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
20 results
Search Results
Now showing 1 - 10 of 20
Item Wavefront measurement by solving the irradiance transport equation for multifocal systems(Optical Engineering, 2001) Quiroga Mellado, Juan Antonio; Gómez Pedrero, José Antonio; Martínez Antón, Juan CarlosA method for sensing wavefronts is presented. The method is based on the resolution of the irradiance transport equation, which relates the irradiance distribution and the shape of the wavefront of a light beam propagating along a given direction. The method presents no restrictions in the locations of the measurement planes and incorporates an improved procedure to geometrically correct the acquired images to take into account the effect of ray deflection in the propagation of the irradiance distributions. With the proposed technique, we measure the wavefront at the exit pupil of a progressive addition lens and find good agreement with an alternative deflectometric method.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 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 method for the surface topographic characterization of Fresnel lenses(Optical Fabrication, Testing and Metrology IV, 2011) Martínez Antón, Juan Carlos; Gómez Pedrero, José Antonio; Alonso Fernández, José; Quiroga Mellado, Juan AntonioFresnel lenses and other faceted or micro-optic devices are increasingly used in multiple applications like solar light concentrators and illumination devices. As applications are more exigent this characterization is of increasing importance. We present a technique to characterize the surface topography of optical surfaces. It is especially well adapted to Fresnel lenses where abrupt surface slopes are usually difficult to handle in conventional techniques. The method is based on a new photometric strategy able to codify the height information in terms of optical absorption in a liquid. A detailed topographic map is simple to acquire by capturing images of the surface. Some experimental results are presented. A single pixel height resolution of similar to 0.1 mu m is achieved for a height range of similar to 50 mu m. A surface slope analysis is also made achieving a resolution of similar to +/- 0.15 degrees.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.