Color Temperature Of Light Research Articles

A Study on the Effect of Microlens Arrays on the Correlated Color Temperature and Color Rendering Index of Quantum Dot Lighting

A Study on the Effect of Microlens Arrays on the Correlated Color Temperature and Color Rendering Index of Quantum Dot Lighting

An Investigation into the Effects of Correlated Color Temperature and Illuminance of Urban Motor Vehicle Road Lighting on Driver Alertness.

Current international optical science research focuses on the non-visual effects of lighting on human cognition, mood, and biological rhythms to enhance overall well-being. Nocturnal roadway lighting, in particular, has a substantial impact on drivers' physiological and psychological states, influencing behavior and safety. This study investigates the non-visual effects of correlated color temperature (CCT: 3000K vs. 4000K vs. 5000K) and illuminance levels (20 lx vs. 30 lx) of urban motor vehicle road lighting on driver alertness during various driving tasks. Conducted between 19:00 and 20:30, the experiments utilized a human-vehicle-light simulation platform. EEG (β waves), reaction time, and subjective evaluations using the Karolinska Sleepiness Scale (KSS) were measured. The results indicated that the interaction between CCT and illuminance, as well as between CCT and task type, significantly influenced driver alertness. However, no significant effect of CCT and illuminance on reaction time was observed. The findings suggest that higher illuminance (30 lx) combined with medium CCT (4000K) effectively reduces reaction time. This investigation enriches related research, provides valuable reference for future studies, and enhances understanding of the mechanisms of lighting's influence on driver alertness. Moreover, the findings have significant implications for optimizing the design of urban road lighting.

Tunable cold/warm white light emitting devices based on carbon dots with multiple emissive centers

The correlated color temperature (CCT) of lighting is closely related to human emotions. However, there is still a relative lack of white light emitting devices (W-LEDs) with tunable CCT to meet application demands in different scenarios. Here, we develop a W-LED with tunable CCT based on multiple emissive centers of carbon dots (CDots) synthesized through controlled thermal carbonization of citric acid and urea. The reaction at 160 °C for 4 h results in amorphous CDots, which exhibit excitation wavelength dependent photoluminescence (PL) containing two peaks at 446 and 520 nm. However, by increasing the reaction temperature and duration, crystalline CDots are obtained, which show broad PL peaking at 650 nm. Based on their complementary spectral ranges, a W-LED with an extremely high color rendering index of 96 is demonstrated. Moreover, a W-LED with both 365 and 405 nm electroluminescent chips is designed. The W-LED shifts from cold to warm white, when the excitation chips switch from 365 to 405 nm. This adjustable CCT can create a harmonious, enjoyable, and safe lighting environment to meet the demands of different scenes.

P‐9: Integrated Ambipolar a‐Si TFT with Active Pixel Sensing Array Applied for Ambient Color Temperature and UV Sensing

In this paper, we integrate ambipolar a‐Si TFT with an active sensing pixel array for ambient color temperature and UV light intensity estimation. The algorithm calculates color temperature using RGBW data, while UV intensity is estimated using effective UV‐blocking ITO glass. Experimental results confirm the system is suitable for multicolor sensing across diverse applications.

An experimental investigation on the effect of lighting colour of localized radiant panel thermal comfort system

This study investigated the effect of different correlated colour temperature (CCT) lighting on perceived thermal comfort in a simulated domestic environment with radiant heating. A prototype with adjustable CCT lighting (4000K neutral, 1800K warm, 6500K cold) alongside electric radiant panels was installed in an environmental chamber set to 18 °C. The investigation involved sixty participants who each underwent 30-min exposure sessions to one of the lighting scenarios in a blinded setup, during which they filled out thermal comfort questionnaires at predetermined intervals. Overall, the findings revealed satisfactory comfort levels, with average global comfort votes of “good” and 82.32 % thermal acceptability, across scenarios. The radiant heating prototype successfully maintained thermal comfort in the less-conditioned space. Looking at the different lighting scenarios, the “warm” lighting initially provided the highest thermal comfort, aligning with the hue-heat hypothesis, with global comfort votes of 1.13, compared to 0.96 for “neutral” and 0.78 for “cold” after the first 10 min. However, differences became less pronounced over time. Contrary to hypotheses, the “cold” lighting scenario did not reduce comfort compared to “neutral”. Moreover, Participants indicated greater thermal satisfaction under “warm” lighting. Although changes in lighting CCT did not drastically alter thermal perceptions, they did have a subtle influence on comfort, particularly during the initial stages of the experiment. This finding suggests the need for further research into how visual and thermal comfort interactions can be optimized.

