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Conference 12239
Unconventional Imaging and Adaptive Optics 2022
23 - 24 August 2022
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Information
Session 1:
Atmospheric Propagation and Characterization I: Joint Session with Conferences 12237 and 12239
Session Chair:
Jeremy P. Bos, Michigan Technological Univ. (United States)
This session is of related interest to Conference 12237: Laser Communication and Propagation through the Atmosphere and Oceans XI and Conference 12239: Unconventional Imaging and Adaptive Optics 2022
Show Abstract +
The characterization of a one-way laser communication link was conducted outdoors on a 1 km range in a littoral environment. During communication, the bit error rate and received power were measured on the receiver side of the link. Additionally, the local atmospheric conditions were measured and utilized by link analysis tools, including the NAVSLAM, COAMPS, and PCS. These tools have been used to quantify the turbulence and path losses and evaluated against range measurements. The bit error rate and received power were also computed and compared with the measurements on the range to evaluate link predictive capabilities.
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We have built a 1.55 mu laser link over a 3.5 km stretch of water between the port of Den Helder and the island of Texel in The Netherlands. The intensity and beam profile after propagation have been measured. Supplementing data was provided by an large-aperture scintillometer, aerosol counters and standard meteorological equipment. The system will be presented as well as the data collected, The analysis of the data focuses on relating laser beam properties to turbulence characteristics over the water surface.
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The Naval Information Warfare Center (NIWC) Pacific will present recent lab results for a Digital Adaptive Optics system using QR codes that mitigates turbulence in ISR systems.
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Abstract
Free Space Optical links suffer from atmospheric effects where turbulence causes the beam to break up (scintillation), which could increase the variance in the signal at the receiver and ultimately worsening the optical link. Various techniques to reduce scintillation exist to alter how the atmosphere will affect the beam, one of them being wavelength diversity of the optical source. Diversifying the wavelength can reduce the scintillation of the optical beam due to the wavelength dependence on the refractive index of the atmosphere. An experiment was conducted comparing a broadband laser source and a monochromatic source over an instrumented 13.5km path. Beam profile and scintillation measurements were conducted along with BLS-2000 Cn2 measurements. This experiment investigates the affects of a short-coherence length / broad-band nature of a source and its ability to reduce scintillation in turbulent atmosphere. This paper will discuss the experimental setup, analysis, and conclusions of this novel experiment.
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An experimental campaign consisting on the propagation of laser modes carrying orbital angular momentum (OAM) has been carried out in our campus between two buildings, for a total distance of 1 km. in this presentation we describe our experiment and an analysis of the recorded beams, including intensity fragmentation, beam wonder, loss of spatial coherence, and crosstalk between modes as a function of the turbulent strength.
Session 2:
Atmospheric Propagation and Characterization II: Joint Session with Conferences 12237 and 12239
Session Chair:
Santasri R. Bose-Pillai, Air Force Institute of Technology (United States)
This session is of related interest to Conference 12237: Laser Communication and Propagation through the Atmosphere and Oceans XI and Conference 12239: Unconventional Imaging and Adaptive Optics 2022
12239-1
Non-classical models of optical turbulence
(Invited Paper)
Show Abstract +
Tatarskii’s first book on wave propagation through the turbulent atmosphere was published in English in 1961 and describes what we refer to as the classical theory of optical turbulence. It relies on a number of simplifying assumptions, such as the assumption of locally homogeneous and isotropic, fully developed turbulence; the Corrsin-Obukhov similarity theory; Taylor’s frozen-turbulence hypothesis; and the assumption of weak scattering. In this invited presentation, we review and discuss non-classical models of optical turbulence, which account for non-classical effects and phenomena, including anisotropy, intermittency, outer-scale effects, and non-Gaussianity of refractive-index increments.
Show Abstract +
An implementation of differential scintillations to characterize the C2n(z) profile along a nearly horizontal propagation path measured by a Shack-Hartmann wavefront sensor is developed and demonstrated. Measurements from a Small Mobile Atmospheric Sensing Hartmann (SMASH) instrument using an LED source to characterize 500 m, 1 km and 2 km paths at the Environmental Laser Test Facility (ELTF) are presented.
Show Abstract +
A deep neural network (DNN) model designed for the refractive index structure parameter Cn2 prediction based on processing of pupil and focal plane laser beam intensity patterns was used for analysis of turbulence inner and outer scale impact on spatial features of intensity and wavefront phase. Wave-optics numerical simulations were used to generate large datasets of short-exposure intensity distributions in an optical receiver pupil and focal planes for a remotely (7 km) located Gaussian laser beacon under various turbulence conditions (different Cn2 values), Cn2 profile along the propagation path and turbulence inner and outer scales. These datasets were used for DNN model training, validation, and inference.
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This study evaluates the feasibility of a method using infrared (IR) imagery, and a mini-tower of wet and dry paper towels to psychometrically obtain surface layer temperature and moisture gradients and fluxes. First, the possible utility of using a single IR thermometer/detector to evaluate moisture and heat fluxes near the surface was explored. The feasibility of this single IR detector method to provide with reasonable certainty values of surface layer heat and moisture fluxes suggests the technique could be exploited with more efficiency and accuracy with a calibrated imaging IR camera or sensor array. Uncertainty statistics are calculated and evaluated to quantify effectiveness.
Session 3:
Atmospheric Propagation and Characterization III: Joint Session with Conferences 12237 and 12239
Session Chairs:
Italo Toselli, Fraunhofer-Institut für Optronik, Systemtechnik und Bildauswertung IOSB (Germany), Conor M. Pogue, Naval Information Warfare Ctr. Pacific (United States)
This session is of related interest to Conference 12237: Laser Communication and Propagation through the Atmosphere and Oceans XI and Conference 12239: Unconventional Imaging and Adaptive Optics 2022
Show Abstract +
Sonic anemometers have been used extensively to measure virtual temperature fluctuations associated with turbulence and thereby determine the temperature structure function parameter. While it is common to utilize the temperature power spectrum in such an analysis, it is similarly possible to use a structure function based approach. In this work, we consider the details involved and benefits/disadvantages of processing by each method.
Show Abstract +
In an effort to estimate the significant influence of Mie scattering (fog) over wireless optical links, an evaluation of terrestrial Free Space Optical (FSO) systems by means of artificial fog sources is proposed. For this purpose, fog fluids based on highly purified glycols and water are applied. Having introduced empirical Particle Size Distribution (PSD) fog functions together with Mie theory approach, the assessment of optical Mie scattering attenuation due to two types of glycol-water solutions are evaluated and compared to pure water vapor fog. Moreover, the results are additionally compared based on measured PSDs for two types of fog machines that operate also with glycol-water fog fluids.
Show Abstract +
The use of self-mixing interferometry for taking nodal measurements of the refractive index structure constant Cn2 is explored. Experimental data from deployed self-mixing interferometers is compared against sonic anemometers and a scintillometer.
Show Abstract +
The TISTEF Camera and Anemometer Turbulence System (T-CATS) is a single ended system for estimating the refractive index structure parameter (Cn2) along a given path. This instrument was developed by the Wave Propagation Research Group and utilizes a wide-angle camera, a jetson Nano, and an Applied Technologies SATI3A sonic anemometer. The instrument combines single point measurements of Cn2 with real time imagery of the path to extrapolate Cn2 to distances up to 1 kilometer. T-CATS was deployed and evaluated at the TISTEF laser range. The system was compared against several point measurements from sonic anemometers, as well as against a BLS 900 and a MZA DELTA.
Session 4:
Atmospheric Propagation and Characterization IV: Joint Session with Conferences 12237 and 12239
Session Chair:
Mark F. Spencer, Air Force Research Lab. (United States)
This session is of related interest to Conference 12237: Laser Communication and Propagation through the Atmosphere and Oceans XI and Conference 12239: Unconventional Imaging and Adaptive Optics 2022
Show Abstract +
Phase-based techniques to measure atmospheric turbulence have potential advantages when used over long ranges since they do not suffer from saturation issues as the irradiance-based techniques. The present work uses time-lapse imagery of a non-cooperative target from multiple spatially separated cameras to extract turbulence distribution along the imaging path. By measuring the differential motion of pairs of target features sensed by a single camera or between cameras, turbulence profiles can be obtained. The use of multiple cameras instead of a pair of cameras is expected to improve the profiling resolution and to increase the fraction of the path that can be reasonably profiled. The mathematical framework will be discussed and the time-lapse derived results will be compared to point measurements from 3D sonic anemometers placed at different locations along the path. By imaging elevated targets in the future, turbulence changes with altitude can be investigated as well.
Show Abstract +
The inner scale plays a critical role in beam scintillation and branch point evolution in optical propagation
through atmospheric turbulence. Understanding this parameter, in-situ, during experiments is therefore of great
interest. We compare different methods of estimating the inner scale using AFRL's Small Mobile Atmospheric
Sensing Hartmann (SMASH). The investigations are conducted with data collected at Kirtland, AFB in New
Mexico along multiple paths varying from weak to strong irradiance fluctuation conditions.
