J. of IEIJ Vol.84, No.5

To evaluate how the level of shading on the ground interferes with the broadcasting of a sporting event on television, we make clear if the value of the depth of shadow is proper for an actual depth of shadow, and also it has any influence to watch on TV. We found that the depth of the shadow shows that the shading is graded at the same interval as a sensitivity of human. Therefore, the influence of the depth of the shadow can be used to evaluate the discomfort caused by the shadow. For example, if the depth of the shadow is readjusted to less than 0.5 to the "Just admissible" level, we will be able to watch TV without any discomfort.

KEYWORDS: sports-lighting, modeling, shadow, TV

Guidelines for the input current harmonic distortion of electronic equipment have been established world-wide to prevent equipment interference through AC main lines. Electronic ballasts for fluorescent lamps with an inverter circuit using an active filter circuit have been commercialized. To simplifily their circuitry the inverter uses a new technique that combines the inverter with an active filter circuit. In this paper, an electronic ballast combined with an HF inverter and a boost converter are reviewed. The dimming control and stability against a variable load are examined by using simulation and measurement.

KEYWORDS: electronic ballast, inverter, converter

We measured the characteristics of categorical color perception in the peripheral visual field under low illumination conditions and compared with those under 2000 lx illuminance in our previous study [J.Illum. Engng. Inst. Jpn. 83 (1999)]. OSA color chips, simulated by the LCD projector, were presented at the fovea (0 deg), at eccentricities of 30 and 50 deg in the nasal visual field, and at 30, 50, 70, and 80 deg in the temporal visual field. A large gray surrounding field, made with a hemisphere, was illuminated by D65 fluorescent lamps at 5 or 0.1 lx. The stimulus was subtended 4 deg and presented for 3 s. The observer reported the color appearance of the stimulus with 1 of 11 basic color terms. The response of color categories at the fovea showed almost no difference to the 50 deg temporal under 5 lx illuminance. Beyond the 30 deg nasal and the 70 deg temporal, the response of achromatic categories increased, and that of green, purple and pink categories decreased. Under 0.1 lx the response of achromatic categories dominated. Our results show that categorical color perception in the central visual field is constant across a large visual area under a wide range of illumination conditions.

KEYWORDS: categorical color perception, peripheral visual field, color vision, basic color

As an application of dielectric barrier discharge (DBD) lamps vacuum-ultraviolet (VUV) exposure systems of both Ar2* and Kr2* excimers have been developed and their basic performance has been evaluated. Each system comprises a 20-W DBD excimer lamp, a sinusoidal wave high-voltage power supply, and a cylindrical lamp holder. A high-voltage transformer and a lamp are designed to be set as close together as possible in the holder. The inside of the holder is purged by nitrogen gas when it is in use. The excimer lamp has an MgF2 window at the lamp end and is a "head-on type" lamp.
The head-on type Ar2* excimer VUV system produced monochromatic light at 127nm (with a 9.8nm FWHM). It's irradiance had an almost homogeneous distribution within a 15-mm diameter planar circle at 50? from the output window and was about 0.4mW/cm2.
The head-on type Kr2* excimer VUV system produced monochromatic light at 147nm (with a 13.2-nm FWHM). It's irradiance had an almost homogeneous distribution within a 15-mm diameter planar circle at 50? from the output window and was about 1.4mW/ cm2.
The lifetime of the lamps in these system is defined as the time point at which irradiance drops to 50% of its initial value. It was 500 and 1500 h, respectively, for the Ar2* and Kr2* excimer lamps.

KEYWORDS: Ar2* excimer Kr2* excimer, excimer lamp, exposure system, dielectric barrier discharge, vacuum ultraviolet

We have developed a road traffic signal head based on the code for "Phantom prevention type of lamp unit" provided by the Metropolitan Police Department. The National Police Agency does not yet have specifications for sun-phantom prevention-type signal heads, although it is examing such specifications. The signal head we developed satisfies the standard for luminous intensity distribution specified by the National Police Agency, and the shading function is more effective than previous heads.

KEYWORDS: mask-film, road traffic signal head, luminous intensity distribution, sun-phantom prevention

We generally express color as some categorical color even though we have the ability to discriminate millions of colors. Most studies of categorical color perception have been based on color naming, so they have been affected by vocabulary. We have identified the locations of categorical color perception without the effect of a vocabulary by using a color space classification method. Five observers classified a set of 424 OSA color samples and an additional 6 JIS-munsell chips into several (2-14)groups. The locations of the classified categories were similarly arranged in color space across the observers. The classified categories had at least four stages, probably corresponding to multi-stage categorical color perception. Some classified categories had regions dissimilar to the categories derived with a color naming method.

KEYWORDS: color vision, categorical perception, color naming

Methods were investigated to improve the lamp characteristics of inductively coupled electrodeless metal halide lamps to make them practical.
First, evaluating lamp efficacy by adjusting the lamp parameters showed that a lamp efficacy of 180 lm/W with white color could be attained.
Second, the conditions generating free iodine and bulb deterioration, the main factors limiting the life of these lamps, were investigated. For long-life-type lamps, which had 130 lm/W of lamp efficacy, the lamp lumen level did not decrease during 21000 hours of overload operation (corresponding to 58000 hours of rated-load operation). These lamps thus have excellent lumen maintenance and life performance compared with conventional electrode metal halide lamps.
Third, improving circuit reliability by decreasing the Q value of the resonant circuit was investigated for long-life-type lamps which had 145 lm/W of lamp efficacy. The relationship between the Q value and the lamp parameters was analyzed, and the Q value was decreased to 78% its value while maintaining the same lamp performance.

KEYWORDS: electrodeless metal halide lamp, free iodine, long life, lumen maintenance