High correlated color temperature artificial lighting impairs retinal pigment epithelium integrity and chloride ion transport: A potential mechanism for choroidal thinning

Among the environmental factors contributing to myopia, the role of correlated color temperature (CCT) of ambient light emerges as a key element warranting in-depth investigation. The choroid, a highly vascularized and dynamic structure, often undergoes thinning during the progression of myopia, though the precise mechanism remains elusive. The retinal pigment epithelium (RPE), the outermost layer of the retina, plays a pivotal role in regulating the transport of ion and fluid between the subretinal space and the choroid. A hypothesis suggests that variations in choroidal thickness (ChT) may be modulated by transepithelial fluid movement across the RPE. Our experimental results demonstrate that high CCT illumination significantly compromised the integrity of tight junctions in the RPE and disrupted chloride ion transport. This functional impairment of the RPE may lead to a reduction in fluid transfer across the RPE, consequently resulting in choroidal thinning and potentially accelerating axial elongation. Our findings provide support for the crucial role of the RPE in regulating ChT. Furthermore, we emphasize the potential hazards posed by high CCT artificial illumination on the RPE, the choroid, and refractive development, underscoring the importance of developing eye-friendly artificial light sources to aid in the prevention and control of myopia.

Study of Lighting Design for Interior Spaces

Due to the continuous progress of lighting fixture technology, people's requirements for commercial space design are also rising, and the comfortable, convenient, artistic, and technological combination of space is more and more emphasized by designers. The author has collected a large amount of visual subjective evaluation data through actual investigation and experimentation and conducted extensive and in-depth research on the light source's low radiation, luminous flux, luminous intensity, illuminance, luminance, color temperature, color deviation, color tolerance, beam angle, and maintenance coefficient. This paper takes the lighting quality parameters as the benchmark, analyzes the formal aesthetic relationship between commercial space and lighting design, and has a certain reference value for both lighting workers and academic research.

The effects of light distribution, color temperature, and Illuminance on the drawings’ quality of fine arts and Design students

The effects of light distribution, color temperature, and Illuminance on the drawings’ quality of fine arts and Design students

Verification of the Applicability of Obstacle Recognition Distance as a Measure of Effectiveness of Road Lighting on Rainy and Foggy Roads

Adverse weather conditions at night are very fatal to drivers, causing serious traffic accidents. Road lighting is a facility that can alleviate these dangerous situations. Nevertheless, road lighting has only rarely been studied during adverse weather. The reason is that the current road lighting performance evaluation method is presented based on normal weather. The current road lighting performance evaluation method uses a luminance meter to measure the road surface, which is not suitable due to scattering during adverse weather such as rain and fog. Therefore, this study proposes obstacle recognition distance as a measure of effectiveness to evaluate the performance of road lighting during adverse weather. There is a lack of actual research on whether obstacle recognition distance can be used as a measure of effectiveness for road lighting during adverse weather. Therefore, in this study, 30 subjects were used to measure the subjects’ obstacle recognition distance according to changes in weather conditions, road lighting grade, and road lighting color temperature. As a result, it was analyzed that there was a clear trend of change in obstacle recognition distance depending on the change in each condition. It was found that, under the same road lighting performance conditions, there was a difference of up to 72.86% by weather condition; under the same weather conditions, there was a difference of up to 22.75% by road lighting grade; and by color temperature, there was a difference of up to 21.87%. In addition, a statistical significance test was performed to support the existence of a difference, and the results were synthesized to suggest that obstacle recognition distance can be used as a performance measure of effectiveness of road lighting in adverse weather.

