On June 1, 2005 AFOSR awarded a grant to Michigan Technological University to investigate image reconstruction, wave front sensing, and adaptive optics in extreme imaging conditions. This is the final report for this program. The overall goal was to understand imaging under conditions where seeing is exceedingly poor, such as for space surveillance of objects at very low elevation angles, and during daytime hours. In these situations, scintillation and small isoplanatic angles dominate the image measurement and reconstruction problems. Our work was focused on performing trade-offs in the adaptive optics control algorithms for imaging under conditions of poor seeing arising from large zenith angles. In particular, we have developed a closed loop simulation of an adaptive optics system which is physically similar to the AEOS system, that uses the conventional least squares reconstructor, the exponential reconstruction, and the so-called "slope discrepancy" reconstructor. We have also examined the use of the stochastic parallel gradient descent (SPGD) algorithm for deformable mirror control in problems dominated by scintillation and anisoplanatism, and conducted a laboratory experiment to demonstrate this idea. In this report we document the results. Our work with maximum likelihood-based image reconstruction algorithms has been applied to the results provided by the adaptive optics simulation, and representative results are included here.

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.

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.

"The work presented in this dissertation explores the use of several unconventional imaging and wavefront sensing modalities in the presence of distributed-volume, or "deep," atmospheric turbulence. This dissertation focuses on the propagation of coherent light from laser sources through the atmosphere, and imaging/wavefront sensing at optical and infrared laser wavelengths. Such wavelengths are negatively affected by deep turbulence. We use a coherent detection method known as digital holography to (1) coherently image distant objects and (2) to sense and correct for aberrations due to turbulence along the propagation path. We showed that compensated-beacon adaptive optics can be used with a digital holographic wavefront sensor or a Shack-Hartmann wavefront sensor to improve the performance of beam projection to distant objects over uncompensated beacon adaptive optics. We saw performance gains of 17% for the Shack-Hartmann wavefront sensor and 26% for the digital holographic wavefront sensor on average for several turbulence scenarios. We explored multi-wavelength 3D imaging with digital holography along with two speckle decorrelation mechanisms that degrade 3D imaging performance in a theoretical framework. Upon establishing this framework, we simulated multi-wavelength 3D imaging of distant objects through deep turbulence and reconstructed the imagery using sharpness metric maximization for 3D data. The results showed that the reconstruction process was more successful if using more corrective phase screens along the digital propagation path. Additionally we showed that sharpness metric maximization suffered in performance in the presence of scintillated illumination patterns, also known as uplink scintillation. Finally we explored motion compensated, multi-wavelength 3D imaging with digital holography and a pilot tone in theory. Our theoretical framework predicted that one would see increased noise in range images, known as range chatter, over highly-sloped object facets relative to the optical axis, and simulations bore this out explicitly. We showed that range chatter increases as a function of object facet slope, optical illumination bandwidth, optical frequency spacing, and turbulence. Going further we used sharpness metric maximization to improve the range chatter that was brought about by turbulence."--Pages xiv-xv.

Due to the wide application of adaptive optical systems, an understanding of optical wave propagation in randomly inhomogeneous media has become essential, and several numerical models of individual AOS components and of efficient correction algorithms have been developed. This monograph contains detailed descriptions of the mathematical experiments that were designed and carried out during more than a decade's worth of research.

The Sun as a Guide to Stellar Physics illustrates the significance of the Sun in understanding stars through an examination of the discoveries and insights gained from solar physics research. Ranging from theories to modeling and from numerical simulations to instrumentation and data processing, the book provides an overview of what we currently understand and how the Sun can be a model for gaining further knowledge about stellar physics. Providing both updates on recent developments in solar physics and applications to stellar physics, this book strengthens the solar–stellar connection and summarizes what we know about the Sun for the stellar, space, and geophysics communities. Applies observations, theoretical understanding, modeling capabilities and physical processes first revealed by the sun to the study of stellar physics Illustrates how studies of Proxima Solaris have led to progress in space science, stellar physics and related fields Uses characteristics of solar phenomena as a guide for understanding the physics of stars

This open access book provides a comprehensive overview of the application of the newest laser and microscope/ophthalmoscope technology in the field of high resolution imaging in microscopy and ophthalmology. Starting by describing High-Resolution 3D Light Microscopy with STED and RESOLFT, the book goes on to cover retinal and anterior segment imaging and image-guided treatment and also discusses the development of adaptive optics in vision science and ophthalmology. Using an interdisciplinary approach, the reader will learn about the latest developments and most up to date technology in the field and how these translate to a medical setting. High Resolution Imaging in Microscopy and Ophthalmology – New Frontiers in Biomedical Optics has been written by leading experts in the field and offers insights on engineering, biology, and medicine, thus being a valuable addition for scientists, engineers, and clinicians with technical and medical interest who would like to understand the equipment, the applications and the medical/biological background. Lastly, this book is dedicated to the memory of Dr. Gerhard Zinser, co-founder of Heidelberg Engineering GmbH, a scientist, a husband, a brother, a colleague, and a friend.