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Light-emitting diodes (LEDs) play a major role in many applications where intense light irradiation is necessary. There are several LED radiation pattern models, which are widely used, but are valid only for far-field. In this work, we... more
Light-emitting diodes (LEDs) play a major role in many applications where intense light irradiation is necessary. There are several LED radiation pattern models, which are widely used, but are valid only for far-field. In this work, we propose a mathematical model for the spatial distribution of irradiance of LEDs at near working distances.
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Ray tracing in a metasurface is the process to obtain the three-dimensional (3D) light path under reflection and transmission, which may be helpful in the optical design of metalenses and other metaoptical devices. In this work, first we... more
Ray tracing in a metasurface is the process to obtain the three-dimensional (3D) light path under reflection and transmission, which may be helpful in the optical design of metalenses and other metaoptical devices. In this work, first we deduce the 3D vector form of Snell's law for metasurfaces by using a geometric approach. And then, we deduce the general equations to calculate the direction of the reflected and refracted beams in any metasurface, and for any incident beam. In other words, we derive vector form equations for the 3D direction of transmitted and reflected beams at a metasurface with arbitrary 2D phase profile, and for any 3D direction of incident light.
Research Interests: Physics, Optics, Ray Tracing, Law of refraction, Geometrical Optics, and 3 moreRay, Metasurface, and metalens
Ray tracing in a metasurface is the process to obtain the three-dimensional (3D) light path under reflection and transmission, which may be helpful in the optical design of metalenses and other metaoptical devices. In this work, first we... more
Ray tracing in a metasurface is the process to obtain the three-dimensional (3D) light path under reflection and transmission, which may be helpful in the optical design of metalenses and other metaoptical devices. In this work, first we deduce the 3D vector form of Snell's law for metasurfaces by using a geometric approach. And then, we deduce the general equations to calculate the direction of the reflected and refracted beams in any metasurface, and for any incident beam. In other words, we derive vector form equations for the 3D direction of transmitted and reflected beams at a metasurface with arbitrary 2D phase profile, and for any 3D direction of incident light.
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Aggregates of superparamagnetic colloids confined in liposomes in the presence of a controllable external magnetic field are studied here by computer simulation. A model of a hard sphere with a central dipole has been used to simulate... more
Aggregates of superparamagnetic colloids confined in liposomes in the presence of a controllable external magnetic field are studied here by computer simulation. A model of a hard sphere with a central dipole has been used to simulate secondary particles of colloids confined to move within a liposome, which is modelled as a hard spherical cavity. We focus our study on the structure of aggregates created by secondary particles, which in turn are formed by superparamagnetic particles. This study was performed by using the conventional Monte Carlo simulations and the cluster-moving Monte Carlo method. The results obtained with both methods show a dependence on the number of particles and on the ratio cavity-colloid diameters. However, the usual Monte Carlo method does not allow the collective movement of the aggregates. The simulation results show, that for the particular case of the liposome diameter obtained from the experiments , the formation of a single ribbons located at the centre of the cavity for N = 30 and N = 60. In addition, we analyse the structure formation for different values of , the equilibrium structures are chains for systems for lower , whereas ribbons formation are structures of equilibrium for . GRAPHICAL ABSTRACT
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In this work, we deduce an exact analytical solution of irradiance produced by a Lambertian rectangular source at short distances, which may approximate the irradiance of a typical light-emitting diode (LED) with rectangular shape.
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Many emerging light-emitting diode (LED) applications require short-distance illumination. For that, we derive an exact formula of the illumination profile produced by Lambertian LEDs, in which all parameters are fundamental constants.... more
Many emerging light-emitting diode (LED) applications require short-distance illumination. For that, we derive an exact formula of the illumination profile produced by Lambertian LEDs, in which all parameters are fundamental constants. Moreover, we propose a general, simple, but accurate mathematical model of the irradiance pattern, valid for Lambertian and non-Lambertian LEDs at short distances. This model provides the irradiance profile as a function of both the LED-target distance and the coordinates of every point on the irradiated surface. The model is formulated in terms of simple sigmoid functions, in which LED size and light flux are fundamental parameters. The accuracy of the irradiance pattern model is tested both with theory and with experimental measurements.
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Strong emission of green light in ceramic glass was obtained. The intensity of the emitted signal changes with the heat treatment temperature.
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Strong green-yellow emission in Eu2+ doped glass ceramic as a function of rare earth concentration was obtained. Proof of concept for solid state white lighting with high power AC LED was fabricated.
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Convolutional neural networks (CNNs) and digital holographic interferometry (DHI) can be combined to improve the calculation efficiency and to simplify the procedures of many DHI applications. In DHI, for the measurements of concentration... more
Convolutional neural networks (CNNs) and digital holographic interferometry (DHI) can be combined to improve the calculation efficiency and to simplify the procedures of many DHI applications. In DHI, for the measurements of concentration differences between liquid samples, two or more holograms are compared to find the difference phases among them, and then to estimate the concentration values. However, liquid samples with high concentration difference values are difficult to calculate using common phase unwrapping methods as they have high spatial frequencies. In this research, a new method to skip the phase unwrapping process in DHI, based on CNNs, is proposed. For this, images acquired by Guerrero-Mendez et al. (Metrology and Measurement Systems 24, 19–26, 2017) were used to train the CNN, and a multiple linear regression algorithm was fitted to estimate the concentration values for liquid samples. In addition, new images were recorded to evaluate the performance of the proposed...
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A multichip light-emitting diode (LED) should not be treated as a point source at short-distance illumination. For that, we propose a general, simple, but accurate mathematical model of the irradiance spatial distribution for multichip... more
A multichip light-emitting diode (LED) should not be treated as a point source at short-distance illumination. For that, we propose a general, simple, but accurate mathematical model of the irradiance spatial distribution for multichip LEDs, valid at very short distance illumination. This model provides the irradiance profile as a function of both the LED-target distance and the coordinates of every point on the irradiated surface. The model is formulated in function of the chip array geometry, number chips, multichip LED size, and light flux. The accuracy of the irradiance pattern model is tested both with theory and with experimental measurements.
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Resumen es: Al planear un experimento con la tecnica fotopiroelectrica, se deben encontrar los parametros adecuados del equipo de medicion para evitar la distorsion ...
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We have implemented an exact ray trace through a plano-freeform surface for an incident plane wavefront. We obtain two caustic surfaces and provide the critical points related to the ray tracing process. Additionally, we study the... more
We have implemented an exact ray trace through a plano-freeform surface for an incident plane wavefront. We obtain two caustic surfaces and provide the critical points related to the ray tracing process. Additionally, we study the propagation of the refracted wavefronts through the plane-curved surface. Finally, by using the Ronchi-Hartmann type null screen and placing the detection plane within the caustic region, we have evaluated the shape of a plano-freeform optical surface under test, obtaining an RMS difference in sagitta value of 6.3 μm.
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To date, many studies on the optimization of the spectral power distributions (SPDs) have been conducted to maximize the energy performance and color quality of white light-emitting diodes (LEDs). Here, not only for LEDs but for any light... more
To date, many studies on the optimization of the spectral power distributions (SPDs) have been conducted to maximize the energy performance and color quality of white light-emitting diodes (LEDs). Here, not only for LEDs but for any light source, we numerically calculate the SPDs which maximize luminous efficacy of radiation (LER) in function of the color rendering index and of color temperature. As previously reported in the literature, we obtain optimal SPDs that are discrete spectra rather than continuous, but with considerably higher LER values. Such optimal SPDs may be used to design various lighting technologies: incandescent, fluorescent, high-intensity discharge, laser, and solid-state lighting.
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A method for modeling the irradiance spatial distribution by light-emitting diodes (LEDs) on near distance targets has been developed. The model can easily handle the complex simulation of non-homogenous emitting LEDs, multichip LEDs, LED... more
A method for modeling the irradiance spatial distribution by light-emitting diodes (LEDs) on near distance targets has been developed. The model can easily handle the complex simulation of non-homogenous emitting LEDs, multichip LEDs, LED arrays, and phosphor coated LEDs. The LED irradiation profile is obtained by image processing one photograph of the emitting LED, taken with a smartphone. The method uses image convolution or image correlation between the LED image and a special kernel. The model provides the irradiation spatial pattern in function of the irradiation distance. And the model is tested both with theory and with experimental measurements.
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So far, metalenses have only been studied in imaging optics, where a point from the object space is mapped to a corresponding point in the image space. Here we explore metalenses and metamirrors for dealing with the optimal transfer of... more
So far, metalenses have only been studied in imaging optics, where a point from the object space is mapped to a corresponding point in the image space. Here we explore metalenses and metamirrors for dealing with the optimal transfer of light energy. Owing to its compactness and high design flexibility, metasurface-based flat optics may open new opportunities in the nonimaging field, which deals with light concentration and illumination. The building blocks of metalenses are subwavelength-spaced scatterers. By suitably adjusting their shape, size, position, and orientation , one can control the light spatial distribution, as is desired in nonimaging problems. In this Letter, we introduce nonimaging metaoptics, review its basics, and briefly explore three cases: the compound-metasurface concentra-tor [analogous to the compound parabolic concentrator (CPC)], the total internal reflection (TIR) metalens (analogous to the TIR lens), and a simple condensing metalens.
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Many emerging light-emitting diode (LED) applications require short-distance illumination. For that, we derive an exact formula of the illumination profile produced by Lambertian LEDs, in which all parameters are fundamental constants.... more
Many emerging light-emitting diode (LED) applications require short-distance illumination. For that, we derive an exact formula of the illumination profile produced by Lambertian LEDs, in which all parameters are fundamental constants. Moreover, we propose a general, simple, but accurate mathematical model of the irradiance pattern, valid for Lambertian and non-Lambertian LEDs at short distances. This model provides the irradiance profile as a function of both the LED-target distance and the coordinates of every point on the irradiated surface. The model is formulated in terms of simple sigmoid functions, in which LED size and light flux are fundamental parameters. The accuracy of the irradiance pattern model is tested both with theory and with experimental measurements.
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Many emerging light-emitting diode (LED) applications require short-distance illumination. For that, we derive an exact formula of the illumination profile produced by Lambertian LEDs, in which all parameters are fundamental constants.... more
Many emerging light-emitting diode (LED) applications require short-distance illumination. For that, we derive an exact formula of the illumination profile produced by Lambertian LEDs, in which all parameters are fundamental constants. Moreover, we propose a general, simple, but accurate mathematical model of the irradiance pattern, valid for Lambertian and non-Lambertian LEDs at short distances. This model provides the irradiance profile as a function of both the LED-target distance and the coordinates of every point on the irradiated surface. The model is formulated in terms of simple sigmoid functions, in which LED size and light flux are fundamental parameters. The accuracy of the irradiance pattern model is tested both with theory and with experimental measurements.
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An analytical expression is derived for the tilt introduced into a wave front by a Dove prism with manufacturing errors in the prism's base angles and pyramidal angle. We found that the tilt decreases when the base angles are... more
An analytical expression is derived for the tilt introduced into a wave front by a Dove prism with manufacturing errors in the prism's base angles and pyramidal angle. We found that the tilt decreases when the base angles are increased above the values of traditional design. The increase in the length-aperture ratio of a prism is detrimental to the prism's performance. However, a Dove prism with a widened aperture increases throughput and maintains a manageable prism weight for implementation in a rotational shearing interferometer. Thus we propose a Dove prism designed with a widened aperture to increase throughput in a rotational shearing interferometer and with larger base angles to minimize the wave-front tilt introduced by manufacturing errors. Experimental results implemented in a rotational shearing interferometer demonstrate the feasibility of this design.
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A single-chip white light LED is commonly modeled by considering the phosphor coating as a homogeneous Lambertian light source. However, this approach leads to an incorrect optical simulation of phosphor-coated multi-chip LEDs due to the... more
A single-chip white light LED is commonly modeled by considering the phosphor coating as a homogeneous Lambertian light source. However, this approach leads to an incorrect optical simulation of phosphor-coated multi-chip LEDs due to the presence of a previously ...
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ABSTRACT A novel light luminaire is proposed and experimentally analyzed, which efficiently mixes and projects the tunable light from red, green and blue (RGB) light-emitting diodes (LEDs). Simultaneous light collimation and color mixing... more
ABSTRACT A novel light luminaire is proposed and experimentally analyzed, which efficiently mixes and projects the tunable light from red, green and blue (RGB) light-emitting diodes (LEDs). Simultaneous light collimation and color mixing is a challenging task because most collimators separate colors, and most color mixers spread the light beam. We performed an experimental study to find a balance between optical efficiency and color uniformity by changing light recycling and color mixing.