Programmable directional color dynamics using plasmonics

Adaptive multicolor filters have emerged as key components for ensuring color accuracy and resolution in outdoor visual devices. However, the current state of this technology is still in its infancy and largely reliant on liquid crystal devices that require high voltage and bulky structural designs. Here, we present a multicolor nanofilter consisting of multilayered ‘active’ plasmonic nanocomposites, wherein metallic nanoparticles are embedded within a conductive polymer nanofilm. These nanocomposites are fabricated with a total thickness below 100 nm using a ‘lithography-free’ method at the wafer level, and they inherently exhibit three prominent optical modes, accompanying scattering phenomena that produce distinct dichroic reflection and transmission colors. Here, a pivotal achievement is that all these colors are electrically manipulated with an applied external voltage of less than 1 V with 3.5 s of switching speed, encompassing the entire visible spectrum. Furthermore, this electrically programmable multicolor function enables the effective and dynamic modulation of the color temperature of white light across the warm-to-cool spectrum (3250 K–6250 K). This transformative capability is exceptionally valuable for enhancing the performance of outdoor optical devices that are independent of factors such as the sun’s elevation and prevailing weather conditions.

Effect of the Light Environment on Image-Based SPAD Value Prediction of Radish Leaves

This study aims to clarify the influence of photographic environments under different light sources on image-based SPAD value prediction. The input variables for the SPAD value prediction using Random Forests, XGBoost, and LightGBM were RGB values, HSL values, HSV values, light color temperature (LCT), and illuminance (ILL). Model performance was assessed using Pearson’s correlation coefficient (COR), Nash–Sutcliffe efficiency (NSE), and root mean squared error (RMSE). Especially, SPAD value prediction with Random Forests resulted in high accuracy in a stable light environment; CORRGB+ILL+LCT and CORHSL+ILL+LCT were 0.929 and 0.922, respectively. Image-based SPAD value prediction was effective under halogen light with a similar color temperature at dusk; CORRGB+ILL and CORHSL+ILL were 0.895 and 0.876, respectively. The HSL value under LED could be used to predict the SPAD value with high accuracy in all performance measures. The results supported the applicability of SPAD value prediction using Random Forests under a wide range of lighting conditions, such as dusk, by training a model based on data collected under different illuminance conditions in various light sources. Further studies are required to examine this method under outdoor conditions in spatiotemporally dynamic light environments.

Study on the subjective brightness of photonic crystal structural colored wood products

ABSTRACT Photonic crystal structural color is a novel method in the field of colored coating on the surface of wood products. However, the subjective brightness of photonic crystal structural colored wood products under different color temperature light sources has not been studied. In this study, poly(styrene-methyl methacrylate-acrylic acid) latex microspheres with different diameters were used to construct photonic crystal coatings on wood surface. The subjective brightness psychological quantity under different color temperature light sources was obtained. Combined with the optical properties of the coatings, the correlation between the physical optical properties of the photonic crystal coating, the color temperature of the light source and the subjective brightness of the coating was obtained. The photonic crystal coating in the near red visible light wavelength range had higher subjective brightness under low color temperature light source, and coating in the near purple visible light wavelength range had higher subjective brightness under high color temperature light source. The subjective brightness of the photonic crystal coating was very closely related to the light source color temperature and closely related to the reflectivity of the coating. This study expands the research on the optical properties of photonic crystal structure colored wood products.

Dynamics of Bioactive Compounds under the Influence of Yellow, Blue, and Violet Light Filters on Hippophae rhamnoides L. (Sea Buckthorn) Fruits

