control system. One such unobservable mode is termed stair mode and is appropriately identified by a stair-step pattern of piston phase across the individual subapertures that comprise a tiled aperture. This paper investigates the effects of turbulence and thermal blooming on phased beam projection from tiled apertures using wave-optics simulations. To represent different array fill factors in the source plane, both seven and 19 element hexagonal close-packed tiled apertures are used in the simulations along with both Gaussian and flat-top outgoing beamlets. Peak Strehl ratio and power in the bucket are calculated in the target plane over multiple random realizations that are then averaged. This is done for all simulation setups with and without the presence of stair mode.
    Proc SPIE 09/2013;
  • Melissa A. Sawyer, Milo W. Hyde
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    ABSTRACT: A new method for characterization of unknown targets using passive multispectral polarimetric imagery is pre sented. Previous work makes use of a pBRDF derived equation for the degree of linear polarization and with the aid of multiple incidence angles estimates refractive index and re ection angle. This work uses known incidence and re ection angles along with dispersion equations and polarimetric data at multiple wavelengths to recover the index of refraction. Experimental results are presented showing the new method's ability to characterize a range of materials.
    Proc SPIE 09/2013;
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    ABSTRACT: The scattering of a partially-coherent wave from a statistically rough material surface is investigated via derivation of the scattered field cross-spectral density function. Two forms of the cross-spectral density are derived using the physical optics approximation. The first is applicable to smooth-to-moderately rough surfaces and is a complicated expression of source and surface parameters. Physical insight is gleaned from its analytical form and presented in this work. The second form of the cross-spectral density function is applicable to very rough surfaces and is remarkably physical. Its form is discussed at length and closed-form expressions are derived for the angular spectral degree of coherence and spectral density radii. Furthermore, it is found that, under certain circumstances, the cross-spectral density function maintains a Gaussian Schell-model form. This is consistent with published results applicable only in the paraxial regime. Lastly, the closed-form cross-spectral density functions derived here are rigorously validated with scatterometer measurements and full-wave electromagnetic and physical optics simulations. Good agreement is noted between the analytical predictions and the measured and simulated results.
    Optics Express 03/2013; 21(6):6807-25. · 3.55 Impact Factor
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    ABSTRACT: Military applications that use adaptive optics (AO) often require a point source beacon at the target to measure and correct for wavefront aberrations introduced by atmospheric turbulence. However, turbulence prevents the formation of such a point beacon. The extended beacons that are created instead have finite spatial extents and exhibit varying degrees of spatial coherence. Modeling these extended beacons using a Gaussian Schell-model (GSM) form for the autocorrelation function would be a convenient approach due to the analytical tractability of Gaussian functions. We examine the validity of using such a model by evaluating the field scattered from a rough impedance surface using a full-wave computational technique called the method of moments (MoM). The MoM improves the fidelity of the analysis since it captures all the physics of the laser-target interaction, such as masking, shadowing, multiple reflections, etc. Two rough-surface targets with different roughness statistics are analyzed. The simulation results are verified with experimental bidirectional reflectance distribution function measurements. It is seen that for rough surfaces, in general, the scattered-field autocorrelation function is not of a GSM form. However, under certain conditions, modeling an extended beacon as a GSM source is legitimate. This analysis will aid in understanding the behavior of extended beacons and how they affect the overall performance of an AO system.
    Optical Engineering 03/2013; · 0.88 Impact Factor
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    ABSTRACT: A transmission/reflection material characterization technique that uses dual-ridged waveguides is presented. The proposed dual-ridged-waveguide system combines many of the positive aspects of traditional transverse electromagnetic-mode (e.g., coaxial, free space, and stripline) and rectangular waveguide systems, i.e., broadband measurements and accurate calibration. A brief discussion on the derivation of the theoretical scattering parameters, required for the extraction of permittivity and permeability of a material under test, is provided. Two methods for computing the cutoff wavenumber of the dual-ridged waveguide-essential to the material characterization process-are also discussed. The first, which utilizes the mode-matching technique, is applicable to dual-ridged-waveguide apertures composed of right-angled corners. The second uses the surface equivalence principle and a magnetic-field integral equation formulation to find the cutoff wavenumber. This approach is applicable to dual-ridged waveguides with rounded corners, which often result from the dual-ridged waveguide manufacturing process. Thus, for the first time, the effect of rounded dual-ridged-waveguide aperture corners on the measurement of permittivity and permeability is assessed. Experimental material characterization results of a magnetic absorbing material are presented and analyzed to validate the proposed technique. An extensive error analysis on the extracted values of permittivity and permeability is also performed by taking into account manufacturer-specified dual-ridged-waveguide design tolerances as well as uncertainties in sample position, sample thickness, sample-holder length, and measured scattering parameters.