Show Abstract +
Sonic detection and ranging (SODAR) is a technique for measuring wind and turbulence from back-scattered sound waves. The instrument used here was a Scintec MFAS flat array SODAR. Backscatter strength appears to be a direct indicator of the turbulence strength, but calibration and an estimate of temperature versus height is needed to process this strength into values for CT2 and Cn2. Consequently, it is interesting to compare results with other turbulence measurements such as sonic anemometry and image based techniques. With a sonic anemometer on a small UAV the techniques can measure the same path.
Session 5:
Unconventional Adaptive Optics
Session Chairs:
Matthew R. Kemnetz, Air Force Research Lab. (United States), James R. Fienup, The Institute of Optics, Univ. of Rochester (United States)
Show Abstract +
We discuss the capability of adaptive optics to increase the performance of laser systems operating in atmospheric
turbulence.Our approach is based on the Zernike filter functions, Taylor’s frozen-flow hypothesis, and bandwidth
limitations of a realistic servo control system. System performance is analyzed in terms of the Strehl ratio on target.
Our results for plane and spherical wave geometry indicate that adaptive optics can be effective even when engaging fast moving targets and that moderate closed-loop bandwidths of about 100 Hz would suffice for most analyzed scenarios.Applications of interest are beam delivery systems and free-space optical communications.
Show Abstract +
In this work, we present experimental results for a computational field sensor designed to produce estimates of an object’s optical phase and speckle-free synthetic aperture images using direct detection and a single-speckle-realization. Our sensor combines pupil-plane phase modulation with dual-plane direct-detection measurements of the image and pupil-plane intensities. Our reconstruction algorithm uses a regularized-inversion estimation framework, similar to those used in Fourier Ptychography, that couples a data-fidelity model, a physics-based model for rough surface scattering of coherent light, and a convolutional neural network model for natural images. Using a controlled laboratory setup, we show that the resulting senor accurately reconstructs high-resolution estimates of the optical phase and speckle-free images, even at low SNRs and with a relatively-low number of measurements.
Show Abstract +
Flow measurements inside oscillating droplets are crucial for revealing potentials to save energy. However, aberrations of the light at the surface of the droplets results. In this paper, a novel measurement system is presented for both 3D imaging with only one camera and aberration correction. 3D imaging is achieved by introducing a Double-Helix Point Spread Function. The dynamically introduced aberrations of the phase boundary are measured with a Fresnel Guide Star and are corrected with a deformable mirror in a closed-loop system with low latency.
Session 6:
Digital Holography and LADAR
Session Chairs:
Cameron J. Radosevich, Sandia National Labs. (United States), Kenneth J. Jerkatis, Ball Aerospace (United States)
12239-12
Show Abstract +
Image sharpening is a method of image reconstruction for aberrations caused by distributed volume turbulence. For uniform turbulence along the propagation path, one must estimate multiple phase screens in order to reconstruct images of extended objects. Multi-plane estimation exhibits challenges such as degenerate solution spaces, telescoping, and image warping. This study explores several regularization methods that are designed to combat these challenges. We simulate several different strengths of uniform turbulence and examine the performance of image sharpening using several metrics to compare the different regularization methods.
Show Abstract +
Digital holography model based iterative reconstruction (DHMBIR) has proven to be successful in providing a high-quality reconstruction of wave-front phase-errors. However, the application of DHMBIR, particularly real time sensing, is limited by the speed at which this wave-front changes and computational time. To meet the demands of real time wave-front sensing correction, we propose a new method of DHMBIR. Our proposed method reduces the number of iterations required for a temporally stable reconstruction of the wave-front and consequently, underlying reflectance image. This is accomplished through adaptive temporal phase prediction (atpp), a method in which the atmospheric phase distortion in the future is predicted using previous phase distortions. The results indicate that the number of DHMBIR iterations per time sample can be reduced to 1, while maintaining a high Strehl ratio for the phase-error estimate, and low normalized root mean square error (nrmse) for the estimated reflectance image.
Show Abstract +
There have been recent advances toward sensing and correcting moderate turbulence using digital holography (DH). With DH, we use optical heterodyne detection to sense the amplitude and phase of the light reflected from an object. Phase information allows us to digitally propagate the measured field to estimate and correct distributed-volume aberrations. We developed a model-based iterative reconstruction (MBIR) algorithm for sensing and correcting atmospheric turbulence using multiple holographic measurements. Here, we demonstrate the validity of our method using multiple calibrated Kolmogorov phase screens along the propagation path to emulate distributed-volume turbulence. This setup allowed us to demonstrate our algorithm’s performance in deep turbulence conditions.
Show Abstract +
This paper gives new insights on Laser Range Profiling. In this paper we explore the advantages of Laser Range Profiling or High Temporal Resolution Ladar to identify objects at long ranges with high probability. In the first part of the paper, we focus on the electromagnetic simulation of laser range profiles of objects. In the second part of the paper, we study the identification function of the system, and describe an algorithm which correlates the measured signatures of the unknown object with the closest range profile related to the aspect angles of the object in the database.
Session 7:
Aero Effects
Session Chairs:
Casey J. Pellizzari, U.S. Air Force Academy (United States), David G. Voelz, New Mexico State Univ. (United States)
12239-16
The story of the Airborne Aero-Optics Laboratory
(Invited Paper)
Show Abstract +
This paper describes the origin of the Airborne Aero-Optics Laboratory (AAOL), its development and its Contributions. With the program drawing to a close in early 2023, it seems appropriate to tell the story of the AAOL program that has covered a span of 15 years of airborne-laser beam control research. The program that actually was three programs began with flight test operations in Cessna Citations and evolved into the use of Falcon 10s in order to be able to exceed Mach 0.8. Each step along the development of flight operations was a step into unknown design decisions and risk and unknown flight maneuvers and procedures. In the end, difficult instrumentation development and special flight conditions needed to address each new area of research became almost routine, having developed excellent working relationships with various on and off-campus shops, the FAA DERs and DAR’s and graduate students and faculty within the Notre Dame Aero-Optics Group. The paper will mention the numerous discoveries and methods of taking and reducing optical data that were a constant product of the programs.
Show Abstract +
Predictive Adaptive Optics (AO) control is a promising technology for AO applications in high-disturbance and low-signal environments. Predictive AO utilizes future state predictions of an optical wavefront propagated through a turbulent medium to drive correction, thereby mitigating the limits imposed by inherent latency in the AO system. In this work we present a novel Artificial Neural Network (ANN) approach for embedding the flow dynamics for a range of transonic turbulent regimes into a single turbulent flow prediction model. We analyze this combined model’s ability to forecast turbulent wavefronts, and consider the implications for ANN-based AO correction of high-speed, turbulent flow.
Show Abstract +
Pending OPSEC review
Show Abstract +
Pending OPSEC review.
Session 8:
Unconventional Imaging I
Session Chairs:
Jean J. Dolne, The Boeing Co. (United States), Victor L. Gamiz, Tau Technologies LLC (United States)
Show Abstract +
Many transient events consist of rapidly varying spatial, spectral, and temporal information. This information is often key to fully characterizing the event. The transient event four-dimensional data datacube (spatial, spectral, temporal) is not measurable with a single traditional 2-dimensional imaging system. Recent advances in compressive/computational optical methods allow for measurement of the full 4-D datacube. In this work we designed, built, and tested a compact diffuser-based high-speed spectral computational optical imaging system. In this conference proceeding we describe successful testing of the system in a lab-based setting. Specifically, we collected spatial, spectral, and temporal imagery of exploding bridgewires.
Show Abstract +
Optical microscopy (OM) is diffraction limited when viewing nanoscale object (NO). To date, people have used scanning electron microscopy (SEM) and super-resolution (SR) imaging techniques to image NO. However, SEMs are expensive, have large physical footprints and have narrow fields of view. An alternative to an SEM is using artificial intelligence (AI) to enable resolving images beyond the diffraction limit. Here, we show that correlated SEM and optical microscopy imaging can be used to train convolutional neural network (CNN) and generative adversarial network (GAN) to enable imaging beyond the diffraction limit with a simple optical microscope.
Show Abstract +
Deep learning has been widely used in image processing, quantitative analysis and other applications in optical-resolution photoacoustic microscopy (OR-PAM). It requires a large amount of photoacoustic data for training and testing. However, due to the complex structure, high cost, slow imaging speed and other factors of OR-PAM, it is difficult to obtain enough data required by deep learning, which limits the research of deep learning in OR-PAM to a certain extent. To solve this problem, a virtual OR-PAM based on k-Wave is proposed. The virtual photoacoustic microscopy mainly includes the setting of excitation light source and ultrasonic probe, scanning and signal processing, which can realize the common Gaussian-beam and Bessel-beam OR-PAM. The system performance (lateral resolution, axial resolution and depth of field) was tested by imaging a vertically tilted fiber, and the effectiveness and feasibility of the virtual simulation platform were verified by 3D imaging of virtual vascular network. The ability to the generation of the dataset for deep learning was aslo verified. The construction of the virtual OR-PAM can promote the research of OR-PAM and the application of deep learning in OR-PAM.
