Search results for "Spatial"
showing 10 items of 2121 documents
Off-axis digital holographic multiplexing for rapid wavefront acquisition and processing
2020
Off-axis holographic multiplexing involves capturing several complex wavefronts, each encoded into off-axis holograms with different interference fringe orientations, simultaneously, with a single camera acquisition. Thus, the multiplexed off-axis hologram can capture several wavefronts at once, where each one encodes different information from the sample, using the same number of pixels typically required for acquiring a single conventional off-axis hologram encoding only one sample wavefront. This gives rise to many possible applications, with focus on acquisition of dynamic samples, with hundreds of scientific papers already published in the last decade. These include field-of-view multi…
Superresolved common-path phase-shifting digital inline holographic microscopy using a spatial light modulator.
2012
Common-path phase-shifting lensless holographic microscopy has been recently proposed as a novel approach capable of high numerical aperture imaging in a lensless digital inline holographic microscopy layout [Opt. Lett.35, 3919 (2010)]. Here we present proof-of-concept validation for improving the resolution limit imposed by diffraction in such a setup. This is accomplished by shifting the phase lens displayed at the spatial light modulator, which moves the illumination point source to different off-axis positions. For each off-axis position, a set of inline phase-shifted holograms are recorded by the digital sensor and stored at the computer’s memory for later digital postprocessing. As a …
Quantitative Phase Imaging in Microscopy Using a Spatial Light Modulator
2010
In this chapter, we present a new method capable of recovery of the quantitative phase information of microscopic samples. Essentially, a spatial light modulator (SLM) and digital image processing are the basics to extract the sample’s phase distribution. The SLM produces a set of misfocused images of the input sample at the CCD plane by displaying a set of lenses with different power at the SLM device. The recorded images are then numerically processed to retrieve phase information. Computations are based on the wave propagation equation and lead to a complex amplitude image containing information of both amplitude and phase distributions of the input sample diffracted wave front. The prop…
Structure of longitudinal chromomagnetic fields in high energy collisions
2014
We compute expectation values of spatial Wilson loops in the forward light cone of high-energy collisions. We consider ensembles of gauge field configurations generated from a classical Gaussian effective action as well as solutions of high-energy renormalization group evolution with fixed and running coupling. The initial fields correspond to a color field condensate exhibiting domain-like structure over distance scales of order the saturation scale. At later times universal scaling emerges at large distances for all ensembles, with a nontrivial critical exponent. Finally, we compare the results for the Wilson loop to the two-point correlator of magnetic fields.
OGC-to-W3C Services: A Wrapper-Based Solution for Geospatial Metadata Exchange
2018
When trying to compose services that are developed according to different standards, interoperability issues arise that are often faced by developing ad-hoc solutions. A typical example is represented by the composition of W3C and OGC services, which were developed more or less concurrently by independent organizations. In such a context, developing a wrapper that abstracts as much as possible the inner details and logic of a wrapped service well embraces the low-coupled nature of the general Service Oriented Computing paradigm. This paper focuses on the proper management of geospatial metadata into a W3C-based environment and is based on the development of a wrapper that exposes OGC functi…
Definition of a Workflow for Web Browsing of 3D Models in Archaeology
2016
The Cultural Heritage (CH) is a fundamental element of promotion of territories and of tourism development. Publishing 3D models of archaeological sites and their three-dimensional reconstruction on the Web is one of the best ways to spread their knowledge. However, many recent scientific researches in this field have highlighted the limitations and difficulties related to the networking of interactive 3D models. The main difficulties are related to the complexity and the size of models, which influence the access speed, and the cost of software and hardware needed for the publication on the WEB. In light of this background, this article describes the further advances of research activities…
Characterization of the human visual system threshold performance by a weighting function in the Gabor domain
1997
Abstract As evidenced by many physiological and psychophysical reports, the receptive fields of the first-stage set of mechanisms of the visual process fit to two-dimensional (2D) compactly supported harmonic functions. The application of this set of band-pass filter functions to the input signal implies that the visual system carries out some kind of conjoint space/spatial frequency transform. Assuming that a conjoint transform is carried out, we present in this paper a new characterization of the visual system performance by means of a weighting function in the conjoint domain. We have called this weighting function (in the particular case of the Gabor transform) the Gabor stimuli Sensiti…
Spatial Coherence of Tropical Rainfall at the Regional Scale
2007
AbstractThis study examines the spatial coherence characteristics of daily station observations of rainfall in five tropical regions during the principal rainfall season(s): the Brazilian Nordeste, Senegal, Kenya, northwestern India, and northern Queensland. The rainfall networks include between 9 and 81 stations, and 29–70 seasons of observations. Seasonal-mean rainfall totals are decomposed in terms of daily rainfall frequency (i.e., the number of wet days) and mean intensity (i.e., the mean rainfall amount on wet days).Despite the diverse spatiotemporal sampling, orography, and land cover between regions, three general results emerge. 1) Interannual anomalies of rainfall frequency are us…
Spatial coherence of monsoon onset over Western and Central Sahel (1950-2000)
2009
Abstract The spatial coherence of boreal monsoon onset over the western and central Sahel (Senegal, Mali, Burkina Faso) is studied through the analysis of daily rainfall data for 103 stations from 1950 to 2000. Onset date is defined using a local agronomic definition, that is, the first wet day (>1 mm) of 1 or 2 consecutive days receiving at least 20 mm without a 7-day dry spell receiving less than 5 mm in the following 20 days. Changing either the length or the amplitude of the initial wet spell, or both, or the length of the following dry spell modifies the long-term mean of local-scale onset date but has only a weak impact either on its interannual variability or its spatial coher…
Application of daily rainfall principal component analysis to the assessment of the rainy season characteristics in Senegal
2003
The interannual variability of the onset and cessation dates of the rainy season (RS) in Senegal is analyzed over the 43 yr period 1950-1992, using daily rainfall data for 34 stations. The use of principal component analysis, based on rainfall only, is explored to identify aggregate, regional indexes for the onset and cessation of the rains. The minimum and maximum values of the cumula- tive scores of principal component 1, for each year, are used to locate the onset and cessation dates, respectively. Very distinct spatial rainfall patterns are found before and after the onset/cessation dates. Mean dates compare favorably with those based on other definitions, though our method is not meant…