The current study was carried out to monitor the dynamics of phenolic compounds and vitamin C variations in Hippophae rhamnoides L. (sea buckthorn) under the influence of different color filters, as follows: yellow (590 nm), blue (450 nm), and violet (400 nm). The fruits were harvested at maturity from different parts of the canopy (i.e., base, middle, and top), immediately stored at −18 °C, and afterward lyophilized to reduce the loss of compounds for preparing the chemical assays that were carried out. HPLC-DAD-ESI+ was used to determine the phenolic compounds and vitamin C content of the fruits. EPR (electron paramagnetic resonance) measurements were also carried out to confirm the antioxidant character of the berries. This is the first study to examine the effect of different color filters on the accumulation of phenolic compounds and vitamin C content in the fruits of sea buckthorn. Among the three color filters used, the violet filter proved to be the most beneficial for the accumulation of total phenolic compounds (3.326 mg/g) and vitamin C (1.550 mg/g) in the berries. To reach high contents of phenolic compounds and vitamin C, the best setup included using very-high-energy emission LEDs as close as possible to blue and violet (400–450 nm). Therefore, the different light color intensities and temperatures on each level of a canopy play key roles in enhancing the phenolic compound content, antioxidant activity, and vitamin C content of sea buckthorn fruits. This knowledge will help provide insights into the accumulation of secondary metabolites and improve future production strategies in sea buckthorn.

Impact of color temperature and illuminance of ambient light conditions on the accuracy of complete-arch digital implant scans.

The purpose of the present study was to assess the influence of color temperature and illuminance of ambient light on the accuracy of different intraoral scanners (IOSs) in complete-arch implant scans. An edentulous model with six implants and scan bodies was digitized by using a laboratory scanner (DW-7-140; Dental Wings) to obtain a reference mesh. Fifteen scans were performed employing two intraoral scanners (Trios 4;3Shape A/S and i700; Medit Co) at two illuminances (500 and 1000 lux) and three color temperatures (3200, 4400, and 5600 K). Scanning accuracy was measured by using a 3D metrology software program (Geomagic Control X). Kruskal-Wallis, one-way ANOVA, and pairwise comparison tests were used to analyze the data (α = .05). Significant differences in trueness and precision values were found among the different IOSs under the same ambient lighting condition and among the different lighting conditions for a given IOS (p < .05) except for trueness in i700 groups (p > .05). The influence on the accuracy of color temperature and illuminance varied depending on the intraoral scanner. An optimal ambient scanning light condition was not found; this should be adjusted based on the specific IOS system used. 3200 K of ambient light influences the precision of i700 when performed at 1000 lux, decreasing the accuracy. The variation of color temperature at the same illuminance does not affect the scanning accuracy of TRIOS 4, which obtained better accuracy in all scans at 1000 lux.

Recommendations on Use of DIC in Experimental Geotechnics

Abstract Image-based deformation measurement techniques, like digital image correlation (DIC), are used to measure the displacement of soil particles and thereby to investigate the behavior of geo-structure in experimental geotechnics. The precision of the measurement from the DIC technique depends on the position of the camera and light panels, the color temperature of light, size of the region of interest (RoI), type and relative density of sand, seeding ratio, type of camera, and strain rate used in experiments. In the paper, the effect of above-mentioned parameters is investigated experimentally in 1-g model tests. The studies show that the precision in DIC measurements is dependent on the position of camera and light panels, size of RoI, texture of the sand, and seeding ratio. However, the relative density of sand and strain rate do not significantly affect the results from the DIC analysis. The efficacy in the measurement of the large deformations and suitability of smartphone cameras using DIC are also addressed. Last, we developed recommendations to obtain precise results from DIC in experimental geotechnics.

Artificial Lighting’s Relation to Visitors’ Activity Place in Coffee Shops: An Analysis

Artificial lighting is lighting that comes from manufactured light sources such as lamps. To make the room comfortable and function properly, the lighting must be able to accommodate various activities in the space. This study aimed to determine the relationship of artificial lighting to the visitor’s activity in coffee shops. The artificial lighting studied included light intensity, light color temperature, and lighting distribution. The results of the data collected were then analyzed using descriptive analysis methods. The study’s results indicate that artificial lighting affects the visitor’s activity. Areas with higher light intensity, light color within the white spectrum, and a more even light distribution have more activity variety.

The influence of multisensory indoor environment on the perception of orange juice

Drinking (as well as eating) represents a fundamental multisensory experience of our lives. Recent studies have proposed the implementation of multisensory contexts to improve the taste perception of food and beverages. This topic becomes relevant when considering the possibility of promoting the consumption of healthy beverages (e.g., orange juice). Only a few studies have concentrated on the multisensory features of the indoor environment (e.g., acoustic and visual context) reporting effects on the perception of healthy beverages. This study investigates how multisensory indoor environments modify the taste perception while drinking orange juice. By controlling the room microclimate and combining the correlated colour temperature of lighting (i.e. warm and cool) and the background wall colour (i.e., red, green) in the Sens i-Lab, with different audio stimuli (i.e. low and high-frequency pure tone), participants were invited to taste the low-sugar orange juice and to rate the fruit juice aroma, sweetness, sourness, bitterness, freshness, and thickness. The results showed that listening to a high-frequency tone in an environment with warm lighting and a red background increases the sweetness perception of orange juice compared to the control environment. In addition, compared to the control condition, the juice aroma was rated more intense in almost all multisensory conditions and thicker with cool lighting and a green background while listening to a low-frequency tone. Our findings suggested that the development of multisensory design can contribute to interior design strategies and design innovation in food architecture, where people can improve their taste in healthy foods and beverages.

Underwater power compensated white light source based on synthetic white laser

The semiconductor white laser light source is used as a light source for underwater illumination. The required standard color temperature of white light is obtained at the underwater target surface. We studied the power compensation of a synthetic white laser source and its application to underwater illumination. First, the power ratios of the red (638 nm), green (520 nm), and blue (450 nm) lasers at a color temperature of 6500 K were obtained by using chromaticity theory. Next, the three-color and synthetic white laser parameters were obtained with transmission distance, according to the exponential attenuation characteristics of different light in clear water and seawater medium. The three-color laser power at the output was compensated, and the underwater target illumination surface reached the standard 6500 K color temperature of the white laser, improving the illumination. Finally, an experimental system for underwater white laser illumination based on power compensation was established. The errors between experimental and theoretical results of color temperature and illuminance are no more than 0.43% and 22.15%. This power-compensated synthetic white laser light source has both the advantages of long-range underwater detection and the spectral advantages of LED white light sources. The white laser light source meets specific requirements by compensating for power and optimizing white light characteristics for underwater lighting applications.

Estimating SpO2 with Deep Oxygen Desaturations from Facial Video Under Various Lighting Conditions: A Feasibility Study.

This paper presents a feasibility study to collect data, process signals, and validate accuracy of peripheral oxygen saturation (SpO2) estimation from facial video in various lighting conditions. We collected facial videos using RGB camera, without auto-tuning, from subjects when they were breathing through a mouth tube with their nose clipped. The videos were record under four lighting conditions: warm color temperature and normal brightness, neutral color temperature and normal brightness, cool color temperature and normal brightness, neutral color temperature and dim brightness. The air inhaled by the subjects was manually controlled to gradually induce hypoxemia and lower subjects' SpO2 to as low as 81%. We first extracted the remote photoplethysmogram (rPPG) signals from the videos. We applied the principle of pulse oximetry and extracted the ratio of ratios (RoR) for two color combinations: Red/Blue and Red/Green. Next, we assessed SpO2 estimation accuracy against the ground truth, a Transfer Standard Pulse Oximeter. We have achieved an RMSE of 1.93% and a PCC of 0.97 under the warm color temperature and normal brightness lighting condition using leave-one-subject-out cross validation between two subjects. The results have demonstrated the feasibility to estimate SpO2 remotely and accurately using consumer level RGB camera with suitable camera configuration and lighting condition.Clinical Relevance- This work demonstrates that SpO2 can be estimated accurately using an RGB camera without auto-tuning and under warm color temperature, enabling continuous SpO2 monitoring applications that require noncontact sensing.

47‐1: Ambipolar Gap‐type a‐Si‐TFT Circuit Applied for a Color Ambient Light Sensor

In this paper, we proposed ambient light sensor (ALS) and color temperature sensor (CTS) circuit integrated in the edge of LCD display panel. The designed circuit is based on the thin film transistor (TFT) technology, the photo TFT can produce high photo current under light for sensor realizing ambient light from 0~50000Lux. Also, CTS circuit are based on ALS circuit but covered with color filter. The result shows that CTS can discriminate different color temperature in ambient light. The biggest advantage of this sensor is that it is compatible with TFT process in manufacturing, and it is small in size and high in efficiency. It has the potential to replace photodiode sensors.