Session 9:
Unconventional Imaging II
Show Abstract +
Fractal-based phase screens are compared to subharmonic-augmented FFT-based phase screens using both analytic and numerical statistical methods. Properties such as homogeneity and stationarity are investigated. It is shown analytically that augmented FFT-based screens are homogeneous and strict-sense stationary. Analytic means are also used to show that fractal-based phase screens are not stationary based on the definition of fractal Brownian surfaces. Corresponding numerical results, show that the structure functions in both cases appear to be stationary or nearly so. Comparisons of imaging reconstruction performance with both types of screens are also performed.
Show Abstract +
For many space-based, ground-staring systems, background clutter is the dominant source of noise. Clouds are a prominent source of clutter, and further complicate image processing due to their movement through a scene. Accurately accounting for high-contrast cloud regions is crucial when modeling EO/IR systems; however, current modeling is limited to computationally expensive scenes rendered by ray-tracing software. In this paper, we analyze the spatial continuity of cloud-containing scenes to produce statistical models and generate synthetic cloud fields conforming to real-world spatial statistics. We compare our model-generated results with that of real-world cloud scenes to assess the utility of our approach.
Show Abstract +
Thermally tunable optics, and thermal emission control of Infrared (IR) nano-antennas necessitates a broadband thermal wavefront reconstruction technique. The Long Wave Infrared (LWIR) (λ = 8-14 µm) is widely used for thermal imaging, spectroscopy, atmospheric imaging, structural fault monitoring, and medical diagnostics. Speckle imaging has demonstrated phase reconstruction through scattering media, in the visible and IR. Speckle images contain sufficient scattered light information to reconstruct wavefronts. Our broadband LWIR wavefront reconstruction setup utilizes a thin scatterer and an uncooled microbolometric camera, and demonstrates quantitative LWIR phase imaging capabilities, with promising future imaging applications through visually opaque samples.
Poster Session
Conference attendees are invited to view a collection of posters within the topics of Nanoscience + Engineering, Organic Photonics + Electronics, and Optical Engineering + Applications. Enjoy light refreshments, ask questions, and network with colleagues in your field. Authors of poster papers will be present to answer questions concerning their papers. Attendees are required to wear their conference registration badges to the poster session.
Poster authors, visit Poster Presentation Guidelines for set-up instructions.
Poster authors, visit Poster Presentation Guidelines for set-up instructions.
Show Abstract +
The adaptive-driving-beam (ADB) headlights is an indispensable technology in the autonomous vehicles. We demonstrate the generation of laser hot-spot by laser-excited single crystal phosphor (SCP) converter layer with white LED for producing wide FOV of ± 16.8° and high ECB for ADB headlight. The wide FOV provides better visibility while the high ECB improves the long-distance illumination of the headlights and accord with the ECE regulation of vehicle headlights. This smart ADB headlight is a promising headlight candidate for use in the next-generation autonomous vehicles.
Show Abstract +
We propose a synthetic aperture telescope by small satellites formation flying. The synthetic aperture telescope is composed of mirror satellites constituting a primary mirror of the telescope and an imaging satellite having a focal plane assembly. By optically synthesizing the light collected by mirror satellites with the imaging satellite, a virtual large aperture telescope is constructed in orbit. In this paper, observations at near infrared to short wavelength infrared are assumed and required specifications are shown. Moreover, we describe optical performance of the synthetic aperture telescope and an adjustment method of the optical system by applying the adaptive optics technique.
Program Committee
Fraunhofer-Institut für Optronik, Systemtechnik und Bildauswertung IOSB (Germany)
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Happy New Year! We’re about a month away from the abstract deadline, which is {[AbstractDueDate]}.
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Please be prepared to submit a manuscript by {[PostMeetingManuscriptDueDate]}, and to secure funds for registration, travel, hotel, etc.
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{[CPCFirstName]} {[CPCLastName]}
Conference Programs and Proceedings Coordinator
SPIE
PO Box 10
Bellingham, WA 98227-0010 USA
Fax: +1 360 647 1445
{[CPCEmail]}
http://SPIE.org
SPIE is the international society for optics and photonics.