    IEEE Transactions on Instrumentation and Measurement 01/2013; 62(12):3168-3176. · 1.36 Impact Factor
  • Mark F. Spencer, Milo W. Hyde
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    ABSTRACT: With an optical phased array, the individual phases of a multi-fiber laser source can be manipulated by exploiting high-bandwidth phase loops to correct for aero-optical flow over the turret and free-stream atmospheric effects along the line of sight; however, rough surface scatter through laser-target interaction adds the additional constraints of speckle and depolarizing effects. In particular, speckle phenomena can cause unobservable modes to arise in the beam control system of optical phased arrays. One such unobservable mode is termed stair mode and is appropriately identified by a stair-step pattern of piston phase across the individual subapertures that comprise a tiled aperture. This paper investigates the effects of stair mode using wave-optics simulations. To represent different array fill factors in the source plane, both seven and 19 element hexagonal close-packed tiled apertures are used in the simulations along with both Gaussian and flat-top outgoing beamlets. Peak Strehl ratio and power in the bucket are calculated in the target plane for all simulation setups and are then averaged for multiple random realizations of stair mode step sizes. In addition, the stair mode target irradiance patterns are imaged with cameras which have decreasing aperture stop diameters. Initial results show that low resolution imaging conditions, i.e. an aperture stop on the order of a subaperture diameter, makes it difficult to distinguish between different realizations of stair mode using a separate camera sensor.
    Proc SPIE 10/2012;
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    ABSTRACT: In many military applications that use Adaptive Optics (AO) a point source beacon is ideally required at the target to measure and to correct for the wavefront aberrations caused by propagation through the atmosphere. However, it is rarely possible to create a point source beacon at the target. The "extended beacons" that are created instead have intensity profiles with a finite spatial extent and exhibit varying degrees of spatial coherence. The Gaussian Schell model might be a convenient way to model these extended sources because of its analytical tractability. The present work examines the validity of using such a model by evaluating the scattered field from a rough surface target using a full wave electromagnetic solution (method of moments). The full wave electromagnetic calculation improves the fidelity of the analysis by capturing all aspects of laser-target interaction i.e. shadowing/ masking, multiple reflections etc. A variety of rough surface targets with different roughness statistics has been analyzed. This analysis will ultimately aid in understanding the key parameters of extended beacons and how they impact the Adaptive Optics (AO) system performance.
    Proc SPIE 05/2012;
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    ABSTRACT: A free-space-backed dual-waveguide probe measurement technique is introduced to determine nondestructively the complex permittivity and permeability of an unknown material. The purpose of this new measurement technique is to complement the existing PEC-backed dual-waveguide probe materialcharacterization method. Provided in this article is the theoretical development of the new technique and its experimental validation. It is shown, by applying Loves equivalence theorem, that a system of coupled magnetic field integral equations can be formulated and subsequently solved for the dominant mode reflection and transmission coefficients using the Method of Moments. Also included in the theoretical development of the new technique is a derivation of the dyadic Greens function for a magnetic current excited two-medium grounded slab environment. Last, experimental complex permittivity and permeability parameters extracted for two magnetic shielding materials are presented and analyzed to validate the new technique.
    IEEE Transactions on Antennas and Propagation 01/2012; · 2.33 Impact Factor
  • M.W. Hyde, M.J. Havrilla
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    ABSTRACT: The design of an open-ended coaxial probe for the nondestructive characterization of PEC-backed materials is presented. The design attempts to maximize the measurement bandwidth while limiting the size of the probe flange plate. These design criteria are met by analyzing the theoretical reflection coefficient's behavior versus frequency and the coaxial line's inner radius. Included in this paper are the theoretical derivation of the reflection coefficient, accomplished using Love's equivalence theorem, the parallel-plate Green's function, and the Method of Moments (MoM), and the results of the design analysis. Future work is also discussed.
    Instrumentation and Measurement Technology Conference (I2MTC), 2012 IEEE International; 01/2012
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    ABSTRACT: Branch points arise in optical transmissions due to strong atmospheric turbulence, long propagation paths, or a combination of both. Unfortunately, these conditions are very often present in desired operational scenarios for laser weapon systems, optical communication, and covert imaging, which suffer greatly when traditional adaptive optics systems either cannot sense branch points or implement non-optimal methods for sensing and correcting branch points. In this research we create a MATLAB simulation of the real-time AO system at the Air Force Institute of Technology. Utilizing a self-referencing interferometer as the high-order wavefront sensor - this type of sensor being theoretically immune to scintillation - this effort has extended previous theoretical work by adding realistic noise effects to the SRI's measurements before reconstructing the wavefronts and applying the control law. Previous research by Pellizzari presents a thorough analysis of various novel branch point tolerant reconstructors in the absence of noise. This study provides a foundation to guide hardware implementation in the future, where noise effects will be present.
    Aerospace Conference, 2012 IEEE; 01/2012
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    ABSTRACT: In this paper, a material-classification technique using polarimetric imagery degraded by atmospheric turbulence is presented. The classification technique described here determines whether an object is composed of dielectric or metallic materials. The technique implements a modified version of the LeMaster and Cain polarimetric maximum-likelihood blind-deconvolution algorithm in order to remove atmospheric distortion and correctly classify the unknown object. The dielectric/metal classification decision is based on degree-of-linear-polarization (DOLP) maximum-likelihood estimates provided by two novel DOLP priors (one being representative of dielectric materials and the other being representative of metallic materials) developed in this paper. The DOLP estimate, which maximizes the log-likelihood function, determines the image pixel's classification. Included in this paper is the review and modification of the LeMaster and Cain deconvolution algorithm. Also provided is the development of the novel DOLP priors, including their mathematical forms and the physical insight underlying their formulation. Lastly, the experimental results of two dielectric and metallic samples are provided to validate the proposed classification technique.
    IEEE Transactions on Geoscience and Remote Sensing 02/2011; · 3.47 Impact Factor
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    ABSTRACT: In this paper, a novel technique is developed to practically and accurately measure the permittivity and permeability of low-loss materials using the two flanged waveguides measurement geometry (originally designed to characterize strongly absorbing materials only). A review of the two flanged waveguides measurement technique (tFWMT) as well as the Green's function-based flange-design criterion is provided. This review is followed by the introduction of the novel method (called tFWMT time-domain gating). It is shown that tFWMT time-domain gating extends the range of applicability of the tFWMT to low-loss materials and provides a clear flange-size design requirement which, for low-loss materials, is approximately two orders of magnitude smaller than that stipulated by the existing Green's function-based criterion. Lastly, material-characterization measurement results of low-loss acrylic and ECCOSORB® FGM-125, using flanges of two different sizes, are presented to validate the new technique. This paper was presented at MMA2010, the 6th Conference on Microwave Materials and Their Applications, held in Warsaw, Poland, on 1-3 September 2010. One other paper from that meeting also appears in this issue.
    Measurement Science and Technology 01/2011; 22(8). · 1.44 Impact Factor
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    ABSTRACT: A non-destructive material characterization technique for obtaining the permittivity and permeability of conductor-backed media using a conformable broadband microstrip probe is introduced. The material properties are extracted via comparison of theoretical and measured scattering parameters using an iterative algorithm. Expressions for the theoretical scattering parameters are obtained via an EFIE formulation and a network analyzer is utilized to acquire the measured scattering parameters. Advantages of the flexible microstrip probe are discussed and experimental results for sample materials are provided and compared to manufacturer data in order to validate the analysis.
    01/2011;
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    ABSTRACT: An enhanced material-classification algorithm using turbulence-degraded polarimetric imagery is presented. The proposed technique improves upon an existing dielectric/metal material-classification algorithm by providing a more detailed object classification. This is accomplished by redesigning the degree-of-linear-polarization priors in the blind-deconvolution algorithm to include two subclasses of metals--an aluminum group classification (includes aluminum, copper, gold, and silver) and an iron group classification (includes iron, titanium, nickel, and chromium). This new classification provides functional information about the object that is not provided by existing dielectric/metal material classifiers. A discussion of the design of these new degree-of-linear-polarization priors is provided. Experimental results of two painted metal samples are also provided to verify the algorithm's accuracy.
    Optics Letters 11/2010; 35(21):3601-3. · 3.39 Impact Factor
  • M.W. Hyde, M.J. Havrilla
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    ABSTRACT: The purpose of this paper is to demonstrate how the flanged-waveguide material-characterization technique, originally designed to characterize lossy materials only, can be extended to accurately extract permittivity and permeability of low-loss materials. Provided in this paper is a summary of the flanged-waveguide technique. This is followed by a discussion of how time-domain gating can be utilized to mitigate the error introduced by waves reflected from the edges of the flanges. Furthermore, it is demonstrated that by utilizing time-domain gating, the cross-sectional dimensions of the flanges can be significantly reduced. Lastly, material measurement results of plexiglass are provided to validate the time-domain gating technique.
    Electromagnetics in Advanced Applications (ICEAA), 2010 International Conference on; 10/2010

Publication Stats

32 Citations
33.08 Total Impact Points

Institutions

  • 2007–2013
    • Air Force Institute of Technology
      • Department of Electrical & Computer Engineering
      Dayton, Ohio, United States
  • 2009–2010
    • Wright-Patterson Air Force Base
      Dayton, Ohio, United States
  • 2008
    • Michigan State University
      • Department of Electrical and Computer Engineering
      East Lansing, Michigan, United States