Person:
Martínez Antón, Juan Carlos

First Name

Juan Carlos

Last Name

Martínez Antón

URI

https://hdl.handle.net/20.500.14352/79892

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Óptica y Optometría

Department

Óptica

Area

Optica

Identifiers

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Now showing 1 - 10 of 14

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.
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.
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, Stuart
Recent 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.
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.
Problemática fotométrica y conceptual de los sistemas de desinfección basados en radiación UV-C
(2022) Vázquez Moliní, Daniel; Álvarez Fernández-Balbuena, Antonio; Martínez Antón, Juan Carlos; Brun Torres, Alejandro; Moreno Fernández, Sandra; Prada, Luis; Estrada, Luis; Ruiz, Martina; Mayorga Pinilla, Santiago; Alda, Javier
La pandemia creada por el COVID19 ha puesto de actualidad nuevamente los sistemas de desinfección basados en el empleo de radiación ultravioleta de tipo C. Esta es una tecnología ampliamente conocida y empleada profusamente en determinados sectores desde el primer tercio del siglo XX. No obstante, la necesidad urgente de una aplicación extensiva junto con la existencia de nuevas tecnologías de control y caracterización, ha generado un nuevo escenario que debe ser analizado en detalle. En el presente trabajo se ha caracterizado el nivel de radiación para desinfección de un determinado nivel de eficacia, el efecto de la radiación sobre diversos materiales, la caracterización radiométrica de dispositivos y las herramientas de simulación necesarias.
Geometrical limits for UV-C inactivation of pathogens
(Optik, 2022) Quintana Benito, Jaime; Álvarez Fernández-Balbuena, Antonio; Martínez Antón, Juan Carlos; Vázquez Moliní, Daniel; Prada, Luis; Estrada, Luis; Alda Serrano, Javier
The inactivation of pathogens through the irradiation of ultraviolet light depends on how light propagates within the medium where the microorganism is immersed. A simple geometrical optics analysis, and a fluence evaluation reveal some reservoirs where the pathogen may hide and be weakly exposed to the incoming radiation. This geometrical hide-outs also generate a tail in the plot of the total inactivation plot vs. the incoming fluence. We have analyzed these facts using geometrical optics principles and illumination engineering computational packages. The results obtained from previous biomedical measurements involving SARS-CoV-2 have been used to evaluate the inactivation degree for an spherical geometry applicable to airborne pathogens, and for an spherical cap geometry similar to that used in biomedical experiments. The case presented here can be seen as the worst-case scenario applicable under collimated illumination.
Light losses in hollow, prismatic light guides related to prim defects: a transmittance model
(Chinese Optics Letters, 2015) García Fernández, Berta; Vázquez Moliní, Daniel; Álvarez Fernández-Balbuena, Antonio; García Botella, Ángel; Martínez Antón, Juan Carlos
Hollow, cylindrical, prismatic light guides (CPLGs) are optical components that, using total internal reflection (TIR), are able to transmit high-diameter light beams in daylight and artificial lighting applications without relevant losses. It is necessary to study the prism defects of their surfaces to quantify the behavior of these optical components. In this Letter, we analyze a CPLG made of a transparent dielectric material. Scanning electron microscopy (SEM) and the topographic optical profilometry by absorption in fluids (TOPAF) imaging technique are conducted to determine if there are defects in the corners of the prisms. A model for light guide transmittance that is dependent on prism defects is proposed. Finally, a simulation and an experimental study are carried out to check the validity of the proposed model.
Method for the characterization of Fresnel lens flux transfer performance
(Proceedings of SPIE, 2011) Martínez Antón, Juan Carlos; Vázquez Moliní, Daniel; Muñóz de la Luna, Javier; Gómez Pedrero, José Antonio; Álvarez Fernández-Balbuena, Antonio
Fresnel lenses and other faceted or micro-optic devices are increasingly used in multiple applications like solar light concentrators and illumination devices, just to name some representative. However, it seems to be a certain lack of adequate techniques for the assessment of the performance of final fabricated devices. As applications are more exigent this characterization is a must. We provide a technique to characterize the performance of Fresnel lenses, as light collection devices. The basis for the method is a configuration where a camera images the Fresnel lens aperture. The entrance pupil of the camera is situated at the focal spot or the conjugate of a simulated solar source. In this manner, detailed maps of the performance of different Fresnel lenses are obtained for different acceptance angles.