17,208 research outputs found
Finetti C., Minardi M., Osti Guerrazzi A., Un secolo di sindacato. La Camera del lavoro a Modena nel Novecento, Ediesse, Roma 2001
No full textRecensione al volume: Finetti C., Minardi M., Osti Guerrazzi A., Un secolo di sindacato. La Camera del lavoro a Modena nel Novecento, Ediesse, Roma 200
A new camera for high-resolution infrared imaging of works of art
No full textA new camera – SIRIS (scanning infrared imaging system) – developed at the National Gallery in London allows high-resolution images to be made in the near infrared region (900–1700 nm). The camera is based on a commercially available 320 × 256 pixel indium gallium arsenide area array sensor. This relatively small sensor is moved across the focal plane of the camera using two orthogonal translation stages to give images of c. 5000 × 5000 pixels. The main advantages of the SIRIS camera over scanning infrared devices or sequential image capture and mosaic assembly are its comparative portability and rapid image acquisition – making a 5000 × 5000 pixel image takes less than 20 minutes. The SIRIS camera can operate at a range of resolutions; from around 2.5 pixels per millimetre over an area of up to 2 × 2 m to 10 pixels per millimetre when examining an area measuring 0.5 × 0.5 m. The development of the mechanical, optical and electronic components of the camera, including the design of a new lens, is described. The software used to control image capture and to assemble the individual frames into a seamless mosaic image is mentioned. The camera was designed primarily to examine underdrawings in paintings; preliminary results from test targets and paintings imaged in situ are presented and the quality of the images compared with those from other cameras currently used for this application
Optimizing Compton camera performance
No full textAmore realistic simulation approach is used to study the behavior of the Compton camera in
this thesis than previous studies to date. The Compton camera differs from gamma cameras
in that the collimator is replaced by a detector known as the ‘scatterer’. Gamma rays may be
Compton scattered in the scatterer and subsequently detected by an ‘absorber’ which is the
equivalent of the detector in a gamma camera. By measuring the energies and the positions
of the points on the scatterer and the absorber where the incident and scattered gamma rays
interacted with the detectors, an image of the source can be reconstructed. Because there is
no collimator present, the potential sensitivity of the Compton camera is much higher than
the gamma camera, resulting in reduced acquisition times.
Most of the work described in this thesis was done with the GEANT4 Monte Carlo
simulation software. GEANT4 has been proven to be very robust and efficient in modelling
physics problems of radiation transport and interactions with matter in complex geometries.
Four major studies are carried out to estimate and optimize the performance of this
novel equipment. The first study takes a look at the scatterer’s imaging parameters with
the aim of prescribing an optimal scatterer material and geometry. In the second study,
the contribution of the absorber to the overall Compton camera performance is evaluated,
considering detector material, interaction type and geometry. The third study explores the
limitations imposed by the detector energy threshold and dead time on the Compton camera
performance, using a simplified model of the general electronic architecture. An evaluation
of Compton camera for scintimammography was performed in the fourth study. For
this study, three dual-head Compton camera models (Si/CZT, Si/LaBr₃:Ce and Si/NaI(Tl)
Compton cameras) were simulated, and the effect of scintillation photons’ interactions with
the photomultipliers was implemented.
The results show that silicon of about 1 cm thickness would be adequate as the Compton
camera scatterer. Analyses suggest however, that the choice of silicon is not completely
flawless. Doppler broadening for this detector material contributes as much as 7.3 mm
and 2.4 mm to full-width-at-half-maximum (FWHM) image resolution at 140.5 keV and
511 keV respectively. On the other hand, detector spatial resolution which accounts for
the least image degradation at 140.5 keV is found to be the dominant degrading factor
at 511 keV, suggesting that the absorber parameters play major roles in image resolution
at higher diagnostic energies. Findings further suggest that cadmium zinc telluride (CZT)
would be themost suitable detector as the absorber since thematerial demonstrated the highest efficiency and least positioning error due to multiple interactions as well as good spatial
resolution. The inclusion of the energy threshold and detector dead time at 140.5 keV, reduced
the Compton camera detection efficiency by 48% and 17% respectively, but improved
the image resolution from 10.7 mm to 9.5 mm at the source-to-scatterer distance of 5 cm.
At 511 keV, the inclusion of these parameters reduced the efficiency by 6% and 13% respectively,
but made no significant difference on the camera resolution. For a challenging
detection case in scintimammography, 5 mm breast tumours of tumour/background uptakes
of 10:1 and 6:1 at 511 keV were used. The best signal-to-noise ratio (SNR) was attained
for the Si/CZT Compton camera model, with the SNR values of 12.2 and 5.3.
