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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 995401 (2016) https://doi.org/10.1117/12.2256093
This PDF file contains the front matter associated with SPIE Proceedings Volume 9954, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 995403 (2016) https://doi.org/10.1117/12.2240465
Solid-state lighting (SSL) offers a new technology platform for lighting designers and end-users to illuminate spaces
with low energy demand. Two types of SSL sources include organic light-emitting diodes (OLEDs) and light-emitting
diodes (LEDs). OLED is an area light source, and its primary competing technology is the edge-lit LED panel. Generally,
both of these technologies are considered similar in shape and appearance, but there is little understanding of how people
perceive discomfort glare from large area light sources. The objective of this study was to evaluate discomfort glare for
the two lighting technologies under similar operating conditions by gathering observers’ reactions. The human factors
study results showed no statistically significant difference in human response to discomfort glare between OLED and
edge-lit LED panels when the two light sources produced the same lighting stimulus. This means both technologies
appeared equally glary beyond a certain luminance.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 995404 (2016) https://doi.org/10.1117/12.2237255
We performed the simulation of white LEDs packaging with different chessboard structures of white light
converting phosphor layer covered on GaN die chip. Three different types of chessboard structures are called type 1,
type 2 and type 3, respectively. The result of investigation according to the phosphor thickness show the increasing
of thickness of phosphor layer are, the decreasing of output blue light power are. Meanwhile, the changes of yellow
light are neglect. Type 3 shows highest packaging efficiency of 74.3 % compares with packaging efficiency of type
2 and type 1 (72.5 % and 71.3 %, respectively). Type 3 also shows the most effect of forward light. Attention that
the type 3 chessboard structure gets packaging efficiency of 74.3 % at color temperature of daylight as well as high
saving of phosphor amount. The color temperatures of three types of chessboard structure are higher than 5000 K, so
they are suitable for lighting purpose. The angular correlate color temperature deviation (ACCTD) of type 1, type 2
and type 3 are 6500K, 11500K and 17000K, respectively.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 995405 (2016) https://doi.org/10.1117/12.2240424
The objective of this study was to investigate an indirect method of measuring the average junction temperature of a
white organic light-emitting diode (OLED) based on temperature sensitivity differences in the radiant power emitted by
individual emitter materials (i.e., “blue,” “green,” and “red”). The measured spectral power distributions (SPDs) of the
white OLED as a function of temperature showed amplitude decrease as a function of temperature in the different
spectral bands, red, green, and blue. Analyzed data showed a good linear correlation between the integrated radiance for
each spectral band and the OLED panel temperature, measured at a reference point on the back surface of the panel. The
integrated radiance ratio of the spectral band green compared to red, (G/R), correlates linearly with panel temperature.
Assuming that the panel reference point temperature is proportional to the average junction temperature of the OLED
panel, the G/R ratio can be used for estimating the average junction temperature of an OLED panel.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 995406 (2016) https://doi.org/10.1117/12.2235262
In this paper, we consider the problem of designing energy efficient light emitting diodes (LEDs) layout
while satisfying the illumination constraints. Towards this objective, we present a simple approach to the
illumination design problem based on the concept of the virtual LED. We formulate a constrained optimization
problem for minimizing the power consumption while maintaining a near-uniform illumination throughout
the room. By solving the resulting constrained linear program, we obtain the number of required LEDs and
the optimal output luminous intensities that achieve the desired illumination constraints.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 995407 https://doi.org/10.1117/12.2235625
A new scheme of high-reliability laser light engine (LLE) employing a novel glass-based phosphor-converted layer is proposed and demonstrated. The LLE module consists of a high-power blue light laser array and a color wheel, which includes two glass-based phosphor-converted layers of yellow Ce:YAG and green Ce:LuAG and a micro motor. The combinations of blue, yellow, and green lights produce high-purity phosphor-converted white-laser-diodes (PC-WLDs). The lumen degradation and chromaticity shift in the glass-based phosphor-converted layer under different laser powers are presented and compared with those of silicon-based PC-WLDs. The results showed that the glass based PC-WLDs exhibited in lower lumen loss and less chromaticity shifts than the silicon-based PC-WLDs. The long term reliability study evaluation in glass- and silicone-based PC-WLDs under high-power 120 W at room temperature for 20,000 hours is also presented and compared. The result showed that the silicone-based PC-WLDs exhibited 50% in lumen decay which failed in operation, while the glass-based PC-WLDs only exhibited 2% in lumen decay. This indicates that the proposed LLE modules are benefit to employ in the area where the silicone-based material fails to stand for long and strict reliability is highly required. This study demonstrates the advantages of adapting novel glass as a phosphor-converted color wheel in the LLE modules that provide unique high-reliability as well as better performance for use in the next-generation laser projector system.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 995408 https://doi.org/10.1117/12.2238043
Group III-V semiconductor nanostructures have been at the forefront of numerous
applications in high-power, high frequency optical and optoelectronic devices.
