Person:
Álvarez Fernández-Balbuena, Antonio

First Name

Antonio

Last Name

Álvarez Fernández-Balbuena

URI

https://hdl.handle.net/20.500.14352/79920

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Óptica y Optometría

Department

Óptica

Area

Optica

Identifiers

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Search Results

Now showing 1 - 10 of 10

Skylight: a hollow prismatic CPC
(Proceedings of the SPIE, 2009) García Fernández, Berta; García Botella, Angel; Álvarez Fernández-Balbuena, Antonio; Vázquez Molini, Daniel; Bernabéu Martínez, Eusebio; Winston, Roland; Gordon, Jeffrey M.
Many applications involve the use of a compound parabolic concentrator (CPC) like, natural lighting, thermal applications, optics for illuminators, optical fibre coupling and solar energy. The use of a CPC in reverse mode for natural lighting gives the chance to use it as a lighting skylight in ceilings because light output is controlled inside the design angle, on the contrary having a low flux transfer ratio because of the reduced area of the entrance pupil regarding exit pupil. The authors propose an innovative 3D hollow prismatic CPC (HPCPC) made of a dielectric material, which has a high efficiency comparing it with aluminium CPC. The basic idea is to use a hollow prismatic light guide with CPC shape. This paper reports 2D, 3D design and numerical analysis by raytracing software, also experimental results are shown. The system works almost like a true CPC when light enters through standard entrance pupil and also collect light that enters outside entrance pupil. Performance and efficiency of the prismatic CPC is in average 300% higher than standard aluminium CPC for collimated light in a range from 0º to 85º. A prototype has been developed and tested.
Role of Metalloproteases in Retinal Degeneration Induced by Violet and Blue Light
(Advances in Experimental Medicine and Biology, 2009) Sánchez Ramos, Celia; Vega, J.A.; Del Valle, M.E.; Álvarez Fernández-Balbuena, Antonio; Bonnin Arias, Cristina Natalia; Benítez Del Castillo Sánchez, José Manuel; Anderson, RE (Anderson, RE) ; LaVail, MM (LaVail, MM) ; Hollyfield, JG (Hollyfield, JG) ; Mandal, MNA (Mandal, MNA)
Introduction: An essential role for metalloproteases (MMPs) has been described in blood vessel neoformation and the removal of cell debris. MMPs also play a key role in degenerative processes and in tumors. The participation of these enzymes in light-induced phototoxic processes is supported by both experimental and clinical data. Given that patients with age-related macular degeneration often show deposits, or drusen, these deposits could be the consequence of deficient MMP production by the pigment epithelium. Objective: To gain insight into the regulation of metalloproteases in the pathogenia of retinal degeneration induced by light. Materials and methods: We examined the eyes of experimental rabbits exposed for 2 years to circadian cycles of white light, blue light and white light lacking short wavelengths. For the trial the animals had been implanted with a transparent intraocular lens (IOL) and a yellow AcrySof((R)) IOL, one in each eye. After sacrificing the animals, the retinal layer was dissected from the eye and processed for gene expression analyses in which we examined the behavior of MMP-2, MMP-3 and MMP-9. Results: MMP-2 expression was unaffected by the light received and type of IOL. However, animals exposed to white light devoid of short wavelengths or those fitted with a yellow IOL showed 2.9- and 3.6-fold increases in MMP-3 expression, respectively compared to controls. MMP-9 expression levels were also 3.1 times higher following exposure to blue light and 4.6 times higher following exposure to white light lacking short wavelengths or 4.2 times higher in eyes implanted with a yellow IOL. Conclusion: Exposure to long periods of light irrespective of its characteristics leads to the increased expression of some MMPs. This alteration could indicate damage to the extracellular matrix and have detrimental effects on the retina.
Louvers design for LED displays for sunny days
(Displays, 2007) Vázquez Moliní, Daniel; Álvarez Fernández-Balbuena, Antonio; Alda Serrano, Javier; Bernabeu Martínez, Eusebio
The use of louvers attached to variable information display needs to be optimized taking into account different intrinsic and extrinsic parameters. The analysis of the performance of the display–louvers system takes into account the location, orientation, and daily and seasonal variations. The observation of the system is divided depending on the distance of observation. The far distance vision performance use the background luminance. The medium distance performance needs the use of the Contrast Sensitivity Function of the eye.
Neuroprotective effects of different absorption filters: exploring macular degeneration in pigmented rats.
