It is well known that the glow to thermionic-arc transition time of HID lamps when the lamp ignites has close relationship to lamp-life characteristics. High-pressure sodium lamps with five different electrode constructions filled with Ne-Ar Penning gas were used for experiments. It became clear that lighter electrode-weight with emitter had shorter glow to thermionic-arc transition time and showed good life performance, as long as the emitter was shielded from the discharge space.

View full abstract

We have studied the relation between light extraction from light-emitting diodes (LEDs) and the characteristics and shape of resin by using ray tracing simulations. Light extraction efficiency (η_ext) was calculated for various resins of with different refraction indexes, transmittances and radii of curvature of the air-resin interface of a fixed LED package. The models of the LED packages included the packaging substrate, reflector, resin, and LED chip, which consisted of an InGaN chip on a patterned sapphire substrate (PSS). It was found that light extraction from LED packages is enhanced by optimization of the extraction paths of the rays by changing the resin characteristics or curvatures.

View full abstract

High-power light-emitting diodes (LEDs) have been fabricated through multi-chip integration of small near-ultraviolet (n-UV) LED chips by using a direct flip-chip bonding technique. Based on optical measurements, the absorption of light between adjoining LED chips was not observed when temperature was held constant, although the luminescence characteristics of the LED decreased with increasing package temperature. Large-scale integration LEDs (LSILEDs) with radiant fluxes over 2 W and 121 LED chips in a single package were fabricated. Four types of packages with different chip densities revealed the importance of thermal management through the control of the number and density of the LED chips in order to obtain high radiant flux and high efficiency.

View full abstract

We compared the work environment in different kinds of offices in Argentina and in Sweden. It was hypothesised that symptoms of discomfort would have multiple causes related to the physical conditions of the building and the psychosocial climate of the work force. It was further hypothesised that these responses would be influenced by the age, gender and cultural background of the office workers. Questionnaires were administered to the personnel during the morning in the middle of the working week. Measurements of lighting, temperature, humidity, and noise were carried out at the same occasion. The results showed that the Swedish offices were more illuminated, and that the Argentinean offices were noisier, comparatively speaking. Subjective reports of complaints were more prevalent in Argentina than in Sweden, and there were also more building-and-work-related symptoms in Argentina than in Sweden. However, the prevalence of BWRS was not only related to the physical environment, but also to the psychosocial climate. High values in social intensity and in familiarity seemed to reduce the symptoms.

View full abstract

Investigation of the brightness of LED on traffic information board or traffic signs under foggy conditions is an important practical consideration, because LED becomes fainter and contrast is reduced. Especially when fog occurs at daytime, fogs appear to be whitish. In these conditions brightness of LED is much dispersion into the fog. In this paper, by evaluating LED brightness with human visual sensitivity, it is understood that in daytime fog condition and different fog densities do affecting brightness evaluation. The colored LED light that contains a red component has high brightness evaluation point and the blue component has low brightness evaluation in all fog densities. However, blue color that containing red color also has high evaluation point. This paper result can contribute to air and land traffic safety which can present further accident happen.

View full abstract

When different images are presented separately to both eyes, an alternation of two views often occurs. Especially, differences in the color of two view fields can also cause rivalry, which is known as “ Color Rivalry”. In this research, we measured the dominant wavelength limits Δλ_d of binocular color fusion on peripheral visions of retinal eccentricity of 0(central vision), 3, 6 and 9 degrees on horizontal meridian respectively, by using a three-dimensional display to present dichoptic stimuli to the left and right eye separately. The dominant wavelength range of the stimuli was from 450 to 650 nm. The size of stimulus was 2° arc of visual angle and the luminance was set 15cd/m². The results show that the binocular color fusion ceases when the color difference introduced between the left and right eyes exceeds a certain threshold value.The results also reveal that color fusion occurs more difficult on central visual field than on peripheral visual field and the color fusion limit Δλ_d becomes larger with the increase of the retinal eccentricity.

