Person: Martínez Antón, Juan Carlos
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First Name
Juan Carlos
Last Name
Martínez Antón
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Óptica y Optometría
Department
Óptica
Area
Optica
Identifiers
9 results
Search Results
Now showing 1 - 9 of 9
Item Smooth light extraction in lighting optical fibre(Illumination Optics II, 2011) Álvarez Fernández-Balbuena, Antonio; Vázquez Molini, Daniel; García Botella, Ángel; Martínez Antón, Juan Carlos; Bernabeu Martínez, Eusebio; Kidger, Tina E.; David, StuartRecent advances in LED technology have relegated the use of optical fibre for general lighting, but there are several applications where it can be used as scanners lighting systems, daylight, cultural heritage lighting, sensors, explosion risky spaces, etc. Nowadays the use of high intensity LED to inject light in optical fibre increases the possibility of conjugate fibre + LED for lighting applications. New optical fibres of plastic materials, high core diameter up to 12.6 mm transmit light with little attenuation in the visible spectrum but there is no an efficient and controlled way to extract the light during the fibre path. Side extracting fibres extracts all the light on 2π angle so is not well suited for controlled lighting. In this paper we present an extraction system for mono-filament optical fibre which provides efficient and controlled light distribution. These lighting parameters can be controlled with an algorithm that set the position, depth and shape of the optical extraction system. The extraction system works by total internal reflection in the core of the fibre with high efficiency and low cost. A 10 m length prototype is made with 45° sectional cuts in the fibre core as extraction system. The system is tested with a 1W white LED illuminator in one side.Item Optical interference method to obtain thickness and refractive-indexes of a uniaxial medium(Review of scientific instruments, 1994) Carreño Sánchez, Fernando; Martínez Antón, Juan Carlos; Bernabeu Martínez, EusebioOptical interference fringe measurements of the thickness of weakly absorbing media can be rapid, accurate, and nondestructive. When the refractive index n of the sample is known, it will give us the layer thickness d. If, however, n is unknown, at least two independent spectrophotometric measurements are needed to obtain both n and d. A statistically based scheme is proposed to analyze the interference pattern in order to determine the refractive index and the thickness of the sample. The absolute interference order is also determined with the proposed technique. The major approximation inherent in the method is that the layer must be weakly absorbing and nondispersive over the wavelength region of interest. The method is applied to determine the optical constants of a uniaxial medium with the optical axis parallel to the faces.Item Classification of surface structures on fine metallic wires(Applied Surface Science, 2001) Bernabeu Martínez, Eusebio; Sánchez Brea, Luis Miguel; Siegmann, Philip; Martínez Antón, Juan Carlos; Gómez Pedrero, José Antonio; Wilkening, Günter; Koenders, Ludger; Müller, Franz; Hildebrand, M.; Hermann, HartiIn this report a classification of the main surface structures found on fine metallic wires is carried out (between ∼20 and 500 μm in diameter). For this, we have analyzed a series of wires of different metallic materials, diameters and production environments by scanning electron microscopy, atomic force microscopy, and confocal microscopy. A description and the images of the structures is given and, in addition, a nomenclature to be used by manufacturers, customers and researches is proposed. With this information the surface quality of fine metallic wires may be improved in a fabrication level. One of the objectives of this catalogue of defects is to serve as a basis for measuring the quality of the surface of the wires during the production process and the development of a measuring device for that purpose.Item Diffraction in wide slits with semi-cylindrical edges(Optik, 2002) Siegmann, Philip; Sánchez Brea, Luis Miguel; Martínez Antón, Juan Carlos; Bernabeu Martínez, EusebioWe present an analytical model to obtain the diffraction pattern in far field of a metallic, thick slit based on the Geometrical Theory of Diffraction. The edges of the slit are modelled as semicylinders. We have considered that the thickness of the slit is sufficiently small compared to the width, so that the influence of multiple reflections between the edges may be neglected. The material in which the slit is made, as well as the polarization and angle of the incident beam, are considered. Notorious differences are obtained when compared to the classical diffraction from flat slits.Item High performance Feussner-type polarizers based on stretched poly(ethylene-terephthalate) films(Applied physics Letters, 2002) Martínez Antón, Juan Carlos; Bernabeu Martínez, EusebioStretched poly(ethylene-terephthalate) films appear to be an interesting optical plastic for use in polarization control devices. By means of stretching ratios its birefringence, in practice, can be tailored from ∼0 to ∼0.17. It has a very wide transmission window (∼0.32–5.70 μm) and good thermal, mechanical, and chemical properties. We propose using it for polarizers based on the Feussner design. By implementing this configuration with a biaxially stretched film, we have obtained a polarizer with an achromatic extinction ratio better than 1 part in 50 000. This is comparable with conventional Glan–Thompson polarizers but with additional advantages. The principal refractive indices of the film (in the 0.43–5.7 μm range) and the operational range of the polarizer presented are also provided.Item Static and dynamic detection of axial surface defects on metallic wires by conical triple laser reflection(Optics and Lassers in Engineering, 2004) Siegmann, Philip; Martínez Antón, Juan Carlos; Bernabeu Martínez, EusebioThe quality of the surface of metallic wires is relevant for different applications. The reflection of a laser beam on the surface of a metallic cylindrical wire provides an efficient way to inspect the quality of its surface. Our interest is focused in the detection of axially oriented defects, which are the most relevant for the wire drawing process. We present a simple interference-geometrical model to describe the light pattern reflected from a wire with defects. This model adequately accounts for the observed results from an industrial prototype developed for the purpose. It incorporates three-laser beams incident on the wire at equidistant locations in its perimeter, which produce three reflection cones with a CCD. This configuration permits to explore the whole perimeter of the wire. Several results are presented, both in static operation and in production line, in agreement with qualitative and quantitative predictions.Item On Babinet's principle and a diffraction-interferometric technique to determine the diameter of cylindrical wires(Metrologia, 2001) Martínez Antón, Juan Carlos; Serroukh, Ibrahim; Bernabeu Martínez, EusebioLaser diffraction is a robust and precise technique for measuring wire diameters. However, classical Fraunhofer diffraction formulas are inappropriate for determining the size of three-dimensional objects. Babinet's principle (from classical diffraction theory) allows the use of such formulas only for angles of diffraction tending to zero. In practice diffraction measurements require a finite angular range (about 10°) for good resolution. We show that use of the classical slit-diffraction formula for this extended angular interval introduces significant error. We develop a simple diffraction model valid for cylindrical shapes and a formula to obtain the diameter of cylindrical wires. To validate the diffraction formula we calibrate the diameter of the wires using an independent interferometric technique, which to our knowledge is original for this particular task. We have verified our diffraction formula to within about 0.2 µm for various wire materials and diameters (30 µm to 300 µm) and a wide angular range (±25°). Two different experimental set-ups were implemented to increase the reliability of the results. The calibration procedure revealed a systematic disagreement with Babinet's principle, in particular a systematic overestimation of the diameter by about 0.6 µm, almost independent of the material and the diameter itself. This is particularly relevant to metrological applications involving diffraction phenomena and based on classical diffraction theory.Item Comparison between optical techniques and confocal microscopy for defect detection on thin wires(Applied Surface Science, 2004) Siegmann, Philip; Sánchez Brea, Luis Miguel; Martínez Antón, Juan Carlos; Bernabeu Martínez, EusebioConventional microscopy techniques, such as atomic force microscopy (AFM), scanning electron microscopy (SEM), and confocal microscopy (CM) are not suitable for on-line surface inspection of fine metallic wires. In the recent years, some optical techniques have been developed to be used for those tasks. However, they need a rigorous validation. In this work, we have used confocal microscopy to obtain the topography z(x,y) of wires with longitudinal defects, such as dielines. The topography has been used to predict the light scattered by the wire. These simulations have been compared with experimental results, showing a good agreement.Item Achromatic Fresnel Lens with Improved Efficiency for PV Systems(International Journal of Photoenergy, 2014) González Montes, Mario; Martínez Antón, Juan Carlos; Vázquez Molini, Daniel; Álvarez Fernández-Balbuena, Antonio; Bernabeu Martínez, EusebioThis work is aimed to design and evaluate different achromatic Fresnel lens solutions capable of operating as concentrators aimed at photovoltaic cells systems. Throughout this study, the theoretical parametric design of the achromatic lens will be shown together with a series of simulations to verify the performance of each lens topology. The results will be compared with a standard Fresnel lens to ascertain the validity and effectiveness of the obtained design. Finally, a novel kind of hybrid lens is proposed, which combines the advantages of each type of lens (standard and Fresnel) according to the optimal operating region of each design. Efficiency and concentration ratios of each particular lens are shown, regarding lens dimension, light’s incidence angle, or wavelength. Through this innovative achromatic design concentration ratios above 1000 suns, which hardly reach standard Fresnel lenses. Furthermore chromatic dispersion is minimized and the efficiency rate is over 85% of efficiency for a wide spectral range (from 350 nm to 1100 nm).