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At least 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

High-performance compression of astronomical images

Astronomical images have some rather unusual characteristics that make many existing image compression techniques either ineffective or inapplicable. A typical image consists of a nearly flat background sprinkled with point sources and occasional extended sources. The images are often noisy, so that lossless compression does not work very well; furthermore, the images are usually subjected to stringent quantitative analysis, so any lossy compression method must be proven not to discard useful information, but must instead discard only the noise. Finally, the images can be extremely large. For example, the Space Telescope Science Institute has digitized photographic plates covering the entire sky, generating 1500 images each having 14000 x 14000 16-bit pixels. Several astronomical groups are now constructing cameras with mosaics of large CCD's (each 2048 x 2048 or larger); these instruments will be used in projects that generate data at a rate exceeding 100 MBytes every 5 minutes for many years. An effective technique for image compression may be based on the H-transform (Fritze et al. 1977). The method that we have developed can be used for either lossless or lossy compression. The digitized sky survey images can be compressed by at least a factor of 10 with no noticeable losses in the astrometric and photometric properties of the compressed images. The method has been designed to be computationally efficient: compression or decompression of a 512 x 512 image requires only 4 seconds on a Sun SPARCstation 1. The algorithm uses only integer arithmetic, so it is completely reversible in its lossless mode, and it could easily be implemented in hardware for space applications.

White, Richard L.↗
NASA NTRS1997

Video Skimming and Characterization through the Combination of Image and Language Understanding Techniques

Digital video is rapidly becoming important for education, entertainment, and a host of multimedia applications. With the size of the video collections growing to thousands of hours, technology is needed to effectively browse segments in a short time without losing the content of the video. We propose a method to extract the significant audio and video information and create a "skim" video which represents a very short synopsis of the original. The goal of this work is to show the utility of integrating language and image understanding techniques for video skimming by extraction of significant information, such as specific objects, audio keywords and relevant video structure. The resulting skim video is much shorter, where compaction is as high as 20:1, and yet retains the essential content of the original segment.

IMAGE PROCESSING↗
NASA NTRS1986

Correlation of the deply technique with the ultrasonic imaging of impact damage in graphite/epoxy composites

A quantitative ultrasonic technique for the nondestructive assessment of impact damage is described. The method, which involves digitizing the entire backscattered ultrasonic wave from a sample, was applied to two test panels removed from a 16-ply graphite/epoxy laminate and impacted with an aluminum ball fired at a velocity of 150 ft/sec. The results of the ultrasonic NDE were compared with the results obtained using the destructive deply technique of Freeman (1984). The NDE method provides through-the-thickness information on damage and only requires access to a single side of the material, while the deply technique gives exact information on the actual damage. Good quantitative agreement between the two techniques was obtained.

Smith, B. T.↗
NASA NTRS1996

Determination of Local Densities in Accreted Ice Samples Using X-Rays and Digital Imaging

At the NASA Lewis Research Center's Icing Research Tunnel ice shapes, similar to those which develop in-flight icing conditions, were formed on an airfoil. Under cold room conditions these experimental samples were carefully removed from the airfoil, sliced into thin sections, and x-rayed. The resulting microradiographs were developed and the film digitized using a high resolution scanner to extract fine detail in the radiographs. A procedure was devised to calibrate the scanner and to maintain repeatability during the experiment. The techniques of image acquisition and analysis provide accurate local density measurements and reveal the internal characteristics of the accreted ice with greater detail. This paper will discuss the methodology by which these samples were prepared with emphasis on the digital imaging techniques.

Broughton, Howard↗
DOE OSTI2015

Liquid-liquid phase separation in aerosol particles: Imaging at the Nanometer Scale

Atmospheric aerosols can undergo phase transitions including liquid-liquid phase separation (LLPS) while responding to changes in the ambient relative humidity (RH). Here, we report results of chemical imaging experiments using environmental scanning electron microscopy (ESEM) and scanning transmission x-ray microscopy (STXM) to investigate the LLPS of micron sized particles undergoing a full hydration-dehydration cycle. Internally mixed particles composed of ammonium sulfate (AS) and either: limonene secondary organic carbon (LSOC), a, 4-dihydroxy-3-methoxybenzeneaceticacid (HMMA), or polyethylene glycol (PEG-400) were studied. Events of LLPS with apparent core-shell particle morphology were observed for all samples with both techniques. Chemical imaging with STXM showed that both LSOC/AS and HMMA/AS particles were never homogeneously mixed for all measured RH’s above the deliquescence point and that the majority of the organic component was located in the shell. The shell composition was estimated as 65:35 organic: inorganic in LSOC/AS and as 50:50 organic: inorganic for HMMA/AS. PEG-400/AS particles showed fully homogeneous mixtures at high RH and phase separated below 89-92% RH with an estimated 50:50% organic to inorganic mix in the shell. These two chemical imaging techniques are well suited for in-situ analysis of the hygroscopic behavior, phase separation, and surface composition of collected ambient aerosol particles.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2015

Benefits of utilizing CellProfiler as a characterization tool for U–10Mo nuclear fuel

Automated image processing techniques have the potential to aid in the performance evaluation of nuclear fuels by eliminating judgment calls that may vary from person-to-person or sample-to-sample. Analysis of in-core fuel performance is required for design and safety evaluations related to almost every aspect of the nuclear fuel cycle. This study presents a methodology for assessing the quality of uranium–molybdenum fuel images and describes image analysis routines designed for the characterization of several important microstructural properties. The analyses are performed in CellProfiler, an open-source program designed to enable biologists without training in computer vision or programming to automatically extract cellular measurements from large image sets. The quality metric scores an image based on three parameters: the illumination gradient across the image, the overall focus of the image, and the fraction of the image that contains scratches. The metric presents the user with the ability to ‘pass’ or ‘fail’ an image based on a reproducible quality score. Passable images may then be characterized through a separate CellProfiler pipeline, which enlists a variety of common image analysis techniques. The results demonstrate the ability to reliably pass or fail images based on the illumination, focus, and scratch fraction of the image, followed by automatic extraction of morphological data with respect to fission gas voids, interaction layers, and grain boundaries. - Graphical abstract: Display Omitted - Highlights: • A technique is developed to score U–10Mo FIB-SEM image quality using CellProfiler. • The pass/fail metric is based on image illumination, focus, and area scratched. • Automated image analysis is performed in pipeline fashion to characterize images. • Fission gas void, interaction layer, and grain boundary coverage data is extracted. • Preliminary characterization results demonstrate consistency of the algorithm.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1988

Optical Image Subtraction

Report reviews optical image subtraction techniques developed during years 1975 through 1985. Useful in such disciplines as studies of earth resources, meteorology, automatic surveillance, pattern recognition, studies of urban growth, and compression of bandwidth in communication systems. Describes following real-time techniques: source encoding, polarization modulation, pseudocolor image-difference detection, holographic-shear-lens technique, and nonlinear electro-optics. Reported non-real-time image-subtraction techniques are following, all of which involve intensity subtraction: speckle-diffuser encoding, speckle-pattern encoding, halftone-screen encoding,and polarization-shifted carrier encoding. Offers an attractive alternative to digital electronic image subtraction, is faster and treats all parts of images simultaneously.

Liu, Hua-Kuang↗
NASA NTRS1993

New techniques for reversible compression of multispectral data

While spatial correlations are adequately exploited by standard lossless image compression techniques, little success has been attained in exploiting spectral correlations when dealing with multispectral image data. In this paper, we present some new lossless image compression techniques that capture spectral correlations as well as spatial correlation in a simple and elegant manner. The schemes are based on the notion of a prediction tree, which defines a non-causal prediction model for an image. We present a backward adaptive technique and a forward adaptive technique. We then give a computationally efficient way of approximating the backward adaptive technique. The approximation gives good results and is extremely easy to compute. Simulation results show that for high spectral resolution images, significant savings can be made by using spectral correlations in addition to spatial correlations. Furthermore, the increase in complexity incurred in order to make these gains is minimal.

Memon, N. D.↗
NASA NTRS1995

Fabricating Sub-Collimating Grids for an X-Ray Solar Imaging Spectrometer Using LIGA Techniques

A proposed NASA mission uses a High Energy Solar Spectroscopic Imager (HESSI) to image solar X-rays. The HESSI instrument consists of twelve rotating pairs of high aspect ratio, high Z grids, each pair of which is separated by 1.7 meters and backed by a single Ge detector. Discussed are the fabrication of these proof-of-concept sub-collimating X-ray grids which are to be used in HESSI.

solar↗
NASA NTRS1987

Automated reduction of instantaneous flow field images

An automated data reduction system for the analysis of interference fringe patterns obtained using the particle image velocimetry technique is described. This system is based on digital image processing techniques that have provided the flexibility and speed needed to obtain more complete automation of the data reduction process. As approached here, this process includes scanning/searching for data on the photographic record, recognition of fringe patterns of sufficient quality, and, finally, analysis of these fringes to determine a local measure of the velocity magnitude and direction. The fringe analysis as well as the fringe image recognition are based on full frame autocorrelation techniques using parallel processing capabilities.

