The effect of LED lighting on color discrimination and preference of elderly people

The purpose of this study is to find out the effects of light‐emitting diode (LED) lighting on elderly people's color discrimination and preference, to improve the lighting environment for elderly people. In this study, experiments were conducted under LED lighting with two different spectra (with color‐correlated temperature [CCT] of 2800K and 6000K), and three different illuminance levels (30lx; 100lx; 1000lx). Six elderly observers (aged 55–65 years) participated in the experiments and were exposed to each lighting condition to finish one trial of a color discrimination test (Farnsworth–Munsell 100‐Hue Test) and a 7‐scale, 6‐item preference evaluation test. We conclude that elderly people perform better in color discrimination with higher CCT of LED light sources, which compensate for their decreased lens transmission at short wavelength. Their performance also increases with higher illuminance (30lx‐1000lx) of LED lighting. Meanwhile, they prefer higher illuminance, which makes them find the lighting environment more comfortable, brighter, and better for reading; but for CCT, although they feel a higher CCT is better for reading, they still have different tastes regarding CCT of light sources. © 2011 Wiley Periodicals, Inc.     

Effect of correlated color temperature and illuminance on sustained attention collected via electroencephalography signals

This study aimed to explore the differences in the subjects' sustained attention under the impact of nine lighting conditions consisting of the combination of three commonly used correlated color temperature (CCT) (3300 K, 4300 K, and 5300 K) and illuminance levels (300 lx, 500 lx, and 750 lx) to provide guidance on the adjustment of CCT and illuminance level parameters for indoor lighting. We selected 24 physically and mentally healthy university students (12 male and 12 female) as the experimental subjects. The subjects were required to perform sustained attention to response task (SART) activities under the nine different lighting conditions and collected the alpha (α) waves (8–12 Hz) from the electroencephalography signals. Subsequently, the mean power spectral density of the α waves and various SART parameters were analyzed and tested. Finally, the effects of different CCT and illuminance levels on the subjects' attention were compared. With the increase in CCT, the attention level tended to increase linearly, whereas the attention level was the lowest at 300 lx and the highest at 500 lx and appeared as an inverted “U” shape. The subjects' attention level was the highest at the combination of CCT of 5300 K and illuminance level of 500 lx and the lowest at the combination of CCT of 3300 K and illuminance level of 500 lx. These results provide important data to elucidate the impact of lighting condition on attention.     

Effects of lensed-indirect and parabolic lighting on the satisfaction,visual health,and productivity of office workers

Abstract

A pre- and post-renovation survey evaluated the reactions of office workers to two office lighting systems: a parabolic downlighting system and a ceiling suspended, lensed-indirect uplighting system. Questionnaire data on work content, perception of ambient environmental conditions (including office lighting), work-related health symptoms, job stress, job satisfaction, and self-reported productivity, and environmental data on illumination, air temperature, and relative humidity were collected. The lensed-indirect lighting system was more favourably rated on several subjective lighting impressions scales, and for computer work workers reported fewer screen glare problems, and fewer and less frequent problems with tired eyes and eye focusing. Productivity was less hindered by the lensed-indirect lighting, and satisfaction with office lighting and ratings of lighting quality were significantly higher for this system. These reactions were not associated with any differences in levels of illumination between the lighting systems. Ratings of lighting satisfaction and lighting importance were inversely related. Overall, some two-thirds of workers indicated a preference for working under the lensed-indirect lighting system.     

Conditions of emergency lighting

Emergency illumination must be provided in case of power failure in public buildings or places of work. A laboratory study of the mobility of subjects under simulated emergency illumination was performed to determine the level of emergency illumination necessary for a rapid exit, and to establish whether this level depends upon the normal illumination. Both young and elderly subjects were used. The experimental conditions were selected to simulate situations in which the occupants are not familiar with the escape route. In addition to measuring the time that the subjects needed to complete an escape, the subjects were asked to evaluate the lighting on several scales; and their ‘spare mental capacity’ during the escape was measured by their performance on a secondary mental task. The results showed that all measures of performance worsen as the emergency lighting is decreased below 2 Ix. The figure of 2 lx is appropriate for both normal light levels tested, 250 and 1000 lx. Where many elderly people are apt to be present, a minimum of 41x is advisable. These recommendations are higher than those prescribed by the British Standards (0-2 lx) and the Deutsche Industrie Norm (10 lx).     

