A vacuum ultraviolet (VUV) emission spectroscopy was carried out to determine carbon monoxide (CO) gas discharge. The intensive emission lines in the VUV range were assigned as a “4th positive group”. The results showed that the VUV intensity increased as the pressure decreased even though the input power was reduced. During the test, the stability of the discharge and the precipitation of carbon contamination were examined. The carbon contamination was insignificant at the lower gas pressures. The reaction of CO molecules in the discharge will be discussed in this paper.

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In this paper the phenomena of mode transition and hysteresis in xenon ICP (Inductively Coupled Plasma) discharge are studied. Xenon has been used as an alternative for mercury since there are environmental issues related to mercury. The transition from E-mode (electrostatic mode) discharge to H-mode (electromagnetic mode) discharge in a xenon cylindrical tube was investigated. RF energy at 13.56 MHz was induced to the tube through matching network. In this study, all the transitions occurred at a certain threshold input power which is a function of the xenon pressure. Hysteresis was observed as the input power was varied from 1 to 100 W. When the input power is increased the discharge starts in E-mode changes into H-mode, whereas when the input power is decreased the H-mode turns into the E-mode or there is a sudden switch-off as the function of the gas pressures. Mode transition is determined by sudden and huge change of luminance. H-mode is characterized by a much higher luminance and plasma density. Luminance and optical emission spectra were recorded. At high pressure more power is required to transform the discharge mode compared to low pressure. Continuum visible emission was obtained only in H-mode. At H-mode, many ionic and atomic spectrum are observed compared to E-mode. With high luminance and continuum visible emission that obtained from H-mode xenon ICP discharge, xenon is one of the most suitable alternatives in developing mercury-free light sources.

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The profile of vacuum ultraviolet (VUV), visible and near IR emissions of xenon and xenon-rare gas pulsed discharge fluorescent lamps were observed as a fundamental research on developing a mercury-free fluorescent lamp. All lamps were operated by pulsed dielectric barrier discharge (DBD). As the pulse width decreases, higher intensity of VUV emissions is obtained, while luminance and efficacy also increase. As the pulse frequency increases, the intensity of VUV emissions increases, however the radiative output per one pulse period decreases and the efficacy decreases. The decay time of VUV emissions which are exciting a phosphor, can be controlled by introducing a rare-gas mixture into xenon.

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The characteristics of xenon fluorescent lamp with two pairs of anode and cathode in pulsed discharge are demonstrated. By increasing the number of electrodes from one pair to two pairs, luminance is improved by 13 % and achieves 9500 cd/m² but estimated efficacy at a positive column is decreased from 68.0 lm/W to 45.6 lm/W. The narrow pulse width is preferred for higher luminance because a higher current density can be attained. It is also shown that there is the critical value of the energy consumed from the time when the current is turned on to the time when the current value reaches maximum and that when the energy excess this limit the discharge state changes from diffused to contracted one.

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A rare gas fluorescent lamp, which has a pair of external electrodes, is widely used as a means for image illumination in offices. However, few studies and reports have been conducted on this lamp. Thus, we examined its energy balance. What we found was that over 90% of the lamp input power changes into thermal energy. To improve the luminous efficacy, we developed a novel structure in which a pair of electrodes was used, one on an inner and the other on an outer surface of a lamp bulb. A comparison was done with a conventional bulb. At the same inverter conditions, the new lamp could be run at only 77% of the voltage of the conventional one. Consequently, the lamp input power increased about 6%, and the illuminance increased about 7∼8%. No luminous efficacy improvement was observed.

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This paper presents a digital technique for simulating image processing algorithms performed in a human perception on estimation of good scenery. The technique evaluates the landscape quality in the way of digital box counting method. In order to define good scenery, 15 examples of the paintings are selected from world-widely well known painters of the impressionists' school all acknowledged as ideal samples of good landscape scenery. When fractal dimension analysis is applied to the samples, we found that in every case the value of fractal dimension is always within the range of 1.400 to 1.700 in the case of 2D samples. We conclude that the digital image process is very useful for simulating human perception's work and the special range of values in fractal dimension may reveal equivalently human perceptions reaction for comportable feeling given by good scenery.

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A new evaluation method for “brightness of a space” was investigated. First, we have examined the basic relationship between arrival direction of the light and brightness by using the full-scale model. The results are as follows: 1) Brightness changed due to the subject's action, even if the condition of the light was absolutely the same. 2) The light from horizontal direction is more effective for brightness. 3) Brightness changed due to the balance of arrival direction of the light, even if the total amount of the light is same. Next, the measurement tool for obtaining data of the light that comes from all directions was developed. We examined two effects of “quantity of the light” and “the spatial balance of the light” on the brightness of the space using got value from the tool. As a result, we discovered that former can be explained at the value which horizontally integrated 360° in the weighting of (1+cosθ)/2 and latter can be explained at the angle of visibility and directional diffusivity.

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The objective of this study is to clarify the influence of adaptation time and initial adaptation level by applying a suitable illuminance for relaxation that is adjusted by the subjects and evaluations of their satisfaction level of a space in terms of relaxation. The experiment is carried out in a room of W2.7m×D2.7m×H2.6m with floor reflectance 26% and wall reflectance 93%. The experiment is conducted under six different conditions that are set by combining two initial adaptation levels of 20 lx and 150 lx, where the subjects are adapted before entering the room and three patterns of lighting methods, namely luminous ceiling, point source at the center of the ceiling and point source at the center of the wall on the right of the subject. The following results are obtained through this study.
1) The adjusted illuminance and satisfaction level suitable for relaxation are influenced by elapsed time and initial adaptation level.
2) The influence of initial adaptation level on adjusted illuminance is compatible with the influence of elapsed time.
3) The adjusted illuminance for relaxation obtained in this study is lower than that proposed in previous studies and the major reasons for this are considered to be the initial adaptation level and the length of time afforded to the subjects before making their evaluations.

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