Reynolds, G. A.↗
DOE OSTI2021

Enabling phase quantification of anhydrous cements via Raman imaging

The phase composition of Portland cements is typically determined using conventional techniques like X-ray Diffraction (XRD) Rietveld analysis, optical microscopy point counting, and electron microscopy. However, these techniques have several limitations that may affect their accuracy in certain sample-specific scenarios. Here, we report a highly accurate phase quantification of 11 different types of commercial, anhydrous cements using a new and complementary technique: Raman imaging. Specifically, for the 4 principal phases, composition from our extensive data (250,000 Raman spectra per sample, error < 0.71%) and those obtained from XRD Rietveld and supplier data have high coefficients of determination (R{sup 2} > 0.98, mean deviation <2%). Additionally, we also quantify 8 secondary phases present in cement clinkers (gypsum, anhydrite, bassanite, syngenite, dolomite, calcite, quartz, and portlandite) with a high degree of confidence, thereby demonstrating that Raman imaging is a highly versatile tool for anhydrous phase quantification in a broad variety of cements.

36 MATERIALS SCIENCE↗
NASA NTRS1984

Development and evaluation of techniques for using combined microwave and optical image data for vegetation studies

Techniques for using combined image data from the Shuttle Imaging Radar (SIR-B) and the LANDSAT Thematic Mapper (TM) or Multispectral Scanner (MSS) for studies of irrigated crops, and boreal and deciduous forests are developed and evaluated. The effects of the structure and composition of crop canopies and soil surfaces on multiangle L-band HH (Horizontal polarization for transmission and reception) backscattering and on optical reflectance (in TM or MSS bands viewed at the nadir) are investigated. The relative accuracy of digital, calibrated SIR-B image data and LANDSAT TM or MSS image data is evaluated. Textural information extraction-techniques are developed for radar and optical image analysis.

Paris, J. F.↗
DOE OSTI2016

DERIVING THE PROPERTIES OF CORONAL PRESSURE FRONTS IN 3D: APPLICATION TO THE 2012 MAY 17 GROUND LEVEL ENHANCEMENT

We study the link between an expanding coronal shock and the energetic particles measured near Earth during the ground level enhancement of 2012 May 17. We developed a new technique based on multipoint imaging to triangulate the three-dimensional (3D) expansion of the shock forming in the corona. It uses images from three vantage points by mapping the outermost extent of the coronal region perturbed by the pressure front. We derive for the first time the 3D velocity vector and the distribution of Mach numbers, M {sub FM}, of the entire front as a function of time. Our approach uses magnetic field reconstructions of the coronal field, full magnetohydrodynamic simulations and imaging inversion techniques. We find that the highest M {sub FM} values appear near the coronal neutral line within a few minutes of the coronal mass ejection onset; this neutral line is usually associated with the source of the heliospheric current and plasma sheet. We illustrate the variability of the shock speed, shock geometry, and Mach number along different modeled magnetic field lines. Despite the level of uncertainty in deriving the shock Mach numbers, all employed reconstruction techniques show that the release time of GeV particles occurs when the coronal shock becomes super-critical ( M {sub FM} > 3). Combining in situ measurements with heliospheric imagery, we also demonstrate that magnetic connectivity between the accelerator (the coronal shock of 2012 May 17) and the near-Earth environment is established via a magnetic cloud that erupted from the same active region roughly five days earlier.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1995

World-Wide Web Tools for Locating Planetary Images

The explosive growth of the World-Wide Web (WWW) in the past year has made it feasible to provide interactive graphical tools to assist scientists in locating planetary images. The highest available resolution images of any site of interest can be quickly found on a map or plot, and, if online, displayed immediately on nearly any computer equipped with a color screen, an Internet connection, and any of the free WWW browsers. The same tools may also be of interest to educators, students, and the general public. Image finding tools have been implemented covering most of the solar system: Earth, Mars, and the moons and planets imaged by Voyager. The Mars image-finder, which plots the footprints of all the high-resolution Viking Orbiter images and can be used to display any that are available online, also contains a complete scrollable atlas and hypertext gazetteer to help locating areas. The Earth image-finder is linked to thousands of Shuttle images stored at NASA/JSC, and displays them as red dots on a globe. The Voyager image-finder plots images as dots, by longitude and apparent target size, linked to online images. The locator (URL) for the top-level page is http: //ic-www.arc.nasa.gov/ic/projects/bayes-group/Atlas/. Through the efforts of the Planetary Data System and other organizations, hundreds of thousands of planetary images are now available on CD-ROM, and many of these have been made available on the WWW. However, locating images of a desired site is still problematic, in practice. For example, many scientists studying Mars use digital image maps, which are one third the resolution of Viking Orbiter survey images. When they douse Viking Orbiter images, they often work with photographically printed hardcopies, which lack the flexibility of digital images: magnification, contrast stretching, and other basic image-processing techniques offered by off-the-shelf software. From the perspective of someone working on an experimental image processing technique for super-resolution, the discovery that potential users are often not using the highest resolution already available, nor using conventional image processing techniques, was surprising. This motivated the present work.

