scholarly journals Spectral Image Processing for Museum Lighting Using CIE LED Illuminants

Sensors ◽  
2019 ◽  
Vol 19 (24) ◽  
pp. 5400 ◽  
Author(s):  
Miguel Ángel Martínez-Domingo ◽  
Manuel Melgosa ◽  
Katsunori Okajima ◽  
Víctor Jesús Medina ◽  
Francisco José Collado-Montero
Keyword(s):  
Light Emitting Diode ◽  
Chromatic Adaptation ◽  
Spectral Image ◽  
Local Study ◽  
Light Emitting ◽  
Heritage Science ◽  
Color Differences ◽  
Restoration Techniques ◽  
Colorimetric Study ◽  
The One

This work presents a spectral color-imaging procedure for the detailed colorimetric study of real artworks under arbitrary illuminants. The results demonstrate this approach to be a powerful tool for art and heritage professionals when deciding which illumination to use in museums, or which conservation or restoration techniques best maintain the color appearance of the original piece under any illuminant. Spectral imaging technology overcomes the limitations of common area-based point-measurement devices such as spectrophotometers, allowing a local study either pixelwise or by selected areas. To our knowledge, this is the first study available that uses the proposed CIE (Commission Internationale de l’Éclairage) light-emitting diode (LED) illuminants in the context of art and heritage science, comparing them with the three main CIE illuminants A, D50, and D65. For this, the corresponding colors under D65 have been calculated using a chromatic adaptation transform analogous to the one in CIECAM02. For the sample studied, the CIE LED illuminants with the lowest average CIEDE2000 color differences from the standard CIE illuminants are LED-V1 for A and LED-V2 for D50 and D65, with 1.23, 1.07, and 1.57 units, respectively. The work studied is a Moorish epigraphic frieze of plasterwork with a tiled skirting from the Nasrid period (12th–15th centuries) exhibited in the Museum of the Alhambra (Granada, Spain).

scholarly journals New wavelength calibration of the HARPS spectrograph

2019 ◽  
Vol 629 ◽  
pp. A27 ◽  
Author(s):  
A. Coffinet ◽  
C. Lovis ◽  
X. Dumusque ◽  
F. Pepe
Keyword(s):  
Radial Velocity ◽  
Frequency Comb ◽  
Light Emitting Diode ◽  
Laser Frequency ◽  
Wavelength Calibration ◽  
Light Emitting ◽  
Before And After ◽  
Doppler Spectroscopy ◽  
One Year ◽  
The One

Context. Doppler spectroscopy has been used in astronomy for more than 150 yr. In particular, it has permitted us to detect hundreds of exoplanets over the past 20 yr, and the goal today of detecting Earth-like planets requires a precision around 0.1 m s−1 or better. Doppler spectroscopy has also been and will be of major importance for other studies such as the variability of fundamental constants and cosmological studies. For all these applications, it is crucial to have the best possible wavelength calibration. Despite the fact that the HARPS spectrograph has been operational at the 3.6-m ESO telescope for more than 15 yr, and that it provides among the most precise Doppler measurements, improvements are still possible. One known problem, for instance, is the non-fully regular block-stitching of the charge-coupled devices (CCDs), which in some cases introduces one-year period parasitic signals in the measured radial velocity. Aims. The aim of the presented work is to improve the wavelength calibration of the HARPS spectrograph to push further its planet-detection capabilities. Methods. The properties of the CCD stitching-induced pixel-size anomalies were determined with light-emitting-diode (LED) flat-field frames, and then a physical, gap-corrected map of the CCDs is used for the fitting model of the spectral orders. We also used a new thorium line list, based on much higher-accuracy measurements than the one used up to now. We derive new wavelength solutions for the 15 yr of HARPS data, both before and after the fibre upgrade that took place in 2015. Results. We demonstrate that we do indeed correct the gap anomalies by computing the wavelength solutions of laser frequency comb exposures, known to have a very low dispersion, both with and without taking the gap correction into account. By comparing the rms of the most stable stars of the HARPS sample, we show that we globally decrease the radial velocity (RV) dispersion of the data, especially for the data acquired after the change of fibres of 2015. Finally, the comparative analysis of several individual systems shows that we manage to attenuate the periodogram power at one year in most cases. The analysis of the RVs derived from individual stellar lines also shows that we indeed correct the stitching-induced RV variation. Conclusions. This improved calibration of the HARPS spectrograph allows to go deeper in the search for low-amplitude radial-velocity signals. This new calibration process will be further improved by combining the thorium calibration spectra with laser frequency comb and Fabry–Perot calibration spectra, and this will not only be used for HARPS but notably also for HARPS-N and the new ESPRESSO spectrograph.

scholarly journals Data Communication Security Issues of Wi-Fi over Li-Fi

2019 ◽  
Vol 8 (3) ◽  
pp. 1977-1981
Keyword(s):  
Light Emitting Diode ◽  
Denial Of Service ◽  
Data Communication ◽  
Electrical Signal ◽  
Visible Light Communications ◽  
Light Emitting ◽  
Security Issues ◽  
The One ◽  
Audio Video ◽  
Led Lights

Visible Light Communications (VLC) system is called Light Fidelity One such example, analog data is passed to a LED (Light-Emitting Diode) bulb (using signal processing technology), after that it transmits data (which is implanted in its beam) to the detector or photodiode. The small commutes in the brisk feeble of LED bulbs is modulated by the receiver circuit into electrical signal. The signal is then reversed into a duplex data runnel that could be recognized in the same way that of audio, video and web programs that run on devices that has internet enabled. Wi-Fi is vulnerable to breaches involving various security issues such as Rouge Access Points, Denial of Service, Wireless Trespasser, Data Interruption, End point attacks etc. To overcome such restrictions, this paper proposes application level substructure for data communication using Li-Fi (Light Fidelity) Technology. By using LED lights as a transmission medium, the indoor wireless communication is achieved in much faster rate than the one WiFi (Wireless Fidelity) can provide.

scholarly journals Lifetime and optical analyses of LED lamps

2021 ◽  
Vol 40 (1) ◽  
Author(s):  
Emerson Roberto Santos ◽  
Hélio Akira Furuya ◽  
Elvo Calixto Burini Junior
Keyword(s):  
Light Emitting Diode ◽  
The Other ◽  
Optical Characteristics ◽  
Integrating Sphere ◽  
Initial Moment ◽  
Direct Relation ◽  
Light Emitting ◽  
Elapsed Time ◽  
The One

In this study, optical and lifetime analyses of commercial light-emitting diode (LED) lamps were carried out with the objective to better understand these characteristics. Lamps of different manufacturers and powers were used: Ourolux of 9 watts, Kian of 9 watts, Black+Decker of 9 watts, FLC of 8 watts, Galaxy of 7 watts and Brilia of 7 watts. These LED lamps remained on by 24 hours/day for 4,291.16 hours. Illuminance measurements were analyzed once a week by each lamp inside the integrating sphere with a sensor of lux meter coupled. Results showed decrease of illuminance by elapsed time, due to the degradation. Results of the illuminance obtained between the initial moment of the experiment and the final one were calculated, revealing degradation of 19% to Ourolux, 20% to FLC, 26% to Black+Decker, 28% to Kian, 29% to Galaxy and 33% to Brilia. This study suggests that the diffusers can have different transmittance values interfering on the illuminance, since the FLC LED lamp presented illuminance with highest values than the other LED lamps tested with similar electrical and optical characteristics. This experiment showed that the nominal power of the LED lamp has no direct relation to the illuminance and, comparing the lifetime, the LED lamp manufactured by Black+Decker was the only one to reach 5,521 hours, that is a lifetime much shorter than the one described at the packages (25,000 hours) for all LED lamps tested

Analysis of Modified Current Controller and its Implementation in Automotive LED

2017 ◽  
Vol 6 (04) ◽  
pp. 01-06
Author(s):  
Prof. Bhushan Thakre, Dr. R.M Thakre
Keyword(s):  
Supply Voltage ◽  
Light Emitting Diode ◽  
Control Voltage ◽  
Process Technology ◽  
Light Emitting ◽  
Led Lighting ◽  
Current Controller ◽  
Dimming Control ◽  
Simulation Purpose ◽  
The One

A novel highly dimmable current controller which is a linear one is employed in the application of low power automotive is discussed here. Light Emitting Diode is the one which drives current that is linearly controlled to decrease the intensity of LED to limit the destruction of the LED and improve its reliability. Although many dimming techniques for LED lighting are available, our proposed method outperforms the existing methods in terms of power consumption and the no. of transistors used in the proposed design. This emits 100mA and decrease the LED current which is going linearly based on the theory of dimming control voltage. Toggling of LED is avoided finally in comparison with the existing system. This circuit is developed in 0.18μm process technology and Cadence ADE with Spectre is employed for simulation purpose. The proposed method utilizes a maximum power of 392.85 mW when the supply voltage is 4V and the control voltage is 4V at the temperature of 27oC.

