446 research outputs found
Characterization and application of objective pilling classification to patterned fabrics
Previously, the authors proposed a new, simple method of frequency domain analysis based on the two-dimensional discrete wavelet transform to objectively measure the pilling intensity in sample fabric images. The method was further characterized, and the results obtained indicate that standard deviation and variance are the most appropriate measures of the dispersion of wavelet details coefficients for analysis, that the relationship between wavelet analysis scale and fabric inter-yarn pitch was empirically confirmed, and, that fabrics with random patterns do not appear to impact on the effectiveness of the analysis method. <br /
Digital Holography at Shot Noise Level
By a proper arrangement of a digital holography setup, that combines off-axis
geometry with phase-shifting recording conditions, it is possible to reach the
theoretical shot noise limit, in real-time experiments.We studied this limit,
and we show that it corresponds to 1 photo-electron per pixel within the whole
frame sequence that is used to reconstruct the holographic image. We also show
that Monte Carlo noise synthesis onto holograms measured at high illumination
levels enables accurate representation of the experimental holograms measured
at very weak illumination levels. An experimental validation of these results
is done
Exploring shot noise and Laser Doppler imagery with heterodyne holography
Heterodyne Holography is a variant of Digital Holography, where the optical
frequencies of signal and reference arms can be freely adjusted by
acousto-optic modulators. Heterodyne Holography is an extremely versatile and
reliable holographic technique, which is able the reach the shot noise limit in
sensitivity at very low levels of signal. Frequency tuning enables Heterodyne
Holography to become a Laser Doppler imaging technique that is able to analyze
various kinds of motion.Comment: Information Optics (WIO), 2010 9th Euro-American Workshop on,
Helsinki : Finland (2010
Imaging velocities of a vibrating object by stroboscopic sideband holography
We propose here to combine sideband holography with stroboscopic illumination
synchronized with the vibration of an object. By sweeping the optical frequency
of the reference beam such a way the holographic detection is tuned on the
successive sideband harmonic ranks, we are able to image the instantaneous
velocities of the object. Since the stroboscopic illumination is made with an
electronic device, the method is compatible with fast (up to several MHz)
vibration motions. The method is demonstrated with a vibrating clarinet reed
excited sinusoidally at 2 kHz, and a stroboscopic illumination with cyclic
ratio 0.15. Harmonic rank up to n = 100 are detected, and a movie of the
instantaneous velocities is reported
Three dimensional tracking of gold nanoparticles using digital holographic microscopy
In this paper we present a digital holographic microscope to track gold
colloids in three dimensions. We report observations of 100nm gold particles in
motion in water. The expected signal and the chosen method of reconstruction
are described. We also discuss about how to implement the numerical calculation
to reach real-time 3D tracking
Naming and discovery in networks : architecture and economics
In less than three decades, the Internet was transformed from a research network available to the academic community into an international communication infrastructure. Despite its tremendous success, there is a growing consensus in the research community that the Internet has architectural limitations that need to be addressed in a effort to design a future Internet. Among the main technical limitations are the lack of mobility support, and the lack of security and trust. The Internet, and particularly TCP/IP, identifies endpoints using a location/routing identifier, the IP address. Coupling the endpoint identifier to the location identifier hinders mobility and poorly identifies the actual endpoint. On the other hand, the lack of security has been attributed to limitations in both the network and the endpoint. Authentication for example is one of the main concerns in the architecture and is hard to implement partly due to lack of identity support. The general problem that this dissertation is concerned with is that of designing a future Internet. Towards this end, we focus on two specific sub-problems. The first problem is the lack of a framework for thinking about architectures and their design implications. It was obvious after surveying the literature that the majority of the architectural work remains idiosyncratic and descriptions of network architectures are mostly idiomatic. This has led to the overloading of architectural terms, and to the emergence of a large body of network architecture proposals with no clear understanding of their cross similarities, compatibility points, their unique properties, and architectural performance and soundness. On the other hand, the second problem concerns the limitations of traditional naming and discovery schemes in terms of service differentiation and economic incentives. One of the recurring themes in the community is the need to separate an entity\u27s identifier from its locator to enhance mobility and security. Separation of identifier and locator is a widely accepted design principle for a future Internet. Separation however requires a process to translate from the identifier to the locator when discovering a network path to some identified entity. We refer to this process as identifier-based discovery, or simply discovery, and we recognize two limitations that are inherent in the design of traditional discovery schemes. The first limitation is the homogeneity of the service where all entities are assumed to have the same discovery performance requirements. The second limitation is the inherent incentive mismatch as it relates to sharing the cost of discovery. This dissertation addresses both subproblems, the architectural framework as well as the naming and discovery limitations
Video-rate laser Doppler vibrometry by heterodyne holography
We report a demonstration video-rate heterodyne holography in off-axis
configuration. Reconstruction and display of 1 Megapixel holograms is achieved
at 24 frames per second, with a graphics processing unit. Our claims are
validated with real-time screening of steady-state vibration amplitudes in a
wide-field, non-contact vibrometry experiment.Comment: Optics Letters (2011) 00
Holographic microscopy for the three-dimensional exploration of light scattering from gold nanomarkers in biological media
The 3D structure of light scattering from dark-field illuminated live 3T3
cells marked with 40 nm gold nanomarkers is explored. For this purpose, we use
a high resolution holographic microscope combining the off-axis heterodyne
geometry and the phase-shifting acquisition of the digital holograms. Images
are obtained using a novel 3D reconstruction method providing longitudinally
undistorted 3D images. A comparative study of the 3D reconstructions of the
scattered fields allows us to locate the gold markers which yield, contrarily
to the cellular structures, well defined bright scattering patterns that are
not angularly titled and clearly located along the optical axis. This
characterization is an unambiguous signature of the presence of the gold
biological nanomarkers, and validates the capability of digital holographic
microscopy to discriminate them from background signals in live cells
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