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Frame Selection And Bispectrum For Speckle Imaging Through Atmospheric Turbulence
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Book Synopsis Frame Selection and Bispectrum for Speckle Imaging Through Atmospheric Turbulence by : Elizabeth A. Harpold
Download or read book Frame Selection and Bispectrum for Speckle Imaging Through Atmospheric Turbulence written by Elizabeth A. Harpold and published by . This book was released on 1995 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Role of Frame Selection and Bispectrum Phase Reconstruction for Speckle Imaging Through Atmospheric Turbulence by :
Download or read book The Role of Frame Selection and Bispectrum Phase Reconstruction for Speckle Imaging Through Atmospheric Turbulence written by and published by . This book was released on 1995 with total page 191 pages. Available in PDF, EPUB and Kindle. Book excerpt: Frame selection using quality sharpness metrics have been shown in previous AFIT theses, to be effective in improving the final product of images obtained using adaptive optics. This thesis extends this idea to noncompensated speckle image data. Speckle image reconstruction is simulated with and without frame selection. Speckle images require the processing of hundreds of data frames. Frame selection is a method of reducing the amount of data required to reconstruct the image. A collection of short exposure image data frames of a single object are sorted based on sharpness metrics. Only the highest quality frames are retained and processed for the final image. The phase spectrum is reconstructed using the bispectrum technique. The benefits of frame selection for point (star) sources and extended (satellite) sources are examined by comparing composite image data with and without frame selection. The resulting power spectrum is evaluated through the SNR gain measurements, and the resulting phase spectrum is evaluated by measuring the phase error between the composite image and the object. In both cases, the results show that frame selection does not improve the power or the phase spectrums. For point sources, results show frame selection causes slight decrease in performance. For extended sources, the change in performance is insignificant. However, frame selection does offer a means for data reduction without significantly reducing performance in a wide variety of target brightness levels and atmospheric turbulence conditions. (AN).
Book Synopsis Imaging Through Turbulence by : Michael C. Roggemann
Download or read book Imaging Through Turbulence written by Michael C. Roggemann and published by CRC Press. This book was released on 2018-02-06 with total page 389 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn how to overcome resolution limitations caused by atmospheric turbulence in Imaging Through Turbulence. This hands-on book thoroughly discusses the nature of turbulence effects on optical imaging systems, techniques used to overcome these effects, performance analysis methods, and representative examples of performance. Neatly pulling together widely scattered material, it covers Fourier and statistical optics, turbulence effects on imaging systems, simulation of turbulence effects and correction techniques, speckle imaging, adaptive optics, and hybrid imaging. Imaging Through Turbulence is written in tutorial style, logically guiding you through these essential topics. It helps you bring down to earth the complexities of coping with turbulence.
Book Synopsis Imaging Through Turbulence by : Michael C. Roggemann
Download or read book Imaging Through Turbulence written by Michael C. Roggemann and published by CRC Press. This book was released on 2018-02-06 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: Learn how to overcome resolution limitations caused by atmospheric turbulence in Imaging Through Turbulence. This hands-on book thoroughly discusses the nature of turbulence effects on optical imaging systems, techniques used to overcome these effects, performance analysis methods, and representative examples of performance. Neatly pulling together widely scattered material, it covers Fourier and statistical optics, turbulence effects on imaging systems, simulation of turbulence effects and correction techniques, speckle imaging, adaptive optics, and hybrid imaging. Imaging Through Turbulence is written in tutorial style, logically guiding you through these essential topics. It helps you bring down to earth the complexities of coping with turbulence.
Book Synopsis Improving Imaging Through Turbulence Via Aperture Partitioning by :
Download or read book Improving Imaging Through Turbulence Via Aperture Partitioning written by and published by . This book was released on 2010 with total page 14 pages. Available in PDF, EPUB and Kindle. Book excerpt: Speckle imaging techniques make it possible to do high-resolution imaging through the turbulent atmosphere by collecting and processing a large number of short-exposure frames, each of which effectively freezes the atmosphere. In severe seeing condition, when the characteristic scale of atmospheric fluctuations is much smaller than the diameter of the telescope, the reconstructed image is dominated by?turbulence noise? caused by redundant baselines in the pupil. I describe a generalization of aperture masking interferometery that dramatically improves imaging performance in this regime. The approach is to partition the aperture into annuli, form the bispectra of the focal plane images formed from each annulus, and recombine them into a synthesized bispectrum form which the object may be retrieved. This may be implemented using multiple cameras and special mirrors, or with a single camera and a suitable pupil phase mask. I report results from simulations as well as experimental results using telescopes at the Air Force Research Lab's Maui Space Surveillance Site.
