Optimization of Computer generated holography rendering and optical design for a compact and large eyebox Augmented Reality glass

Thesis (Master of Science in Informatics)--University of Tsukuba, no. 41288, 2019.3.2

Acceleration of split-field finite difference time-domain method for anisotropic media by means of graphics processing unit computing

The implementation of split-field finite difference time domain (SF-FDTD) applied to light-wave propagation through periodic media with arbitrary anisotropy method in graphics processing units (GPUs) is described. The SF-FDTD technique and the periodic boundary condition allow the consideration of a single period of the structure reducing the simulation grid. Nevertheless, the analysis of the anisotropic media implies considering all the electromagnetic field components and the use of complex notation. These aspects reduce the computational efficiency of the numerical method compared with the isotropic and nonperiodic implementation. Specifically, the implementation of the SF-FDTD in the Kepler family of GPUs of NVIDIA is presented. An analysis of the performance of this implementation is done, and several applications have been considered in order to estimate the possibilities provided by both the formalism and the implementation into GPU: binary phase gratings and twisted-nematic liquid crystal cells. Regarding the analysis of binary phase gratings, the validity of the scalar diffraction theory is evaluated by the comparison of the diffraction efficiencies predicted by SF-FDTD. The analysis for the second order of diffraction is extended, which is considered as a reference for the transmittance obtained by the SF-FDTD scheme for periodic media.This work was supported by the Ministerio de Economía y Competitividad of Spain under projects FIS2011-29803-C02-01 and FIS2011-29803-C02-02 and by the Generalitat Valenciana of Spain under projects PROMETEO/2011/021, ISIC/2012/013, and GV/2012/099

A discrete dipole approximation solver based on the COCG-FFT algorithm and its application to microwave breast imaging

We introduce the discrete dipole approximation (DDA) for efficiently calculating the two-dimensional electric field distribution for our microwave tomographic breast imaging system. For iterative inverse problems such as microwave tomography, the forward field computation is the time limiting step. In this paper, the two-dimensional algorithm is derived and formulated such that the iterative conjugate orthogonal conjugate gradient (COCG) method can be used for efficiently solving the forward problem. We have also optimized the matrix-vector multiplication step by formulating the problem such that the nondiagonal portion of the matrix used to compute the dipole moments is block-Toeplitz. The computation costs for multiplying the block matrices times a vector can be dramatically accelerated by expanding each Toeplitz matrix to a circulant matrix for which the convolution theorem is applied for fast computation utilizing the fast Fourier transform (FFT). The results demonstrate that this formulation is accurate and efficient. In this work, the computation times for the direct solvers, the iterative solver (COCG), and the iterative solver using the fast Fourier transform (COCG-FFT) are compared with the best performance achieved using the iterative solver (COCG-FFT) in C++. Utilizing this formulation provides a computationally efficient building block for developing a low cost and fast breast imaging system to serve under-resourced populations

NASA scientific and technical publications: A catalog of special publications, reference publications, conference publications, and technical papers, 1989

This catalog lists 190 citations of all NASA Special Publications, NASA Reference Publications, NASA Conference Publications, and NASA Technical Papers that were entered into the NASA scientific and technical information database during accession year 1989. The entries are grouped by subject category. Indexes of subject terms, personal authors, and NASA report numbers are provided

Acceleration Techniques for Photo Realistic Computer Generated Integral Images

The research work presented in this thesis has approached the task of accelerating the generation of photo-realistic integral images produced by integral ray tracing. Ray tracing algorithm is a computationally exhaustive algorithm, which spawns one ray or more through each pixel of the pixels forming the image, into the space containing the scene. Ray tracing integral images consumes more processing time than normal images. The unique characteristics of the 3D integral camera model has been analysed and it has been shown that different coherency aspects than normal ray tracing can be investigated in order to accelerate the generation of photo-realistic integral images. The image-space coherence has been analysed describing the relation between rays and projected shadows in the scene rendered. Shadow cache algorithm has been adapted in order to minimise shadow intersection tests in integral ray tracing. Shadow intersection tests make the majority of the intersection tests in ray tracing. Novel pixel-tracing styles are developed uniquely for integral ray tracing to improve the image-space coherence and the performance of the shadow cache algorithm. Acceleration of the photo-realistic integral images generation using the image-space coherence information between shadows and rays in integral ray tracing has been achieved with up to 41 % of time saving. Also, it has been proven that applying the new styles of pixel-tracing does not affect of the scalability of integral ray tracing running over parallel computers. The novel integral reprojection algorithm has been developed uniquely through geometrical analysis of the generation of integral image in order to use the tempo-spatial coherence information within the integral frames. A new derivation of integral projection matrix for projecting points through an axial model of a lenticular lens has been established. Rapid generation of 3D photo-realistic integral frames has been achieved with a speed four times faster than the normal generation

Advances in computational methods for transmission electron microscopy simulation and image processing

Modern electron microscopes are fitted with ever larger charge-coupled device (CCD) cameras capable of faster acquisition rates which in turn drives a concomitant increase in the bandwidth of data that is being collected and the amount of information in our datasets. At the same time, current increases in computational performance are largely being delivered through the addition of parallel execution units rather than explicit increases in the speed of single processors, this means techniques that cannot exploit their inherent parallelism are seeing little performance benefit from the generational improvements in computer processors. Many techniques used in electron microscopy to process these large datasets have not been adapted to utilise the modern methods available for parallel data processing which can lead to lengthy offline data processing techniques which could otherwise be performed in near real-time. Reimagining these methods to suit highly parallel computational architectures such as graphics processing units (GPUs) can offer improved performance orders of magnitude higher than their central processing unit (CPU) counterparts. In this thesis I have looked specifically at the case of transmission electron microscopy (TEM) image simulation via the multislice procedure, and exit wave reconstruction (EWR), which can both potentially see huge benefits by adapting these algorithms to exploit their parallelism. Software has been developed for performing multislice simulations using GPU computation where the increase in computational power also allows for modifications to be made which can increase the accuracy of the simulations at the expense of simulation time. The multislice software developed here has no minimum slice thickness limitations and the slice thickness no longer has to be coupled to the structure being simulated to ensure accuracy. The CCD detector characteristics and electron dose have also been incorporated within the simulation process. The use of GPUs has allowed these simulations to be performed in vastly less time than CPUs based equivalent simulations. Software has also been developed for performing EWR on either multicore CPUs or GPUs which lowers the time required to perform EWR sufficiently that real-time reconstruction at typical CCD frame-rates is a distinct possibility. This EWR software additionally features mutual information (MI) based image alignment which can handle accurate image alignment in cases where other methods are prone to failure. These software are used to aid in the investigation of fluorinated graphene conformation via multislice simulation and EWR, and in the study of self-assembled block co-polymer assemblies also by EWR

Standard interest profiles - Development of technical subjects Final report

NASA university program for technology transfer, and development of Standard Interest Profiles /SIP

Fiscal year 1973 scientific and technical reports, articles, papers, and presentations

Formal NASA technical reports, papers published in technical journals, and presentations by MSFC personnel in FY73 are presented. Papers of MSFC contractors are also included

Early-state damage detection, characterization, and evolution using high-resolution computed tomography

Safely using materials in high performance applications requires adequately understanding the mechanisms which control the nucleation and evolution of damage. Most of a material\u27s operational life is spent in a state with noncritical damage, and, for example in metals only a small portion of its life falls within the classical Paris Law regime of crack growth. Developing proper structural health and prognosis models requires understanding the behavior of damage in these early stages within the material\u27s life, and this early-stage damage occurs on length scales at which the material may be considered ``granular\u27\u27 in the sense that the discrete regions which comprise the whole are large enough to require special consideration. Material performance depends upon the characteristics of the granules themselves as well as the interfaces between granules. As a result, properly studying early-stage damage in complex, granular materials requires a means to characterize changes in the granules and interfaces. The granular-scale can range from tenths of microns in ceramics, to single microns in fiber-reinforced composites, to tens of millimeters in concrete. The difficulty of direct-study is often overcome by exhaustive testing of macro-scale damage caused by gross material loads and abuse. Such testing, for example optical or electron microscopy, destructive and further, is costly when used to study the evolution of damage within a material and often limits the study to a few snapshots. New developments in high-resolution computed tomography (HRCT) provide the necessary spatial resolution to directly image the granule length-scale of many materials. Successful application of HRCT with fiber-reinforced composites, however, requires extending the HRCT performance beyond current limits. This dissertation will discuss improvements made in the field of CT reconstruction which enable resolutions to be pushed to the point of being able to image the fiber-scale damage structures and the application of this new capability to the study of early-stage damage