It is therefore envisioned that with an optimal camera geometry, improved reconstruction
technique and adequate filter algorithm, the combination of Si and CZT as the scatterer
and the absorber of the Compton camera would make a very promising imaging system for
nuclear medicine studies at higher gamma ray energies where the collimated SPECT systems
perform very poorly due to increased septal penetration. It is equally evident from the
studies that with improved technology, new detectors such as LaBr₃:Ce could replace the
traditional NaI(Tl) detector as imaging detectors
Automated camera ranking and selection using video content and scene context
No full textPhDWhen observing a scene with multiple cameras, an important problem to solve is to automatically
identify “what camera feed should be shown and when?” The answer to this question is of interest
for a number of applications and scenarios ranging from sports to surveillance. In this thesis we
present a framework for the ranking of each video frame and camera across time and the camera
network, respectively. This ranking is then used for automated video production. In the first stage
information from each camera view and from the objects in it is extracted and represented in a way
that allows for object- and frame-ranking. First objects are detected and ranked within and across
camera views. This ranking takes into account both visible and contextual information related to
the object. Then content ranking is performed based on the objects in the view and camera-network
level information. We propose two novel techniques for content ranking namely: Routing Based
Ranking (RBR) and Multivariate Gaussian based Ranking (MVG). In RBR we use a rule based
framework where weighted fusion of object and frame level information takes place while in MVG
the rank is estimated as a multivariate Gaussian distribution. Through experimental and subjective
validation we demonstrate that the proposed content ranking strategies allows the identification of
the best-camera at each time.
The second part of the thesis focuses on the automatic generation of N-to-1 videos based on the
ranked content. We demonstrate that in such production settings it is undesirable to have frequent
inter-camera switching. Thus motivating the need for a compromise, between selecting the best
camera most of the time and minimising the frequent inter-camera switching, we demonstrate that
state-of-the-art techniques for this task are inadequate and fail in dynamic scenes. We propose three
novel methods for automated camera selection. The first method (¡go f ) performs a joint optimization
of a cost function that depends on both the view quality and inter-camera switching so that a
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Abstract ii
pleasing best-view video sequence can be composed. The other two methods (¡dbn and ¡util) include
the selection decision into the ranking-strategy. In ¡dbn we model the best-camera selection
as a state sequence via Directed Acyclic Graphs (DAG) designed as a Dynamic Bayesian Network
(DBN), which encodes the contextual knowledge about the camera network and employs the past
information to minimize the inter camera switches. In comparison ¡util utilizes the past as well
as the future information in a Partially Observable Markov Decision Process (POMDP) where the
camera-selection at a certain time is influenced by the past information and its repercussions in
the future. The performance of the proposed approach is demonstrated on multiple real and synthetic
multi-camera setups. We compare the proposed architectures with various baseline methods
with encouraging results. The performance of the proposed approaches is also validated through
extensive subjective testing
More Accurate Pinhole Camera Calibration with Imperfect Planar Target
No full textThis paper presents a novel approach to camera calibration that improves final accuracy with respect to standard methods using precision planar targets, even if now inaccurate, unmeasured, roughly planar targets can be used. The work builds on a recent trend in camera calibration, namely concurrent optimization of scene structure together with the intrinsic camera parameters. A novel formulation is presented that allows maximum likelihood estimation in the case of inaccurate targets, as it extends the camera extrinsic parameters into a tight parametrization of the whole scene structure. It furthermore observes the special characteristics of multi-view perspective projection of planar targets. Its natural extensions to stereo camera calibration and hand-eye calibration are also presented. Experiments demonstrate improvements in the parametrization of the camera model as well as in eventual stereo reconstruction
Automatic camera selection for activity monitoring in a multi-camera system for tennis
No full textIn professional tennis training matches, the coach needs to be able to view play from the most appropriate angle in order to monitor players' activities. In this paper, we describe and evaluate a system for automatic camera selection from a network of synchronised cameras within a tennis sporting arena. This work combines synchronised video streams from multiple cameras into a single summary video suitable for critical review by both tennis players and coaches. Using an overhead camera view, our system automatically determines the 2D tennis-court calibration resulting in a mapping that relates a player's position in the overhead camera to their position and size in another camera view in the network. This allows the system to determine the appearance of a player in each of the other cameras and thereby choose the best view for each player via a novel technique. The video summaries are evaluated in end-user studies and shown to provide an efficient means of multi-stream visualisation for tennis player activity monitoring
Scalable software architecture for on-line multi-camera video processing