Book Synopsis Comparing Speckle Imaging Methods by :
Download or read book Comparing Speckle Imaging Methods written by and published by . This book was released on 2009 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: We will compare speckle imaging reconstruction results for several speckle imaging approaches. In particular, we will compare and contrast four methods: 1) Knox-Thompson, using a hidden phase-finder in the object spectrum phase reconstruction; 2) Knox-Thompson, using a phasor-based phase reconstruction; 3) Bispectrum, using only two bispectrum planes; Bispectrum, using four bispectrum planes. In each application of the four approaches we first calculate the modulus of the object spectrum using a Wiener-Helstrom filter to remove the speckle transfer function. The methods then differ only in their object spectrum phase reconstructions. In the simulations, we will assume that the only aberrations are those introduced by atmospheric turbulence, setting the ratio of the telescope diameter, D, to the Fried Parameter equal to ten. Additionally, we assume that the focal-plane detector array is photon-noise limited, the illumination is narrow-band (essentially monochromatic) and the atmosphere is static during each data frame. First, we will implement all four methods on a simple binary star object at low photon-per-frame light levels. Next, we will apply the methods to complex extended objects.
Book Synopsis An Examination of Selective Imaging Techniques by : Andrew Grant Smith
Download or read book An Examination of Selective Imaging Techniques written by Andrew Grant Smith and published by . This book was released on 2010 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: An extensive empirical study of the frame selection method of high-resolution astronomical imaging, also known as lucky imaging, has been carried out. This method involves the capture of many hundreds or thousands of short exposure frames, the scanning and ranking of all the frames for sharpness, and the co-alignment and averaging of only the best frames into a final image. The performance of the selective imaging technique was tested by imaging several bright stars, binaries and clusters, and using the brightest pixel value in each frame as the sharpness metric. The lucky imaging parameters are the frame exposure time, telescope aperture, seeing, frame selection fraction, colour band, and distance from the co-alignment position. By using a range of aperture masks and colour filters, and a camera with adjustable exposure, we explored the widest range of parameter space of any frame selection study to date. -- The results from the stellar images show that frame selection is very effective at reducing the effects of atmospheric turbulence on astronomical images. When all frames in an observation are combined, the seeing disc is diminished and a bright central core is apparent. By selecting just the best 1% of frames the core is brighter while the halo almost vanishes. In many of these cases faint spikes and dark rings appeared, indicating difraction limited images. The results were best when small apertures were used, particularly at longer wavelengths. It was found that, for the Siding Spring site, the exposure time should be limited to 10 ms, although images were improved at all times tested. It was also found that when image frames of binaries and clusters were co-aligned on the brightest star, the improvement in sharpness was greatest at this point, and the improvement decreased with angular radius. -- To prepare for future research, solar system planets and lunar features were also imaged. These were processed with sharpness metrics suited to extended objects. It was found that frame selection was effective at improving the planetary images over traditional long exposure images. However the results were not as good as for the stellar images. Possible reasons for this are discussed.
Book Synopsis Atmospheric Turbulence Distortion in Video by : Benjamin J. Sanda
Download or read book Atmospheric Turbulence Distortion in Video written by Benjamin J. Sanda and published by . This book was released on 2020 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt: The removal of atmospheric turbulence (AT) distortion in long range imaging is one of the most challenging areas of research in imaging processing with an immediate need for solutions in several applications such as in military and transportation systems. AT exacerbates distortion due to non-linear geometric blur and scintillations in long-distance images and videos, severely reducing image quality and information interpretation. AT negatively impacts both human and computer vision systems, compromising visibility essential for accurate object identification and tracking. In this dissertation, a novel sparse analysis framework is developed to address efficient AT blur and scintillation removal in video. Operating under the premise that distortion-free images should be sparse in a transform domain, the application of the dual-tree complex wavelet transform is utilized on frame bursts, allowing for a new near shift-invariant complex transform space that results in higher sparsity, higher object tracking accuracy, and better resilience against camera shake, geometric distortion, and imperfect frame registration encountered in real-world AT-distorted sequences. Using this new complex transform space the novel Frame-Burst Coefficient Shimmer Thresholding (FBST) algorithm is developed. FBST considers the complex coefficient shimmer across multiple frames to address threshold selection and moving object blur, issues still present in other methods which utilize techniques such as averaging and empirical threshold selection. In fact, by evaluating video sequences of moving vehicles with visible license plates, we show FBST produces up to an 85% sparse reconstruction with superior visual results compared to weighted and simple thresholding approaches while preserving object motion, reducing AT distortion, and enhancing object contrast and visibility. Moreover, compressed sensing (CS) methods to sparse AT distortion removal are also investigated through direct CS sampling of the coefficients of the complex wavelet transform, allowing us to sparsely sample and reconstruct a restored output image. This essentially develops a means to sample in real-time, store the reduced size dataset, and reconstruct a de-blurred output in the cloud for low-power portable systems. Results using AT-distorted traffic sequences indicate that CS provides up to a 75% sparse reconstruction, contrast enhancement, and de-blurring, while using only one-fifth the number of coefficients for sampling. Overall, this dissertation presents a sparse analysis framework that is well suited to provide robust AT distortion removal that does not blur moving objects and provides a highly sparse representation with reduced storage requirements for distributed-processing and low-power monitoring systems.
Book Synopsis Journal of the Optical Society of America by :
Download or read book Journal of the Optical Society of America written by and published by . This book was released on 1992 with total page 664 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author :Astronomisches Recheninstitut Publisher :Springer Science & Business Media ISBN 13 :3662123797 Total Pages :1456 pages Book Rating :4.6/5 (621 download)
Book Synopsis Literature 1992, Part 1 by : Astronomisches Recheninstitut
Download or read book Literature 1992, Part 1 written by Astronomisches Recheninstitut and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 1456 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Astronomy and Astrophysics Abstracts" appearing twice a year has become oneof the fundamental publications in the fields of astronomy, astrophysics andneighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. The abstracts are classified under more than a hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world.
Book Synopsis Restoration of Images Taken Through a Turbulent Medium by : Zhiying Wen
Download or read book Restoration of Images Taken Through a Turbulent Medium written by Zhiying Wen and published by . This book was released on 2010 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates the problem of how information contained in multiple, short exposure images of the same scene taken through (and distorted by) a turbulent medium (turbulent atmosphere or moving water surface) may be extracted and combined to produce a single image with superior quality and higher resolution. This problem is generally termed image restoration. It has many applications in fields as diverse as remote sensing, military intelligence, surveillance and recognition at a long distance, and other imaging problems which suffer from turbulent media, including e.g. the atmosphere and moving water surface. Wide-area/near-to-ground imaging (through atmosphere) and water imaging are the two main focuses of this thesis. The central technique used to solve these problems is speckle imaging, which is used to process a large number of images of the object with short exposure times such that the turbulent effect is frozen in each frame. A robust and efficient method using the bispectrum is developed to recover an almost diffraction-limited sharp image using the information contained in the captured short exposure images. Both the accuracy and the potential of these new algorithms have been investigated. Motivated by the lucky imaging technique which was used to select superior frames for astronomical imaging application, a new and more efficient technique is proposed. This technique is called lucky region, and it is aimed at selecting image regions with high quality as opposed to selecting a whole image as a lucky image. A new algorithm using bicoherence is proposed for lucky region selection. Its performance, as well as practical factors that may affect the performance, are investigated both theoretically and empirically. To further improve the quality of the recovered clean image after the speckle bispectrum processing, we also investigate blind deconvolution. One of the original contributions is to use natural image sparsity as a prior knowledge for the turbulence image restoration problem. A new algorithm is proposed and its performance is validated experimentally. The new methods are extended to the case of water imaging: restoration of images distorted by moving water waves. It is shown that this problem can be effectively solved by techniques developed in this thesis. Possible practical applications include various forms of ocean observation.
Download or read book Unconventional Imaging written by and published by . This book was released on 2005 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis NOAO-ESO Conference on High-Resolution Imaging by Interferometry by : Fritz Merkle
Download or read book NOAO-ESO Conference on High-Resolution Imaging by Interferometry written by Fritz Merkle and published by . This book was released on 1988 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Government Reports Announcements & Index by :
Download or read book Government Reports Announcements & Index written by and published by . This book was released on 1996 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Adaptive Optical Systems and Applications by : Robert K. Tyson
Download or read book Adaptive Optical Systems and Applications written by Robert K. Tyson and published by . This book was released on 1995 with total page 444 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Adaptive Optical System Technologies by : Domenico Bonaccini
Download or read book Adaptive Optical System Technologies written by Domenico Bonaccini and published by . This book was released on 1998 with total page 772 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Observatory Operations to Optimize Scientific Return by :
Download or read book Observatory Operations to Optimize Scientific Return written by and published by . This book was released on 1998 with total page 498 pages. Available in PDF, EPUB and Kindle. Book excerpt:
