Download or read book The Effect of Real Atmospheric Turbulence on Passive Phase Calibration in Optical Aperture Synthesis written by Wilson McKellar and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Digital Phase Correction of a Partially Coherent Sparse Aperture System written by Sarah Elaine Krug and published by . This book was released on 2015 with total page 142 pages. Available in PDF, EPUB and Kindle. Book excerpt: Sparse aperture image synthesis requires proper phasing between sub-apertures. Phasing can be difficult due to hardware misalignments, atmospheric turbulence, and many other causes of optical path differences (OPD). Common synthesis techniques include incoherent and coherent methods. Incoherent methods utilize passive illumination and adaptive optics while coherent methods rely on active illumination and phase reconstruction approaches such as phase retrieval or spatial heterodyne. In this thesis, we present a partially coherent technique with the capability to use either active or passive illumination to digitally correct for piston phase errors. This technique requires an anamorphic pupil relay system and a piston correction algorithm. The anamorphic pupil relay causes two closely spaced sub-apertures in the entrance pupil to appear to be shifted further apart in the exit pupil. Analytic and numerical wave optics models demonstrate the effectiveness of this relay system, matching with experimental results. An analytic model shows that the higher frequency terms are equivalent to scaled cross-correlations of the two sub-apertures, which are shifted due to the anamorphic separation. The constant shifts due to the separation are found experimentally using a registration algorithm with a calibration target. The cross-correlations are dependent on the piston phase errors between sub-apertures. We show that a piston correction algorithm can be used to shift the cross-correlations to their original positions dictated by the entrance pupil, multiply a cross-correlation with the complex conjugate of the auto-correlation, use the summation of this product to calculate the piston, and correct the phase error in each cross-correlation before recombining them with the auto-correlation. Examples show diffraction limited results for both simulated and experimental images that are supported by analytical, numerical, and experimental analysis of the system0́9s modulation transfer function (MTF). In addition, analysis of the piston for multiple wavelengths reveals two effects of bandwidth on the system. First, the impact of a constant spatial separation resulting in different spatial frequency shifts for different wavelengths, referred to as field dependent contrast (FDC), is addressed. Second, the inverse relationship between the bandwidth of the system and OPD tolerances is shown. In future research, diffraction gratings could eliminate the FDC so that partially coherent illumination with a small enough system bandwidth could relax OPD requirements for the sparse aperture array.

Download or read book Effects of Atmospheric Turbulence on Optical Instrumentation written by Randolph A. Becker and published by . This book was released on 1961 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: The results of research on optical turbulence at White Sands Missile Range are presented. It has been shown that elevating camera stations 33 feet above ground level can yield nearly a threefold increase in optical resolution during periods of atmospheric turbulence. Early research postulated the existence of thermal-induced air-lenses as the cause of optical turbulence effects. Recent research has shown that air-lenses can account for most of the observed effects. The 'prism' concept of turbulence appears to be unnecessary for explaining trubulence -induced image motion. The dependence of the optical effects of turbulence upon exposure time and aperture size is discussed qualitatively. The source of optical turbulence in the atmosphere and a method of measuring the trubulence-generating potential of various terrain surfaces are described on the basis of micrometerology. This research has been limited to an investigation of optical turbulence during the period from sunrise to sunset. However, many of the results apply to the nighttime turbulence encountered by astronomers. (Author).

Download or read book 5th International Workshop on Adaptive Optics for Industry and Medicine written by Wenhan Jiang and published by SPIE-International Society for Optical Engineering. This book was released on 2005 with total page 486 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of SPIE present the original research papers presented at SPIE conferences and other high-quality conferences in the broad-ranging fields of optics and photonics. These books provide prompt access to the latest innovations in research and technology in their respective fields. Proceedings of SPIE are among the most cited references in patent literature.

Download or read book Laser Radar written by National Research Council and published by National Academies Press. This book was released on 2014-03-14 with total page 321 pages. Available in PDF, EPUB and Kindle. Book excerpt: In today's world, the range of technologies with the potential to threaten the security of U.S. military forces is extremely broad. These include developments in explosive materials, sensors, control systems, robotics, satellite systems, and computing power, to name just a few. Such technologies have not only enhanced the capabilities of U.S. military forces, but also offer enhanced offensive capabilities to potential adversaries - either directly through the development of more sophisticated weapons, or more indirectly through opportunities for interrupting the function of defensive U.S. military systems. Passive and active electro-optical (EO) sensing technologies are prime examples. Laser Radar considers the potential of active EO technologies to create surprise; i.e., systems that use a source of visible or infrared light to interrogate a target in combination with sensitive detectors and processors to analyze the returned light. The addition of an interrogating light source to the system adds rich new phenomenologies that enable new capabilities to be explored. This report evaluates the fundamental, physical limits to active EO sensor technologies with potential military utility; identifies key technologies that may help overcome the impediments within a 5-10 year timeframe; considers the pros and cons of implementing each existing or emerging technology; and evaluates the potential uses of active EO sensing technologies, including 3D mapping and multi-discriminate laser radar technologies.

Download or read book Interferometry and Synthesis in Radio Astronomy written by A. Richard Thompson and published by Wiley-Interscience. This book was released on 1986-04-28 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: A unified description of the theory and practice of radio interferometry and synthesis mapping techniques as they apply to astronomy and geology. Beginning with an historical review, it goes on to provide a detailed description of all aspects of radio inferometry, from basic principles through instrumental design to data reduction. Over 450 original papers and monographs are cited.

Download or read book Diffraction Limited Imaging with Large and Moderate Telescopes written by Swapan K. Saha and published by World Scientific. This book was released on 2007 with total page 633 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with the fundamentals of wave optics, polarization, interference, diffraction, imaging, and the origin, properties, and optical effects of turbulence in the Earth's atmosphere. Techniques developed during the last few decades to overcome atmospheric image degradation (including passive methods, speckle interferometry in particular, and active methods such as adaptive optics), are highlighted. Also discussed are high resolution sensors, image processing, and the astronomical results obtained with these techniques.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Physics Briefs written by and published by . This book was released on 1993 with total page 1288 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book NASA Tech Briefs written by and published by . This book was released on 1986 with total page 988 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book NASA Technical Memorandum written by and published by . This book was released on 1992 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Earth Resources written by and published by . This book was released on 1986 with total page 760 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 1986 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Current Programs written by and published by . This book was released on 1976 with total page 526 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Government Reports Annual Index written by and published by . This book was released on 1985 with total page 974 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Index to NASA Tech Briefs written by and published by . This book was released on with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optics Letters written by and published by . This book was released on 1980 with total page 468 pages. Available in PDF, EPUB and Kindle. Book excerpt: