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

Full item page

Search Results

Now showing 1 - 10 of 28

Mathematical Model Applied To Improve The Natural Lighting Design
(International Journal of Sustainable Development and Planning, 2017) García Fernández, Berta; Vázquez Moliní, Daniel; Álvarez Fernández-Balbuena, Antonio
Daylighting must be considered as the greenest way to illuminate any space and one of the most important architectural design challenges and opportunities. Human life is strongly influenced by natural lighting, and nowadays we have to add to this factor the importance of energy conservation and pollution reduction objectives. The development of hollow light guides offers people the advantages of natural lighting and the benefits of reduced energy consumption systems, providing changes in architectural form of spaces where sunlight does not have direct access. Hollow Cylindrical Prismatic Light Guides (CPLGs) are transparent optical components able to transmit high diameter light beams in daylight buildings applications without relevant losses. The goal of this paper is to show a novel lighting design based on hollow prismatic light pipes, which let daylight to be introduced inside of buildings. An improved mathematical modelling to predict light transmission efficiency based on realistic software simulations and experimental models is presented.
Improvement of driver night vision in foggy environments by structured light projection.
(Heliyon, 2022) Quintana Benito, Jaime; Álvarez Fernández-Balbuena, Antonio; Martínez Antón, Juan Carlos; Vázquez Moliní, Daniel
Nowadays, fog is still a natural phenomenon that hinders our ability to detect targets, particularly in the field of driving where accidents are increasing. In the literature we find different studies determining the range of visibility, improving the quality of an image, determining the characteristics of fog, etc. In this work we propose the possibility of using a structured lighting system, on which we project the light towards the target, limiting the field lighting. We have developed a scattering light propagation model to simulate and subsequently study the veil luminance, generated by backscattering, to predict the decrease in visibility. This simulation considers the type of fog, the relative orientation of various elements (observer, light source and targets). We have built a fog chamber to validate the experimental params of the described system. The results obtained from both the simulation and the experimental measurements demonstrate that it is possible to obtain a high contrast enhancement for viewing a target when illuminated as described. Clearly, this kind of lighting technology will improve the road safety in foggy night environments. The results of this work can also be extrapolated to any situation in which the visibility of an observer is compromised by the environment, such as heavy rain, smoke from fires, among others.
Advanced daylighting evaluation applied to cultural heritage buildings and museums: Application to the cloister of Santa Maria El Paular
(Renewable Energy, 2016) Mayorga Pinilla, Santiago; Vázquez Moliní, Daniel; Álvarez Fernández-Balbuena, Antonio; Hernández Raboso, Gabriel; Herráez, Juan Antonio; Azcutia, Marta; García Botella, Ángel
A method to evaluate the risk of using daylight in museums and cultural heritage exhibitions is presented along this study. Although daylight is an ecological and sustainable source of energy and sometimes also an intrinsic part of the artwork, the use of Natural lighting may cause damages in them due to the difficulty of controlling its variability. The developed method quantifies the damage produced to the artworks by daylight compared to artificial light taking into account the level of radiation and its spectral distribution in space and time by comparison with the damage caused by an Illuminant A (Global Risk Factor). The method, applied to the permanent paintings exhibition in the cloister of the fifteenth century of the Monastery of Santa Maria de El Paular, certifies that the control and exploitation of Natural Light should consider an optimal balance between exposure and damage.
Efficient and sustainable energy lighting solutions
(Proceedings of SPIE, 2019) García Botella, Ángel; Vázquez Moliní, Daniel; García Fernández, Berta; Álvarez Fernández-Balbuena, Antonio
The electric lighting is responsible for 15% of the electricity consumption, the efficiency in this sector has a good progress in recent years, it can still improve more. Conventional energy sources are polluting and limited, so it is essential to use less aggressive energies with the environment. In lighting, this premise is being implemented in a cross-cutting manner, but in response to varied and sometimes contradictory interests. The development of lighting devices based on solar radiation is an inalienable objective, as is the use of artificial lighting sources that are clean with the environment. To achieve these two objectives, it is essential to know and study the design techniques of non-image optics. In the present work we present new systems design techniques and lighting elements: ray tracing optimization technique, light vector field technique. As well as its implementation and application in various areas of lighting: lighting in office buildings, libraries museums. We show that renewable energy strategy in the field of lighting not only produce energy save, also produce good effects in other aspects of human life like well-being, productivity and heritage conservation.
Iluminar obras de arte mejorando la conservación. El proyecto Zeus
(2015) Benítez, Anton J.; Vázquez Moliní, Daniel; Álvarez Fernández-Balbuena, Antonio
La iluminación de obras de arte se enfrenta al reto de resultar adecuada para la exhibición y de minimizar en lo posible los daños a la superficie y los materiales que las componen. En esta encrucijada, en la que la investigación es imprescindible tanto en tecnología como acerca de la recepción por parte del público, el proyecto Zeus trata de obtener una precisa información sobre el color de la obra, y trasladarla a un modelo de iluminación individualizado punto a punto, que permite simular condiciones precisas y compensar efectos indeseables del deterioro, minimizando la luz absorbida por la obra.
Improvement of driver night vision in foggy environments by structured light projection
(Heliyon, 2022) Quintana Benito, Jaime; Álvarez Fernández-Balbuena, Antonio; Martínez Antón, Juan Carlos; Vázquez Moliní, Daniel
Nowadays, fog is still a natural phenomenon that hinders our ability to detect targets, particularly in the field of driving where accidents are increasing. In the literature we find different studies determining the range of visibility, improving the quality of an image, determining the characteristics of fog, etc. In this work we propose the possibility of using a structured lighting system, on which we project the light towards the target, limiting the field lighting. We have developed a scattering light propagation model to simulate and subsequently study the veil luminance, generated by backscattering, to predict the decrease in visibility. This simulation considers the type of fog, the relative orientation of various elements (observer, light source and targets). We have built a fog chamber to validate the experimental params of the described system. The results obtained from both the simulation and the experimental measurements demonstrate that it is possible to obtain a high contrast enhancement for viewing a target when illuminated as described. Clearly, this kind of lighting technology will improve the road safety in foggy night environments. The results of this work can also be extrapolated to any situation in which the visibility of an observer is compromised by the environment, such as heavy rain, smoke from fires, among others.
High-Dynamic-Range Spectral Reflectance for the Segmentation of Paint Pigment: Application to Dalí’s Oil Painting Dos Figuras (1926)
(Sensors, 2023) Álvarez Fernandez-Balbuena, Antonio; Gómez Manzanares, Ana; Martínez Antón, Juan Carlos; García Gómez-Tejedor, Jorge; Mayorga Pinilla, Santiago; Durán Roque, Humberto; Vázquez Moliní, Daniel; Álvarez Fernández-Balbuena, Antonio; Martínez Antón, Juan Carlos; Vázquez Molini, Daniel
Restorers and curators in museums sometimes find it difficult to accurately segment areas of paintings that have been contaminated with other pigments or areas that need to be restored, and work on the painting needs to be carried out with minimum possible damage. It is therefore necessary to develop measurement systems and methods that facilitate this task in the least invasive way possible. The aim of this study was to obtain high-dynamic-range (HDR) spectral reflectance and spatial resolution for Dalí’s painting entitled Two Figures (1926) in order to segment a small area of black and white pigment that was affected by the contact transfer of reddish pigment from another painting. Using Hypermatrixcam to measure the HDR spectral reflectance developed by this research team, an HDR multispectral cube of 12 images was obtained for the band 470–690 nm in steps of 20 nm. With the values obtained for the spectral reflectance of the HDR cube, the colour of the area of paint affected by the transfer was studied by calculating the a*b* components with the CIELab system. These a*b* values were then used to define two methods of segmenting the exact areas in which there was a transfer of reddish pigment. The area studied in the painting was originally black, and the contamination with reddish pigment occupied 13.87% to 32% of the total area depending on the selected method. These different solutions can be explained because the lower limit is segmentation based on pure pigment and the upper limit considers red as an exclusion of non-black pigment. Over- and under-segmentation is a common problem described in the literature related to pigment selection. In this application case, as red pigment is not original and should be removed, curators will choose the method that selects the highest red area.
