The color appearance of domestic and commercial spaces is becoming increasingly important. Therefore, indices for evaluating visual impressions of lighted objects, such as vividness and brightness, as well as for measuring color preference, are needed. In this study, we conducted visual experiments to evaluate differences in color properties, such as vividness and brightness, as well as color preference, due to the spectral distribution of luminaires used in domestic and commercial spaces, and attempted to predict the experimental results using a color appearance model. Three typical LED light sources (1: blue LED+yellow phosphor; 2: blue LED+RG phosphor; 3: UV LED+RGB phosphor), a fluorescent lamp (three wavelengths) and an incandescent lamp were used as the test light sources. Visual experiments were conducted to compare the color appearance under test and reference light sources of 15 color samples, using the color rendering index. The subjects were 45 young adults and 21 elderly adults. The experimental results were evaluated by principal component analysis. Five principal components were extracted from the results of the young subjects, and four from those of the elderly subjects. In addition, the components for the young and elderly subjects differed in terms of the descriptive adjectives that had large principal component loadings; young people tended to prefer vivid and bright colors, while elderly people tended to prefer calming colors. We attempted to predict the results of principal component analysis using multiple regression analysis with the CIECAM02 model parameters. Strong correlations were obtained between the principal components representing “vivid” and “bright” and a regression equation of the lightness of high chroma colors. The determination coefficient (r2) was 0.66 for young subjects and 0.63 for elderly subjects. The results of this study indicated that predictions based on CIECAM02 parameters could be applied to the results of principal component analysis.
The authors introduce LED tunnel illumination for improving the vertical illuminance by considering the light as vectors when designing the light distribution. This new illuminating devices installed and evaluated the visibility of the road at Hanzan Tunnel for the down line of Takamatsu Expressway. As the result, the vertical illuminance is improved by 40% when increasing the ratio of vector component of light by using the Pro-bean. Actually, according to the questionnaire result of subjects who had a driver’s licence were different by gender, ages and driving experience, by increasing the vertical illuminance the visibility of the leading vehicle are improved significantly. Therefore, it is expected that the Pro-Beam illumination for improving the visibility by increasing the vertical illuminance is effective in reducing traffic accidents in tunnel.
The presence of obstacles on expressways often results in major traffic accidents. Therefore, ensuring the visibility of obstacles on roads is an important factor for maintaining a safe and comfortable visual driving environment. The visibility of obstacles on road, especially in tunnels, is related to the lighting environment. In this study, we have proposed two lighting-control methods and evaluated the visibility of obstacles under a combination of light-distribution control and lighting-time control and a combination of light-distribution control and color-temperature control. Further, we evaluated the effectiveness of these two lighting-control methods and obtained good visibility by combining the pro-beam lighting operated using direct current (DC) and symmetric lighting operated by pulses having a frequency of 60 Hz and a duty ratio of 50%. The visibility can be effectively improved by increasing the luminous contrast between the background road surface and the object. In addition, when lighting-time control was applied, temporal luminance contrast was achieved, and the perceived luminance was enhanced by the pulse (Broca–Sulzer effect), thereby improving the visibility. Further, the visibility can be improved by changing the color temperature with the light-distribution angle because of the difference in chromaticity between the background road surface and the object.
Blue light emitting diode (LED) light is being used various devices for recent decades. Blue LED light has the 450–500 nm wavelengths, and high photon energy compared with green or red LED light. It is known that the exposure to blue LED light causes retinal photoreceptor cells damage. It is unknown whether the blue LED light cut particle containing lens has a protective effect against blue LED light-induced cell damage although the absorbance by colored lens shows a protective effect. Thus, the purpose of this study was to reveal that the protective effect of blue LED light cutting particle containing lens against photoreceptor and corneal epithelial cell damage induced by blue LED light exposure. We irradiated blue LED light to the mouse photoreceptor cells and human cornea epithelial cells with or without lens. The lens containing about one third blue LED light cutting particle (TECHPOLYMER) decreased production of reactive oxygen species and improved cell death rate and cell viability rate. These findings show that TECHPOLYMER containing lens may protect photoreceptor and cornea cells by reducing of reactive oxygen species.