All fiber-optic sensing of light using side-polished fiber overlaid with photoresponsive liquid crystals

This study presents a highly sensitive, all-fiber sensor for in situ detecting light. A fiber-optic light sensing platform was created by overlaying an in-line side-polished fiber (SPF) with a photoresponsive liquid crystal (P-LC) consisting of an azobenzene dye, a chiral dopant, and a nematic LC. The resulting P-LC overlaid SPF light sensor is sensitive to three different light sources, including 380 nm light emitting diode (LED), mercury lamp, and office ceiling lights. Under the light illumination, the energy of irradiation from short wavelengths of light (<450 nm) initiates the trans-to-cis photoisomerization of azobenzene. The photochemical LC-phase transition induced by the generated cis-moiety of azobenzene changes the refractive index of LC-overlaid side-polished area. Light illumination increased the attenuation of the input laser signal. After turning off the illumination, the attenuation returned to its original value, allowing the fiber-optic light sensor to be reused. The sensitivity of the resulting fiber-optic light sensor was 0.16 dB/(μW/cm²) with a detection limit of 5 μW/cm² and 0.06 dB/lx with a detection limit of 45 lx when a 380 nm LED and office ceiling lights were used as illumination sources, respectively. The detection limit increased from 45 to 12 lx when P-LC containing 20 wt% azobenzene was used as light sensing material. The proposed fiber-based light sensor has potential use in harsh environments, such as severely humid and corrosive environments, which could damage mechanical and electronic light sensors.     

Measuring the effects of lighting on the readability of electronic devices

The aim of this study was to understand to what extent people can read e‐paper devices under various conditions of ambient illuminance that can occur indoors. In this study, 110 young to elderly subjects participated in an experiment to evaluate the effects of 14 different levels of ambient lighting on their reading from three different electronic devises and paper text. The participants were asked to undergo a timed read task and then to evaluate the readability of two eReader devices (a regular electronic display and one with a front light) in comparison with a backlit liquid crystal device and conventional paper text. The results indicated that backlit and front lit devices are easier to read at less than 200 lx and the reflective device is easier to read at levels above 500 lx.     

Text - background polarity affects performance irrespective of ambient illumination and colour contrast

In a series of experiments, proofreading performance was consistently better with positive polarity (dark text on light background) than with negative polarity displays (light text on dark background). This positive polarity advantage was independent of ambient lighting (darkness vs. typical office illumination) and of chromaticity (black and white vs. blue and yellow). A final experiment showed that colour contrast (red text on green background) could not compensate for a lack of luminance contrast. Physiological measures of effort and strain (breathing rate, heart rate, heart rate variability and skin conductance level) and self-reported mood, fatigue, arousal, eyestrain, headache, muscle strain and back pain did not vary as a function of any of the independent variables, suggesting that participants worked equally hard in all experimental conditions, so that the interpretation of the primary performance measure was unlikely to be contaminated by a performance-effort trade-off.     

Light for patient safety: Impact of light on reading errors of medication labels

BackgroundIn in-patient care facilities, 1 in 5 medication doses is administered incorrectly. A hospital environment which supports the performance of the health-care staff will positively impact patient safety.ObjectivesDetermine which lighting leads to the least reading mistakes of medication labels.DesignExperimental study with repeated measures.SettingStudy was performed under controlled conditions in the Netherlands.ParticipantsIn total the data of 37 participants are analyzed and described. Inclusion criteria were: female, aged between either 18–30 years old (M = 26.0, SD = 3.1) or between 55 and 67 years old (M = 57.9, SD = 2.7) years old, with normal vision. Eligible participants were personally invited to participate.MethodsPer participant, the readability of three different labels (Blister, Baxter and Orange) and four different font sizes (4.5 pt, 3.5 pt, 3.0 pt, and 2.5 pt Arial Capital) were assessed under nine different light conditions (three illuminances (E),100lx, 500lx, and 1000lx and three correlated color temperatures (T_cp): 3000 K, 4000 K, and 6500 K). The participants had to read out loud text sequences of 10 letters per medication label. The numbers of errors were counted and analyzed.ResultsThe results show a significant difference between numbers of errors related to: 1. Light condition, 2. Age, 3. Label material, 4. Font size. The impact of the light condition is not identical for the different types of label and the font sizes. The impact of the light conditions is the strongest for the smallest font size (2.5 pt) and participants with Visual Acuity < 1.ConclusionLighting has an impact on the number of errors. Older people make more errors than younger people. The type of label has an impact on the number of errors made. The font size has an impact on number of errors made. For font sizes <4.5 pt (Arial), reading medication labels (Blister, Baxter and Orange) under illuminance levels of 100lx, will lead to significantly more errors than E ≥ 500lx. The light condition that generates the least errors for the total test population, all font sizes, and all different materials was the one with an E of 1000lx and a T_cp of 4000 K. People with an insufficient Visual Acuity (VA) benefit most from a higher illuminance level, especially for the Orange labels. When the VA is well-adjusted (sufficient to good) and the font size is as recommended for medication labels (Arial Capital ≥ 4.5 pt) the impact of the lighting on number of errors is limited for all of the age groups.     

基于改进粒子群算法的分布式智能照明系统

针对现有公共建筑照明系统存在的高成本、分布式与集中式控制结合能力不高、交互性不强等问题,应用智能优化算法,在分布式框架上实现区域协同照明控制。通过采集窗户处照度信息,预测透过窗户的自然光在工作面上产生的照度值,当自然光不足需要人工光源补充时,通过协同配合,各区域利用改进粒子群算法计算出区域内最佳的灯具开度组合,达到均匀照明,实现舒适性与节能的最佳综合。当照明需求改变时,可以通过WEB端进行修改。最后,通过实际办公室模型在DIALux evo上进行仿真验证。在不同照明需求和环境条件下,实验结果表明相较于普通控制方式（全开全关）,该方法在节能和舒适度上具有良好的性能,能有效控制工作面照度,各工作面的最大照度误差都在10%之内,控制方案切实可行,具有实用价值。     

Text – background polarity affects performance irrespective of ambient illumination and colour contrast

In a series of experiments, proofreading performance was consistently better with positive polarity (dark text on light background) than with negative polarity displays (light text on dark background). This positive polarity advantage was independent of ambient lighting (darkness vs. typical office illumination) and of chromaticity (black and white vs. blue and yellow). A final experiment showed that colour contrast (red text on green background) could not compensate for a lack of luminance contrast. Physiological measures of effort and strain (breathing rate, heart rate, heart rate variability and skin conductance level) and self-reported mood, fatigue, arousal, eyestrain, headache, muscle strain and back pain did not vary as a function of any of the independent variables, suggesting that participants worked equally hard in all experimental conditions, so that the interpretation of the primary performance measure was unlikely to be contaminated by a performance–effort trade-off.     

Evaluation of Three Tablet Computers at Two Levels of Ambient Illumination

Background: Tablet computers are increasingly widespread in this digital era. During tablet computer use, two important factors are display quality and ambient illumination. The purpose of this experiment was to understand the effects of the display quality of tablet computers (a Sony, a Samsung, and an iPad) and ambient illumination levels (200 lx, 500 lx) on visual fatigue, comfort perception, and task performance.

Methods: Thirty-five university students (17 males and 18 females) were recruited for this experiment. They performed six 40-min trials of playing computer games in all experimental conditions. Visual fatigue, comfort perception, and task performance were collected at the end of each trial.

Results and Discussion: There were no interactions between display model and ambient illumination. Display model had a significant effect on visual fatigue and visual performance, and the best display quality caused less visual fatigue during long periods of viewing. We found no significant effect between 200 lx and 500 lx of ambient illumination on visual fatigue or visual performance; therefore, further research should be conducted to determine what levels of ambient illumination, both high and low, can affect visual fatigue and task performance.     

视觉检测中的光照强度优化研究

为了实现自适应控制光照强度,保障视觉检测系统获得高质量原始图像,研究了彩色图像成像感知模型,建立了图像灰度值与光源光照强度的关系,提出基于HIS彩色空间,单独使用I分量进行光照强度评价,给出了基于数字图像的清晰度和高频信息的光照强度评价函数,并设计了光照强度调控实验系统,通过实验分析了不同测度函数对光照强度变化的评价结果,取得了与人类主观评价一致的结果。实验结果表明,通过提出的方法控制光源强度,可以使视觉系统获得高质量的原始图像,保证检测的质量和精度。     

Modelling and simulation of a lighting control system

The objective of this paper was to regulate the amount of illumination in a room at a constant level, irrespective of the disturbances from outside such as weather conditions or the use of blinds to avoid the glare risk. In order to produce a model of the lighting system in our project, the supply voltage to the lamp dimmer circuits was varied stepwise and the resulting response – measured by the light sensors – was captured with a data-acquisition board. A nonlinear static characteristic in series with a linear 3rd order dynamic system was obtained from this experiment. The model was then used to implement and to validate a lighting system simulator, which was then further used to design, tune, test and evaluate efficient lighting controllers. The control design was rather challenging because the system is highly nonlinear and because undesired interaction occurs between multiple illumination zones in a big office room. The main benefits are a higher level of comfort and a continuous saving of energy.     

天然采光与人工照明的智能结合策略

以‘绿色照明‘为出发点,提出了一个天然采光和人工照明相结合的智能策略.选择一间典型的办公室为试验对象,用BP神经网络建立模型,根据室内天然光的照度水平,自动控制灯具调光输出和遮阳设备状态,从而实现工作区域恒照度的目标.实际应用中,一旦人工照明打开,能检测到的就是天然光和人工光的混合量,很难把天然光分量用设备检测出来,这给控制带来了一定的麻烦.因此提出了一个自适应神经模糊推理系统,用以根据室外的天然光照度来预测室内的天然光照度,作为BP网络的输入.实验数据表明,该方法能有效节约能源,并改善工作环境,提高工作效率.     

Objective and subjective assessments of lighting in a hospital setting: implications for health,safety and performance

A field study was conducted to evaluate the illumination levels, to examine the effect of lighting conditions (including lighting characteristics and disturbances) on employee satisfaction, job performance, safety and health, and to compare the employees' perception of lighting level with actual illuminance levels in a hospital setting using both questionnaire and physical illuminance measurements. The illumination levels varied across different locations within the hospital and were lower than standards for 52.2% of the workplaces surveyed. Most respondents indicated that at least one of the four lighting characteristics (i.e. light level, type of light sources, light colour and use of daylight) was inappropriate, and that at least one of the three lighting disturbances (i.e. flickering lights, glare and unwanted shadows) was a major disturbance to them. The employees' perceptions of illuminance generally reflected the actual illuminance levels. The more appropriate maintenance or installation of lighting fixtures was rated as the most appropriate for improving lighting. The findings suggest that environmental ergonomics should be given a more prominent role in hospital building and workplace design to support safer healthcare facilities (for staff and potentially for patients).

Practitioner Summary: Good lighting is essential to improve employee performance, health and safety. The findings suggest that quantitative physical measurements should be supplemented by qualitative subjective assessments to provide a more holistic approach where specific details about the lighting condition in each working environment are incorporated from the workers' perspective.     