Application of dynamic merit function to nonimaging systems optimization
(Optical Engineering, 2015) Álvarez Fernández-Balbuena, Antonio; González Montes, Mario; García Botella, Ángel; Vázquez Moliní, Daniel
Automatic optimization algorithms have been recently introduced as nonimaging optics design techniques. Unlike optimization of imaging systems, nonsequential ray tracing simulations and complex noncentered systems design must be considered, adding complexity to the problem. The merit function is a key element in the automatic optimization algorithm; nevertheless, the selection of each objective’s weight, {wi}{wi}, inside the merit function needs a prior trial and error process for each optimization. The problem then is to determine appropriate weights’ values for each objective. We propose a new dynamic merit function with variable weight factors {wi(n)}{wi(n)}. The proposed algorithm automatically adapts weight factors during the evolution of the optimization process. This dynamic merit function avoids the previous trial and error procedure by selecting the right merit function and provides better results than conventional merit functions.
Measuring the absorption coefficient of optical materials with arbitrary shape or distribution within an integrating sphere
(Optics Express, 2021) Martínez Antón, Juan Carlos; Gómez Manzanares, Ángela; Álvarez Fernández-Balbuena, Antonio; Vázquez Moliní, Daniel
The absorption coefficient of a material is classically determined by measuring the transmittance of a homogeneous sample contained within flat optical faces and under collimated illumination. For arbitrary shapes this method is impracticable. The characterization of inhomogeneous or randomly distributed samples such as granules, powders or fibers suffers the same problem. Alternatively, an integrating cavity permits us to illuminate a sample under a homogenous and isotropic light field where the analysis simplifies. We revisit this strategy and present a new formal basis based on simple radiometric laws and principles. We introduce a new concept to describe the absorption: the optical form factor. We tackle a rigorous treatment of several regular forms, including full absorption range and the reflection at its surfaces. We also model and improve an integrating sphere setup to perform reliable measurements. Altogether, it permits achieving simple but general conclusions for samples with arbitrary shape or spatial distribution, from weak to highly absorbing, expanding the applicability of quantitative absorption spectroscopy. Finally, we validate it by measuring different sample formats made of PMMA: a cube, groups of granules and injection molding loose parts. The absorption coefficient of PMMA varies near three orders of magnitude in the explored range (380-1650 nm).
Determination of the characteristic inactivation fluence for SARS-CoV-2 under UV-C radiation considering light absorption in culture media
(Scientific reports, 2021) Martínez Antón, Juan Carlos; Brun Torres, Alejandro; Vázquez Moliní, Daniel; Moreno Fernández, Sandra; Álvarez Fernández-Balbuena, Antonio; Alda, Javier
The optical absorption coefficient of culture media is critical for the survival analysis of pathogens under optical irradiation. The quality of the results obtained from experiments relies on the optical analysis of the spatial distribution of fluence which also depends on the geometry of the sample. In this contribution, we consider both the geometrical shape and the culture medium’s absorptivity to evaluate how the spatial distribution of optical radiation affects pathogens/viruses. In this work, we exposed SARS-CoV-2 to UV-C radiation (λ =254 nm) and we calculated – considering the influence of the optical absorption of the culture medium – a characteristic inactivation fluence of F i =4.7 J/m2 , or an equivalent 10% survival (D90 dose) of 10.8 J/m2. Experimentally, we diluted the virus into sessile drops of Dulbecco’s Modified Eagle Medium to evaluate pathogen activity after controlled doses of UV irradiation. To validate the optical absorption mode, we carried out an additional experiment where we varied droplet size. Our model – including optical absorption and geometrical considerations – provides robust results among a variety of experimental situations, and represents our experimental conditions more accurately. These results will help to evaluate the capability of UV disinfecting strategies applied to a variety of everyday situations, including the case of micro-droplets generated by respiratory functions.