We investigate the utility of plenoptic data for extracting information from a scene where the light from objects in the scene is viewable only after scattering from a diffuse surface. The relationship between the object and the scattered light is cast in terms of a system of Fredholm integral equations of the first kind with the BRDF of the scattering surface, and the object information is reconstructed by solving the equations. Based on the Fourier transformation, we analyze the error in the reconstructions and obtain regularized solutions under a variety of conditions. A comparison with experimental results is reported.

Formation of images in deep turbulence (spherical wave Rytov amplitude variance greater than 0.3) is a well-known challenge. Such imaging with coherent active illumination poses special difficulties due to the presence of laser speckle in the image, which is similar to atmospheric speckle and so it is difficult to separate the two forms of speckle. However, imaging with laser illumination has the potential benefit of enhanced signal and added information in the laser speckle. In this paper, several image processing approaches are investigated with simulation that show promise for good image quality in such conditions. These approaches include pupil-plane techniques that filter phase based on an assumed atmospheric spatial phase structure function, branch-cut filtering and intensity-weighted branch cut minimization. Also included in the analyses are focal-plane techniques. Significant improvements can be found for Rytov variances up to and beyond 0.4 and up to 10 atmospheric coherence lengths (r0) across the aperture, in uniform-turbulence scenarios over a 30 km range with objects of limited extent. The approaches are optimized for fast execution and minimal number of image frames required to form an acceptable image. The results are compared using several image metrics and also compared with a corresponding idealized adaptive-optics approach using an incoherent beacon.

In this paper a woofer-tweeter pair of Xinetics deformable AO mirrors are characterized and analyzed using Fizeau interferometer surface measurements. 3D measurements are taken of the influence of each actuator on the mirror surface individually. The direct measurements are then processed to be used as influence functions that define the influence of each actuator on the mirror. Using the measured data as a spanning set, an orthonormal basis is computed for the span of the set using singular value decomposition. Real surface measurements are taken of the orthonormal basis influences to test for both linear independence of the actuators and actuator linearity with respect to voltage. The efficacy of using the measured basis function data to converge toward a more accurate basis in an iterative process is evaluated. Performance of lower range (compressed) bases are also evaluated.

Wave Optics Simulations (WOS) are a valuable tool for exploring the effects of atmospheric turbulence on laser beam propagation and imaging. Obtaining accurate results from WOS requires careful selection of simulation parameters. Specifically, the inter-screen spacing, spatial sampling of source and receiver planes, and phase screen sampling are all important parameters. The parameter space for WOS in Kolmogorov turbulence is well characterized and while it is often assumed that similar requirements hold for simulation of non-Kolmogorov atmospheres, we find this is not the case. In this talk we will discuss the practical limits of modeling optical propagation in non-Kolmogorov turbulence using the split-step phase screen method underlying WOS.

We present the results of a Wave Optics Simulation (WOS) campaign featuring the propagation of a partially coherent Gaussian-Schell model beam in non-Kolmogorov atmospheres. It is well known that introducing partial coherence reduces the received intensity scintillation compared to a collimated Gaussian profile beam. In this work, we explore the effect of introducing partial coherence when the slope spatial power spectrum deviates from the Kolmogorov value of -11/3. Specifically, we examine the effect of increasing the power spectrum near to the analytical maximum value of four and also toward the minimum value of three. The effect on scintillation index as a function of Rytov number will be presented for various values of the beam coherence length.

The output of a holographic modal wavefront sensor suffers from inter-modal crosstalk that may arise due to the presence of large number of aberration modes in the incident beam. In the present work we will provide an analytical estimate towards the presence of inter-modal cross-talk on the output of the sensor when the input comprises various aberration modes. The presence of inter-modal crosstalk will be demonstrated in the form of a concise expression comprising of a multiplication factor (F) that affects the sensor output relative to that of cross-mode free output. Both simulation and experimental results will be presented in support of the analytical approach.

In this work, we propose a method capable of determining the centroid of the elongated spots even in the presence of truncation. The key ideas are to model the observed images with Poisson noise and to employ a grid search strategy to determine the position of the spot. Finally, we show that the proposed method provides better results when compared to current methods.

A method to measure turbulence distribution along a path using a Hartmann Turbulence Sensor (HTS) and two laser sources is introduced. By measuring the variances of the difference in wavefront tilts due to the two sources sensed by a pair of Hartmann subapertures with different separations, turbulence information along the entire path can be extracted. The method relies on deriving a set of path weighting functions, each weighting function dipping to zero at a range where the two sensing paths from the beacons to the subapertures intersect, thus canceling out the effect of turbulence at this location on the differential tilt signal. The mathematical framework will be discussed and the technique will be applied on simulated and/ or experimental data.

