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).
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:
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.
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.
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.
Download or read book Encyclopedia of Optical and Photonic Engineering Print Five Volume Set written by Craig Hoffman and published by CRC Press. This book was released on 2015-09-22 with total page 3726 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first edition of the Encyclopedia of Optical and Photonic Engineering provided a valuable reference concerning devices or systems that generate, transmit, measure, or detect light, and to a lesser degree, the basic interaction of light and matter. This Second Edition not only reflects the changes in optical and photonic engineering that have occurred since the first edition was published, but also: Boasts a wealth of new material, expanding the encyclopedia’s length by 25 percent Contains extensive updates, with significant revisions made throughout the text Features contributions from engineers and scientists leading the fields of optics and photonics today With the addition of a second editor, the Encyclopedia of Optical and Photonic Engineering, Second Edition offers a balanced and up-to-date look at the fundamentals of a diverse portfolio of technologies and discoveries in areas ranging from x-ray optics to photon entanglement and beyond. This edition’s release corresponds nicely with the United Nations General Assembly’s declaration of 2015 as the International Year of Light, working in tandem to raise awareness about light’s important role in the modern world. Also Available Online This Taylor & Francis encyclopedia is also available through online subscription, offering a variety of extra benefits for researchers, students, and librarians, including: Citation tracking and alerts Active reference linking Saved searches and marked lists HTML and PDF format options Contact Taylor and Francis for more information or to inquire about subscription options and print/online combination packages. US: (Tel) 1.888.318.2367; (E-mail) [email protected] International: (Tel) +44 (0) 20 7017 6062; (E-mail) [email protected]
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.
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:
Download or read book Propagation and Imaging Through the Atmosphere written by and published by . This book was released on 1999 with total page 300 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analysis of Phase Retrieval in Active Imaging written by J. R. Fienup and published by . This book was released on 1990 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes a collection of research tasks which develop techniques to reconstruct fine-resolution images of satellites coherently illuminated by lasers. Two major imaging modes were developed. In the first, called imaging correlography, an incoherent image of the coherently illuminating target is reconstructed from multiple realizations of the intensity of the nonimaged (aperature-plane) laser speckle pattern backscattered from the target. In the second mode, a coherent image of the target is reconstructed from a single realization of the nonimaged laser speckle pattern. In the latter mode, reconstruction methods were developed for the case in which contains a strong glint (or glints) and for the case in which one has partial information about the phase of the optical field backscattered by the target. Keywords: Phase retrieval; Image reconstruction; Speckle; Atmospheric turbulence; Intensity interferometry; Imaging correlography.
Download or read book Frame Selection Performance Limits for Statistical Image Reconstruction of Adaptive Optics Compensated Images written by and published by . This book was released on 1994 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt: The U.S. Air Force uses adaptive optics systems to collect images of extended objects beyond the atmosphere. These systems use wavefront sensors and deformable mirrors to compensate for atmospheric turbulence induced aberrations. Adaptive optics greatly enhance image quality, however, wavefront aberrations are not completely eliminated. Therefore, post-detection processing techniques are employed to further improve the compensated images. Typically, many short exposure images are collected, recentered to compensate for tilt, and then averaged to overcome randomness in the images and improve signal-to-noise ratio. Experience shows that some short exposure images in a data set are better than others. Frame selection exploits this fact by using a quality metric to discard low quality frames. A composite image is then created by averaging only the best frames. Performance limits associated with the frame selection technique are investigated in this thesis. Limits imposed by photon noise result in a minimum object brightness of visual magnitude +8 for point sources and +4 for a typical satellite model. Effective average point spread functions for point source and extended objects after frame selection processing are almost identical across a wide range of conditions. This discovery aliows the use of deconvolution techniques to sharpen images after using the frame selection technique. A new post-detection processing method, frame weighting, is investigated and may offer some improvement for dim objects during poor atmospheric seeing. Frame selection is demonstrated for the first time on actual imagery from an adaptive optics system. Data analysis indicates that signal-to-noise ratio improvements are degraded for exposure times longer than that allowed to "freeze" individual realizations of the turbulence effects.
Download or read book Bispectral Reconstruction of Speckle degraded Images written by Song Jin and published by . This book was released on 1992 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The bispectrum of a signal has useful properties such as being zero for a Gaussian random process, retaining both phase and magnitude information of the Fourier transform of a signal, and being insensitive to linear motion. It has found applications in a wide variety of fields. The use of these properties for reducing speckle in coherent imaging systems was investigated. It was found that the bispectrum could be used to restore speckle-degraded images. Coherent speckle noise is modeled as a multiplicative noise process. By using a logarithmic transformation, this speckle noise is converted to a signal independent, additive process which is close to Gaussian when an integrating aperture is used. Bispectral reconstruction of speckle-degraded images is performed on such logarithmically transformed images when we have independent multiple snapshots."--Abstract.
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.
Download or read book Optical Engineering written by and published by . This book was released on 1994-10 with total page 1062 pages. Available in PDF, EPUB and Kindle. Book excerpt: Publishes papers reporting on research and development in optical science and engineering and the practical applications of known optical science, engineering, and technology.
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:
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:
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:
