High pressure sodium lamp is known as a light source in which convection phenomena of the arc are so small. Recently, arc tubes with larger diameter and high pressure xenon filling have been used for the HPS lamps with high color rendition or high luminous efficacy. It was found that the convection phenomena were not negligible in such HPS arc tubes. This was confirmed by measuring the 475 nm sodium line intensity and knowing by the displacement of the arc axis. The results are:
(1) The convection becomes larger with increase in arc tube diameter and filling xenon pressure.
(2) The convection becomes smaller with increase in the power input.
The temperature difference between the upper and lowerside of the arc tube wall in the horizontal operation reaches 40-50°C and this local heating of the arc tube will be a problem in the life of HPS lamps.

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Sc-Na metal halide lamps are occupying an important place as energy saving light sources because of the high luminous efficacy and the good color rendition. In order to realize higher luminous efficacy, authors have investigated the effect of lamp design factors on radiation properties and luminous efficacy under the condition of higher NaScl₄ mole fraction. Based on the results of the precise measurements, the effects of the lamp design factors related to the cold sport temperature on the radiation properties have been well understood. The novel approach as well as the optimization of the lamp design factors at lower cold temperature have realized a high luminous efficacy of 121 lm/W in 400 W scandium-sodium lodide lamps.

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Stable white ultraviolet reflecting materials are necessary for studies of polymer weatherability. It was found that barium sulfate aqueous paste containing 30% water manufactured for X-ray contrast media is adequate for these purposes. Water was evaporated slowly and formed cracks were pushed off carefully, then considerably hard blocks having excellent optical properties were obtained. Poly (vinyl alcohol) having mass average degree of polymerization 2400 and containing 1.2 mol% residual vinyl acetate was used as binder. About 0.2% binder was found to be sufficient for obtaining enough flexural strength.

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The contour integration formula, E=L/2∫_s cosδ·dω for calculating the illuminance of a flat surface source is composed of cosδ and dω, which are not easy to solve. Based on analysis of a three dimensional model, the above formula was modified into the following formulae:
(1) When the surface source is parallel to the illuminated plane:
E'=L/2∫^b_an/l²)dx
(2) When the surface source is inclined to the illuminated plane by ∠β:
(E')=L/2cosβ∫^b_an/l²dx
(3) When the surface source is perpendicular to the illuminated plane:
((E'))=-L/2z∫^b_a1/l²dx
where E'=the illuminance component of the interval A to B on the boundary of the flat surface source, n=the length of an intercept on the y axis by the tangent to the boundary, l=the distance between the illuminated point and the minute segment AB on the boundary of the flat surface source. Since n and l² in these formulae can easily be obtained from x, y and z, all calculations of the illuminance of a flat surface source of an arbitrary shape that can be expressed by x and y can easily be obtained from the sum of the illuminance components E'.

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In this paper, the four types which concern the relationship between sensory tolerance and sensiveness for environmental sensory stimuli were proposed theoretically. These hypothetical four types were supported by the results obtained from factor analytical approach. The two checklists were compiled in place of actual psycho-physical measurements in order to apply the factor analysis. The first version of the checklist was applied to the 100 male subjects, and the second version to the 229 male subjects. The eight factors which resulted from the first version of the list were the following: A) General sensitivity, B) Temporal sensitivity, C) Orientation to the strong and prolonged sensory (the two factors were included in this label), D) Orientation to the weak stimuli (the two factors were included also), E) Activation level, F) Abnormal temporal sensitivity. The six factors were obtained from the second version of the list. Five factors of these six, s were the same as to each of above mentioned A to E. The other one was G) Sensory-motor reactivity. The four factors, A to D, which resulted from two large sample of the subjects, and from the different checklists, were the sensory properties common to inter-moeal senses. The factors A and B related to “the culture free behavior”, and the factor C and D related to “the culture bound behavior”. These four factors gave support to the existence of the four types.

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HID lamps cannot be reignited instantly after they are extinguished, since the breakdown voltage is too high. As the result of investigation about the mothod that lowers the breakdown voltage at restart, we found that it is effective to set a heater as a preheated cathode in the discharge tube, and to utilize the thermionic emission from it. In order to investigate this effect of the heater more precisely, the discharge tube which had a heater at the end portion of the tube, and which was filled only with mercury, was prepared. Mercury vapor density in the tube was controlled in a furnace and the measurement of breakdown voltage was made in the heater temperature range up to 2,100°C. In the case of mercury density of more than 4.2×10¹⁸m^-3, the results of the measurement have shown that the breakdown voltage was almost constant until the heater temperature reached about 1,700°C, and then it decreased greatly, while it reached a minimum voltage at about 2,000°C.

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This paper describes computer-aided design procedurers for predicting the luminous intensity distribution for the HID lamp luminaire having an asymmetrical reflector for tunnel lighting and the like. The proposed procedures first divide a light source and a reflector into minor parts, then trace three-dimensional optical paths from each direction oriented by every minor part combination of the source and the reflector, and finally total both reflected and direct rays from the light source to predict the luminous intensity distribution of the luminaire. The arithmetical weight of the minor light source intensity is given prior to the calculation by means of measuring luminance, and the differences among reflected light distributions made by the glossiness of the reflector surface is also considered.

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