Digital cultural heritage imaging via osmosis filtering

In Cultural Heritage (CH) imaging, data acquired within different spectral regions are often used to inspect surface and sub-surface features. Due to the experimental setup, these images may suffer from intensity inhomogeneities, which may prevent conservators from distinguishing the physical properties of the object under restoration. Furthermore, in multi-modal imaging, the transfer of information between one modality to another is often used to integrate image contents. In this paper, we apply the image osmosis model proposed in [4, 10, 12] to solve correct these problems arising when diagnostic CH imaging techniques based on reflectance, emission and fluorescence mode in the optical and thermal range are used. For an efficient computation, we use stable operator splitting techniques to solve the discretised model. We test our methods on real artwork datasets: the thermal measurements of the mural painting “Monocromo” by Leonardo Da Vinci, the UV-VIS-IR imaging of an ancient Russian icon and the Archimedes Palimpsest dataset

Algunas aplicaciones del láser

Este artículo describe algunas aplicaciones del láser. La Sección I, Fotoelasticimetría, está dedicada a la observación de franjas isocromáticas en un modelo de plástico cargado usando la técnica de luz dispersada. En la Sección II se incluyen dos aplicaciones interfe- rométricas. La primera está relacionada con medidas de espesor o índice de refracción de una lámina traslúcida plano paralela usando un interferómetro de Fabry-Perot. La segunda describe un interferómetro triangular a incidencia rasante para ser usado en el control de superficies de calidad no óptica. La Sección III trata sobre holografía y sus aplicaciones en la medida interferómetrica de la deformación de una barra de acero cargada.This paper describes some laser applications. Section I (Photoelasticity) is devoted to the observation of isochromatic fringes in a loaded plastic model by using the scattered light technique. Two interferometric applications hate been included in Section II. The first one, is related with measurements of thickness or refractive index of a translucent plane parallel plate by using an open Fabry-Perot interferometer. The second one, describes a laser grazing incidence triangular singlepass interferometer to be used in checking-out surfaces of non-optical quality. The Section III deals with holography and its applications in interferometric measurements of deformations in a loaded steel bar

Anisotropic osmosis filtering for shadow removal in images

We present an anisotropic extension of the isotropic osmosis model that has been introduced by Weickert et al.~(Weickert, 2013) for visual computing applications, and we adapt it specifically to shadow removal applications. We show that in the integrable setting, linear anisotropic osmosis minimises an energy that involves a suitable quadratic form which models local directional structures. In our shadow removal applications we estimate the local structure via a modified tensor voting approach (Moreno, 2012) and use this information within an anisotropic diffusion inpainting that resembles edge-enhancing anisotropic diffusion inpainting (Weickert, 2006, Gali\'c, 2008). Our numerical scheme combines the nonnegativity preserving stencil of Fehrenbach and Mirebeau (Fehrenbach, 2014) with an exact time stepping based on highly accurate polynomial approximations of the matrix exponential. The resulting anisotropic model is tested on several synthetic and natural images corrupted by constant shadows. We show that it outperforms isotropic osmosis, since it does not suffer from blurring artefacts at the shadow boundaries

Advanced Experimental Techniques for RF and DC Breakdown Research

Advanced experimental techniques are being developed to analyze RF and DC breakdown events. First measurements with a specially built spectrometer have been made with a DC spark setup [1] at CERN and will soon be installed in the CLIC 30GHz accelerating structure test stand to allow comparison between DC and RF breakdown phenomena. This spectrometer is able to measure the light intensity development during a breakdown in narrow wavelength bands in the visible and near infrared range. This will give information about the important aspects of the breakdown including chemical elements, temperature, plasma parameters and possibly precursors of a breakdown

Espectrómetro de doble paso, simple y económico, para analizar radiación láser

En distintas épocas, antes y después del advenimiento del láser, se han diseñado espectrómetros ópticos para incrementar la dispersión con la cual se desea analizar la radiación o bien para reducir lo más posible la luz difundida en los elementos dispersivos, prismas o redes de difracción. Una vez que el láser pasó a ser una eficaz herramienta de laboratorio, varios campos de la óptica encontraron la oportunidad de lograr desarrollos sensacionales. La holografía y la espectroscopia de la radiación dispersada por la materia, constituyen ejemplos notables de aquellos campos de la óptica en los que el láser provocó una situación de avance sin precedentes. En el caso de los estudios de la radiación dispersada por la materia, fue necesario el diseño de espectrómetros especiales para detectar, por ejemplo, las débiles señales Stokes y anti-Stokes, excitadas por láseres diversos, en gases, líquidos o sol idos. Los espectrómetros ópticos o monocromadores usados en la investigación del efecto Raman, pueden clasificarse en tres tipos: a) los monocromadores de doble paso; b) los monocromadores duales y c) los monocromadores en tándem

Study of the discharge gas trapping during thin film growth

Discharge gas trapping in thin films produced by sputtering is known to be due to high energy neutrals bouncing back from the cathode. Qualitatively, the phenomenon is enhanced by raising the discharge voltage and is strongly dependent on the atomic masses of the discharge gas and of the cathode material. In addition to these known effects it is shown that, for a given gas, the trapped amount decreases with increasing the melting temperature of the deposited material. The results obtained both by sample melting and laser ablation are presented and discussed

Design Aspects of the RF Contacts for the LHC Beam Vacuum Interconnects

The LHC requires a very low longitudinal and transverse beam coupling impedance, in particular at low frequencies. This implies an admissible DC contact resistance of less than 0.1 m$\Omega$ for the RF contacts inside the vacuum bellows which must carry the image current (up to 50 A peak) of the beam at each vacuum chamber interconnect. Technological aspects, measurement methods and test results are presented for the contacts which will be used in the LHC. The modified mechanical design and the justifications for specific choices will be discusse

Experimental Studies of Carbon Coatings as Possible Means of Suppressing Beam Induced Electron Multipacting in the CERN SPS

Electron cloud build-up is a major limitation for the operation of the SPS with LHC beam above nominal intensity. These beams are envisaged in the frame of the LHC luminosity upgrade and will be available from the new injectors LPSPL and PS2. A series of studies have been conducted in order to identify possible means to suppress electron multipacting by coating the existing SPS vacuum chambers with thin films of amorphous carbon. After a description of the experimental apparatus installed in the SPS, the results of the tests performed with beam in 2008 will be presented

Secondary electron yield reduction by femtosecond pulse laser-induced periodic surface structuring

The electron-cloud phenomenon is one cause of beam instabilities in high intensity positive particle accelerators. Among the proposed techniques to mitigate or control this detrimental effect, micro-/nano-geometrical modifications of vacuum chamber surfaces are promising to reduce the number of emitted secondary electrons. Femtosecond laser surface structuring readily allows the fabrication of Laser Induced Periodic Surface Structures (LIPSS) and is utilized in several fields, but has not yet been tested for secondary electron emission reduction. In this study, such treatment is carried out on copper samples using linearly and circularly polarized femtosecond laser pulses. The influence of the formed surface textures on the secondary electron yield (SEY) is studied. We investigate the morphological properties as well as the chemical composition by means of SEM, AFM, Raman and XPS analyses. Surface modification with linearly polarized light is more effective than using circularly polarized light, leading to a significant SEY reduction. Even though the SEY maximum is only reduced to a value of ~1.7 compared to standard laser-induced surface roughening approaches, the femtosecond-LIPSS process enables to limit material ablation as well as the production of undesired dust, and drastically reduces the number of redeposited nanoparticles at the surface, which are detrimental for applications in particle accelerators. Moreover, conditioning tests reveal that LIPSS processed Cu can reach SEY values below unity at electron irradiation doses above 10−3 C/mm2