Although, significant progress has been made in fabrication and characterization of
these materials, there are still challenges in the formation of compositional uniform
indium-rich ternary epilayers, embedded in wide bandgap III-N’s. For example,
nanoscale lateral compositional inhomogeneities at the growth surface lead to bulk
phase segregations will reduce the structural quality of the semiconductor
heterostructures both in macro and nanometer scales if not controlled through the
process parameter space at the surface. Studying and understanding the fundamental
physical and structural properties at the nanoscale level and correlating the findings
with processing parameters is essential to mitigate compositional fluctuations in
multinary III-N compounds. In this work we introduce infrared scattering type
scanning near-field microscopy (s-SNOM) for spectroscopic study of nanoscale
optical properties of InGaN epilayers on GaN- or InN templates. S-SNOM possesses
spatial resolution of few nanometers (~15 nm) far below the diffraction limit and
allows spectroscopic imaging of simultaneous chemical and structural information
correlated with morphology. We correlate s-SNOM near-field amplitude and phase
optical contrasts at infrared frequencies to the dielectric constants and growth
parameters of InN/InGaN heterostructures and/or single nanoparticles. We observed
that both the real and imaginary dielectric function values of mono-/bi-layers of
InN/InGaN can be extracted from s-SNOM data. By performing nano-spectroscopy
on lithographically patterned samples, we also show that self-assembled InGaN
nanoparticles have similar dielectric function values as that of thin film InGaN.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 995409 (2016) https://doi.org/10.1117/12.2236318
Recently, the investigation of quantum dots (QDs) as color converters for white light-emitting diodes (WLEDs) has
attracted a significant amount of attention, because the emission wavelength and broad excitation band of QDs can be
controlled by their particle sizes and compositions. However, owing to the thermal effect, the long-term stability of QDWLEDs
is one of the important tasks for their application. Moreover, the commercial WLEDs have low color rendering
index (CRI) and the reabsorption effect. Therefore, in order to increase the device stability and CRI, in this study, we have
used easy one-pot process to synthesize the colloidal ternary Zn0.8Cd0.2S (ZnCdS) QDs with wide emission, a quantum
yield (QY) of 42 % and a particle size of 3.2 ± 0.5 nm. Three methods have been applied to encapsulate the QDs and their
average CRIs are 78. We have demonstrated that the QDs-based WLEDs can achieve color converter robust against photooxidation,
thermal quenching, and scattering, and can be applied to fabricate reliable P-QD1 device with an air gap between
the emission layers. This encapsulation setup can protect the color converter and maintain the best stability over 750 hours
operation time, and the Commission International d’Eclairage (CIE) chromaticity coordinates and luminous efficacy can
be tuned from (0.36, 0.40) to (0.32, 0.33) and 4.5 to 3.2, respectively.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540A (2016) https://doi.org/10.1117/12.2236473
Light emitting diodes (LEDs) for visible light communication (VLC) as radio sources is a solution to channel crowding
of radio frequency (RF) signal. However, for the application on high-speed communication, getting higher bandwidth of
LEDs is always the problem which is limited by the spontaneous carrier lifetime in the multiple quantum wells. In this
paper, we proposed GaN-based LEDs accompanied with photonic crystal (PhC) nanostructure for high speed
communication. Using the characteristic of photonic band selection in photonic crystal structure, the guided modes are
modulated by RF signal. The PhC can also provide faster mode extraction. From time resolved photoluminescence (TRPL)
at room temperature, carrier lifetime of both lower- and higher-order modes is shortened. By observing f-3dB -J curve, it
reveals that the bandwidth of PhC LEDs is higher than that of typical LED. The optical - 3-dB bandwidth (f-3dB) can be
achieved up to 240 MHz in the PhC LED (PhCLED). We conclude that the higher operation speed can be obtained due to
faster radiative carrier recombination of extracted guided modes from the PhC nanostructure.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540B (2016) https://doi.org/10.1117/12.2237152
A white light emission CdSe quantum dots (QDs) can be prepared by chemical route under 180°C. An organic oleic acid
(OA) is used to react with CdO to form Cd-OA complex. Hexadecylamine (HDA) and 1-Octadecene (ODE) were used
as co-surfactants. By controlling the reaction time, a white light emission CdSe QDs can be obtained after reacts for 3 to
10 min. The luminescence spectra compose two obvious emission peaks and entire visible light ranges from 400 to 650
nm. Based on TEM measurement result, spherical morphologies with particle size 2.39±0.27 nm can be obtained. The
quantum yields (QYs) of white CdSe QD are between 20 and 60 %, which depends on reaction time. A white CdSe QDs
were mixed with UV cured gel (OPAS-226) with weight ratios 50.0 wt. %, and putted the mixture into reflective cup
(3020, 13 mil) as convert type. The white LEDs have controllable CIE coordinates and correlated color temperature
(CCT). The luminous efficacy of the device is less than 3 lm/W, but the color rendering index (CRI) for all devices are
higher than 80. Since the luminous efficacy of hybrid devices has a direct dependence on the external QY of the
UV-LED as well, the luminous efficacy can be improved by well dispersion of CdSe QDs in UV gel matrix and using
optimized LED chips. Therefore, in this study, we provide a new and simple method to prepare high QY of white CdSe
QDs and its have a potential to applicate in solid-state lighting.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540C (2016) https://doi.org/10.1117/12.2237736
We present the use of a micromirror to dynamically improve an optical wireless communications link. The
signal-to-noise ratio (SNR) is improved by directing the output of a 675 nm laser diode modulated at 10
MHz toward a receiver and by varying the divergence of the output beam using a varifocal, tip-tilt-piston
micromirror. The SNR has a dynamic range of 30 dB for a diffuse source, all by optimizing the overall shape
and direction of the mirror.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540D (2016) https://doi.org/10.1117/12.2239515
The steady advances in light-emitting diode (LED) technology have motivated the use of LEDs in optical wireless
communication (OWC) applications such as indoor local area networks (LANs) and communication between
mobile platforms (e.g., robots, vehicles). In contrast to traditional radio frequency (RF) wireless communication,
OWC utilizes electromagnetic spectrum that is largely unregulated and unrestricted. OWC communication may
be especially useful in RF-denied environments, in which RF communication may be prohibited or undesirable.
However, OWC does present some challenges, including the need to maintain alignment between potentially
moving nodes. We describe a novel system for link alignment that is composed of a hyperboloidal mirror,
camera, and gimbal. The experimental system is able to use the mirror and camera to detect an LED beacon of
a neighboring node and estimate its bearing (azimuth and elevation), point the gimbal towards the beacon, and
establish an optical link.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540E (2016) https://doi.org/10.1117/12.2237737
State of the art fabrication of LED modules based on chip-on-board (COB) technology comprises some shortcomings
both with respect to the manufacturing process itself but also with regard to potential sources of failures and
manufacturing impreciseness. One promising alternative is additive manufacturing, a technology which has gained a lot
of attention during the last years due to its materials and cost saving capabilities. Especially direct-write technologies like
Aerosol jet printing have demonstrated advantages compared to other technological approaches when printing high
precision layers or high precision electronic circuits on substrates which, as an additional advantage, also can be flexible
and 3D shaped. Based on test samples and test structures manufactured by Aerosol jet printing technology, in this
context we discuss the potentials of additive manufacturing in various aspects of LED module fabrication, ranging from
the deposition of the die-attach material, wire bond replacement by printed electrical connects as well as aspects of high-precision
phosphor layer deposition for color conversion and white light generation.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540G (2016) https://doi.org/10.1117/12.2240464
LED products have started to displace traditional light sources in many lighting applications. One of the commonly
claimed benefits for LED lighting products is their long useful lifetime in applications. Today there are many
replacement lamp products using LEDs in the marketplace. Typically, lifetime claims of these replacement lamps are in
the 25,000-hour range. According to current industry practice, the time for the LED light output to reach the 70% value
is estimated according to IESNA LM-80 and TM-21 procedures and the resulting value is reported as the whole system
life. LED products generally experience different thermal environments and switching (on-off cycling) patterns when
used in applications. Current industry test methods often do not produce accurate lifetime estimates for LED systems
because only one component of the system, namely the LED, is tested under a continuous-on burning condition without
switching on and off, and because they estimate for only one failure type, lumen depreciation. The objective of the study
presented in this manuscript was to develop a test method that could help predict LED system life in any application by
testing the whole LED system, including on-off power cycling with sufficient dwell time, and considering both failure
types, catastrophic and parametric.
The study results showed for the LED A-lamps tested in this study, both failure types, catastrophic and parametric, exist.
The on-off cycling encourages catastrophic failure, and maximum operating temperature influences the lumen
depreciation rate and parametric failure time. It was also clear that LED system life is negatively affected by on-off
switching, contrary to commonly held belief. In addition, the study results showed that most of the LED systems failed
catastrophically much ahead of the LED light output reaching the 70% value. This emphasizes the fact that life testing of
LED systems must consider catastrophic failure in addition to lumen depreciation, and the shorter of the two failure
modes must be selected as the system life. The results of this study show a shorter time test procedure can be developed
to accurately predict LED system life in any application by knowing the LED temperature and the switching cycle.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540H (2016) https://doi.org/10.1117/12.2236638
As internet of things (IOT) has become a popular topic in current consumer electronics, there is a demand for cost-effective
sensors to monitor bio-signals. Traditional optical sensors employ low-dimensional gratings and high-resolution
spectrometers to detect the refractive index changes of the solutions. In this work, we develop an alternative
approach to correlate the concentration of molecules to the band diagrams of the photonic crystals. A relatively low-resolution
spectrum analyzer can be employed, yet achieves higher sensitivity than traditional approaches.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540I (2016) https://doi.org/10.1117/12.2240463
The concept of connected lighting systems using LED lighting for the creation of intelligent buildings is becoming
attractive to building owners and managers. In this application, the two most important parameters include power
demand and the remaining useful life of the LED fixtures. The first enables energy-efficient buildings and the second
helps building managers schedule maintenance services. The failure of an LED lighting system can be parametric (such
as lumen depreciation) or catastrophic (such as complete cessation of light). Catastrophic failures in LED lighting
systems can create serious consequences in safety critical and emergency applications. Therefore, both failure
mechanisms must be considered and the shorter of the two must be used as the failure time. Furthermore, because of
significant variation between the useful lives of similar products, it is difficult to accurately predict the life of LED
systems. Real-time data gathering and analysis of key operating parameters of LED systems can enable the accurate
estimation of the useful life of a lighting system. This paper demonstrates the use of a data-driven method (Euclidean
distance) to monitor the performance of an LED lighting system and predict its time to failure.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540J (2016) https://doi.org/10.1117/12.2237033
At present, broadband radiometric LED measurements with uniform and low-uncertainty results are not available.
Currently, either complicated and expensive spectral radiometric measurements or broadband photometric LED
measurements are used. The broadband photometric measurements are based on the CIE standardized V(λ) function,
which cannot be used in the UV range and leads to large errors when blue or red LEDs are measured in its wings, where
the realization is always poor. Reference irradiance meters with spectrally constant response and high-intensity LED
irradiance sources were developed here to implement the previously suggested broadband radiometric LED measurement
procedure [1, 2]. Using a detector with spectrally constant response, the broadband radiometric quantities of any LEDs or
LED groups can be simply measured with low uncertainty without using any source standard. The spectral flatness of
filtered-Si detectors and low-noise pyroelectric radiometers are compared. Examples are given for integrated irradiance
measurement of UV and blue LED sources using the here introduced reference (standard) pyroelectric irradiance meters.
For validation, the broadband measured integrated irradiance of several LED-365 sources were compared with the
spectrally determined integrated irradiance derived from an FEL spectral irradiance lamp-standard. Integrated
responsivity transfer from the reference irradiance meter to transfer standard and field UV irradiance meters is discussed.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540K (2016) https://doi.org/10.1117/12.2240650
Recently, light-emitting diode (LED) lighting systems have become popular due to their increased system performance.
LED lighting system performance is affected by heat; therefore, it is important to know the temperature of a target
surface or bulk medium in the LED system. In-situ temperature measurements of a surface or bulk medium using
intrusive methods cause measurement errors. Typically, thermocouples are used in these applications to measure the
temperatures of the various components in an LED system. This practice leads to significant errors, specifically when
measuring surfaces with high-luminous exitance.
In the experimental study presented in this paper, an infrared camera was used as an alternative to temperature probes in
measuring LED surfaces with high-luminous exitance. Infrared thermography is a promising method because it does not
respond to the visible radiation spectrum in the range of 0.38 to 0.78 micrometers. Usually, infrared thermography
equipment is designed to operate either in the 3 to 5 micrometer or the 7 to 14 micrometer wavelength bands. To
characterize the LED primary lens, the surface emissivity of the LED phosphor surface, the temperature dependence of
the surface emissivity, the temperature of the target surface compared to the surrounding temperature, the field of view
of the target, and the aim angle to the target surface need to be investigated, because these factors could contribute
towards experimental errors. In this study, the effects of the above-stated parameters on the accuracy of the measured
surface temperature were analyzed and reported.
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S. Schweitzer, C. Schinagl, G. Djuras, M. Frühwirth, H. Hoschopf, F. Wagner, B. Schulz, W. Nemitz, V. Grote, et al.
Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540L (2016) https://doi.org/10.1117/12.2237897
In recent years, LED lighting became an indispensable alternative to conventional lighting systems. Sophisticated
solutions offer not only comfortable white light with a good color rendering. They also provide the possibility of
changing illuminance and color temperature. Some systems even simulate daylight over the entire day, some including
natural variations as due to clouds. Such systems are supposed to support the chronobiological needs of human and to
have a positive effect on well-being, performance, sleep-quality and health.
Lighting can also be used to support specific aims in a situation, like to improve productivity in activation or to support
recreation in relaxation. Research regarding suitable light-settings for such situations and superordinate questions like
their influence on well-being and health is still incomplete.
We investigated the subjective preferences of men and women regarding light-settings for activation and relaxation. We
supplied two rooms and four cubes with light sources that provide the possibility of tuning illuminance, color
temperature and deviation from Plackian locus. More than 80 individuals – belonging to four groups differing in gender
and age – were asked to imagine activating and recovering situations for which they should adjust suitable and pleasant
lighting by tuning the above mentioned light properties. It was shown that there are clear differences in the lighting
conditions preferred for these two situations. Also some combined gender- and age-specific differences became apparent.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540M https://doi.org/10.1117/12.2237139
In this thesis, on the basis of the phosphor optical models, green and red phosphor mixture optical model has been well established. Under some specific green to red phosphor doping proportions, this model can be utilized to simulate the chromatic properties, spatial CCT distributions, and packaging efficiency. There are some benefits of applying the phosphor optical model, one is that the confusion about mixture or layer phosphor configuration can perform better could be solved. Another is that the comparison and analysis of these phosphor configurations can be made not only in experiment but also in simulation, and will be more details to be discuss in the simulation. There are several types of packaging structures in high color quality applications. Consequently, the importance of phosphor optical model cannot be overestimated. After few steps above and with the help of experimental analysis and optimized in simulation, a packaging structure with high color quality and high efficiency has been approved. Finally, this light source with high performance will be utilized in the luminaire to improve the color and energy saving properties.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540N (2016) https://doi.org/10.1117/12.2235834
Light emitting diode (LED) has been recognized as an applicable light source for indoor and outdoor lighting, city
beautifying, landscape facilities, and municipal engineering etc. Conventional LED has superior characteristics such as
long life time, low power consumption, high contrast, and wide viewing angle. Recently, LED with high color-rendering
index and special spectral characteristics has received more and more attention. This paper is intended to report a solar
spectrum simulated by multichip LED light source. The typical solar spectrum of 5500k released by CIE was simulated
as a reference. Four types of LEDs with different spectral power distributions would be used in the LED light source,
which included a 430nm LED, a 480nm LED, a 500nm LED and a white LED. In order to obtain better simulation
results, the white LED was achieved by a 450nm LED chip with the mixture of phosphor. The phosphor combination
was prepared by mixing green phosphor, yellow phosphor and red phosphor in a certain proportion. The multichip LED
light source could provide a high fidelity spectral match with the typical solar spectrum of 5500k by adjusting injection
current to each device. The luminous flux, CIE chromaticity coordinate x, y, CCT, and Ra were 104.7 lm, 0.3337, 0.3681,
5460K, and 88.6, respectively. Because of high color-rendering index and highly match to the solar spectrum, the
multichip LED light source is a competitive candidate for applications where special spectral is required, such as
colorimetric measurements, visual inspection, gemstone identification and agriculture.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540O (2016) https://doi.org/10.1117/12.2236652
Recently, there is an interest in the laser-based white light source for illumination and display applications. The laser-based
white lights inherently have much higher luminance than the corresponding LEDs. Moreover, laser diodes are often more
efficient when operating at higher current densities and are with smaller form factors, which may outperform LEDs in the
future. Based on this, in this paper, we combine the design of the light guide and reflective type remote phosphor structures
in order to improve the overall performance of the laser-based white light source. In addition, these well-designed white
light sources will provide the more flexible architecture for designing the subsequent lighting system. With the introduction
of the innovative design for the laser-based illumination system, multiple applications incorporating laser and remote
phosphor elements for improving lighting efficiency and quality were obtained.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540P (2016) https://doi.org/10.1117/12.2236827
In this study, the design of the projector type headlamp using LEDs with different structure parameters is proposed. The
ellipsoidal reflector with different major and minor axis would contribute different aperture and focal lengths of the
ellipsoidal reflector, and then collimate the light to the converging lens. With specific converging lens and metal-based
baffle plate in the projector type headlamp system, we systematical analysis of the ellipsoidal reflector in the projector
type headlamp. The systematical analysis of the ellipsoidal reflector can be a reference to design a projector type
headlamp with compact size and high photometry performance.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540Q (2016) https://doi.org/10.1117/12.2237441
Direct imaging has widely applied in lithography for a long time because of its simplicity and
easy-maintenance. Although this method has limitation of lithography resolution, it is still adopted in
industries. Uniformity of UV irradiance for a designed area is an important requirement. While
mercury lamps were used as the light source in the early stage, LEDs have drawn a lot of attention for
consideration from several aspects. Although LED has better and better performance, arrays of LEDs
are required to obtain desired irradiance because of limitation of brightness for a single LED. Several
effects are considered that affect the uniformity of UV irradiance such as alignment of optics,
temperature of each LED, performance of each LED due to production uniformity, and pointing of
LED module. Effects of these factors are considered to study the uniformity of LED Light Illumination.
Numerical analysis is performed by assuming a serious of control factors to have a better understanding
of each factor.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540R (2016) https://doi.org/10.1117/12.2237957
This contribution presents results on the structural and optoelectronic properties of InN layers grown on AlN/sapphire
(0001) templates by Migration-Enhanced Plasma Assisted Metal Organic Chemical Vapor Deposition (MEPAMOCVD).
The AlN nucleation layer (NL) was varied to assess the physical properties of the InN layers. For ex-situ
analysis of the deposited structures, Raman spectroscopy, Atomic Force Microscopy (AFM), and Fourier Transform
Infrared (FTIR) reflectance spectroscopy have been utilized. The structural and optoelectronic properties are assessed by
Raman-E2 high FWHM values, surface roughness, free carrier concentrations, mobility of the free carriers, and high
frequency dielectric function. This study focus on optimizing the AlN nucleation layer (e.g. temporal precursor
exposure, nitrogen plasma exposure, plasma power and AlN buffer growth temperature) and its effect on the InN layer
properties.
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Proceedings Volume Fifteenth International Conference on Solid State Lighting and LED-based Illumination Systems, 99540T (2016) https://doi.org/10.1117/12.2235851
The LED luminaires are nowadays the mainstream of road lighting for the merit of durable, fast response, controllable,
energy saving, and environmental friendly. For the evaluation of highway with LED lightings, we have recently
developed on-site measurement of the photometric characteristics of lane and luminaire by luminance image,
illuminance and spectral illuminance distribution which be evaluated as uniformity, colorimetry and glare parameters
that were measured under the different height and spacing of the lampposts in the experimental field for expressway. We
applied the image luminance measurement device to achieve the on-site and real time road lighting evaluation especially
for the expressway. Some preliminary results were obtained from these experiments. These results will be applied to
developing the standards and specification for road lighting in expressway.
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