Changes In Color Temperature Research Articles

On-Off Switching of Singlet Self-Trapped Exciton Emission Endows Antimony-Doped Indium Halides with Excitation-Wavelength-Dependent Luminescence.

Excitation-wavelength-dependent (Ex-De) emitters are a fascinating category of luminescent materials whose emission properties vary with the wavelength of the light used for excitation. Antimony (Sb3+)-doped indium (In)-based metal halides are efficient light emitters; however, the peak fluorescence emission of most Sb3+-activated In-halide remains independent of the excitation wavelength. Here, the study introduces a new Sb3+-doped In-halide cluster, (BDPA)2InCl5:Sb (BDPA+ = C15H18N+, benzyldimethylphenylammonium), which demonstrates efficient Ex-De emission originating from the on-off switchable fluorescence behavior of singlet self-trapped exciton (STE) in 5-coordinate Sb3+ dopant. Interestingly, when excited within the range of 240-370nm, photoluminescence (PL) spectra of (BDPA)2InCl5:Sb show both singlet and triplet STE emission. However, under excitation wavelengths of 370 to 420nm, the singlet STE emission is absent, resulting in a noticeable correlated color temperature change from 1700 to 3800 K. The study provides a new approach to designing color-tunable Sb3+-based luminophores, and also presents a novel application scenario for the widely recognized Sb3+ doping strategy.

Portable hydrogel kit driven by bimetallic carbon dots nanozyme for H2O2-self-supplying dual-modal monitoring of atmospheric CH3SH

Due to the typical volatility of gaseous pollutant methyl mercaptan (CH3SH), the development of a facile, reliable, and accurate onsite environmental surveillance of highly toxic CH3SH faces many challenges, but it is critical to environmental atmosphere assessment and safeguarding public health. Here, we prepared a novel bimetallic carbon dots (Fe&Cu@CDs) nanozyme with high peroxidase-mimicking activity to design a portable hydrogel kit for onsite visual H2O2-self-supplying enzymatic cascade catalytic colorimetric and photothermal signal synergistic amplification dual-modal monitoring of CH3SH in atmospheric environment. Assisted by alcohol oxidase (AOX), CH3SH could be specifically converted into H2O2 for oxidizing chromogenic substrate 3,3′,5,5′-tetramethylbenzidine (TMB) catalyzed by Fe&Cu@CDs to produce dark blue ox-TMB with absorption at 652 nm and photothermal characters. Consequently, a CH3SH concentration-dependent change both in naked-eye color and photothermal effect-triggered temperature were observed. By hybridizing AOX-assisted Fe&Cu@CDs + TMB with agarose, a H2O2-self-supplying colorimetric and photothermal signal synergistic amplification sensory hydrogel kit integrated with Color Picker APP-installed smartphone and 660 nm laser-equipped handheld thermal imager for CH3SH was proposed with acceptable results in atmospheric environment around wastepile (e.g., solid waste and food waste piles), which exhibited great potentials to further develop commercial onsite monitoring platforms in warning-early abnormal atmospheric CH3SH for safeguarding environmental health.

Urban Park Lighting Quality Perception: An Immersive Virtual Reality Experiment

Green areas and parks are increasingly important in improving citizens’ physical and mental recovery. Lighting systems play a considerable role in affecting city park life and activities along with people’s moods and behavior in the evening and at night. Immersive virtual reality laboratory experiments may support urban and lighting research by providing information on the combination of lighting setup and visual context of existing or new urban parks. Gaze behaviors obtained from eye-tracking recordings and self-reported measurements using the perceived outdoor lighting quality questionnaire were used to determine the factors affecting human perception, comfort, and cognitive load, as the overall illuminance levels of the scene and correlated color temperature changes. Results pointed out that overall illuminance level and CCT significantly affect the perceived strength and comfort qualities of lighting with a dominance of the first compared with the latter when subjects were free to explore the lit environment. Low CCT and intermediate or high overall illuminance levels can improve the sense of accessibility as well as minimize the cognitive load.

A Method of Generating Real-Time Natural Light Color Temperature Cycle for Circadian Lighting Service.

The light intensity and color temperature of natural light periodically change and promote the circadian entrainment of the human body. In addition, the color temperature cycle of natural light that is unique to each region is formed by its location and geographic and environmental factors, affecting the health of its residents. Research on lighting and construction to provide the color temperature of real-time natural light has continued to provide the beneficial effect of natural indoor lighting. However, lighting technology that provides the real-time color temperature of natural light could not be realized since it is challenging to select a color temperature cycle zone due to abrupt color temperature changes at sunrise and sunset. Such drastic shifts cause an irregular measurement of color temperature over time due to general weather or atmospheric conditions. In a previous study, a method of generating a color temperature cycle using deep learning was introduced, but the performance at the beginning and end of the color temperature cycle was unreliable. Therefore, this study proposes generating a real-time natural light color temperature cycle for the circadian lighting service. The characteristics of the daily color temperature cycle were analyzed based on the measured natural light characteristics database, and a data set for learning was established. To improve the color temperature cycle generation performance, a deep learning (TadGAN) model was implemented by searching for the lowest point of the color temperature at the start and end points of the color temperature cycle and applying the boot and ending datasets to these points. The color temperature cycle zone was accurately detected in real-time in the experiment, and the generation performance of the color temperature cycle was maintained at the beginning and end of the color temperature cycle. The mean absolute error decreased by about 67%, confirming the generation of a more accurate real-time color temperature cycle.

The Influence of Energy Transfer on the Color Temperature Change in Color-Tunable Organic Light Emitting Diodes with Interface Exciplex

The color-tunable white organic light-emitting diode (CT-WOLED) with wide correlation color temperature (CCT) has many advantages in optimizing the artificial light source to adapt to the human physiological cycle. The research on the change trend of CCT and the law of extending the change range of CCT will help to further improve the performance of this kind of device. The present work fabricated a series of CT-WOLED devices with a simple structure, which are all composed of two ultra-thin phosphor layers (PO-01 and Flrpic) and a spacer interlayer. The yellow interface exciplex (TCTA/PO-T2T) formed between the spacer layer (PO-T2T) and transmission material (TCTA) in EML will decrease the CCT value at low voltage. The relationship between the energy transfer in EML and CCT change trend is investigated by adjusting the interface exciplexes and the thickness of the interlayer or the phosphor layer in devices A, B and C, respectively. The results demonstrate that a simple OLED device with an interlayer inserted between two ultra-thin phosphor layers can achieve a wider CCT span from 3359 K to 6451 K at voltage increases from 2.75 V to 8.25 V.

NPR 이미지의 색 항상성 - 애니메이션 장면을 중심으로

Animation is a video made up of non-photorealistic expressive still images considering the human perspective. There is an increasing need to clarify the color expression characteristics of NPR images to facilitate the animation production. This study paid attention to the color constancy, which recognizes the color of the surface as the same color even when the lighting color of the environment changes to various colors. Therefore, the color constancy was researched in NPR animation images. The subjects produced animation images including the character and the background, considering the color composition including 6 objects (apple, banana, leaf, soil, tree, skin) based on the basic color term. According to the change of time, the colors were set to 12:00 PM (6500K) at noon, 6:00 PM (4000K) at sunset, and 12:00 PM (20000K) at night. As a result, the CIE LAB values of the object color shown in the NPR animation image were obtained, and the Color Constancy Index (CI) was calculated according to the color temperature change to confirm the effect of color constancy. As a result, the CI of all object colors except for the sky at 4000K was higher than 0.6, confirming the effect of the color constancy. In addition, at 20000K, lower than CI=0.5 was obtained for all objects except for the skin, confirming the action of the low color constancy. This study is different from the existing color constancy studies focusing on photographed images, and it can help to build a color database required from the viewpoint of animation creators.

Effects of Automated Diurnal Variation in Electronic Screen Temperature on Sleep Quality in Young Adults: A Randomized Controlled Trial

ABSTRACT Objective Determine whether automated changes in electronic screen color temperature of personal electronic devices is associated with changes in objective and self-reported indices of sleep and mental health in young adults, as well as determine feasibility and acceptability of the experimental manipulation. Participants A single-blind randomized controlled trial was conducted at a large public university in the Pacific Northwest region of the United States. Fifty-five participants (female=78%, mean age=19.45 years) who reported using a smartphone and/or laptop computer two hours before bedtime were randomized into either an experimental group (EG; n=29) or active control group (ACG; n=26). Methods Both the EG and ACG had installed on their devices a piece of software that automatically lowers the color temperature of these devices’ screens as the day progresses (“f.lux”). However, only the EG had the blue-light-reducing features activated, and participants were blind to condition. Before and after the one-week long experimental manipulation period, participants completed the Pittsburgh Sleep Quality Index (PSQI), Pediatric Daytime Sleepiness Scale (PDSS), Pre-Sleep Arousal Scale (PSAS), and Patient Health Questionnaire (PHQ) and wore an actiwatch for seven consecutive nights. Results Participants in the EG did not show greater improvement in objective sleep, self-reported sleep, or mental health compared to participants in the ACG. Participants in the EG rated the software as more distracting and purposely disabled the software more often compared to participants in the ACG. Conclusions Automated diurnal variation in electronic screen temperature in personal devices did not improve sleep or mental health in young adults.

Research on high luminous efficiency, high color rendering index chips on board light emitting diode and excitation and excitation saturation effect of phosphor

AbstractA kind of chips on board (COB) package of light emitting diode (LED) light source is designed and produced. By reducing the current density and using the mirror aluminum substrate with high reflectivity to improve the luminous efficiency. Meanwhile, three kinds of red phosphors with peak wavelength of 630 nm, 631 nm and 639 nm are added on the basis of yellow‐green phosphors, which increase within the range of red light LED spectrum composition, improve the LED color rendering index. The measurement results show that under 500 mA forward current, the luminous flux density of LED on the luminous surface with an area of 227 mm2 reaches 14.4 lm/mm2, the luminous efficiency reaches 175.5 lm/W, and the color rendering index reaches 89.3. It is found in the process of measuring the LED color temperature changes slightly with the current change, and by calculating that the proportion of blue photons in the LED spectrum is increasing gradually, the cause of this phenomenon is the phosphor excitation efficiency is saturation when the optical power density is high, which is influenced in two aspects: the proportion of photons absorbed by phosphor or the phosphor excitation efficiency decreases, the two factors together or separately cause the phosphor excitation saturation effect.

Study on National Technical Specification of the Standard Retroreflectivity Measurement Device

Start your abstract here…The study aims to explore the technical specifications of the standard retroreflectivity measurement devices. Based on the measurement principle of retroreflection coefficient, the metrological characteristics of standard retroreflectivity measurement devices were proposed and the three main metrological indices of light source (color temperature, illuminance and positioning error of incident angle) were experimentally explored. The allowable error range of the retroreflection coefficient measurements was determined to calculate the corresponding ranges of metrological indices. With the entropy weight method, the weight of the influence of each index on retroreflection coefficient measurements was analyzed. The analysis results showed that the illuminance had the most significant influence on the retroreflection coefficient and accounted for 41.30%, followed by color temperature (34.43%) and angle change (24.26%). The study provides the important technical support for the development of technical specifications of standard retroreflectivity measurement devices.

Tunable white light emission of an anti-ultraviolet rare-earth polysiloxane phosphors based on near UV chips.

A novel white-light copolymer matched with 365 nm chips is prepared by bonding the vinyl-functionalized complexes Eu(TTA)2(Phen)(MAA), Tb(p-BBA)3(UA) and Zn(BTZ)(UA) to polysiloxaneprepolymer(synthesized by polycondensation of vinyltrimethoxysilane and diphenylsilanediol) through a technical route of polymerization after coordination. Its structure was characterized by infrared and ultraviolet. Under the excitation of 365 nm, when the ratio of the tricolor complexes is controlled to be 0.5: 3: 1.5, white light copolymer with CIE color coordinates of (0.327, 0.321) was obtained and packaged to get white light LED devices. After aging, the CIE color coordinates of the device change from (0.325, 0.329) to (0.341, 0.348), the color rendering index changes from 91 to 88, and the correlated color temperature changes from 5967 K to 5612 K. The loss of brightness is only 10.4%, which shows good resistance to UV aging. Moreover, the initial decomposition temperature of the copolymer is 235°C. The above results show that the bonding-type anti-ultraviolet copolymer phosphor has potential application in near ultraviolet LEDs.

ABOUT THE CREATION OF AN LED LIGHT SOURCE WITH VARIABLE COLOR TEMPERATURE

The article is devoted to the development and research of an LED lamp of the A65 form factor and the type of E27 base with a choice of color temperature when the lamp is alternately connected to the supply network. The description of LEDs, driver, radiator, housing, base is given. Analysis of the results of measurements of lighting characteristics showed that the luminous flux and power consumption of the LED lamp amounted to 1004.1 lm and 12.5 W at a measured color temperature of 3056 K and 1059.8 lm and 12.37 W at 4120 K. Change in the color temperature of the lamp from 3056 K to 4120 K is characterized by an increase in the spectral density in the region of short-wave radiation with an increase in the proportion of blue, blue and violet colors. The shape of the lamp luminous intensity curve is close to the diffuse distribution. The change in color temperature is carried out by turning off and then turning on the lamp in the mains for no more than 5 seconds.

Interrelation between Colorimetric and Spectral Parameters of White Led Lamps

The interrelation between colorimetric (correlated color temperature) and spectral (intensity ratio of spectral emission bands) parameters of white LED lamps for general lighting has been established based on an analysis of test results for a set of lamps during aging. Deconvolution of the lamp radiation spectra is used to show that the change in color temperature is mainly due to a change in the intensity ratio of the 450-nm band originating from the diode heterostructure and the long-wavelength component of the nonelementary yellow band of the phosphor radiation with a maximum at 580 nm. However, the shorter-wavelength component with a maximum of 530 nm manifests itself mainly in the change of the total luminous flux. A possible cause of the change in the intensity of the spectral components of the nonelementary phosphor radiation band may be both thermal effects and structural changes in the phosphor material.

Monitoring supplied domestic water quality at Thu Dau Mot water supply enterprise

The current status assessment research of water use and quality of supplied domestic water in Thu Dau Mot city, Binh Duong province, as well as the clean water use situation of the local people. Sampling and assessment of the quality of supplied water at Thu Dau Mot Water supply enterprise. The water treatment process here is strictly conducted to ensure stability, constant pressure, inlet and outlet water flow. The analysis results of physical and chemical parameters of water quality at Thu Dau Mot Water supply enterprise show parameters within the allowable limits of water standards for domestic use QCVN 02: 2009/BYT and domestic water QCVN 01: 2009/BYT. However, during the water treatment process in the rainy season, it is time consuming and costly for the use of many chemicals in the treatment process, as high turbidity and high color temperature, low TDS, low pH, low chloride, high SS, Fe and Mn content changes in the wet season higher than in the dry season. After sampling for analysis and treatment, the output water meets the clean water standard to meet the needs of the people in Thu Dau Mot City and surrounding areas.

Low blue light hazard for tunable white light emitting diode with high color fidelity and circadian performances

Referring to the standard of International Electrotechnical Commission (IEC), purple and azure light emitting diodes (LEDs) are used to obtain the blue vision and avoid the blue light hazard (BLH). In order to get the high color fidelity for mixed white LED, the other monochromatic LEDs are chosen according to the CIE 1931 chromaticity diagram and Grassmann Color Law of additive color mixture. Using the mathematical model of monochromatic LEDs and restrictions of chromaticity coordinates on Planckian blackbody locus, there are only 2 independent variables in the simulation to a certain combination of peak wavelengths. The optimized peak wavelengths of the five monochromatic LEDs are 385, 467, 524, 564, and 632 nm. The blue light hazard efficiency of radiation (BLHER) of the practical mixed white light is always less than 0.06 when its correlated color temperature (CCT) changes from 2500 to 7000 K. The BLHER is as low as the incandescent lamp at 2700 K and is much lower than other conventional lighting sources. The measured color rendering index (CRI), color fidelity score (Rf), and color gamut score (Rg) of the mixed white light are more than 84.9, 80.4, and 98.1, respectively. The circadian action factor (CAF) is measured as from 0.23 to 0.89 in the above CCT ranges. At last, the limitations of this work and some potential solutions are discussed.

High performance TADF-phosphorescence hybrid warm-white organic light-emitting diodes with a simple fully doping-free device structure

White organic light-emitting diodes (WOLEDs) with doping-free emissive layer (EML) structures have been increasingly attracting attention due to their excellent advantages, such as easier manufacturing process and more flexible structure design. In this paper, a series of highly efficient hybrid WOLEDs is manufactured using a simple doping-free EML structure, which is composed of two blue thermally activated delayed fluorescence (TADF) emitters and an ultrathin (<0.1 nm) orange phosphorescent emitter. Through the thickness optimization of the blue TADF emitters, the optimal device shows a maximum external quantum efficiency, power efficiency, current efficiency, and luminance of 9.1%, 22.7 lm/W, 29.0 cd/A, and 14 530 cd/m2, respectively. When the brightness is increased from 1000 cd/m2 to 10 000 cd/m2, the chromaticity coordinates migrate from (0.44, 0.48) to (0.41, 0.47), and the correlated color temperature changes from 3454 to 3881 K, which belongs to the warm-white light emission zone. The result indicates that the use of a doping-free blue–orange–blue structure provides a common path for fabricating efficient, simple, and low cost WOLEDs.

High pressure responsive luminescence of flexible Eu3+ doped PVDF fibrous mats

Exploring lanthanide doped materials and their high-pressure optical properties is important from the perspective of designing pressure sensors, piezoelectric materials, scintillators, and optoelectronic devices, just to mention a few. Understanding the high-pressure optical properties of polymeric fibrous mats provides significant advantages in terms of flexibility, tunability, facile processability, and malleability. In this work, we have developed flexible polyvinylidene difluoride (PVDF) fibrous mats doped with an Eu3+ source of Eu(NO3)3·5H2O (EN-PF) or Eu2(SO4)3 (ES-PF) by a Forcespinning® method. Microstructural analysis of these two systems indicates that Eu(NO3)3·5H2O and Eu2(SO4)3 are homogeneously distributed and dispersed into the PVDF matrix. Fiber formation promotes a β-phase PVDF. Eu3+ doping increases the β-phase. Its fraction is larger for the ES-PF mats. To understand their high-pressure optical properties, their photoluminescence spectra have been taken at various pressures up to 58 GPa in a diamond anvil cell. High-pressure luminescence illustrates a clear change in asymmetry ratio, peak intensity, peak breadth, color coordinate, and color temperature of Eu3+ ions from both EN-PF and ES-PF with a different extent of changes. Specifically, Eu3+ ions in the ES-PF mats switch from asymmetric to symmetric environment as pressure increases. Those in the EN-PF mats present symmetric environment for all tested pressures. Both of the Eu3+ doped PVDF systems present irreversible changes. Therefore, the EN-PF fibrous mats present an opportunity to make pressure induced red-orange-yellow tunable phosphors for multifunctional applications.

长焦距无热化星敏感器光学系统设计

Optical system is the core component of autonomous navigation star sensor to realize the collection of star light and high-precision attitude measurement. In this paper, the optical system of high precision star sensor was taken as the research object, the influence mechanism of the accuracy of optical system for detecting different color temperature stars were studied and analyzed. It is difficult to suppress the centroid drift caused by the changes of star color temperature and ambient temperature through later calibration, which needs to be controlled under the stage of optical design. The calculation model and allocation method of optical system design wavelength weight were established, and the performance evaluation was carried out. In addition to the conventional energy concentration, distortion and asymmetric aberrations, the centroid drift of star color temperature and ambient temperature change were proposed as the main index of accuracy evaluation. According to the application requirements, a long focal star sensor optical system based on space satellite platform was designed, with the focal length of 95 mm, the relative aperture of f 2.4, the field view of 8°× 8°, the spectrum range of 450-1 000 nm, and the energy concentration of more than 85% in 3×3 pixels. Based on the regular glass materials, the lateral color aberration of the optical system was corrected under ultra-wide spectral range and long focal. The lateral color aberration of the full field was less than 0.9 μm; The results of accuracy analysis show that the accuracy of centroid position is less than 0.36 μm in the range of 2 600-9800 K, and the change of focal length is less than 2.7 μm in the range of 0-40℃, and the accuracy of centroid position caused by temperature is less than 0.45 μm.

Correlation Analysis of Image Reproduction and Display Color Temperature Change to Prevent Sleep Disorder

This paper aims to determine the effect of the smartphone warm color temperature function that relieves display's HEVL (high-energy visible light and short wavelength series blue light), which is known to cause suppression of melatonin secretion on actual image reproduction quality. For this study, the author of this paper measured the display based on the color difference in 26 sampling colors. It was found that for correlated color temperature (CCT) of 4000 K or less, the color difference rose sharply, centering around red and green. In hardware or software, a low CCT was realized by reducing the output centered on blue and green, but in actual color quality, a problem arose in the red and green channels. As far as tone gradation is concerned, ΔE increased for CCT of 4500 K or less while the accuracy of the shadow detail was reduced. With regard to color gamut reproduction, for the coverage of sRGB color space, the color gamut became narrow for CCT of 5500 K or less, and for volume, the color gamut became narrow sharply for CCT of 4000 K. It was found that the maximum CCT changes to prevent a decline in melatonin secretion at a level of minimizing the degradation of image quality is 4000-4500 K.

Spectral Tuning of White Light Allows for Strong Reduction in Melatonin Suppression without Changing Illumination Level or Color Temperature.

Studies with monochromatic light stimuli have shown that the action spectrum for melatonin suppression exhibits its highest sensitivity at short wavelengths, around 460 to 480 nm. Other studies have demonstrated that filtering out the short wavelengths from white light reduces melatonin suppression. However, this filtering of short wavelengths was generally confounded with reduced light intensity and/or changes in color temperature. Moreover, it changed the appearance from white light to yellow/orange, rendering it unusable for many practical applications. Here, we show that selectively tuning a polychromatic white light spectrum, compensating for the reduction in spectral power between 450 and 500 nm by enhancing power at even shorter wavelengths, can produce greatly different effects on melatonin production, without changes in illuminance or color temperature. On different evenings, 15 participants were exposed to 3 h of white light with either low or high power between 450 and 500 nm, and the effects on salivary melatonin levels and alertness were compared with those during a dim light baseline. Exposure to the spectrum with low power between 450 and 500 nm, but high power at even shorter wavelengths, did not suppress melatonin compared with dim light, despite a large difference in illuminance (175 vs. <5 lux). In contrast, exposure to the spectrum with high power between 450 and 500 nm (also 175 lux) resulted in almost 50% melatonin suppression. For alertness, no significant differences between the 3 conditions were observed. These results open up new opportunities for lighting applications that allow for the use of electrical lighting without disturbance of melatonin production.

Low-cost solution of LED driving, designed for tunable white lighting systems

Aiming at increased lighting comfort, new types of light fixtures may currently be seen that may not only be dimmed, but can also adjust the temperature of the light. The ability to adjust the brightness and color temperature is not only supposed to create a pleasant atmosphere, but it may also have a positive effect on human organism, especially if luminaries can be controlled to get as close as possible to the dynamics of natural light. The change in color temperature is known to affect the production of the melatonin hormone in the human body. This capacity is especially useful in situations where we need to increase the alertness of people working at night and thus increase their performance when carrying out certain tasks.This paper deals with the design of a low-cost solution for the power supply units of LED light fittings able to adjust the brightness and temperature of light aiming to achieve the best electrical parameters. While working on the design, the possibility of adding other electronic components to the power supply was considered, which would further increase its usefulness in the future. Experimental results of the power supply efficiency measurements for different control frequencies are presented.