Thermal Analyses of LED Light Bars and Backlight Modules

2016 ◽  
Vol 33 (3) ◽  
pp. 331-339 ◽  
Author(s):  
M.-Y. Tsai ◽  
C.-Y. Tang ◽  
C.-E. Zheng ◽  
Y.-Y. Tsai ◽  
C.-H. Chen
Keyword(s):  
Heat Dissipation ◽  
Light Emitting Diode ◽  
Thermal Analyses ◽  
Heat Sinks ◽  
Junction Temperature ◽  
Thermal Interface Materials ◽  
Light Emitting ◽  
Led Light ◽  
The One ◽  
Interface Materials

AbstractThe effects of various parameters, such as thermal properties of substrates, thermal interface materials (TIMs) and heat sinks on the thermal performance of the light emitting diode (LED) light bars and backlight module are investigated experimentally and numerically in terms of junction temperature (Tj) and thermal resistances from junction to air (Rj-a). The results show that the measured Rj-a of the light bars by powering-on five LEDs in the test is different from one by powering-on only one LED, resulting from the extra heat coming from the adjacent LED packages affecting the Tj for the case of powering-on five LEDs. For the modules, Rj-a is significantly reduced by using the heat sinks for all backlight modules, and aluminum and iron heat sinks do not show any obvious difference in heat dissipation along with any substrates and TIMs. Furthermore, both experimental and simulation results show that the thermal conductivity of the substrates are more important and dominant than TIM and heat sink for the Rj-a of the backlight modules concerned, and also demonstrate that the thermal field for the local model can represent the one in full-scale backlight module.

scholarly journals Spectral analysis of sphygmogram

2019 ◽  
Keyword(s):  
Spectral Analysis ◽  
Optical Sensor ◽  
Light Emitting Diode ◽  
The State ◽  
Low Frequencies ◽  
Light Emitting ◽  
Computer Methods ◽  
Heart Work ◽  
The One ◽  
Methods Of Control

Actuality. The heart system executes the important role in the organism. It is important task of medicine to diagnose of the state of this system. Electrocardiogram is the one of methods of control its state. Cardiointervalgram is another way of study of the state of the heart system. I studies the change of rhythm of heart as reaction of organism on external influences. Sphygmografia is the method of graphic registration of pulses vibrations of vessels, allowing to judge about their resiliently-viscid properties. The method of registration is used by a pair light-emitting diode and photo-diode. A signal, which is forming is due to the change of volume of blood in the place of indication. The most comfortable place for the location of sensor is the finger of Purpose of work. The spectral analysis of the sphygmogram impulses gives the information about heart system. The spectrum of sphygmogram of healthy man is wider. Numeral coefficients, which are characterizing correlation high and low frequencies, are offered. This was offered to analysis the spectrum of signal from the optical sensor, which is containing information by the of impulses and cardiountervals. These signals contain more information, than cardiointervalgram and single impulse of sfigmogram only. Methods. The spectrums of signals from the optics-electronic sensor was analyzed by computer methods. Results. The spectrum of cardiointervalgram contains information about the slow waves of heart work. The spectrum of sphygmogram contains information about frequency of heart work and about higher frequencies also. Conclusion. The analysis of heart work was made by the spectrum of cardiointervalgram and on the spectrum of sphygmogram. The second method allows to obtain more information about health of man.

Enhancement in electron transport and exciton confinement in OLEDs: role of n-type doping and electron blocking layers

2019 ◽  
Vol 86 (1) ◽  
pp. 10201 ◽  
Author(s):  
Anjaly Soman ◽  
K.N. Narayanan Unni
Keyword(s):  
Electron Transport ◽  
High Efficiency ◽  
Light Emitting Diode ◽  
Transport Layer ◽  
Electron Transport Layer ◽  
Light Emitting ◽  
Organic Light Emitting Diode ◽  
Organic Light ◽  
The One

Doped transport layers are essential for achieving high efficiency in organic light emitting diodes (OLEDs). We have studied the effect of doping the electron transport layer (ETL), tris-(8-hydroxyquinoline) aluminum (Alq3) with different percentages of lithium fluoride (LiF). We have also studied the effect of different electron blocking layers (EBLs) such as Tris (4-carbazoyl-9-ylphenyl)amine (TCTA), N,N'-Bis (naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine(NPB), and Di-[4-(N,N-di-p-tolyl-amino)-phenyl]cyclohexane (TAPC) in an Alq3:2,3,6,7-Tetrahydro-1,1,7,7,-tetramethyl-1H, 5H, 11H −10-(2-benzothiazolyl)quinolizino[9,9a, 1gh] coumarin (C545T) based organic light emitting diode (OLED) with optimized ETL doping. TCTA was found to effectively block the electrons and influence the recombination region in the process. At a brightness of 1000 cd/m2, an improvement of 27.8% was observed in external quantum efficiency (EQE) for the device with TCTA as the EBL and doped Alq3 as the ETL, compared to the one with just NPB as both EBL and HTL.

scholarly journals Study of N-doping in (Bi2MoO6, MoO3)/SnOx:N photocatalys in the degradation of RhB using visible light

2021 ◽  
pp. 2141007
Author(s):  
David Jui-Yang Feng ◽  
Chien-Yu Lai ◽  
Ming-Chang Shih ◽  
Millie Yang ◽  
Wen-How Lan ◽  
...  
Keyword(s):  
Visible Light ◽  
Light Emitting Diode ◽  
Spray Pyrolysis Method ◽  
X Ray Diffraction ◽  
Photocatalytic Ability ◽  
Light Emitting ◽  
Excited System ◽  
N Doping ◽  
One Step ◽  
The One

Novel composites operating in visible light (VL) energy are an important issue in photon excited system. The (Bi2MoO6, MoO3)/SnO[Formula: see text]:N composite photocatalysts were prepared by the one-step spray pyrolysis method. The effect of N-doping in SnO[Formula: see text] layer with controlled N/Sn ratio in precursor to the photocatalystic ability of the composite was studied. The photocatalytic ability of the composites was evaluated by photodegradation of Rhodamine B (RhB) under visible-light emitting diode illumination. The composites were characterized by film optical absorption analysis, X-ray diffraction and scanning electron microscopy. Film with suitable N-doping shows the improved visible-light photocatalytic ability with rate constant 0.019 min[Formula: see text]. With the electrical property of SnO[Formula: see text]:N films and the scavenger analysis of the composites, the photocatalytic mechanism was discussed.

Visible light-emitting diode light-driven one-pot four component synthesis of poly-functionalized imidazoles under catalyst- and solvent-free conditions

2020 ◽  
Vol 44 (31) ◽  
pp. 13295-13300
Author(s):  
Geetika Patel ◽  
Ashok Raj Patel ◽  
Subhash Banerjee
Keyword(s):  
Visible Light ◽  
Light Emitting Diode ◽  
Solvent Free ◽  
One Pot ◽  
Light Emitting ◽  
Solvent Free Conditions ◽  
The One

A visible light-emitting diode light-driven green and sustainable protocol has been demonstrated for the one-pot four component synthesis of poly-functionalized imidazoles under catalyst- and solvent-free conditions.

scholarly journals Analysis and Recommendations for LED Catastrophic Failure Due to Voltage Stress

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 540
Author(s):  
Shimi Sudha Letha ◽  
Math H. J. Bollen ◽  
Sarah K. Rönnberg
Keyword(s):  
Service Life ◽  
Lower Energy ◽  
Light Emitting Diode ◽  
Light Emitting ◽  
Led Lighting ◽  
Voltage Quality ◽  
University Of Technology ◽  
Voltage Stress ◽  
Different Types ◽  
The One

Light-emitting diode (LED) lighting has, compared to other types of lighting, a significantly lower energy consumption. However, the perceived service life is also important for customer satisfaction and here there is a discrepancy between customers’ experience and manufacturers’ statements. Many customers experience a significantly shorter service life than claimed by the manufacturers. An experiment was carried out in the Pehr Högström Laboratory at Luleå University of Technology in Skellefteå, Sweden to investigate whether voltage disturbances could explain this discrepancy. Over 1000 LED lamps were exposed to high levels of voltage disturbances for more than 6000 h; the failure rate from this experiment was similar to the one from previous experiments in which lamps were exposed to normal voltage. The discrepancy thus remains, even though some possible explanations have emerged from the project’s results. The lamps were exposed to five different types of voltage disturbances: short interruptions; transients; overvoltage; undervoltage; and harmonics. Only overvoltage resulted in failure of the lamps, and only for a single topology of lamp. A detailed analysis has been made of the topology of lamps that failed. This lamp type contains a different internal electronics circuit than the other lamp types. Failures of the lamps when exposed to overvoltage are due to the heat development in the control circuit increasing sharply when the lamps are exposed to a higher voltage. Hence, it is concluded that there are lamps that are significantly more sensitive to voltage disturbances than other lamp types. Manufactures need to consider the voltage quality that can be expected at the terminal of the lamp to prevent failure of lamps due to voltage disturbances. This paper therefore contains recommendations for manufacturers of lighting; the recommendations describe which voltage disturbances lamps should cope with.

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