The Experts below are selected from a list of 321 Experts worldwide ranked by ideXlab platform
Erkki Ikonen - One of the best experts on this subject based on the ideXlab platform.
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multifunctional integrating sphere setup for Luminous Flux measurements of light emitting diodes
Review of Scientific Instruments, 2010Co-Authors: Tuomas Poikonen, Pasi Manninen, Petri Karha, Erkki IkonenAbstract:A multifunctional setup based on the absolute integrating sphere method for measuring Luminous Flux of light emitting diodes (LEDs) is presented. The total Luminous Flux in 2π and 4π geometries and partial Luminous Flux with variable cone angle can be measured with the same custom-made integrating sphere. The number and area of ports and baffles of the sphere was minimized. The sphere has three ports: a main port, a detector port, and an auxiliary port, located in the same hemisphere. The other hemisphere is free of ports. The main port is used for the calibration of the sphere as well as for the LED under test. Only one absolute calibration of the integrating sphere photometer is needed for measuring LEDs in all three geometries. The spatial nonuniformity correction is needed only for LEDs with low directivity or having significant minor beams. The expanded uncertainty (k=2) for the measurement setup varies between 1.2% and 4.6% depending on the measurement geometry, color, and the angular spread of the ...
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realization of the unit of Luminous Flux at the hut using the absolute integrating sphere method
Metrologia, 2004Co-Authors: Jari Hovila, P Toivanen, Erkki IkonenAbstract:A description of a detector-based realization of the unit of Luminous Flux (lumen) at the Helsinki University of Technology (HUT) is presented. The realization is based on the absolute integrating-sphere method developed at the National Institute of Standards and Technology (NIST), with some modifications. The measurement set-up consists of a 1.65 m integrating sphere, two photometers, a precision aperture and an external Luminous-Flux source. The characterization and maintenance of the measurement system are described and the uncertainty budget of the realization is presented. The uncertainty analysis indicates a relative expanded uncertainty (k = 2) of 4.7 × 10−3 for the realization. According to the results of an earlier bilateral comparison between the HUT and the NIST, the ratio of the measured Luminous Flux value of HUT to that of NIST was 1.0006 with an expanded uncertainty (k = 2) of 10 × 10−3, including uncertainties due to realization of the units. Another indirect test measurement indicated a corresponding ratio of 0.9984 with the Luminous Flux measurements of BIPM with an expanded uncertainty (k = 2) of 11 × 10−3, including uncertainties due to realization of the units.
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International comparison of the illuminance responsivity scales and units of Luminous Flux maintained at the HUT (Finland) and the NIST (USA)
Metrologia, 2002Co-Authors: Jari Hovila, Erkki Ikonen, P Toivanen, Yoshi OhnoAbstract:An international comparison has been conducted to compare the illuminance responsivity scales (A/lx) and the units of Luminous Flux (lm) maintained at the National Institute of Standards and Technology (NIST, USA) and the Helsinki University of Technology (HUT, Finland). Both laboratories realize the illuminance unit by absolutely calibrated photometers and the Luminous Flux unit by the absolute integrating-sphere method. Standard photometers were used as transfer standards for the illuminance responsivity comparison, and standard lamps in the Luminous Flux comparison. The ratio of the measured illuminance responsivity values (HUT/NIST) was 0.9992 with an expanded uncertainty (k = 2) of 0.0013, and the ratio of the measured Luminous Flux values was 1.0006 with an expanded uncertainty (k = 2) of 0.0018. The relative expanded uncertainties of the agreement of the units, including the uncertainties of the realizations of the units as well as the uncertainty of the comparison, were 0.0047 and 0.0101, respectively.
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Realization of the Luminous-Flux unit using a LED scanner for the absolute integrating-sphere method
Metrologia, 2000Co-Authors: K. Lahti, Jari Hovila, P Toivanen, E. Vahala, Ilkka Tittonen, Erkki IkonenAbstract:In the absolute integrating-sphere method, the total Luminous Flux of a lamp inside an integrating sphere is determined by comparing it with a known Flux introduced into the sphere from an external light source. As the measurement geometry of the lamps to be compared is different, the spatial non-uniformity of the sphere surface may affect the results. In order to evaluate this effect, the spatial response must be measured. Miniature incandescent lamps have been used as scanning-beam sources in previous realizations, but these lamps are not widely available. In the present realization of the Luminous-Flux unit by the Helsinki University of Technology (HUT), light-emitting diodes (LEDs) were used as the light source in scanning the spatial response. Preliminary results confirm the applicability of the LED scanner and indicate moderate deviations of about 1 % from earlier Luminous-Flux calibrations.
Maciej Zajkowski - One of the best experts on this subject based on the ideXlab platform.
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The Concept of Measuring Luminous Flux Distribution Emitted from Sports Facilities Using Unmanned Aerial Vehicles
Lecture Notes in Electrical Engineering, 2019Co-Authors: M. Sielachowska, Damian Tyniecki, Maciej ZajkowskiAbstract:The dynamic development of cities is associated with a significant increase in the luminance of architectural buildings, advertisements or usable spaces. Objects that emit a significant amount of Luminous Flux to the environment are also various types of sports buildings, such as city stadiums, football pitches or tennis courts. The need to protect the environment determinates the need to reduce and prevent the effect of light pollution. The article analyzes the possibilities of using unmanned aerial vehicles to assess light pollution by measuring the distribution of Luminous Flux emitted by sports facilities. The method of light measurement based on a goniometric system using unmanned aerial vehicles was presented and their positioning in three-dimensional space was taken into account. A method for controlling the photometric probe and calibrating the measurement system has been proposed.
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Luminous Flux ring mixer
2016 IEEE Lighting Conference of the Visegrad Countries (Lumen V4), 2016Co-Authors: Maciej Zajkowski, Łukasz Budzyński, Damian TynieckiAbstract:LED modules emitting a Luminous Flux, implement near-field luminance distribution or colorimetric distribution depending on emitters location. In the far field there is complete mixing of Luminous Flux, both in terms of quantity as well as because of distribution color parameters. To achieve these mixing light in a short distance of the LEDs is necessary to use optical elements. The article presents the results of creating light distribution and luminance by using the ring optical elements.
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Luminous Flux of the side optical fiber with scattering layers
Optical Fibers and Their Applications 2014, 2014Co-Authors: Maciej ZajkowskiAbstract:The basic, well-known of the fiber task is to transmit the optical signal along an optical fiber. To achieve this, you should reduce energy losses which result from reflections on the border of core - clad. However, in some cases, the light output can be derived by side surface the fiber. Luminous Flux through side surface of optical fiber is realized in many ways. It is possible to change local shape of cylindrical fiber or scattering light on border between core and clad. Side optical fiber with helical spiral core have a different way of side emission. It is the result of controlled scattering inside the optical fiber [1].
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Luminous Flux emission calculation analysis in side light illumination optical fibers
Photonics applications in astronomy communications industry and high-energy physics experiments. COnference, 2005Co-Authors: Maciej ZajkowskiAbstract:The following paper presents results of simulations and calculations of the Monte Carlo based Flux method employed for analysis of the Luminous Flux distribution in "side-light" optical fibers. The characteristics of the Luminous Flux emitted from the side surface of the optical fiber were presented for various total, internal reflection coefficients and variable geometric parameters.
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Characteristics of the Luminous Flux for side-light optical fibers
2004Co-Authors: Maciej ZajkowskiAbstract:This article aims at presenting the attempt of quantitative description of Luminous Flux distribution in the side-light optical fibers. The basic relations, regarding emission of the Luminous Flux are presented here. Construction of an algorithm, aiming at calculating balance of the radiation emitted from side-light optical fiber, was proposed.
Guoqi Zhang - One of the best experts on this subject based on the ideXlab platform.
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Predicting of Luminous Flux for a LED array using artificial neural network
2020 21st International Conference on Thermal Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE), 2020Co-Authors: Weiyi Yuan, Wei Chen, Min Li, Guoqi ZhangAbstract:Because of its compact size, low power consumption, fast response, and high reliability, light-emitting diode (LED) becomes a new generation of light source to replace the traditional ones. To meet the needs of high illumination, the LED array is often used in light module. However, high temperature and high current will result in the Luminous efficacy depreciation of the LED array module. This study proposes the artificial neural network (ANN) methods to predict the Luminous Flux of the LED array module and their accuracies are verified under different operation conditions. In detail, the Back Propagation (BP) and Genetic Algorithm-Back Propagation (GA-BP) NNs are firstly applied regarding the case temperature and current as inputs. Then, the feasibilities of the proposed methods are verified and compared. The results show that: 1) the Luminous Flux prediction accuracies of BP and GA-BP NNs are all higher than 98.5%; 2) compared to BP NN, GA-BP NN has higher prediction accuracy but costs more computation time.
