Download or read book Correlation Techniques for Imaging Through Atmospheric Turbulence written by Geoffrey Robert Ayers and published by . This book was released on 1989 with total page 0 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 Reconstruction of Computer Simulated Atmospheric Turbulence Degraded Astronomical Objects by Application of the Knox Thompson and Triple Correlation Phase Recovery Techniques written by and published by . This book was released on 1990 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: Atmospheric turbulence severely degrades images of astronomical objects. Providing images that accurately reflect the true nature of these objects is essential to their understanding. Several object recovery techniques exist within the field of speckle imaging that produce accurate representations of astronomical objects. This thesis provides an in-depth comparison of two such techniques, Knox-Thompson and triple-correlation. Through computer simulation, this thesis accurately compares the abilities of both recovery techniques to enhance turbulence degraded objects by exploiting the diffraction-limited information contained in short exposure, or speckle, images. The simulation produced these images by creating an object and several phase screens which simulated the effects of turbulence. Together, the object and the appropriate quantity of phase screens yielded the required short exposure images. Application of the Knox-Thompson and triple-correlation techniques to identical sets of these degraded images produced the resulting reconstructed objects, their signal-to-noise ratios and their azimuthal RMS phase errors. Comparison of these three factors over several imaging criteria concluded that the superior phase recovery technique was triple-correlation.
Download or read book Experimental Investigations of Optical Propagation in Atmospheric Turbulence written by Michael W. Fitzmaurice and published by . This book was released on 1971 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: The pertinent theoretical background and the results of a group of experiments conducted over 0.4- and 1.17-km near-ground horizontal ranges are presented. (1) The log-amplitude variances for HeNe (0.633 μm) and CO2 (10.6 μm) laser beams were found to have a ratio of 26.8, which is in close agreement with the predictions of Rytov-based spherical-wave theory. (2) Published measurements of the saturation level of the log-amplitude variance are reviewed and several inconsistencies noted. (3) The spatial correlation function of irradiance field was measured and found to agree with theory. The degree of correlation between different frequency beams which had traversed the same optical path was also measured and compared to theory. The data exhibited an unacceptably large scatter and did not show the wavelength dependence. (4) The log-normal, Rayleigh, and Rice probability distributions are discussed in terms of their applicability to irradiance statistics. Relatively weak 10.6 μm irradiance fluctuations were found to be equally well described by the log-normal and Rice distributions; strong fluctuations obtained at 0.488 μm were clearly best described by the log-normal distribution.
Download or read book NASA Reference Publication written by and published by . This book was released on 1990 with total page 490 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 524 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Correlation of Atmospheric Turbulence written by Lear Siegler. Instrument Division and published by . This book was released on 1964 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Very High Angular Resolution Imaging written by J.G. Robertson and published by Springer Science & Business Media. This book was released on 2013-12-01 with total page 505 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 1990s are proving to be a very exciting p&iod for high angular resolution astronomy. At radio wavelengths a combination of new array instruments and pow erful imaging algorithms have generated images of unprecedented resolution and quality. In the optical and infrared, the great technical difficulties associated with constructing separated-aperture interferometers have been largely overcome, and many new instruments are now operating or are being developed. As these pro grams start to produce observational results they will be able to draw extensively on the experience gained by the radio-interferometry community. Thus it seemed that the time was ripe for a meeting which would bring together workers from all wavelength ranges to discuss the details of the science and art of "Very High Angular Resolution Imaging" . While the main emphasis of Symposium No. 158 was on high resolution tech niques from the radio, mm-wave, infrared and optical bands, it also provided an opportunity for presentation of astronomical results from these techniques. As well as giving our colleagues from the Northern Hemisphere a break from midwinter, the location of the Symposium in Australia recognised the continuing development of astronomical interferometry in this country, especially the recent completion of the Australia Telescope radio array, and the progress toward com missioning of the Sydney University Stellar Interferometer. A number of the par ticipants visited these instruments during the post-symposium tour.
