Search results for "Spatial"
showing 10 items of 2121 documents
Variable fractional Fourier processor: a simple implementation
1997
A new set of optical implementations of the fractional Fourier transform (FRT) is developed by use of Wigner matrix algebra. The reinterpretation of some elementary operations that synthesize a rotation in the phase-space domain allows us to propose a lensless setup for obtaining the FRT. This compact configuration is also very flexible, because the fractional degree of the transformation can be varied continuously by shifting the input and the output planes along the optical axis by proper amounts. The above results permit one to build an optical FRT processor formed by two FRT systems in cascade, with a spatial filter between them. We present the design of such a variable FRT processor, w…
Multiple Matched Spatial Filter Performed With Nonsymmetrical Fourier Transformers
1987
MULTIPLE MATCHED SPATIAL FILTER PERFORMED WITH NONSYMMETRICAL FOURIER TRANSFORMERSCARLOS FERREIRA and CARMEN VAZQUEZDepartamento de Optica. Universitat de Valencia.C/ Dr. Moliner, 50. 46100 Burjassot, Spain.1. INTRODUCTIONClassical matched spatial filters (CMSF) have been successfully employed for optical pattern recog-nition. To detect different signals, multiple matched spatial filters can be synthesized and several me-thods to perform the filters have been developed. Based on the sensitivity to input orientation of CMSF,we proposed a filter [1] where the signals to be detected were rotated by different angles when recordingthe hologram. Thus, the recognition of a signal is only achieved …
Determinants of spatial intensity of stop locations on cruise passengers tracking data
2021
This paper aims at analyzing the spatial intensity in the distribution of stop locations of cruise passengers during their visit at the destination through a stochastic point process modelling approach on a linear network. Data collected through the integration of GPS tracking technology and questionnaire-based survey on cruise passengers visiting the city of Palermo are used, to identify the main determinants which characterize their stop locations pattern. The spatial intensity of stop locations is estimated through a Gibbs point process model, taking into account for both individual-related variables, contextual-level information, and for spatial interaction among stop points. The Berman…
RIFLESSIONI SU LINGUAGGIO E COGNIZIONE SPAZIALE Un confronto tra lingue vocali e lingue dei segni
2012
Depending on which theoretical paradigm is used, the relationship between spatial language and spatial thought could be presented in different ways. What is the nature of this relationship? Are spatial cognitive abilities a prerequisite for spatial language or, vice-versa, is it spatial language that shapes and affects our spatial reasoning? This paper is aimed at highlighting the dynamic interaction between spatial language and spatial cognition. That is, we need some spatial abilities in order to acquire spatial language. We share most of these core spatial abilities with other animals. These structures are the basis for spatial language, and this explains the presence of universal featur…
Single-channel polychromatic pattern recognition by the use of a joint-transform correlator.
2010
We present a single-channel system for color image recognition that is based on a joint-transform correlator setup. The color images are encoded as phase and amplitude functions, inspired from the Munsell color representation. A real-time implementation of the new codification method can be achieved by the use of a spatial light modulator operating in phase-only modulation mode. We determine the optimal codification for a linear color-phase code. Its performance is compared with a conventional multichannel correlator by means of computer simulations. Experimental results are also presented.
Dispersion management in two-photon microscopy by using diffractive optical elements.
2013
We demonstrate efficient generation of wide-field fluorescence signals in two-photon microscopy exploiting diffractive optical elements and short pulses by using a dispersion-compensated beam delivery optics module. Computer-generated holograms are codified onto a phase-only spatial light modulator, which allows for arbitrary single-shot patterning of the sample. Spatiotemporal shaping of the pulse is mandatory to overcome spatial chirp and pulse-front tilt effects that spread both in space and time the irradiance patterns, thus limiting not only the spatial resolution but also the signal-to-noise ratio in two-photon microscopy. By using a multipass amplifier delivering 30 fs, 0.8 mJ pulses…
Dynamical binary modulation of ultrabroadband light beams by using principal states of polarization of liquid crystal devices
2009
Dynamical modulation of ultrabroadband beams, such as those produced by femtosecond laser or incoherent sources, is not an easy task due to the dispersive nature of the devices commonly employed. Phase modulation has been performed by means of deformable micromirror arrays. These devices are expensive and do not permit amplitude modulation. For micro- and nano-structuring of materials with femtosecond lasers is common to pattern the surface with the light irradiance produced by a computer generated hologram implemented onto a liquid crystal (LC) type spatial light modulator. This enables dynamical patterning [1,2]. Reduced spectral bandwidths, of the order of tens of nanometers, have been u…
Super Resolution Methods Implementing Diffractive Masks Having a Certain Degree of Periodicity
2011
This section presents an approach that provides super resolved imaging at the center of the field of view and yet allows to see the remaining of the original field of view with original resolution. This operation resembles optical zooming while the zoomed and the nonzoomed images are obtained simultaneously. This is obtained by taking a single snap-shot and using a single imaging lens. The technique utilizes a special static/still coding element and a postprocessing algorithmic, without any mechanical movements.
ICA of full complex-valued fMRI data using phase information of spatial maps.
2015
Background ICA of complex-valued fMRI data is challenging because of the ambiguous and noisy nature of the phase. A typical solution is to remove noisy regions from fMRI data prior to ICA. However, it may be more optimal to carry out ICA of full complex-valued fMRI data, since any filtering or voxel-based processing may disrupt information that can be useful to ICA. New method We enable ICA of the full complex-valued fMRI data by utilizing phase information of estimated spatial maps (SMs). The SM phases are first adjusted to properly represent spatial phase changes of all voxels based on estimated time courses (TCs), and then these are used to segment the voxels into BOLD-related and unwant…
A spiking network for spatial memory formation: Towards a fly-inspired ellipsoid body model
2013
Neural centers devoted to spatial memory and path integration were largely studied in rats and in different insect species like ants and bees. In this paper a neural-based model for the formation of a spatial working memory is proposed mirroring some peculiarities of the Drosophila central brain and in particular the ellipsoid body. Simulation results are reported opening the way to applications on roving platforms.