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Reliability Assessment of Light-Emitting Diode Packages With Both Luminous Flux Response Surface Model and Spectral Power Distribution Method
IEEE Access, 2019Co-Authors: Wei Chen, Bin Pu, Cheng Qian, Guoqi ZhangAbstract:The inherent Luminous characteristics and stability of LED packages during the operation period are highly dependent on their junction temperatures and driving currents. In this paper, the Luminous Flux of LED packages operated under a wide range of driving currents and junction temperatures are investigated to develop a Luminous Flux response surface model. The coefficients of the proposed model are further extracted to compare the Luminous efficacy decay mechanisms of LED packages with different packaging structures. Furthermore, a spectral power distribution (SPD) method modeled by the Gaussian function is proposed to analyze the long-term degradation mechanisms of all selected LED packages. The results of this study show that: (1) The Luminous Flux of phosphor converted white LED decreases to accompany with the increase of junction temperature, while that of bare blue LED die keeps relatively stable; (2) The proposed general Luminous Flux response surface model can be used to predict the Luminous Flux of LEDs with different packaging technologies accurately, and it can be known from the proposed model that the influences of driving current and temperature on LED chip and phosphor vary with different packaging structures; and (3) The driving current and temperature dependent sensitivities and degradation mechanisms of LED packages can be investigated by using both the Luminous Flux response surface model and the spectral power distribution method.
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Luminous Flux modeling for high power LED automotive headlamp module
2017 18th International Conference on Electronic Packaging Technology (ICEPT), 2017Co-Authors: Chaohua Yu, Cheng Qian, Guoqi ZhangAbstract:The development of automotive lighting systems with high illumination quality and high reliability is essential for driving safe and comfort. LEDs have many superiorities over the traditional light sources, such as high reliability, good color quality, long lifetime, energy and space saving, environment friendly and so on, when they are operated under an effective health management (such as thermal, electrical and optical managements). In the recent decades, LEDs have been widely applied in automotive as dashboard lightings, interior and exterior signal lightings. However, when they are introduced as a light source into automotive headlight system, LEDs must be required to have both high Luminous Flux (>1000 lm for low beam) and high thermal stability, because automotive headlamps are always installed near engine and their typical ambient temperature is about 80°C. The Luminous Flux model has often been used to describe the light output behavior of a LED as function of the driven current (If) and junction temperature (Tj), which can be used to represent LED's state of performance. This paper introduces the Luminous Flux model for a high power LED automotive headlamp module. Firstly, the junction temperatures of LED modules are estimated and verified under the conditions of different driven currents and case temperatures (Tc). The characterization data with the measured Luminous Flux (Φ), the estimated Tj and If are then used to estimate the coefficients in the Luminous Flux models with the Goodness-of-Fit method. The result shows that the modified Luminous Flux model can describe the actual nonlinearity of LED's Luminous Flux when it is operated at the condition of high temperature and high driven current.
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Prediction of a statistical distribution of Luminous Flux for LED modules with an analytical model
2015 First International Conference on Reliability Systems Engineering (ICRSE), 2015Co-Authors: Cheng Qian, Guoqi Zhang, Jinmin LiAbstract:In this paper, an analytical model is developed to predict the statistical distribution of the Luminous Flux of LED modules based on the statistical properties of their components. This proposed model has only one parameter C which can be easily extracted from a single test on an LED lighting module. To validate the proposed model, ray-tracing optical simulations were performed on a number of ideal LED modules. In each ideal LED module, the Luminous Flux of the LED package, the transmittance of the lens and reflectance of the substrate were assumed as some specific distributions. The results show great agreements between the simulation results and the model predictions on the Luminous Flux distribution of the ideal LED modules. Thus, this proposed model has the advantage of effectively predicting the Luminous Flux distribution of LED lighting modules, provided the statistical properties of their components are known.
Jari Hovila - One of the best experts on this subject based on the ideXlab platform.
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realization of the unit of Luminous Flux at the hut using the absolute integrating sphere method
Metrologia, 2004Co-Authors: Jari Hovila, P Toivanen, Erkki IkonenAbstract:A description of a detector-based realization of the unit of Luminous Flux (lumen) at the Helsinki University of Technology (HUT) is presented. The realization is based on the absolute integrating-sphere method developed at the National Institute of Standards and Technology (NIST), with some modifications. The measurement set-up consists of a 1.65 m integrating sphere, two photometers, a precision aperture and an external Luminous-Flux source. The characterization and maintenance of the measurement system are described and the uncertainty budget of the realization is presented. The uncertainty analysis indicates a relative expanded uncertainty (k = 2) of 4.7 × 10−3 for the realization. According to the results of an earlier bilateral comparison between the HUT and the NIST, the ratio of the measured Luminous Flux value of HUT to that of NIST was 1.0006 with an expanded uncertainty (k = 2) of 10 × 10−3, including uncertainties due to realization of the units. Another indirect test measurement indicated a corresponding ratio of 0.9984 with the Luminous Flux measurements of BIPM with an expanded uncertainty (k = 2) of 11 × 10−3, including uncertainties due to realization of the units.
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International comparison of the illuminance responsivity scales and units of Luminous Flux maintained at the HUT (Finland) and the NIST (USA)
Metrologia, 2002Co-Authors: Jari Hovila, Erkki Ikonen, P Toivanen, Yoshi OhnoAbstract:An international comparison has been conducted to compare the illuminance responsivity scales (A/lx) and the units of Luminous Flux (lm) maintained at the National Institute of Standards and Technology (NIST, USA) and the Helsinki University of Technology (HUT, Finland). Both laboratories realize the illuminance unit by absolutely calibrated photometers and the Luminous Flux unit by the absolute integrating-sphere method. Standard photometers were used as transfer standards for the illuminance responsivity comparison, and standard lamps in the Luminous Flux comparison. The ratio of the measured illuminance responsivity values (HUT/NIST) was 0.9992 with an expanded uncertainty (k = 2) of 0.0013, and the ratio of the measured Luminous Flux values was 1.0006 with an expanded uncertainty (k = 2) of 0.0018. The relative expanded uncertainties of the agreement of the units, including the uncertainties of the realizations of the units as well as the uncertainty of the comparison, were 0.0047 and 0.0101, respectively.
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Realization of the Luminous-Flux unit using a LED scanner for the absolute integrating-sphere method
Metrologia, 2000Co-Authors: K. Lahti, Jari Hovila, P Toivanen, E. Vahala, Ilkka Tittonen, Erkki IkonenAbstract:In the absolute integrating-sphere method, the total Luminous Flux of a lamp inside an integrating sphere is determined by comparing it with a known Flux introduced into the sphere from an external light source. As the measurement geometry of the lamps to be compared is different, the spatial non-uniformity of the sphere surface may affect the results. In order to evaluate this effect, the spatial response must be measured. Miniature incandescent lamps have been used as scanning-beam sources in previous realizations, but these lamps are not widely available. In the present realization of the Luminous-Flux unit by the Helsinki University of Technology (HUT), light-emitting diodes (LEDs) were used as the light source in scanning the spatial response. Preliminary results confirm the applicability of the LED scanner and indicate moderate deviations of about 1 % from earlier Luminous-Flux calibrations.
Wanlu Zhang - One of the best experts on this subject based on the ideXlab platform.
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study on methodology of led s Luminous Flux measurement with integrating sphere
Journal of Physics D, 2008Co-Authors: Xiaoli Zhou, Wenyi Li, Yuyang Chen, Wanlu ZhangAbstract:Errors are introduced when using traditional methods for measuring the total Luminous Flux of LEDs since an LED is quite different from traditional light sources in terms of physical size, Flux level, spectrum and spatial distribution. This paper uses commercial lighting simulation software named Tracepro to simulate the self-absorption effect when using traditional integrating sphere methods to measure the total Luminous Flux of LEDs and then presents a modified method for the measurement. The LED under investigation or a specially designed narrow beam standard lamp is placed on the interior wall of the sphere in our method. The results show that the measurement method presented here can lead to better precision in the evaluation of the total Luminous Flux of LEDs.