Download or read book Propagation and Imaging Through the Atmosphere written by and published by . This book was released on 2000 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Literature 1988 Part 2 written by Astronomisches Rechen-Institut and published by Springer Science & Business Media. This book was released on 2013-06-29 with total page 1308 pages. Available in PDF, EPUB and Kindle. Book excerpt: From the reviews: "Astronomy and Astrophysics Abstracts has appeared in semi-annual volumes since 1969 and it has already become one of the fundamental publications in the fields of astronomy, astrophysics and neighbouring 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." Space Science Reviews#1 "Dividing the whole field plus related subjects into 108 categories, each work is numbered and most are accompanied by brief abstracts. Fairly comprehensive cross-referencing links relevant papers to more than one category, and exhaustive author and subject indices are to be found at the back, making the catalogues easy to use. The series appears to be so complete in its coverage and always less than a year out of date that I shall certainly have to make a little more space on those shelves for future volumes." The Observatory Magazine#2
Download or read book Imaging Through Atmospheric Turbulence Via Cepstral Averaging written by Herbert William Swan and published by . This book was released on 1982 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Investigation of Atmospheric Turbulence by Stellar Observations written by Jack Lytle Bufton and published by . This book was released on 1971 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study of the optical effects of atmospheric turbulence concentrates on the stellar observation problem. When an infinite plane wave from an incoherent stellar source is sampled by an earth-based telescope, the resultant stellar image exhibits random fluctuations in intensity, position, and size due to turbulence-induced scattering in the intervening atmosphere. One familiar aspect of this problem is the scintillation of starlight apparent to the naked eye. The central aim is to express optical statistics in terms of refractive-index structure constant which pertains to strength of turbulence along the optical path. Data is presented on stellar and meteorological observations made between fall 1968 and spring 1969 with a 0.152-meter diameter refracting telescope. Data was recorded simultaneously on the three parameters of image intensity, motion, and size. The data is interpreted in terms of the theory and used to estimate strength of turbulence. The central result is a series of profiles for refractive-index structure constant along the vertical path. These are constructed using stellar data to calculate parameters of a model.
Download or read book General Theory of Light Propagation and Imaging Through the Atmosphere written by T. Stewart McKechnie and published by Springer. This book was released on 2015-08-05 with total page 639 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book lays out a new, general theory of light propagation and imaging through Earth’s turbulent atmosphere. Current theory is based on the – now widely doubted – assumption of Kolmogorov turbulence. The new theory is based on a generalized atmosphere, the turbulence characteristics of which can be established, as needed, from readily measurable properties of point-object, or star, images. The pessimistic resolution predictions of Kolmogorov theory led to lax optical tolerance prescriptions for large ground-based astronomical telescopes which were widely adhered to in the 1970s and 1980s. Around 1990, however, it became clear that much better resolution was actually possible, and Kolmogorov tolerance prescriptions were promptly abandoned. Most large telescopes built before 1990 have had their optics upgraded (e.g., the UKIRT instrument) and now achieve, without adaptive optics (AO), almost an order of magnitude better resolution than before. As well as providing a more comprehensive and precise understanding of imaging through the atmosphere with large telescopes (both with and without AO), the new general theory also finds applications in the areas of laser communications and high-energy laser beam propagation.
Download or read book The Development and Clinical Application of Innovative Optical Ophthalmic Imaging Techniques written by Peng Xiao and published by Frontiers Media SA. This book was released on 2022-12-06 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.
Download or read book An Auto correlation Technique for the Measurement of the Power Spectrum of Atmospheric Turbulence written by B. L. Clarkson and published by . This book was released on 1959 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Atmospheric Turbulence Scintillation Effects on Wavefront Tilt Estimation written by James Allan Louthain and published by . This book was released on 1997-12-01 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new atmospheric turbulence screen generator is developed for use in performance calculations of adaptive optics systems valid over a wide range of atmospheric turbulence parameters. The screen generator accounts for diffraction effects caused by weak turbulence and incorporates the phase, amplitude, and cross statistics of the perturbed optical field. The wavefront's phase and amplitude perturbations are taken from the correlation functions developed by Lee and Harp and the cross correlation of the phase and amplitude derived in this thesis. The screen generator uses a modal representation to perform a Fourier series expansion of the wavefront phase and amplitude over a square area. The phase, amplitude, and cross power spectral densities determined from the correlation functions are used in the Fourier series expansion. The mean square value and the structure functions of the phase, amplitude, and cross terms are calculated to within 1% of the theoretical values in a Monte Carlo experiment using the screen generator. Monte Carlo experiments performed using the screen generator showed the amplitude perturbations can significantly reduce the accuracy of full-aperture tilt estimation using image centroid motion. However, since the amplitude perturbations affect the image centroid, the tilt estimate using the combined amplitude and phase screen allows for a higher Strehl ratio than using only the phase to estimate the correction.