View full abstract

According to the machinery statistics by METI, the total number of domestic light bulb production in 2008 was 901 million (91.0% y/y), of which 83 million accounted for general lighting purpose light bulbs (75.6% y/y) and 40 million for halogen lamps (90.9% y/y). The total number of fluorescent lamps produced was 861 million (93.8% y/y). For general-purpose fluorescent lamps excluding backlights, the total production was 279 million (89.9% y/y). The total number of HID lamps produced was 10 million (100.7% y/y). In terms of sales amount against the previous year, general lighting purpose light bulbs was 88.3%, halogen lamps 91.8%, general-purpose fluorescent lamps 100.5%, backlights 82.2%, and HID lamps 97.8%. Within general-purpose fluorescent lamps, the sales amount of bulb-type fluorescent lamps was 13.7.3% y/y. The movement of replacing incandescent lamps has further accelerated, triggered by the policy set forth at the G8 Summit in Toyako, namely to ban the use of incandescent light bulbs. Several exhibitions were held in 2008. Domestic events include, “ Special Exhibition: ‘LED Next Stage’ ” held in conjunction with “ Japan Shop 2008” in March, and “ LED Japan 2008” in October. As for overseas events, a trade show “ Light + Building 2008” was held in Frankfurt, Germany in April. In the area of incandescent lamps, many products designed to replace conventional incandescent lamps with halogen lamps were launched by overseas manufacturers. Development in bulb-type fluorescent lamps, as well as technological advancement in longer life for general fluorescent lamp products, continued to be active. Special editions featuring studies on electrodes were issued by various academic journals. Although the cost per unit luminous flux remains to be high, LED light sources are today on par with conventional light sources (also with fluorescent lamps) in terms of light-emitting efficiency. Development in bulb-type LED products is becoming more vigorous. Progress in technologies for LED chips is robust and improvement in light-emitting efficiency is remarkable. On the other hand, credibility assessment for LED products including life prediction is proactively being reviewed in response to the high expectation toward a long product life exceeding tens of thousands of hours. For HID lamps, product/technology research and development on ceramic metal halide lamps continue to be dominant. A number of fundamental studies based on experiments and modeling schemes was carried out with respect to product development, namely improving light-emitting efficiency, color rendition and product life. The future challenges for HID lamps include gaining further knowledge on filler gases, material behaviors, and the discharge phenomenon. In the area of other discharge lamps, the majority of reports presented were on inductively coupled electrode-less lamps with mercury, microwave discharge lamps, and excimer discharge lamps. There were also reports on new discharge light sources based on nanotechnology application. Several lighting circuit structures for discharge control were proposed for fluorescent lamps, HID lamps, and electrode-less lamps. For lighting circuits for LED, simple circuit structures to achieve miniaturization and cost reduction were introduced in many reports.

View full abstract

According to the statistics by the Ministry of Land, Infrastructure, Transport and Tourism, the total floor space of all building construction starts was 157.41 million m² (2.2% decrease y/y), marking two straight years of decrease. However, in terms of office spaces, it was a 22.0% increase y/y. The target achievement period of the Kyoto Protocol started from 2008 and efforts toward the greenhouse effect gas emission reduction has accelerated. Energy-saving measures for office lighting are beginning to take root through initial illuminance adjustment/control, daylight-use light control and human detection/sensors. As for exhibition pavilions, multipurpose halls, conference halls and religious architectures, environment friendly lighting schemes including CO₂ reduction are being promoted. Moreover, the lighting designs are well balanced with the architectural designs that use natural light from sky lights. For hospitals practicing elderly nursing, it is said that favorable daylight conditions, nice scenic views and associating with nature will help patients to recover. Provision of enhanced dwelling and visual environment is important for elderly nursing facilities. New construction of theatres and halls in the last fiscal year increased approximately 10% y/y and renovations of existing facilities increased 20%. The trend in new constructions is small to medium size halls. Furthermore, small size halls accounted for 70% of all such new construction. A characteristic of newly opened stores and commercial facilities in 2008 was that many introduced energy saving/long life LED apparatus in some way. LEDs are commonly employed in restrooms where light-up hours are long, and on the ceilings above the escalator, vaulted ceilings and to exterior decorative illuminations all of which pose difficult maintenance challenges. In the area of Hotels/Restaurants/Other service industries, a renovation promoting energy saving initiatives with the copious use of LEDs in the entrance and lobby halls in the Windsor Hotel Toya in Hokkaido, the venue of the G8 summit, is introduced. For residential buildings, the use of indirect lighting is common. Lighting designs employing indirect lighting and down lights/pendant lights mounted on the clipped ceiling for the living/dining/kitchen space, and indirect lighting embedded into the handrails serving as lights for the room and the vaulted-ceiling, are introduced.

View full abstract