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
12 results
Search Results
Now showing 1 - 10 of 12
Item Optical characterization of surfaces by robust reflectance determination based on air-gap interference(Applied Surface Science, 2004) Quiroga Mellado, Juan Antonio; Martínez Antón, Juan Carlos; González Moreno, RicardoIn this work we present an optical tool for characterizing the reflectance and polarimetric properties of surfaces. It uses only the image of the interference fringe pattern produced in a thin air-gap between the surface of interest and a glass surface acting as a reference. From only the contrast of the fringe pattern captured with a CCD we may obtain the reflectance of the surface, no need of measuring a reference beam. By taking two images with polarized light, we may get then the polarized reflectance R_p and R_s, but also the ellipsometric magnitude Δ, simply as a phase shift between fringes in p and s polarization. A sample of silicon with a thin layer of thermally grown silica is used to test the method.Item Variable-spectrum solar simulator(2012) Martínez Antón, Juan Carlos; Abengoa Solar New Technologies, S.A.The invention relates to a variable-spectrum solar simulator for characterising photovoltaic systems. The simulator can be used to obtain a spectrum adjusted to the solar spectrum, both for a standard spectrum or a real spectrum adjusted to local irradiation conditions. The simulator also allows the spatial-angular characteristics of the sun to be reproduced. The invention comprises: a broad-spectrum light source, the flux from which is emitted through an aperture; an optical system which collimates the primary source; a system which disperses the beam chromatically; an optical system which forms an image of the dispersed primary source at a given position, at which a spatial mask is placed in order to filter the received irradiance spectrally; an optical system which captures the filtered spectrum and returns, mixes and concentrates same in a secondary source with the desired spectral, angular, and spatial characteristics; an optical system which collimates the secondary source such that it reproduces the angular characteristics of the sun; and a control system.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 Enhancement of surface inspection by Moiré interferometry using flexible reference gratings(Optics Express, 2001) Quiroga Mellado, Juan Antonio; Martínez Antón, Juan Carlos; Canabal Boutureira, Héctor Alfonso; Bernabéu Martínez, Eusebio; Álvaro Labajo, M.; Cortés Testillano, V.We have extended the use of shadow Moiré technique to be implemented in simple curved surfaces by using a flexible grating. Dynamic visual inspection of surface micro-damages is significantly favored by the use of well adapted pliable gratings compared to the use of flat reference gratings. The experimental set-up consists of a plastic foil with a printed Ronchi grating stretched between three points which adapts to any cylindrical or conical convex surface independently of the relative orientation grating/surface. Static quantification of defects profiles is also possible with an attached CCD camera. Visual detection of defects in the range of ~30 μm in depth is obtainable.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.