Mercury-free HPS 150W lamp with high CRI operated on inductive ballast was developed. It has a slender arc tube with high-pressure xenon gas compared with that of mercury-contained arc tube. It has nearly the same haracteristics as those of mercury-contained HPS lamp with high CRI and shows nearly the same hue as that of incandescent lamp. This lamp is suitable for general lighting, such as indoor lighting, flood lighting, street lighting and so on. We present another one application, that is, seedling growth by supplemental lighting. We examined with lettuce and broccoli and got good results by 2 hours supplemental lighting before sunrise, compared with those of only daylight.

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This paper describes a method for controlling the color of luminescence emitted from xenon-mercury fluorescent lamps by using both the internal (axial direction) electrodes and external (radial direction) ones. A mixture containing two kinds of phosphors was coated on the inner surface of the lamp tubes. One of the mixed phosphors is excited by the resonance radiation of mercury and emits white colored light. The other is excited by vacuum ultraviolet (VUV) radiation of xenon and emits red colored light. The lamp was operated alternatively by the internal electrodes forming an axial discharge and external electrodes developing a radial discharge. The color of emitted light was changed from white to red by varying the mixture ratio of axial and radial discharges. When a lamp was operated by the external electrodes, afterglow of mercury spectra was observed for a longer time than that of xenon.

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BaAl₁₂O₁₉ is considered to be a mixture of a Ba-poor aluminate (0.82BaO·6Al₂O₃) and a Ba-rich aluminate (xBaO·6Al₂O₃, x=1.30±0.2). Because the Ba-poor aluminate and BaMgAl₁₀O₁₇ (BAM) have exactly the same crystal structure as β-alumina, both compounds form solid solutions with it. In this study, we prepared various kinds of solid solutions of the Ba-poor aluminate and BAM in which Mn²⁺ was substituted for some or all of the Mg²⁺. These formulae can be expressed as (1-α)(0.82BaO·6Al₂O₃)· α(BaMg_1-βMn_βAl₁₀O₁₇). Their emission properties under 146 nm excitation were studied. As α and β were changed with a constant Mn²⁺ content in the phosphor (α· β=0.12), two kinds of bright solid solutions were found. One was a BAM-poor solid solution (α=0.12, β=1.0) and the other was a BAM-rich solid solution (α=0.92, β=0.13). Substituting Sr²⁺ for Ba²⁺ improved the luminance of the BAM-rich solid solution. For example, the composition of a BAM-rich solid solution in which Sr²⁺ replaced 76% of the Ba²⁺ was Ba_0.24Sr_0.75Mg_0.80Mn_0.12Al_10.2O_17.21. Comparing the properties of this phosphor with those of the conventional BaAl₁₂O₁₉:Mn, we found the luminance was 18% higher, the chromaticity was purer green (x=0.146, y=0.749) and the 1/10 decay time was equivalent (14 ms). This material should serve as a new green phosphor for PDPs, though its lifetime in PDPs remains to be measured.

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The spectral component analysis of heart rate variability, based on the IPFM model, was applied in order to assess the physiological effect of environmental lighting. There appear to be two prominent components in the power spectrum of the heart rate variability. One is the blood pressure vasomotor component which reflects the activities of both the sympathetic and parasympathetic nervous systems. The other is the respiratory component which reflects the activity of the parasympathetic nervous system. Therefore these two components can be the indices of the physiological load. The experiment was carried out under five illuminance levels of 180, 320, 560, 1,000 and 1,800 lx, using fluorescent lamps with color temperatures 2,800 and 5,000 K as the light sources. The results suggested that the physiological load was minimal in the illuminance range 500∼600 lx in both 2,800 and 5,000 K, and increased with increasing or decreasing illuminance from this range. It was obvious that the physiological load was influenced by the psychological effect of lighting. The most desirable illuminance range was 500∼600 lx, where the physiological load was minimal, in 2,800 K. But in 5,000 K a higher level of illuminance scored maximum desirability, than the level corresponding to minimum physiological load. An illuminance range 500∼1,000 lx was acceptable in 5,000 K..

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This paper presents a proposal to design factors for a reasonable lighting environment in Visual Display Terminal (VDT) work, by monitoring changes in the lighting environment by general illumination and partial illumination as a factor of the working environment. We also considered that this factor affects productively and workload from an experimental approach. Since we think that it is not enough to evaluate a lighting environment only by subjective appraisal, we used brain waves as a physiological index for evaluating human mental activity objectively. The evaluation index used in the experiment were obtained by measuring working efficiency and working quality in VDT work, mental changes (stability) recorded by an electroencephalograph (EEG), and determined the workload by a survey of subjective symptoms and by measuring eye fatigue. The results enable us to derive a relationship between reasonable lighting environment and illuminance. The results show the following: 1)When the partial illumination was given to subjects, it was shown to effect their concentration on work and mentally stabilize at the ratio of surround illuminannce to horizontal illuminance was about 0.05. 2)When the ratio of surround illuminance to horizontal illuminance was the same, the effect showed remarkable at the ratio of vertical illuminance to horizontal illuminance was lower.

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This study shows the physical characteristics of the visual environment and the psychological characteristics of the navigation officers. Author has carried out two kinds of experiments on board. One is the measurement of the illuminance at the fore of the inside in the navigation bridge, another one is the measurement of navigation officer's eye movements. The illuminance at the place of fore inside in the navigation bridge can be standardized by the solar altitude. The characteristics of the lookout on board are based on the measurement of navigation officer's eye movements and are brought together as follows.
(1) Average fixation time in the daytime
(2) The relationship between the number of fixation points and the velocity of eye movements, and lookout in the daytime
(3) Lookout on board at twilight

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A new linear uniform colour space has been developed by systematic combinations of tristimulus values X, Y and Z. For colours with constant value of 6 in Munsell space, numerical computer analyses have been made to minimize the deformations of hue circles from uniform circles in the new space by optimizing the coefficients in the formulae of linear transformations. By appropriate transformations, the shapes of hue circles which are distorted in the L^*a^*b^*, L^*u^*v^* and Cube-Root spaces come close to uniform circles, and the warps of hue circles with moderate chroma are reduced to 1/4∼1/5 as compared with those in the traditional colour spaces. In this new space, hue and chroma can be approximated by metric hue angle and metric chroma, respectively, with considerable accuracy for colours of moderate chroma.

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This study examined to know how the function of house exterior lighting, especially gate lighting, entryway lighting and ornament lighting, for the evaluation of lighting environment on the nighttime residential streets. An experiment using a real residential street, where people actually live, was carried out. The results suggested that the evaluation of lighting environment can be improved not only by the amount of light but by the light fittings attached on the gate or at the entryway or on the hedge belonging to private property.

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The sensation of brightness perceived in a living room with downlights was investigated by psychological experiments with seven observers. Three positions and four types of downlight reflector were examined. The method of magnitude estimation was adopted to measure the sensation of brightness. In addition, the luminances of areas related to the sensation of brightness were measured with a CCD camera. The relationships between these luminances and the sensation of brightness are discussed. The results showed that the sensation of brightness for a living room with downlights was strongly affected by the average luminance within the area of the front wall and by the luminance in the comers of the room.

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