(2007) Sánchez Ramos, Celia; García Ayus, D.; Casas Builla Olalla, M.S.; Álvarez Fernández-Balbuena, Antonio; Langa Moraga, Antonio; Navarro Valls, J.J.; Villegas Pérez, M.P.
PURPOSE: Visible light has a phototoxic effect on photoreceptors and retinal pigment epithelium cells. Short wavelengths are the most dangerous radiations of the visible spectrum. This study was designed to examine the neuroprotective role played by filters that short wavelengths of light in an experimental model of retinal phototoxicity in pigmented rats. METHODS: Famale Lister Hooded pigmented rats, 8 weeks of age, were used in a sequence of 3 experiments in which each group of animals was exposed to different light intensities, being 3086.67 lux the average in the first experiment and 2350 lux in the second one. For the third experiment it was employed a light intensity that oscilated between 700-800 lux, and what was adapted to the standard enviroment conditions of the city of Madrid (Spain); with an irradiance that varied from 1.48 w/m2 until 1.64 w/m2. FIlters that short wavelengths of different absorbance were used as much in second experiment as in the third one. The aimals were exposed to the light for 72 hours after having previously dilated the left pupil of each animal by instiling 1% atropine. The animals were sacrificed 1 or 7 days after light exposure and their retinas processed for microscopy. RESULTS: The light exposed retinas that has no protection or were protected at 5% with filters that short wavelengths, showed a nuclear density of 2-4 nuclei, while retinas exposed to light using filters that afforded a protection of 20% exhibited a nuclear density of 10-12 nuclei. This nuclear density was siilar to that recorded for control retinas, indicating a compensatory effect of these optic elements. CONCLUSIONS: Adapting the illuminance to the values of the eviroment standard conditions, filters of suitable optical density that short wavelengths of light protect retinal neurones, giving rise to similar nuclear densities to control retinas.
Experimental study of filtered light effect in the retina. Its aplication for car windows.
(2007) Sánchez Ramos, Celia; Vega, J.A.; Ochoa Erena, F.J.; Moral Martínez, M.I.; Álvarez Fernández-Balbuena, Antonio
Purpose: exposure ot light seems to be the triggering factor for some age-related retinal diseases, although the portion of the visual spectrum responsible for damage to the retina is as yet unknown. The present study was designed to investigate the role of circadian exposure to white, blue and yellow light on the retina Materials and methods: Adult albino rats were exposed to white, yellos or blue light for 15 days. The animals were sacrificed and the eyes removed and processed for light microscopy. Results: Exposure to white light does not modify the structure of the retina. The retinas of the rats exposed to yellow liht showe a thinner outer plexiform layer, reduced cell numbers in the inner and outer granular layers, and occasionally a lack of photoreceptor external segment of the photoreceptors was absent, and the density of cells severely reduced. Further, most of the animals showed enlarged and dilated choroidal blood vessels. Results were confirmed by quantitative histological techniques. Conclusions: Light exposure induces several retinal changes, with blue light inducing the most remarkable changes. Car windscreens could be a goo support system for the use of filters to block blue light.
Regulations of the neurotrophin receptro TrkB by visible light.
(2008) Sánchez Ramos, Celia; Vega, J.A.; del Valle, M.E.; Langa Moraga, Antonio; Álvarez Fernández-Balbuena, Antonio; Benítez Del Castillo Sánchez, José Manuel
INTRODUCTION: Of all neurotrophins, brain-derived neurotrophic factor (BDNF) seems to show most actions on the retina. Thus, through the TrkB receptor, BDNF controls the remodeling of the neuronal structures of the eye in a cell-specific and expriment-dependent manner. PURPOSE: To examine variations in the BDNF receptor TrkB produced in response to prolonged exposure to circadian cycles of light. METHODS: We examined the eyes of experimental rabbits exposed for two years to circadian cycles of white light, blue light and white light lacking short wavelengths. For the trial the animals had been implanted with a transparent introcular lens (IOL) and a yellow Acrysof (ALCON) IOL, one in each eye. Afeter sacrificing the animals, the retinal layer was dissected from the eye and processed for gene expression analysis using primers for TrkB. RESULTS: Prolonged light exposure resulted in elevated expression levels of the TrkB receptor as follow: 1.8 times in response to white light, 2.3 times in response to blue light, and 3.9 times in response to white light devoid of short wavelengths. In eyes implanted with a yellow IOL, a 4.2-fold increase in TrkB expression was observed. CONCLUSION; Exposure to light, irrespective of its characteristics, led to the incr3eased expression of the TrkB receptor. Expression levels were elevated most in response to white light devoid of short wavelengths. This finding suggets that the cells of the retinal layer expressing the receptor, which have yet to be indentified, are capable of reacting to the neuroprotective stimuli mediated by this molecule.
