J. of IEIJ Vol.85, No.5

 The effects of simulating dawn lighting with an ordinary ceiling light on the quality of awakening were investigated. The subjects were healthy men, aged 24?]27. After sleep for about 7 hours with polysomnographic recordings in a climatic chamber kept at a temperature of 25 and a relative humidity of 50?“, each subject was awakened by an alarm. For the 30 minutes immediately before the subject was awakened the illumination in the chamber was gradually increased simulating the condition of waking up as the sun rises. Alpha attenuation test, measuring blood pressure and awakening feelings were conducted after awakening.
 The time of sleep stage 2 appearing during the 30?]minute simulating dawn lighting was significantly less (p<0.05?GWilcoxon test) than during typical waking conditions (i.e., waking up in the dark), while the time of stage W was higher (p??0.0796). The mood after awakening in the simulatig dawn lighting condition was significantly better (p<0.05). There were no significant differences in the alpha attenuation coefficients and blood pressures after awakening between the two conditions.
 These results suggest that simulating dawn lighting arouses subjects to light sleep, which makes awakening less sudden and more pleasant. There was no evidence that the light sleep immediately before awakening decreased the subjects' cerebral cortex activity or sympathetic nervous activity after awakening.
KEYWORD: simulating dawn lighting, ceiling light, awakening, polysomnography (PSG), sleep stage, mood after awakening

All Sky Model as a Standard Sky Luminance Distribution -- Part 2. A Numerical Expression of Sky Luminance Distributions for All Sky Conditions --
Norio IGAWA, Hiroshi NAKAMURA, Tomoko MATSUZAWA and Yasuko KOGA

 The aim of this research work is to establish a standard sky model for designing excellent daylighting schemes that covers all sky conditions from clear sky to overcast sky.
 In Part 1,the "normalized global illuminance" was defined as a function of the measured global illuminance and solar altitude for estimating the sky luminance distribution.
In this paper (Part 2), the "Relative All Sky Model" is introduced. It is the formulae to show the relative sky luminance distribution as a function of the normalized global illuminance.The equation of the zenith luminance concerning the Relative All Sky Model is also a function of the normalized global illuminance. It is called the "All Sky Zenith Luminance". An absolute standard sky luminance distribution model called the "All Sky Model" is introduced that is the multiplication of the Relative All Sky Model and the All Sky Zenith Luminance. The All Sky Model can be calculated from the normalized global illuminance, i.e., from the measured global illuminance and the solar altitude or from the measured global illuminance, the horizontal diffuse illuminance, and the solar altitude. The global illuminance and horizontal diffuse illuminance are easily obtained from even the simplest daylight measurements.
 The All Sky Model can produce an excellent standard sky for the daylighting design for any place an advanced daylight environment is needed.
KEYWORD:sky luminance distribution, standard sky, daylighting design, All Sky Model

Effect of Electron Energy on Light-emission Luminance and on Luminescent Color ofPhosphors in an Electrodeless Discharge Plasma
Hidenori KASHIWAZAKI, Yasunori OHTSU and Hiroharu FUJITA

 The effects of electron energy distribution on light-emission luminance and on the luminescent color of phosphors in the light source were clarified. Inductively coupled discharge plasma was used as a promising electrodeless lamp for the light source. The light-emission luminance of the phosphors increased with the electron density in the plasma and/or the pressure of noble gas. The luminescent color was affected by the density of electrons with an energy of 5.0 or 6.7eV and by the visible light emission of the noble (Ne, Ar or Hg).

KEYWORD:luminous color, phosphor, electrodeless discharge plasma, electron energy

Effect of Spectral Reflectance Distribution of a Whitish Object on Its Perceived Whiteness
Ichiro KATAYAMA, Kazuyoshi MASUMI and Tsutomu AOKI
 The perceived whiteness of 12 whitish samples with different spectral reflectance distributions (SRDs) was investigated using psychological experiments under two types of illuminants: incandescent lamps and D65 simulated ones. The illuminance level was kept constant at 1000 lx. The scale value of the perceived whiteness was determined visually by paired comparison. An index developed in a previous study[J. Illum. Inst. Jpn. Vol.83 No.11 (1999)]was found to accurately estimate the perceived whiteness under various illuminants. The index is proportional to the ratio between the chromatic and achromatic responses in the visual system. In the present study, the index was modified to estimate the perceived whiteness of whitish samples with various SRDs. The modified index correlated highly with the experimental results. It can thus be used to estimate the perceived whiteness of whitish samples with various SRDs under different illuminants.

KEYWORD:perceived whiteness, paired comparison, spectral reflectance distribution, chromatic strength, brightness

Research on the Perception of Lighting Fluctuation in a Luminous Offices Environment
Tomoaki SHIKAKURA, Hiroyuki MORIKAWA and Yoshiki NAKAMURA

 The non-periodic fluctuation of artificial lighting in offices was investigated to clarify the threshold at which the fluctuation is perceived. The experiments showed that fluctuation ratio of 0.92 - 1.06, i.e. 7% of the fluctuation, is not perceived, when the observers tried to be conscious of the fluctuation. On the other hand under the condition of being unconscious of the fluctuation because of assigned visual tasks, the threshold has a broader range (0.8 - 1.3) and the value rises with the fluctuation period. It is important to dim artificial lighting without causing discomfort to office workers, and the results of this study can be used to better control of fluctuation in office lighting.

KEYWORD:lighting fluctuation, lighting control, fluctuation in illuminance, office lighting

Change in Visual Contrast Sensitivity with Age Depends on Illuminance Level
Michico IWATA, Katsunori OKAJIMA and Hiroyasu UJIKE

 We measured contrast sensitivity function in the vision of young and aged observers under combinations of four different illuminance levels (1,10,100, and 1000 lx) and three different color temperatures (3000,5000, and 6700K). We found that (@) no systematic difference appeared across color temperatures, (A) the sensitivity was relatively worse in aged observers at higher spatial frequencies when the illuminance was high and at all spatial frequencies examined when the illuminance was low, and (B) the deterioration cannot be explained only by the equality of retinal effective illuminance.These results suggest that the contrast sensitivity function can be used as the basis of lighting design for different visual tasks.
KEYWORD:aging effects, contrast sensitivity function, color temperature, retinal effective illuminance, lighting design