Effects of color temperature and luminance of LEDs on color judgments involving various printing materials

This study investigated errors in color judgment related to stimuli (cyan vs. magenta vs. yellow) printed on various materials (coated paper vs. cotton vs. polyester fiber) and occurring in a range of visual environments (color temperature × luminance: 4000 K × 1500 lx vs. 4000 K × 750 lx vs. 2700 K × 1500 lx vs. 2700 K × 750 lx) under illuminated light‐emitting diodes. Participants included 16 female and 14 male Taiwanese college students [age range, 20–26 years (M = 21.92, SD = 2.13)]. Subjects were instructed to perform a series of comparative judgments in which they carefully observed a standard stimulus color under illuminated LEDs and judged which of five simultaneously presented colors under illuminant D65 was the most similar to the standard color. Data analysis revealed that the effect of visual environment on accuracy of color judgments against the standard was significant. Additionally, the accuracy of color judgments against the standard was significantly better for polyester printing material than it was for coated paper. The color of the standard also significantly affected color judgment accuracy: cyan yielded significantly worse accuracy rates than did magenta or yellow. These results have implications for lighting design and interior design.     

Type classification, color estimation, and specific target detection of moving targets on public streets

This paper describes a vision system that recognizes moving targets such as vehicles and pedestrians on public streets. This system can: (1) classify targets {vehicle, pedestrian, others} and, for vehicles, discriminate vehicle types and (2) estimate the main colors of targets. According to the input images to the system, the categories of targets are set as {mule (golf cart for workers), sedan, van, truck, pedestrian (single or plural), and other (such as noise)}. Their colors are set as six color groups {red, orange, yellow; green; blue, light blue; white, silver, gray; dark blue, dark gray, black; dark red, dark orange}. In this experiment, we collected images of targets from 9: 00 a.m. to 5: 00 p.m. on sunny and cloudy days as system training samples. The recognition ratio was 91.1% under the condition that both the recognition results of type and color agreed with the operators judgment. In addition, the system can detect predefined specific targets such as delivery vans, post office vans, and police cars by combining recognition results for type and color. The recognition ratio for specific targets was 92.9%. For the classification and estimation of targets, we employed a statistical linear discrimination method (linear discriminant analysis, LDA) and a nonlinear decision rule (weighted K-nearest neighbor rule, K-NN).Received: 11 March 2004, Accepted: 11 August 2004, Published online: 20 December 2004 Correspondence to: Osamu Hasegawa     

基于天空模型的公共场所照明智能控制

公共场所照明具有全天候、多应用、能耗大的特点;掌握任意时间的天空亮度分布情况是充分利用自然光、实现智能照明的基础;基于国际照明委员会(CIE)给出的天空亮度计算公式,建立自然光对公共照明区域产生的天空照度模型;引入数学和光学相关原理建立公共场所人造光和自然光的混合模型;利用改进蚁群算法求解模型,得出最佳的灯具亮度组合,实现舒适和及节能的综合最优;最后,选择典型的大跨度带天窗建筑物为采光对象完成仿真实验,实验结果验证该策略的有效性。     

An expert system for lighting energy management in public school facilities

Abstract: Lighting accounts for a large part of the energy expenses of a facility, ranging from 40% to 60% of the total energy cost. Therefore, it represents a critical factor to consider in any energy management program. Lighting audits involve complex energy calculations, such as the estimation of light intensity per square unit area, quality of illumination, and required number of light sources to obtain an adequate illumination level in the facility. In this paper we discuss the development and implementation of an easy-to-use expert system for lighting energy management in public schools. The prototype computer-based system can evaluate 11 different areas of a school facility, and it can identify suitable lighting solutions from 17 distinct bulb types and 38 ballast types. The system determines a facility's required number of bulbs, and it performs the cost and saving analysis of its final recommendation. The constructed expert system was successfully validated by two human experts through two case studies, involving the evaluation of a conventional classroom and a medium-size office.