In this work we will present a new method for measurement of the orthogonal aberration modes present in a static or slowly varying wavefront. The proposed method can be considered as a modified version of the modal wavefront sensing technique, having advantages in terms of cross-talk reduction between modes and enhanced linearity, in the process of measurement of various orthogonal modes present in the incident wavefront. The proposed scheme acquisition time and so is appropriate for the measurements involving static or slowly varying wavefront only. We will also present here some of our simulation and experimental results in support of our proposed sensing technique.

Deconvolution techniques for removing the effects of diffraction from the Hubble space telescope have been employed for decades. This paper introduces a new solution for the deconvolution problem that separates the measurements into three sets of complete data. These data sets are a function of the unknown neighborhood around a star, the amplitude of the star that is known to exist and the background light and dark current measured during the acquisition process. In this paper the new method is tested with simulated Hubble space telescope data and compared to the traditional Richardson-Lucy deconvolution algorithm. The results show that the new method can obtain imaging resolution well beyond the classical diffraction-limit and outperforms the Richardson-Lucy method by a substantial margin.

Recent advances are presented for multiframe blind deconvolution of ground based telescope imagery. The advances address speed aspects for operating in real time at frame rates of up to 23 frames/second. The iterative algorithm uses the maximum likelihood estimation optimization criterion. New renditions of the algorithm simplify the phase reconstruction, which is a contributor to the speed improvement. Simulated and real imagery include the effects of diffraction, turbulence, bad pixel and quantum photon noise.

Several superresolution imaging techniques are revisited to determine fundamental trade-offs between the signal bandwidth, the desired imaging resolution, and the field of view. The discussion includes a novel method to construct superoscillating signals of a given bandwidth and the domain of predefined superoscillations. Phase-space optics is used to quantify the trade-offs between the dynamic range of the signal and its space-bandwidth product. This provides an upper limit for the dynamic range as a function of the local frequency distribution. Numerical simulations are used to compare the theoretical results to practical limits observed for superresolution imaging and superoscillations.

A polarized light scanning confocal microscopy is an important imaging technique popular for its ability of determining the information on molecular orientation of the sample being studied. The determination of the molecular orientation is directly dependent on the electric field distribution present around the focus of the imaging lens, which is used to focus the light to illuminated the sample. In this paper, we will study the effect on the electric field orientation at the focus of the lens in the presence of aberration in the illumination beam.

The paper presents the possibility to obtain comprehensive information on the structure of an optical field, including the field skeleton and the regions of constant phase. High accuracy of reconstruction of the phase map, as well as invariance of the phase distributions following from direct simulation provides a new algorithm for solving the inverse phase problem in optics.

An analysis of a “window” 2D/3D Hilbert transform for reconstruction of the phase distribution of the intensity of a speckle field has been carried out. It is shown that the advantage of these approaches consists in the invariance of a phase map to a change of the position of the kernel of transformation and in a possibility to reconstruct the structure forming elements of the skeleton of an optical field. Within the framework of the approach based on the use of the discrete 2D “window” Hilbert transform, we have demonstrated the feasibility for reconstructing the phase of random 2D objects in real time.

Recent advances are presented for multiframe blind deconvolution of ground based telescope imagery. Practical aspects for installation and usage will be presented. These include: (1) an algorithm that corrects for glint due to specular and other bright reflections, (2), efforts to improve speed so that the system works at streaming frame rates of the telescope system, and (3), a computer simulation that models turbulence, noise and other aspects, for testing and evaluation of the deconvolution system.

Scanning laser imaging ladar has the advantages of high resolution and three-dimensional point cloud imaging, which has been widely used in recent years.The laser ranging technology of frequency-modulated continuous wave technology has the advantages of high sensitivity, strong anti-interference ability and high resolution, and has gained more and more attention.In this paper, we solve the frequency modulation continuous wave ranging technology distance and the speed of winding problem, with the appropriate design of laser waveform has realized the speed and distance between the winding problem, and demonstrates the system of based on frequency modulated continuous wave physical target point cloud image, the range resolution is better than that of 0.05 m.

For small satellite remote sensing missions, a large aperture telescope is required to realize high resolution observations. However, it is difficult or expensive to realize the large aperture monolithic primary mirror with high surface accuracy. We studied a synthetic aperture telescope configured by small satellite formation flying from GEO. We describe the conceptual design of the specification for the satellites and numerical simulation results for the optical performance.