No full textIn this paper we present a scalable software architecture for on-line multi-camera video processing, that guarantees a good trade off between computational power, scalability and flexibility. The software system is modular and its main blocks are the Processing Units (PUs), and the Central Unit. The Central Unit works as a supervisor of the running PUs and each PU manages the acquisition phase and the processing phase. Furthermore, an approach to easily parallelize the desired processing application has been presented. In this paper, as case study, we apply the proposed software architecture to a multi-camera system in order to efficiently manage multiple 2D object detection modules in a real-time scenario. System performance has been evaluated under different load conditions such as number of cameras and image sizes. The results show that the software architecture scales well with the number of camera and can easily works with different image formats respecting the real time constraints. Moreover, the parallelization approach can be used in order to speed up the processing tasks with a low level of overhea
HUMAN CIRCULATING MICROPARTICLES: A GLOBAL ASSESSMENT OF THEIR PHISICAL AND ANTIGENIC PROPRIETIES BY A MULTICOLOR FLOW CYTOMETRY APPROACH
No full textBackground-Cell-derived Microparticles (MPs) are cellular membrane fragments with size ranging from 0.1 to 1 μm, derived from activated/apoptotic cells and characterized by an integral plasma membrane expressing population markers of the parental cell. The presence of phosphatidyl serine (PS) on the outer plasma membrane has been widely used as a marker to identify MPs. Recently, it has been suggested that a fraction of circulating PS– MPs may exist. Details on their cellular origin are however still lacking. Aim-We set up a multiparametric flow cytometric approach to identify, among the human circulating PS+ and PS– MPs, their cell origin. By combining the use of a high technology cytometer that allows the visualization of undetectable subpopulation of MPs with a multicolor staining, we are able to obtain an accurate overview of MPs and give a complete analysis of their characteristics and origin. Method-Human platelet free plasma (PFP) MPs from healthy volunteers (HV) (n=15) were characterized by a BD FACSAria IIUTM, a four lasers equipped cell sorter using simultaneously seven markers. Beads with definite and appropriate size (0.5/0.9 μm) were added to the sample to identify MPs; 7AAD was used to exclude debris. Results-The multiparametric approach allowed us to identify two populations of MPs (~70% PS+, ~30% PS-). More than 70% of PS+ MPs were CD31+ CD41+, confirming literature data that reported platelet-derived MPs as the most abundant circulating population. White blood cell (CD45+) derived MPs represented around 3% of total (50% PS-, 50% PS+); 20% of them were CD14+ deriving therefore from monocytes. Red blood cell (CD235+)-derived MPs were 8% of total and were both PS+(48%) and PS–(52%). Conclusions-the multicolor flow cytometry approach allowed us the simultaneous identification of PS+ and PS- MPs in PFP from HV and gives a significant improvement in the methodology applied until now to their characterization
Experimental demonstration of RGB LED-based optical camera communications
No full textRed, green, and blue (RGB) light-emitting diodes (LEDs) are widely used in everyday illumination, particularly where color-changing lighting is required. On the other hand, digital cameras with color filter arrays over image sensors have been also extensively integrated in smart devices. Therefore, optical camera communications (OCC) using RGB LEDs and color cameras is a promising candidate for cost-effective parallel visible light communications (VLC). In this paper, a single RGB LED-based OCC system utilizing a combination of undersampled phase-shift on off keying (UPSOOK), wavelength-division multiplexing (WDM), and multiple-input multiple-output (MIMO) techniques is designed, which offers higher space efficiency (3 bits/Hz/LED), long-distance, and nonflickering VLC data transmission. A proof-of-concept test bed is developed to assess the bit-error-rate performance of the proposed OCC system. The experimental results show that the proposed system using a single commercially available RGB LED and a standard 50-frame/s camera is able to achieve a data rate of 150 bits/s over a range of up to 60 m
Single camera three component planar velocity measurements, using two frequency Planar Doppler Velocimetry (2v-PDV) (2005)
No full textThe work presented here describes a method that allows three component velocity
measurements to be made, quickly and non-intrusively, across a plane in a flow
defined by a laser light sheet. The method, two frequency planar Doppler
Velocimetry (2v-PDV) is a modification of the planar Doppler velocimetry (PDV)
technique, using only a single CCD camera, and sequential illumination of the
flow using two frequencies, separated by about 700 MHz. One illumination
frequency lies on an absorption line of gaseous iodine, and the other just off
the absorption line. The beams sequentially illuminate a plane within a seeded
flow and Doppler-shifted scattered light passes through an iodine vapour cell
onto the camera. The beam at a frequency off the absorption line is not affected
by passage through the cell, and provides a reference image. The other beam
encodes the velocity information as a variation in transmission dependent upon
the Doppler shift. Use of a single camera ensures registration of the reference
and signal images, which is the major problem in any spilt image system such as
a two-camera imaging head, and cost efficiency is improved by the simplification
of the system. A 2v-PDV system was constructed using a continuous-wave Argon ion
laser and acousto-optic modulators to produce two frequencies of illuminating
laser light. This was combined with multiple imaging fibre bundles, to port
three different views of the measurement plane to a CCD camera, allowing the
measurement of three velocity components
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