This paper proposes a modified two-switch boost converter with high power factor, and makes a report concerning the application of it to electronic ballast. First, the behavior of the boost converter with two switching devices is analyzed and experimental results will be shown. The experimental results show that the circuit can decrease the harmonic distortion of the input current like a former boost converter. But the problematic points possessed by the circuit are to be scrutinized. Next, a modified boost converter circuit that can improve the problem is proposed. The proposed circuit has both function of boost chopper and charge pump. The experimental results show that the circuit can improve the power factor. Lastly, it is shown that these two switching devices can be used not only as active switches of the modified boost converter but also as active switches of a half-bridge type inverter for fluorescent lamp. As a result, it is revealed that the harmonic distortion of the input current obtained by the proposed electronic ballast sufficiently satisfies the maximum limit of IEC 1000-3-2 class C. And the electronic ballast realized the high power factor of 0.99.

The possibility of the practical use as an office lighting system, which make the total illuminance of 400 lx and Task and Ambient illuminance ratio of 1.0 on the working desk, by using Task and Ambient Lighting system was reported on the last year research. On this year research, the following aspects were indicated based on the analysis of the psychological queries after two weeks actual work in the specific illuminance level and Task and Ambient illuminance ratio. The illuminance level of 200 lx on a working desk cause some psychological problem as room and desk area 'darkness' and illuminance level 'unevenness'. These problems were improved when the illuminance level of 300 lx was applied. And this analysis suggested that the Task and Ambient illuminance ratio shall be around 1.0. An approximately 20% saving energy can be achieved under this lighting system condition compared with the general office lighting system. KEYWORDS: task and ambient lighting system, illuminance level, illuminance ratio, save energy

A proper glare prediction method is needed to promote visual comfort at workplaces. Only a few formulae have been proposed for discomfort glare of daylight origin, and they are inadequate in real daylight situations. No standard monitoring procedure is available for daylight glare evaluation on a comparative basis. This paper introduces an improved glare evaluation method consisting of a standard monitoring protocol and advanced formulae. The method has been tested against the existing glare evaluation system of Chauvel on different types of window size using Radiance, a lighting simulation program. Given reliable results, the DGIN procedure was coded into a small program and incorporated with Radiance to compute daylight glare indices. The method was developed with the hope that architects and lighting designers would adopt it as an easy and reliable method for evaluating discomfort glare from daylight. The future work, which is an ongoing research, is to create the use of scientific-knowledge computational tools in the later stages of design in an effort to provide optimum choices of daylighting design with respect to light level and glare using the new glare algorithm.

Although a number of studies have been reported on the distribution of the B/L ratio in the chromaticity diagram, most of the results were measured with a simple achromatic surround condition. In real life we encounter a variety of visual environments that contain many colors of different luminance. Thus we measured the distribution of the B/L ratio in the chromaticity diagram under five different surround conditions: one was a dark condition comparable with those in previous studies, and the others were pictures of real scenes such as daytime residential, daytime downtown, nighttime downtown, and nighttime residential areas. The results obtained under the nighttime residential surround showed good agreement with the results of the dark surround, whereas the results of the other three surround conditions showed some deviations from the dark surround results. The average deviation of the B/L ratio from the dark surround results increased as a function of the average luminance of the surround. This suggests that the average luminance of the scenery surround is an important factor in determining the B/L ratio. KEYWORDS: brightness, luminance, B/L ratio, visual environment, chromaticity diagram

Age-related anatomical and physiological changes in the human visual system have been reported such as an increase in the density of the lens, a reduction of pupil size and loss of retinal ganglion cells. Although the retinal stimulus and neural signals are strongly affected by such age-related changes, color appearance is stable throughout the life-span because of parallel losses of cone sensitivities and other compensation mechanisms related to color constancy. On the other hand, there is a loss of sensitivity in color discrimination due, in part, to the reduction of retinal illuminance. The results of recent experimental studies by the author and colleagues indicate that this loss in discrimination is not only caused by the reduction of retinal illumiance, but also by a decrease in the signal-to-noise (S/N) ratio in neural pathways processing signals from S-cones and antagonistic signals from L- and M-cones. This change can be considered as a sort of a trade-off between maintaining a constant signal level from the cones through the life-span and decreasing the signal-to-noise ratio in the human visual system. These results suggest some possible methods for making safer and more comfortable visual environments for the elderly.

The paper presents a multiple reflection method for calculation of luminous flux in interiors. The method of boundary integrals has been applied, as well as a procedure of formulating a system of linear equations describing discrete values of overall luminous flux at particular surface elements of considered interior has been presented. Some calculation examples are reported, as well as discussion of obtained results.