A compact excimer lamp constructed with a piezoelectric transformer (PT) has been developed in our laboratory. This excimer lamp is designed based on the excitation of a dielectric barrier discharge (DBD) in a He-Xe mixture generated by the PT, which is driven with low applied voltages of several tens of volts (15-45V). Vacuum ultraviolet (VUV) radiated from the lamp is detected by a phototube having a spectral response region ranging from 160 to 320 nm in conjunction with an optical filter to discriminate the VUV and UV regions. The VUV radiation in the wavelength range 160-200 nm is recognized in this experiment. This may be derived from the 172-nm light emission by the transitions of the Xe₂ excimers to the ground state. Investigations into the radiated VUV intensity are carried out by varying the gas pressure and the gap length. The optimal condition for the present excimer lamp is determined.

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We have developed a high power and long lifetime white LED module which can be used in general lighting applications. Since the materials in the package are very robust at high temperatures, the device can be operated at junction temperatures (Tj) over 250°C. Moreover, the thermal resistance of the package is less than 20°C/W. Therefore the device can be operated at input power as high as 2.4 W, making it possible to shorten the duration of accelerated lifetime tests. An acceleration ratio greater than 100 has been achieved. Assuming a thermally activated degradation process and applying the Arrhenius model, the LED chip lifetime (defined as a 50% reduction in luminous flux) is determined to be 40,000 hours for a Tj of 130°C. The activation energy of the degradation process was determined to be 1.55 eV.

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Temporal characteristics of fluorescent lighting systems during starting might affect their acceptance in commercial and residential lighting. The immediate, full onset of light is usually experienced when switching on incandescent lamp systems. For certain systems using fluorescent lamps, delayed onset or initially low light levels might be experienced. Such characteristics could make them unwelcome additions to commercial and residential settings. The results of a study to investigate subjective and behavioral responses to lighting systems having different temporal characteristics upon start-up are presented.

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A dimmable task lighting system was installed at six working places in a luminaire factory in France. The factory hall had skylights that prvided a lot of daylight. The purpose was to study which illuminances users select, how often they use additional task lighting, whether they liked the lighting system and if their selections were influenced by the amount of daylight or the type of work. The workers were free to use the task lighting in any way they wanted. The settings of the task lighting were recorded between the winter of 2004 and the spring of 2005. The opinions of the users were sought by means of questionnaires after the testing period. It was found that those workers who worked in the area on more than 20 days in the testing period used the task lighting (viz. switched it on) on average only during 6.5% of the total working time. The task lighting was used more frequently during the times when the amount of daylight was limited (darkness or dark weather) and less frequently when there was more daylight in the area. And the task itself also had an influence on the preferred illuminance, and hence on the frequency of use of the task lighting. The preferred horizontal task illuminances supplied by the task-lighting luminaires varied from person to person, with an average of around 600 lux. The users expressed the wish that they wanted to keep the system after the test period, and 41 per cent of the users felt that the task lighting helped them to perform better.

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This paper shows Typical Annual Weather Data (TWD9302/L) and its application to daylight simulation. Long-term observation data were obtained in Chofu-city, Tokyo from 1993 to 2002 in conformity to the International Daylight Measurement Programme. TWD9302/L contains air temperature, absolute humidity, illuminance, etc., at interval of one minute, and sky luminance distribution and sky radiance distribution at interval of 30 minutes. It is possible to simulate both lighting and thermal annual environment. The methods of complementing the sky luminance around the sun influenced the daylight simulation results at about 2% on average.

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Innumerous attempts to solve the problems of exterior lighting in non-electrified areas of India e.g. highways, hilly areas, rural areas of delta regions have been made in the last two decades. A solar powered lighting system with 11 watt or 18 watt Compact Fluorescent Lamps (CFL) have been mounted in street light fixtures at some places but insufficient amount of light do not always serve the required need of the users specially in foggy weather. This paper reports the development of a battery powered lighting system fitted with a 35 Watt Low Pressure Sodium Vapour (SOX) lamp. It is extremely beneficial in remote non-electrified areas for its far higher light output when fitted in street light or flood light fixtures. The battery may be charged from any non-conventional energy source and is connected to the electronic circuit, which operates at high frequency. The light output of this system fitted with a solar photovoltaic array (SPVA) and the corresponding battery power have been measured and the results have been reported in this paper. This high intensity lighting system has a wide application potential in developing countries throughout the world.

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Discomfort glare from daylight is a common problem without valid prediction methods so far. A new mathematical DGI_N (New Daylight Glare Index) method tries to respond the challenge. This paper reports on experiments carried out in daylit office environment in Japan to test applicability of the method. Slight positive correlation was found between the DGI_N and the subjective evaluation. Additionally, a high L_adaptation value together with the small ratio of L_window to L_adaptation was obviously experienced sufficient to neutralize the effect of glare discomfort. However, subjective assessments are poor glare indicators and not reliable in testing glare prediction methods. DGI_N is a good indicator of daylight glare, and when the DGI_N value is analyzed together with the measured illuminance ratios, discomfort glare from daylight can be analyzed in a quantitative manner. The DGI_N method could serve architects and lighting designers in testing daylighting systems, and also guide the action of daylight responsive lighting controls.

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Mercury which is used in fluorescent lamps for general lighting has a possibility to cause environmental problems. Authors have been developing lamps which contain only rare gases without mercury. The rare gas lamps are environmentally-friendly, but it has lower luminance than the mercury lamp has. Therefore, the authors have tried expanding positive column by using an external electrode, and 12000 cd/m² was achieved by cylindrical xenon fluorescent Lamp. In this paper it is reported that the same method is also useful for flat lamps with multi anodes. An external auxiliary electrode controls electric field and potential in the flat lamp. The external electrode is effective to expand the column in a flat lamp and make it uniform and finally improve luminance.

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