Search results for "photonics"
showing 10 items of 802 documents
Scanning from heating: 3D shape estimation of transparent objects from local surface heating.
2009
Today, with quality becoming increasingly important, each product requires three-dimensional in-line quality control. On the other hand, the 3D reconstruction of transparent objects is a very difficult problem in computer vision due to transparency and specularity of the surface. This paper proposes a new method, called Scanning From Heating (SFH), to determine the surface shape of transparent objects using laser surface heating and thermal imaging. Furthermore, the application to transparent glass is discussed and results on different surface shapes are presented.
Electric-field-controlled reversible order-disorder switching of a metal tip surface
2018
While it is well established that elevated temperatures can induce surface roughening of metal surfaces, the effect of a high electric field on the atomic structure at ambient temperature has not been investigated in detail. Here we show with atomic resolution using in situ transmission electron microscopy how intense electric fields induce reversible switching between perfect crystalline and disordered phases of gold surfaces at room temperature. Ab initio molecular dynamics simulations reveal that the mechanism behind the structural change can be attributed to a vanishing energy cost in forming surface defects in high electric fields. Our results demonstrate how surface processes can be d…
Integrated photonic routers driven by surface acoustic waves
2016
Durante la segunda mitad del siglo XX se produjo un desarrollo excepcional de la capacidad de transmitir y procesar información electrónicamente. Esto fue debido en parte a la capacidad de integrar en un único substrato una gran cantidad de transistores, que son las unidades fundamentales de procesamiento de datos. Este comportamiento quedó resumido en la ley de Moore, que predecía que el número de transistores integrados se duplicaría cada 24 meses. Esta tendencia, que se ha mantenido hasta la actualidad con transistores de tamaño nanométrico, no puede continuar indefinidamente. Uno de los problemas fundamentales reside en la capacidad limitada para disipar el calor que generan los disposi…
Robust three-dimensional best-path phase-unwrapping algorithm that avoids singularity loops.
2009
In this paper we propose a novel hybrid three-dimensional phase-unwrapping algorithm, which we refer to here as the three-dimensional best-path avoiding singularity loops (3DBPASL) algorithm. This algorithm combines the advantages and avoids the drawbacks of two well-known 3D phase-unwrapping algorithms, namely, the 3D phase-unwrapping noise-immune technique and the 3D phase-unwrapping best-path technique. The hybrid technique presented here is more robust than its predecessors since it not only follows a discrete unwrapping path depending on a 3D quality map, but it also avoids any singularity loops that may occur in the unwrapping path. Simulation and experimental results have shown that …
3D photonic crystal intermediate reflector for micromorph thin-film tandem solar cell
2008
The concept of 3D photonic intermediate reflectors for micromorph silicon tandem solar cells has been investigated. In thin-film silicon tandem solar cells consisting of amorphous and microcrystalline silicon with two junctions of a-Si/μc-Si, efficiency enhancements can be achieved by increasing the current density in the a-Si top cell. It is one goal to provide an optimized current matching at high current densities. For an ideal photon-management between top and bottom cell, a spectrally selective intermediate reflective layer (IRL) is necessary, which is less dependent of the angle of incidence than state-of-the-art thickness dependent massive interlayers. The design, preparation and cha…
INVESTIGATION OF THE UNDERGROUND BUILDING HERITAGE AND THE MECHANISM OF WATER FLOWING IN QANĀTS IN PALERMO THROUGH INNOVATIVE SURVEYING TECHNIQUES
2021
Abstract. The valorisation, protection and preservation policies for the underground building heritage are often difficult to implement due to an inadequate knowledge of hypogeal constructions. The complex and widespread underground structures of the vast “Cavo” Heritage (“horizontal wells”, “shelf wells” or “well tunnels”), so called qanāts, hidden underground and built over the centuries in Palermo, representing an evocative testimony to the history of water culture in the ancient city. Through the historical and constructive analyses and the implementation and development of measurement and 3D representation and visualization, first actions have been carried out. The paper will present t…
A 3D REWORKING OF THE URBAN TRANSFORMATIONS OF PALERMO IN RECENT HISTORY FOR A HYPOTHESIS OF A "CITY MUSEUM" BASED ON DIGITAL VISUALIZATIONS
2021
Abstract. The objective that drives this research is given by a multitude of information which, in addition to the contribution of technology, allows us to study, analyze, verify and remodel the sites, monuments and evolutions of the city through graphic processes of perspective restitution that start from the analysis of historical photos. The drawing methods, the digital graphic rendering and through the aid of geometric techniques, contribute to the reconstruction of projects and architectures that are now lost, this is possible thanks to the methods of perspective, axonometry and three-dimensional restitution.This remarkable photographic heritage belonging to Palermo, but also to any ot…
Integrating topographic, photogrammetric and laser scanning techniques for a scan-to-bim process
2021
Abstract. The preservation of historic buildings can often be particularly difficult due to the lack of detailed information about architectural features, construction details, etc.. However, in recent years considerable technological innovation in the field of Architecture, Engineering, and Construction (AEC) has been achieved by the Building Information Modeling (BIM) process. BIM was developed as a methodology used mainly for new construction but, given its considerable potential, this approach can also be successfully used for existing buildings, especially for buildings of historical and architectural value. In this case, it is more properly referred to as Historic – or Heritage – Buil…
PIECEWISE ANOMALY DETECTION USING MINIMAL LEARNING MACHINE FOR HYPERSPECTRAL IMAGES
2021
Abstract. Hyperspectral imaging, with its applications, offers promising tools for remote sensing and Earth observation. Recent development has increased the quality of the sensors. At the same time, the prices of the sensors are lowering. Anomaly detection is one of the popular remote sensing applications, which benefits from real-time solutions. A real-time solution has its limitations, for example, due to a large amount of hyperspectral data, platform’s (drones or a cube satellite) constraints on payload and processing capability. Other examples are the limitations of available energy and the complexity of the machine learning models. When anomalies are detected in real-time from the hyp…
Improved time-resolved acousto-optic technique for optical fiber analysis of axial non-uniformities by using edge interrogation
2015
The time-resolved acousto-optic technique demonstrated recently to be a very useful method for the analysis of fiber axial non-uniformities, able to detect variations of fiber diameter in the nanometric scale with a spatial resolution of few cm. An edge interrogation approach is proposed to improve further the performance of this technique. The detection of subnanometer fiber diameter changes or sub-ppm changes of the core refractive index is demonstrated.