Kanefsky, Bob↗
DOE OSTI2021

Reconstructing magnetic deflections from sets of proton images using differential evolution

Proton imaging is a powerful technique for imaging electromagnetic fields within an experimental volume, in which spatial variations in proton fluence are a result of deflections to proton trajectories due to interaction with the fields. When deflections are large, proton trajectories can overlap, and this nonlinearity creates regions of greatly increased proton fluence on the image, known as caustics. The formation of caustics has been a persistent barrier to reconstructing the underlying fields from proton images. We have developed a new method for reconstructing the path-integrated magnetic fields, which begins to address the problem posed by caustics. Our method uses multiple proton images of the same object, each image at a different energy, to fill in the information gaps and provide some uniqueness when reconstructing caustic features. We use a differential evolution algorithm to iteratively estimate the underlying deflection function, which accurately reproduces the observed proton fluence at multiple proton energies simultaneously. We test this reconstruction method using synthetic proton images generated for three different, cylindrically symmetric field geometries at various field amplitudes and levels of proton statistics and present reconstruction results from a set of experimental images. Here, the method we propose requires no assumption of deflection linearity and can reliably solve for fields underlying linear, nonlinear, and caustic proton image features for the selected geometries and is shown to be fairly robust to noise in the input proton intensity.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

SU-E-I-75: Development of New Biological Fingerprints for Patient Recognition to Identify Misfiled Images in a PACS Server

Purpose: We are trying to develop an image-searching technique to identify misfiled images in a picture archiving and communication system (PACS) server by using five biological fingerprints: the whole lung field, cardiac shadow, superior mediastinum, lung apex, and right lower lung. Each biological fingerprint in a chest radiograph includes distinctive anatomical structures to identify misfiled images. The whole lung field was less effective for evaluating the similarity between two images than the other biological fingerprints. This was mainly due to the variation in the positioning for chest radiographs. The purpose of this study is to develop new biological fingerprints that could reduce influence of differences in the positioning for chest radiography. Methods: Two hundred patients were selected randomly from our database (36,212 patients). These patients had two images each (current and previous images). Current images were used as the misfiled images in this study. A circumscribed rectangular area of the lung and the upper half of the rectangle were selected automatically as new biological fingerprints. These biological fingerprints were matched to all previous images in the database. The degrees of similarity between the two images were calculated for the same and different patients. The usefulness of new the biological fingerprints for automated patient recognition was examined in terms of receiver operating characteristic (ROC) analysis. Results: Area under the ROC curves (AUCs) for the circumscribed rectangle of the lung, upper half of the rectangle, and whole lung field were 0.980, 0.994, and 0.950, respectively. The new biological fingerprints showed better performance in identifying the patients correctly than the whole lung field. Conclusion: We have developed new biological fingerprints: circumscribed rectangle of the lung and upper half of the rectangle. These new biological fingerprints would be useful for automated patient identification system because they are less affected by positioning differences during imaging.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

Optical system case studies

The purpose of this document is to detail the effect of various optical and camera system parameters for two different classes of surveillance imaging scenarios. We will take into account the effects of expected atmospheric turbulence and demonstrate where image enhancement techniques such as speckle imaging[1] can help. In the scenarios considered here, primary factors that determine the limiting resolutions are the range to target, wavelength, focal length, camera pixel size, and aperture size. Depending on the weather, imaging geometry, and the nature of the terrain below the imaging path, the atmospheric effects will vary. For the first scenario, we are interested in studying system parameters for imaging over shorter ranges from 2 to 8 km from very low slant angles over land or water. For the second scenario, we are interested in studying system parameters for imaging from 10 km to 60 km from low slant angles over land.

42 ENGINEERING↗