There are lots of requirements of 3D terrain information in the fields of traffic and forest investigation. In this paper we propose a coherent lidar system that produces 3D information of target by use of circularly scanning system. We use the frequency modulated continuous laser wave as optical source. The frequency information from the targets can be demodulated by the FFT algorithm to get the real distance information and generating a point cloud. The method has advantage of background noise resistance over traditional direct detection system.

We discuss the use of nematic liquid-crystal phase modulators (LCPMs) as repeatable optical disturbance test sources to simulate propagation through deep atmospheric turbulence in a laboratory setting. LCPMs can introduce controlled repeatable, dynamic aberrations into optical systems at low cost, low complexity and high flexibility. Because they are small they can easily be inserted into the optical path of a laboratory system. They are programmable and so can generate repeatable sequences of phase disturbance. The programmed sequence can be modified to simulate changing atmospheric conditions and engagement scenarios. This is in contrast to other turbulence generation devices such as fans and heaters which produce turbulence but are not repeatable or spinning phase plates which are repeatable but can’t be modified once fabricated. LCPMs do have a drawback in that they are not achromatic and so can be used only over a narrow band of optical frequencies, in addition most devices have complicated temporal behavior and work only with polarized light. In this paper we describe phase screens generated with multiple LPCMs set up at different conjugate points in an optical path to simulate multiple atmospheric turbulence layers. The goal is to produce simulated deep turbulence optical propagations to test subsequent wave-front sensors and control algorithms. We plan to investigate phenomena related to deep turbulence propagation such as phase-front branch points and optical field intensity fluctuations with medium to high Rytov number.

The incorporation of polarization control on the illumination beam in a laser scanning confocal microscope (LSCM) allows extraction of the orientational information of submicroscopic features of a sample being studied. In this paper, we present the implementation of an optical arrangement that generates homogeneous as well as non-homogeneous user defined polarization profile over the cross-sectional area of a laser beam. A confocal system is built with this optical arrangement to obtain images of the same target with different polarized illumination beams such that there is considerable reduction in the time gap between two consecutive illuminations of each location of the sample.

We propose to use a type of diffractive optical element (DOE) called a photon sieve in order to detect CSOs in Earth orbit. DOEs offer the ability to apply unique combinations of apodization techniques to modify the imaging performance beyond the capabilities of conventional optical elements. The designed optical system will be able to provide high-contrast imaging with up to 10-10 levels and a few lambda/D from the central object and can be installed on any telescope or used as a telescope. This new kind of apodized DOE has rotational symmetry and provide high-contrast in all directions with just one image. Applications include unresolved companion detection (CSOs) and exo-planet search.

Optimization-based methods to correct the effects of anisoplanatism in spatial heterodyne images have been successful in the past. Typically, these methods utilize discrete phase screen approximations of volumetric turbulence in order to greatly reduce the computational complexity of the problem. In this work, we apply sharpness-based optimization in order to mitigate image aberrations caused by anisoplanatism. We explore the efficacy of different mathematical sharpness metrics and methods of optimization and data processing that yield the best image. Additionally, the method of algorithmic differentiation to represent the forward model and reverse accumulation gradient of the convex optimization is discussed.Optimization-based methods to correct the effects of anisoplanatism in spatial heterodyne images have been successful in the past. Typically, these methods utilize discrete phase screen approximations of volumetric turbulence in order to greatly reduce the computational complexity of the problem.

Shadow imaging is a technique to obtain highly resolved silhouettes of resident space objects (RSOs) which would otherwise be unattainable using conventional terrestrial based imaging approaches. This is done by post processing the measured irradiance pattern (shadow) cast onto the Earth as the RSO occults a star. The research presented here focuses on recent developments in shadow imaging of geosynchronous (GEO) satellites with near stationary orbits approximately 36,000 km from the Earth. An overview of shadow imaging is presented along with recent developments regarding shadow prediction accuracy with respect to previously collected GEO data sets.

To achieve high spectral and spatial resolution, we innovatively propose a multi-domain regularization based material decomposition method for spectral micro-CT. The objective function consists of one data term and two regularization terms: the data term measures the KL-divergence in photon domain; the first regularization term adopts the noise statistical property in projection domain; the second regularization term employs the MS functional to emphasize the gradient sparsity in basic material image domains. All the measurements describe various characteristics in different domains. Both numerical simulations and real experiments are performed, and the results confirm the effectiveness and superiority of our proposed approach.

A new algorithm for MRI fat-water separation, POP (phase estimation by onion peeling), requires the estimation of a smoothly varying phase function over a series of closed enveloping surfaces which are irregular in order to generate a 3-D image. The complex data obtained, via the Dixon method, over the same 3-D region has wrapped phase and is undersampled. In this paper, I investigate the choice of basis functions and methods for projecting them onto irregular surfaces which are typical for applying POP to imaging the soft tissue surrounding hip implants.

