Download or read book Improving Mid frequency Contrast in Sparse Aperture Optical Imaging Systems Based Upon the Golay N Family of Arrays written by Andrew James Stokes and published by . This book was released on 2009 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Passive Synthetic Aperture Array Imaging at Millimeter Wave Frequencies written by and published by . This book was released on 2005 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this effort we investigated the design of synthetic aperture imaging systems for passive imaging of millimeter waves (MMWs) using a novel nano-photonic detector array. The idea is to demonstrate a lightweight and low power MMW imaging system with the highest possible resolution. To increase resolution we investigated the use of a "lensless" interferometric imaging system that is created by placing a sparse array of electro-optical MMW detectors along the fuselage of a UAV, or other airborne platforms. The results included the development of high frequency, W-band, electro-optical modulators with sensitivities that rival MMIC based approaches. Unlike the MMIC approaches, the electro-optical detectors do not require expensive low noise amplifiers and can be constructed monolithically. We also conducted an analytical and numerical study on the use of coherent optical beam forming as a practical approach towards the design of a "sparse array" imaging system. Further work will be devoted towards an experimental proof-of-concept demonstration of the coherent optical beam forming approach coupled with the electro-optical MMW detectors.

Download or read book Generalized Phase Contrast written by Jesper Glückstad and published by Springer. This book was released on 2009-08-20 with total page 322 pages. Available in PDF, EPUB and Kindle. Book excerpt: Generalized Phase Contrast elevates the phase contrast technique not only to improve phase imaging but also to cross over and interface with diverse and seemingly disparate fields of contemporary optics and photonics. This book presents a comprehensive introduction to the Generalized Phase Contrast (GPC) method including an overview of the range of current and potential applications of GPC in wavefront sensing and phase imaging, structured laser illumination and image projection, optical trapping and manipulation, and optical encryption and decryption. The GPC method goes further than the restrictive assumptions of conventional Zernike phase contrast analysis and achieves an expanded range of validity beyond weak phase perturbations. The generalized analysis yields design criteria for tuning experimental parameters to achieve optimal performance in terms of accuracy, fidelity and light efficiency. Optimization can address practical issues, such as finding an optimal spatial filter for the chosen application, and can even enable a Reverse Phase Contrast mode where intensity patterns are converted into a phase modulation.

Download or read book Enhancing the Resolution of Imaging Systems by Spatial Spectrum Manipulation written by and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract : Much research effort has been spent in the 21st century on superresolution imaging techniques, methods which can beat the diffraction limit. Subwavelength composite structures called ``metamaterials" had initially shown great promise in superresolution imaging applications in the early 2000s, owing to their potential for nearly arbitrary capabilities in controlling light. However, for optical frequencies they are often plagued by absorption and scattering losses which can decay or destroy their interesting properties. Similar issues limit the application of other superresolution devices operating as effective media, or metal films that can transfer waves with large momentum by supporting surface plasmon polaritons. In this dissertation, new methods of mitigating the loss of object information in lossy and noisy optical imaging systems are presented. The result is an improvement in the upper bound on lateral spatial resolution. A concentration is placed on metamaterial and plasmonic imaging systems, and the same methods are subsequently adapted to more conventional far-field imaging systems. First, through numerical simulation it is shown that a lossy metamaterial lens has degraded imaging performance which can be partially compensated by deconvolution post-processing of the resultant image. This post-processing procedure is then shown to emulate a physical process called plasmon injection, which has been previously implemented to effectively remove the losses in a plasmonic metamaterial. Next, a more realistic scenario is considered; a thin film of silver acting as a near-field plasmonic ``superlens." In this case, methods are implemented to model incoherent light propagation so that the image can be reconstructed using only intensity data, removing the need for phase measurement. The same procedure from above is followed, and the resolution is enhanced. To push the resolution further, a spatial filtering method called active convolved illumination is developed to overcome the resolution limit set by the noise floor of the system. Finally, the spatial filtering methods are applied to more a more conventional far-field imaging system. Supported by experiment, the lateral resolution of a low numerical aperture imaging system is improved by blocking photons at the Fourier plane. For coherent light, a diffractive superlens is designed which uses the same principles from the above theory, except it encodes the high spatial frequency waves into propagating waves via a diffraction grating. The result is lateral resolution performance that surpasses similar previously published devices by 10 nm at a wavelength more than 80 nm longer.

Download or read book Improving the Contrast Resolution of Synthetic Aperture Imaging written by Yat-Shun Yiu and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Improving the Contrast Resolution of Synthetic Aperture Imaging: Motion Artifact Reduction Based on Interleaved Data Acquisition" by Yat-shun, Yiu, 姚溢訊, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. DOI: 10.5353/th_b4327867 Subjects: Image processing - Digital techniques Interferometry

Download or read book Incoherent Multiple Aperture Optical Imaging Systems Analysis and Design written by Robert T. Reilander and published by . This book was released on 1987 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: Various multiple aperture optical arrays were compared while imaging objects illuminated with incoherent light. The aperture arrays contained from one to four sub-apertures. The objects were edges, slits, rectangles and circles. An emphasis was placed on edge resolution, and the author derived his own set of resolution criteria. Based on this analysis, a tight square four-element array was the best performer. The study concluded with an analysis of design criteria for optimum incoherent imaging resolution. Max sub-aperture size, min sub-aperture spacing, max number of sub-aperture elements, and a symmetric pattern were all determined to be desirable in order to obtain the best performance.

Download or read book Fourier Array Imaging written by Mehrdad Soumekh and published by Prentice Hall. This book was released on 1994 with total page 586 pages. Available in PDF, EPUB and Kindle. Book excerpt: The past forty years have seen a number of imaging modalities developed for radar, sonar, diagnostic medicine, geophysical and celestial exploration, and non-destructive testing. Now, for those involved in designing and developing information processing tools for these imaging systems, author Mehrdad Soumekh offers in-depth coverage of diverse issues such as physical and mathematical modeling of the problem, signal processing, reconstruction, analysis of resolution and system parameter constraints, hardware structure used for data acquisition, and the overall imaging system block diagram (signal flow-chart) indicating how the acquired data are processed to yield the final reconstructed image. Fourier Array Imaging introduces the spatial Doppler phenomenon in conjunction with the most primitive signal processing tools and systems used in array imaging; presents terminologies and tools for two-dimensional signal processing; treats specific array imaging systems via the unifying framework of spatial Doppler processing, including phased-array imaging, synthetic aperture array (SAR and ISAR) imaging, passive array imaging, and bistatic array imaging with emphasis on transmission imaging problems of diagnostic medicine and geophysical exploration; devotes coverage to the analysis of resolution anticipated in an imaging system and to the constraints that are instrumental for selecting parameters of an imaging system; describes some of the classical methods used for image formation in array imaging systems and relates them to the spatial Doppler-based imaging via certain approximations.

Download or read book Coherent Multiple Aperture Optical Imaging Systems written by Dana J. Bergey (2LT, USAF.) and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Incoherent Multiple Aperture Optical Imaging Systems written by Robert T. Reilander (MAJ, CAF.) and published by . This book was released on 1987 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Improving the Contrast Resolution of Synthetic Aperture Imaging written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optical Sparse Aperture Imaging written by Nicholas James Miller and published by . This book was released on 2007 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Computational Phase Correction of a Partially Coherent Multi aperture System written by Sarah Elaine Krug and published by . This book was released on 2020 with total page 233 pages. Available in PDF, EPUB and Kindle. Book excerpt: Multi-aperture arrays can be used to reduce the size, weight, cost, and power of an imaging system. However, all of the apertures in an array need to be properly phased in order to create a synthesized image with the maximum possible resolution gain. Phase errors that obstruct aperture phasing can be caused by hardware misalignments or atmospheric turbulence. Remapping the aperture fields between the entrance and exit pupils of an imaging system can be used for piston, tip, and tilt corrections. Remapping the pupils separates the components of the spatial frequency spectrum of an image, allowing maximum likelihood estimation to be used for piston estimation while a least squares matrix method estimates the tip and tilt errors. Images generated to simulate different amounts of atmospheric turbulence and image noise were used to test these piston, tip, and tilt correction algorithms. It was found that atmospheres with Fried parameters the size of a single aperture show the strongest correction results. Isoplanatic sections of images can be corrected if they are masked to the size of an isoplanatic patch and as long as there is enough spatial frequency support. The final phase corrected results are comparable with, or better than, the results of blind deconvolution for higher signal to noise ratios. Pupil remapping is done using blazed gratings located at an intermediate image plane to create a wavelength dependent aperture shift that results in a constant shift in the spatial frequencies. If the apertures in an array are placed along only one axis, the target or imaging system can be rotated and multiple images can be collected, corrected, and rotationally synthesized to create resolution gain in all directions. Future work could include expanding on isoplanatic correction techniques; improving piston, tip, and tilt estimation methods; and creating an experimental system with more than two apertures that could be tested in the field.

Download or read book Fringe 2013 written by Wolfgang Osten and published by Springer. This book was released on 2016-11-04 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In continuation of the FRINGE Workshop Series this Proceeding contains all contributions presented at the 7. International Workshop on Advanced Optical Imaging and Metrology. The FRINGE Workshop Series is dedicated to the presentation, discussion and dissemination of recent results in Optical Imaging and Metrology. Topics of particular interest for the 7. Workshop are: - New methods and tools for the generation, acquisition, processing, and evaluation of data in Optical Imaging and Metrology (digital wavefront engineering, computational imaging, model-based reconstruction, compressed sensing, inverse problems solution) - Application-driven technologies in Optical Imaging and Metrology (high-resolution, adaptive, active, robust, reliable, flexible, in-line, real-time) - High-dynamic range solutions in Optical Imaging and Metrology (from macro to nano) - Hybrid technologies in Optical Imaging and Metrology (hybrid optics, sensor and data fusion, model-based solutions, multimodality) - New optical sensors, imaging and measurement systems (integrated, miniaturized, in-line, real-time, traceable, remote) Special emphasis is put on new strategies, taking into account the active combination of physical modeling, computer aided simulation and experimental data acquisition. In particular attention is directed towards new approaches for the extension of existing resolution limits that open the gates to wide-scale metrology, ranging from macro to nano, by considering dynamic changes and using advanced optical imaging and sensor systems.

Download or read book Analysis of an Optical Coherence Imaging Modality on the Detection of an Abnormality in Biological Tissue with a Nanoparticle Contrast Agent written by and published by . This book was released on 2007 with total page 348 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is great interest in promoting the use of contrast agents in optical imaging for better diagnosis of diseases. However, until recently, there wasstill no quantitative method existing to assess the ability of contrast agents in improving clinical diagnosis. In this study, we used the method of task-based medical image analysis as a quantitative tool to evaluate the effectiveness of nanoparticles as contrast agents in an OCT imaging modality for clinical diagnosis. The task was formulated as the detection of abnormalities in a biological tissue using a quadratic observer. We derived the test statistics of the quadratic observer, and an analytical expression for the index of detectability for such a quadratic observer. The statistical properties of the OCT data are determined by the stochastic mechanisms in the imaging system as well as the demodulation method in the data acquisition process. In this analysis, we have considered the effect of phase fluctuations from the broadband source, the shot noise fluctuations of the imaging system, and the scattering noise due to refractive index fluctuation in the biological tissue. Our analysis was performed at the system level by integrating to the analysis the data demodulation process based on a mixer scheme. Also, we implemented the dynamic focusing in the scanning process. Optical propagation in biological samples is dominated by scattering due to fluctuations in refractive index. For OCT imaging, it is assumed that only the singly scattered field from the sample will contribute significantly to the interferometric optical power. We modeled the normal biological tissue (the background) as a spatial Poisson field of randomly distributed scattering centers, and the abnormality (the target) as a region with a different concentration of scattering centers embedded in the background. We presented the results on the detectability of abnormalities of different sizes, with or without the presence of contrast agents. We have shown that the application of nanoparticle contrast agents improved the detectability of small abnormalities which are usually difficult to detect. We have thus shown the efficacy of the task-based analysis framework in delivering quantitative assessments of the efficiency of contrast agents.

