This paper discribes the xenon gas effect on the high pressure sodium arc. The previous paper reported that with increasing xenon gas pressure, the spectral broadening of the D-lines increases. In this paper, the arc temperature profiles of 20 Torr filling gas pressure and 300 Torr filling gas pressure of the HPS lamps were measured and the following profiles were estimated
Xe 20 Torr T=4120- (4120-1370) (r/R)^2·3
Xe 300 Torr T=4290- (4290-1350) (r/R)^1·6
Using these profiles, the spectral distributions were calculated by the radiation transfer equation and the calculated results showed the spectral broadening of the D-lines of the Xe 300 Torr arc was a little greater than that of Xe 20 Torr. From this result, it is considered that with increasing xenon pressure, the arc “shrinks” and the thickness of the dark annular space increases so that the broadening of the spectral lines increases.

View full abstract

The conventional high pressure sodium lamps have the yellowish light source color, and find limited applications. We have conducted the study in an effort to improve this defect. In general, the color characteristics of a light source are represented in terms of a color temperature and a color rendering index. Our study, however, revealed the fact that even when the color temperature and the color rendering index are the same, the light source color greatly varies depending upon the specifications of an arc tube and, especially, depending upon the composition ratios of sodium amalgam contained in the arc tube, and that the ability for discriminating the color difference changes, too. We have succeeded in obtaining a lamp of a type which is adapted to a ballast for a 400-watt mercury lamp, with a wattage of 350 W, a luminous efficacy of 105 lm/W, a color temperature of 2150 K, a color rendering index of 65, and a color discrimination index of 29, with the whitish light source color.

View full abstract

When the fluorescent lamp, which is filled low pressure krypton gas and saturated mercury vapor, is operated on a commercial ballast working at 50 or 60 Hz, it has the characteristics as follows; as the electric power of the lamp is reduced at room temperature, it can sustain the same light emission characteristics as the general one. But when the ambient temperature around the lamp is lower than the room temperature, the fluctuation of light emission appears below the critical temperature and the light emission is reduced remarkably. To investigate these defective phenomena in the lamp, we studied the properties of the discharge voltage-current, the fluctuation frequencies and wavelength of moving lights which depend on the ambient temperature at the constant pressure of the filling gas. As the results, we obtained conclusions as follows.
(1) The fluctuation of light emission behaves like as the positive moving striations.
(2) The temperature at which moving striations appear is inferred to be determined by a mole fraction and a mole number in the discharge tube of krypton-mecury vapor mixture.
(3) These moving striations have similar characteristics to “r” wave which is based on the fluctuation of ion density in Ne gas discharge.
(4) In this temperature region in which moving striations appear, the excitation of krypton gas is activated, and the light emission of mercury line decreases.

View full abstract

A fluorescent lamp ballast with a switching circuit for 40W lamp wattage and 100V line voltage is described. The ballast is composed of a series choke and a perallel switching circuit which operates in every half cycle of a.c. voltage. Silicon controlled rectifiers, that cut off the current in a low level by the reverse gate cnrrent, are used in the switching circuit. The ballast consumes 15% less energy and is 50% lighter than conventional ballast.

View full abstract

Aluminum surface mirrors with and without protective coatings of SiO or MgF₂ were prepared under various evaporation conditions. The spectral reflectance of these mirrors was measured soon after their preparation in the wavelength region of 0.4-14μm. Then, they were stored in five different surrounding conditions for six months (two serieses of three months storage). After every three months storage, the reflectance was measured to obtain its change during the storage period. Data of the spectral reflectance measurement for the above mirrors were shown. The reflectance change for the unprotected aluminum mirrors and the MgF₂ coated mirrors was little except the reflectance change for the mirrors stored in saturated water vapor atmosphere. The SiO coated mirrors showed reflectance increase in the visible and nearinfrared region.

View full abstract

Ensuring perceptual conditions that the driver is to be able to detect a critical object ahead, at a sufficient distance, to take necessary driving manoeuvres safely, an attempt was made to find the admissible limit of the uniformity of the road surface luminance (U=Lmin/Lr) in relation to the average road surface luminance (Lr), under full scale road lighting installations with actual driving. (Lmin is the luminance of the darkest part of the road surface.) In the experiments, in total, 56 different combinations of U and Lr were provided and observed. Applying a forced choice method, correct responses of the observers in the car driven at a constant speed of 60 km/h, concerning the lateral positions of object(s) located against the darkest part of the road surface, presented in a random ordar, were collected and analyzed for each combination of U and Lr. Based on the data collected, probabilities of the correct perception of (lateral position of) the critical object were derived. Finally, the admissible limit of U is given as a function of Lr, to perceive the object with a probability of 75%, taking the luminance contrast of the object as a parameter. Consequently, it has been found that the square of the admissible limit of uniformity varies in proportion to a ratio between Lu and Lr, i.e. U²=Lu/Lr, where Lu is the luminance of the road surface necessary to perceive the object when U=1.0. The relation given agrees well with that obtained with the lighting simulator, and those derived from the results of previous researchers.

View full abstract

For calculating absolute color rendering indices which specify the color rendering properties of light sources referring to a single standard illuminant, independent of the correlated color temperature of the sample light sources, a proper combination of a uniform color space and a chromatic adaptation formula is needed. A method of computing evaluation for this combination is here proposed based on the assumption that the Planckian radiators and the CIE daylights in a wide range of correlated color temperature are quite similar to each other in their psychosensorial color rendering properties. Color rendering indices of various light sources are calculated, using several combinations of uniform color spaces and chromatic adaptation correction formulae by changing the reference illuminant. It is assumed here that the smaller the change in the color rendering indices with the change of the reference illuminant the better the combination of the space and the formula. The results show that the combination of the nonlinear transformation formula proposed by Nayatani et al. with the uniform color space CIELAB or Richter’s LABHNU is the best, confirming the results of the former experimental evaluation by the same authors.

View full abstract