Image reconstruction models that deal with Poisson noise have received notable attention for image denoising and deblurring problems. Tomography does not fall into this category, and such methods have yet to be explored for applications such as electron tomography. In this domain, the use of Poisson models becomes much more challenging, where popular methods such as the Richardson-Lucy algorithm cannot be implemented. The purpose of this article is to provide a survey of Poisson image reconstruction models in the context of tomography, and identify the potential of the most successful algorithms and the benefits over the current standard techniques.

Imaging the structures of biological macromolecules is key to our understanding of biological processes and for drug design. X-ray crystallography, the primary method for imaging biomolecules, is currently undergoing a revolution as a result of the recent availability of x-ray free-electron lasers (XFELs); large, billion-dollar facilities that produce extremely intense, ultra-short x-ray pulses. We show that these instruments offer the feasibility of imaging very small 1D and 2D crystalline specimens, as opposed to the 3D crystals that are necessary in conventional x-ray crystallography. This offers some advantages and gives access to some unique biological systems.

We demonstrate the use of a deep convolutional neural network for the enhancement of smartphone microscopy, by eliminating spectral aberrations, increasing the signal-to-noise ratio and improving the spatial resolution of the acquired images. Once trained, the deep neural network is fixed, and rapidly outputs an image, matching the quality of a benchtop microscope image, in a feed-forward, non-iterative manner. This framework is demonstrated using thin tissues sections and blood smears, validating its superior performance even using highly-compressed images. This approach can be broadly applicable to various mobile microscopy systems that can be used for point-of-care medicine and global health applications.

Adaptive-optics (AO) systems correct the distortions caused by atmospheric turbulence for imaging and laser-transmission applications. When the object is uncooperative, the AO system creates a reference wave for wavefront measurement by focusing a laser beam onto the object. Unfortunately, the extended size of the beam introduces speckle noise which degrades the AO system’s correction. In this paper, we use polychromatic illumination to create the reference wave and study the associated reduction in speckle-induced error. To quantify the benefits, we use wave-optics simulations with the spectral-slicing method for polychromatic light. The results show a reduction in speckle-induced error, especially when the object is large.

A fast architecture of centroiding for wavefront sensing implemented in a FPGA is presented, with latency in the order of microseconds, suitable to be implemented in an adaptive optics system. Two centroiding algorithms are implemented, namely SCoG and 1FC, based on stream processing with moving filters, and the 1st Fourier Coefficient approximation respectively. The architecture was tested in laboratory and on-sky with a 0.3m Meade LX200 telescope, and compared with commercial solutions for wavefront sensing, where the developed algorithms showed a clear advantage in timing performance, real state electronics and ease of integration in an adaptive optics system.

We propose a novel optical diagnosis for plasma electron density measurement with the Coherent Modulation Imaging(CMI) method which is a kind of phase retrieval technique and doesn’t need a reference beam. The phase of the diagnostic light can be reconstructed by CMI algorithm. The distribution of electron density can be obtained by dealing with the phase change using Abelian integral formula. Experimental results showed that the area where the plasma generated is ejected from the center. As the energy of laser driver beam increases, the phase difference region resulting from the generation of the plasma becomes larger.

During propagation of the high power laser radiation through atmosphere the quality of the beam significantly reduced due to atmosphere turbulence. Main reason of the atmosphere turbulence is heating airflows and Earth surface. For compensation of the wavefront distortions and improving quality of radiation, as a rule, adaptive optics approaches are used. The 121-elements water-cooled stacked-actuator deformable mirror for this kind of applications is developed.

The fast adaptive optical system can be used, for example, for correction of laser beam passed through a strong turbulent atmosphere. The frequency with which such a system should operate to achieve an acceptable level of wavefront correction is about 1 – 1.5 kHz. There are two most popular methods to develop this system: 1) by using a standard PC computer and 2) by using FPGA. This report presents the advantages and disadvantages of each of these approaches. The results obtained with the use of these systems are presented. Recommendation for achieving higher performance are given.

We investigated the ability to focus laser beam (λ = 0.65 nm), propagated through the scattering suspension of polystyrene microspheres in distilled water, by means of two bimorph mirrors. Shack-Hartmann sensor was used to measure the local slopes of the Poynting vector, and the CCD camera was used to measure the intensity of the focal spot in the far-field. Correction efficiency of the two bimorph deformable mirrors — with 14 and 31 control channels — were compared. Numerical and experimental investigation of the focusing improvement of the laser beam propagated through the scattering medium was performed.