Journal of Light
&
Visual Environment

Volume 26 Number 3, December 2002

CONTENTS

Papers

Improvement in Start Characteristics of Mercury-free Metal Halide Discharge Lamps for Automobiles
M. MUTO, T. NAGAHARA, A. KANEGAE and S. OMORI

English Abstracts

 A novel cold cathode fluorescent lamp (CCFL) with an adiabatic layer suitable for backlighting in PDAs (Personal Data Assistants) is described. The adiabatic layer (100-200É m) is formed between a light tube and an outer tube and is filled with low-pressure gases. This raises the temperature of the light tube to the suitable value (50-70∞C), which maximizes luminous efficacy even in low lamp wattage operation and at low ambient temperatures. The results of experiments and heat transfer analyses show that the optimum pressure in an adiabatic layer lies between 1Pa and 10Pa. At a pressure of less than 1Pa, the lamp temperature maintains a constant level because the conduction loss is lower than the radiation loss.

 To determine the appropriate experimental conditions for measuring the color zone map covering the visual field, the color appearances of red, yellow, green, and blue lights of a CRT display presented across the horizontal meridian of the visual field were measured. The test stimulus settings were equal luminance and equal brightness at the fovea, with dark, gray, or white surround conditions. The perceived strength of the red, yellow, green, and blue hue components in the test stimuli decreased from the fovea to the periphery under all conditions. The luminance level of the test stimuli and the surround conditions did not significantly affect the results. All four of the unique-hue component curves as a function of the eccentricity normalized at the fovea were within the range of the data obtained in previous studies in which monochromatic lights were used as the test stimuli. These curves may thus not depend on whether the test stimulus is monochromatic or complex light. The recommended experimental conditions for measuring the color zone map are equal- luminance test stimuli (no need for brightness-matching testing) with a gray surround (more applicable to actual visual environments than a dark or white surround).

 The luminance conditions were investigated , at that the characters composed of multiple point sources were as legible as a character having a uniformly luminous surface in fog, in order to make the use of variable-message signs practical at airports. As the results, it was found that the thicker the fog or the higher the illuminance, the better the legibility of the point source characters become compared with the uniformly luminous surface characters. It is supposed that the ease of extracting each individual point source makes the characters composed of multiple point sources more legible even if their luminance is low. So the results show that if the conventional luminance standard is applied to the average luminance of a character composed of multiple point sources, a character composed of multiple point sources could be recognized without any degradation in legibility.

 The principal cause of collisions at sea is “improper lookout.” “Visibility Level” (hereinafter VL) is introduced in this study to express the level of visual perception. In order to clarify the cause of visual perceptional difficulties, relation between VL and the distance to the target ship and between VL and visual perception are examined under various solar altitudes.

 In this study, evaluation of the lighting environment in offices, which consists of various attributes that are trade-offs, is conducted using the Conjoint Analysis, common in the field of marketing research. The attributes are illuminance, lighting distribution, glare, design, cost, usage of daylight, and recycling (229 subjects participated.) As a result, preferences of office lighting were quantitatively externalized. In other words, part-worth utilities and importance levels of attributes for office lighting displayed general characteristics of all subjects. Moreover, a method of research by grouping the subjects according to the importance levels of attributes or according to their characteristics is proved to be valuable for better understanding the preferences of office lighting.

 A blue white He-Cd laser composed of three R/G/B component beams is directly applied to fabricate the optical Fourier transform hologram (OFTH). The visual appearance of reconstructed color hologram images is discussed in contrast to that of an ordinary OFTH which is fabricated using a monochromatic He-Ne laser and diode-pumped solid state(Nd:YAG)laser.The characteristic of He-Cd laser is checked from the viewpoint of the visual size and its place of reconstructed color ghost image called cross talk in the reconstruction process. The visual effect of reconstructed hologram ghost image which can be digitally modified and emphasized by means of commercially available software is discussed through this study .

 We investigated the start characteristics (decreasing the breakdown voltage and increasing the luminous flux during run-up time) of mercury-free metal halide discharge lamps. Breakdown voltage of mercury-free metal halide discharge lamp could be reduced if the gas in the outer envelope is Xe or Xe/Ne. Adding indium iodide and supplying higher electrical power could increase luminous flux during run-up time. The run-up requirements in ECE regulation No.99 can be achieved by supplying 90W of power to the lamp during run-up time.