Ideal 3D asymmetric concentrator
(Solar Energy, 2009) García Botella, Ángel; Álvarez Fernández-Balbuena, Antonio; Vázquez Moliní, Daniel; Bernabeu Martínez, Eusebio
Nonimaging optics is a field devoted to the design of optical components for applications such as solar concentration or illumination. In this field, many different techniques have been used for producing reflective and refractive optical devices, including reverse engineering techniques. In this paper we apply photometric field theory and elliptic ray bundles method to study 3D asymmetric – without rotational or translational symmetry – concentrators, which can be useful components for nontracking solar applications. We study the one-sheet hyperbolic concentrator and we demonstrate its behaviour as ideal 3D asymmetric concentrator.
Chromatic perception of non-invasive lighting of cave paintings
(Proceedings of SPIE, 2009) Zoido Chamorro, Jesús Manuel; Vázquez Moliní, Daniel; Álvarez Fernández-Balbuena, Antonio; Bernabeu Martínez, Eusebio; García Botella, Ángel; Herráenz Ferreiro, Juan Antonio; Egido Rodríguez, Marian, del
This work is intended to deal with the problems which arise when illuminanting Paleolithic cave paintings. We have carried out the spectral and colorimetric characterization of some paintings located in the Murcielagos (bats) cave (Zuheros, Córdoba, Spain). From this characterization, the chromatic changes produced under different lighting conditions are analysed. The damage function is also computed for the different illuminants used. From the results obtained, it is proposed an illuminant whose spectral distribution diminishes the damage by minimizing the absorption of radiation and optimises the color perception of the paintings in this cave. The procedure followed in this study can be applied to optimise the lighting systems used when illuminating any other art work.
Hyperparabolic concentrators
(Applied Optics, 2009) García Botella, Ángel; Álvarez Fernández-Balbuena, Antonio; Vázquez Molini, Daniel; Bernabeu Martínez, Eusebio; González Cano, Agustín
We present a family of three-dimensional concentrators constructed from the photic field generated by a Lambertian emitter. The profile of these concentrators is obtained from the field lines for a two-dimensional truncated wedge and is based on the union between a hyperbola and a tilted parabola. By revolution of this profile, we obtain hyperparabolic concentrators (HPCs). In the limiting case when the focal length of the hyperbola becomes the radius of the exit aperture, the HPC becomes the well-known compound parabolic concentrator. On the other hand, when the focal length of the hyperbola becomes infinite, the HPC achieves the thermodynamic limit of concentration.
Absorbing harmful wavelengths of visible light emitted by a welding torch through tue use of a yellow filter: experimental evidence.
(2009) Sánchez Ramos, Celia; Bonnin Arias, Cristina Natalia; Torets, C.; Álvarez Fernández-Balbuena, Antonio; Langa Moraga, Antonio; Forlan, A.; Ramírez, G.
PURPOSE: This study was designed to determine the emission spectrum of a professional welding torch and quantify the absorption of several wavelengths of visible light by yellow filters of different optical densities. METHODS: Three measurements of the emission spectrum of a welding torch were made at 3 distances between 20 to 40cm. Subsequent to this, 6 layers of e-colour-10 yellow filters supplied by Rosco were placed in front of the torch and the transmittances determined of all the light bands emitted by the torch crossing the filter. RESULTS: The measurements obtained were: for 370nm, the torch emitted 680 relative units (RU) of which the filter absorbed 6440 RU (94%); for 415nm emission was 350 RU and absorption by the filter was 100%, for 430nm, amission was 700 RU and absoption 600 RU ( 96%); for 450nm, emission was 270 RU and absorption 100%; for 450, 480nm amission was 350 RU and absortion 300 RU (85%) and for 490nm, amission dropped from 200 RU to 60 RU (70%) CONCLUSIONS: In relative units, the emission of short wavelengths (violet-blue light) by a elding torch is high. A yello filter practically eliminates all the harmful bands of the visible spectrum. The use of these filters to protect the retina is recommended for professional welders.