Download or read book Optical Interference Contrast and Photothermal Techniques in Scanning Imaging Systems written by Mehdi Vaez Iravani and published by . This book was released on 1986 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gated Frequency resolved Optical Imaging with an Optical Parametric Amplifier for Medical Applications written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Implementation of optical imagery in a diffuse inhomogeneous medium such as biological tissue requires an understanding of photon migration and multiple scattering processes which act to randomize pathlength and degrade image quality. The nature of transmitted light from soft tissue ranges from the quasi-coherent properties of the minimally scattered component to the random incoherent light of the diffuse component. Recent experimental approaches have emphasized dynamic path-sensitive imaging measurements with either ultrashort laser pulses (ballistic photons) or amplitude modulated laser light launched into tissue (photon density waves) to increase image resolution and transmissive penetration depth. Ballistic imaging seeks to compensate for these[open-quotes]fog-like[close-quotes] effects by temporally isolating the weak early-arriving image-bearing component from the diffusely scattered background using a subpicosecond optical gate superimposed on the transmitted photon time-of-flight distribution. The authors have developed a broadly wavelength tunable (470 nm -2.4[mu]m), ultrashort amplifying optical gate for transillumination spectral imaging based on optical parametric amplification in a nonlinear crystal. The time-gated image amplification process exhibits low noise and high sensitivity, with gains greater than 104 achievable for low light levels. We report preliminary benchmark experiments in which this system was used to reconstruct, spectrally upcovert, and enhance near-infrared two-dimensional images with feature sizes of 65[mu]m/mm[sup 2] in background optical attenuations exceeding 10[sup 12]. Phase images of test objects exhibiting both absorptive contrast and diffuse scatter were acquired using a self-referencing Shack-Hartmann wavefront sensor in combination with short-pulse quasi-ballistic gating. The sensor employed a lenslet array based on binary optics technology and was sensitive to optical path distortions approaching[lambda]/100.

Download or read book Advances in Phase Contrast Imaging Using Fully and Partially Coherent Wavefields written by Mario Alejandro Beltran Toro and published by . This book was released on 2014 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray phase contrast imaging enables the visualization of an object's features that otherwise would be impossible to obtain with conventional absorption based X-ray imaging. The first part of this thesis focuses specifically on propagation-based phase contrast imaging (PBI). It has a particular emphasis on the quantitative image reconstruction under the assumption that the source of illumination is fully coherent. It presents the existing methods of extracting quantitative information as well as original ones developed in this thesis. The second part of this thesis takes a purely theoretical route, which focuses on studying the forward problem of aberrated optical systems under partially coherent illumination. This thesis begins with a general overview and review of the relevant literature including the theory of coherent X-ray wavefield diffraction, partial coherence, phase-contrast X-ray imaging, and phase-contrast tomography. Particular emphasis is given to PBI. We then move to the original work that involved developing a method to carry out quantitative PBI based tomography on multi-material samples using only a single view per tomographic projection. The samples considered here are those for which (i) the complex refractive index of each component of the sample is known, and (ii) the component materials are spatially quantized. The method was applied to tomographic data obtained at the SPring-8 synchrotron facility in Japan. The sample used was a multi-material test phantom. The refractive index distribution of the test phantom was recovered in three dimensions with a single phase contrast image per projection. The method was applied successfully and was very stable under the presence of noise, opening the possibility of significant dose reduction incurred by samples. The next step in this work sees the application of the aforementioned method to complex biological organs. The chosen organs were the thorax of a rabbit pup and an excised rat brain. Experimental data were also acquired at the SPring-8 synchrotron facility in Japan. Tomographic slices containing the refractive index distribution for each organ were reconstructed using a single phase contrast image per projection. Signal-to-noise ratios for each reconstructions showed significant improvements of up 200 fold compared to absorption contrast reconstructions of the same slices. Finally, this thesis treats the problem of arbitrary aberrations in linear shift-invariant optical systems. This involves mathematically establishing a series of expressions considering arbitrary forms of phase contrast modalities as well as taking into account partially coherent illumination. Expressions are presented for the output cross spectral density under the space-frequency formulation of statistically stationary partially coherent fields. This could broaden the applicability of phase contrast to sources of lower quality.