Milo W. Hyde

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

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Publications (38)37.41 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Two different methodologies for generating an electromagnetic Gaussian-Schell model source are discussed. One approach uses a sequence of random phase screens at the source plane and the other uses a sequence of random complex transmittance screens. The relationships between the screen parameters and the desired electromagnetic Gaussian-Schell model source parameters are derived. The approaches are verified by comparing numerical simulation results with published theory. This work enables one to design an electromagnetic Gaussian-Schell model source with pre-defined characteristics for wave optics simulations or laboratory experiments.
    Optics Express 12/2014; 22(26). · 3.55 Impact Factor
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    ABSTRACT: When using active-illumination systems for directed-energy and remote-sensing applications, more often than not a highly coherent laser beam propagates from the source through the atmosphere resulting in partially coherent beam illumination on the target. Interestingly enough, not much literature exists pertaining to the scattering of partially coherent light from rough surfaces. In an effort to bridge this gap, this paper develops a wave-optics simulation approach to the problem at hand. Specifically, the analysis uses two separate phase screens. The first phase screen is located in the source plane and accounts for the size and coherence properties of the incident illumination. Through multiple phase-screen realizations and far field-field propagation from the source plane to the target plane, the first phase screen allows for the generation of spatially partially coherent beam illumination with a Gaussian Schell-model (GSM) form. The second phase screen is located in the target plane and accounts for the surface parameters, i.e., the surface height standard deviation and correlation length. Through multiple phase-screen realizations in the target plane and far field-field propagation to the observation plane, the second phase screen accounts for the interaction of the incident GSM beam with a perfectly reflecting rough surface. This allows for the formulation of the average scattered irradiance and normalized autocorrelation function in the far field. Initial results show that this wave-optics simulation approach compares well with a previously validated 2D scalar-equivalent solution [Hyde et al., Opt. Express 21, 6807 (2013)].
    SPIE Optical Engineering + Applications; 09/2014
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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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    ABSTRACT: With current phasing technology, the individual beamlets within a tiled aperture can be phased in piston to coherently combine at the target. In practice, this piston phasing of the optical beamlet trains is accomplished using a point-source target. The reflections from the point-source target act as an idealized beacon, which propagate from the target to the tiled aperture through aberrations induced within the optical beamlet trains. Thus, an ideal reference is achieved to perform piston phase compensation by exploiting high-bandwidth phase loops. This paper investigates piston phase compensation of tiled apertures in the presence of horizontal-path turbulence and thermal blooming by 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. Performance is evaluated by calculating peak Strehl ratio and power in the bucket in the target plane for all simulation setups and averaging these performance metrics for multiple realizations of turbulence and thermal blooming. The performance metrics are plotted as a function of the Fried coherence diameter, the log-amplitude variance, and the distortion number for comparison purposes. In general, the results show that piston phase compensation does not perform well when the subaperture diameter is greater than the coherence diameter and when the distortion number is greater than 21 rad. These results are intuitive; however, the trends are often nonlinear with distinct asymptotes. With this said, the results presented in this paper should help future conceptual designs.
    2014 IEEE Aerospace Conference; 03/2014
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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;
  • Milo W. Hyde, Michael J. Havrilla
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    ABSTRACT: form only given. A new single waveguide probe is introduced which utilizes a dual-ridged waveguide (DRWG) to provide nondestructive, broadband material characterization measurements of PEC-backed materials (much like existing coaxial probes, yet more broadly applicable) while maintaining the structural robustness of rectangular/circular waveguide probes. A schematic of the measurement geometry is shown. DRWG attached to an infinite PEC flange plate is placed in contact with a PEC-backed magnetic material of unknown εr and μr. The theoretical expression for the reflection coefficient Sthy11, necessary to characterize the material under test (MUT), is derived. This is achieved by replacing the DRWG aperture with an equivalent magnetic current which maintains the fields in the parallel-plate/MUT region in accordance with Love's equivalence theorem. Enforcing the continuity of the transverse magnetic fields at the DRWG aperture results in a magnetic field integral equation, which when solved using the Method of Moments, yields Sthy11. The εr and μr of the MUT are then found by minimizing the root-mean-square difference between the theoretical and measured reflection coefficients using nonlinear least squares. At a minimum, two independent reflection measurements are required to unambiguously characterize the MUT. In this research, two-thickness method is used for this purpose. To experimentally verify the new probe, broadband material characterization results of a magnetic absorbing material are presented and compared to those obtained using the traditional, destructive Nicolson-Ross-Weir technique. The new probe's sensitivity to sample thickness, flange-plate thickness, and measured S11 uncertainties is also presented.
    2013 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium); 07/2013
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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; · 0.96 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. · 1.71 Impact Factor
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    ABSTRACT: The scattering of a spatially partially coherent wave from a one-dimensional statistically rough metallic surface is investigated. Assuming a Gaussian Schell-model form for the incident field autocorrelation function, a closed-form expression for the scattered field autocorrelation function is derived using the physical optics approximation (Kirchhoff approximation). Two forms of the solution are derived—one applicable to very rough surfaces and the other applicable to moderately rough surfaces. It is shown that for very rough surfaces, the solution, under certain circumstances, remains Gaussian Schell model as has been previously reported. As such, closed-form expressions for the angular coherence radius and angular scattering radius are derived. These expressions are, in general, complicated functions of both the source (size and coherence properties) and surface parameters (surface height standard deviation and correlation length). It is demonstrated that for many scenarios of interest, the angular coherence radius can be safely approximated as a function of just the source parameters and the angular scattering radius can be simplified to a function of just the surface parameters. For the moderately rough surface solution, the scattered field autocorrelation function is, in general, not Gaussian Schell model and it is therefore not possible to derive analytical forms for the angular coherence radius or angular scattering radius. Nonetheless, the form of the autocorrelation function is physically intuitive and is discussed in this work. To verify the presented theoretical analysis, wave optics simulation results are presented and compared to the predictions of the analytical models. This analysis is concluded with a discussion of future work.
    SPIE Optical Systems Design; 12/2012
  • Michael J. Steinbock, Milo W. Hyde
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    ABSTRACT: Adaptive optics is used in applications such as laser communication, remote sensing, and laser weapon systems to estimate and correct for atmospheric distortions of propagated light in real-time. Within an adaptive optics system, a reconstruction process interprets the raw wavefront sensor measurements and calculates an estimate for the unwrapped phase function to be sent through a control law and applied to a wavefront correction device. This research is focused on adaptive optics using a self-referencing interferometer wavefront sensor, which directly measures the wrapped wavefront phase. Therefore, its measurements must be reconstructed for use on a continuous facesheet deformable mirror. In testing and evaluating a novel class of branch-point- tolerant wavefront reconstructors based on the post-processing congruence operation technique, an increase in Strehl ratio compared to a traditional least squares reconstructor was noted even in non-scintillated fields. To investigate this further, this paper uses wave-optics simulations to eliminate many of the variables from a hardware adaptive optics system, so as to focus on the reconstruction techniques alone. The simulation results along with a discussion of the physical reasoning for this phenomenon are provided. For any applications using a self-referencing interferometer wavefront sensor with low signal levels or high localized wavefront gradients, understanding this phenomena is critical when applying a traditional least squares wavefront reconstructor.
    SPIE Optical Engineering + Applications; 10/2012
  • 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

Publication Stats

46 Citations
37.41 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