Many white and/or nearly white objects are in our living and working areas, such as documents written on white paper, white curtains, white clothes, and white walls and furniture. The perceived whiteness of these objects is important to the impression of lighting in these areas. To investigate the perceived whiteness in living areas, a series of experiments were conducted using four different fluorescent lamps in three different environmental conditions. It was found that the areas of perceived whiteness in the living areas were larger than the areas of perceived whiteness under achromatic conditions. Based on the results of these results, a perceived whiteness index is proposed for these experimental conditions.
Fluorescent lamp electrodes breakdown when the oxide on their coil electrodes is exhausted at the end-of-life. Two types of breakdown mechanisms are observed in oxide-less coil electrodes depending on the operation mode. When a lamp is operated continuously after ignition, breakdown occurs at the point where the coil electrode connects to its supporting lead after around 8 seconds. If the lamp is operated using cycles of 4 seconds on and 12 seconds off, breakdown will occur at the coiling part of the coil electrode after around 170 seconds. The experimental results show that the former breakdown mechanism is due to ion bombardment and the latter is due to the evaporation of tungsten wire. Discharge current concentration at the point connecting a coil electrode and its supporting lead, which causes the ion bombardment, will begin after 7 seconds or more, and is independent of the electrode temperature. Thus, if the operation of a lamp at the end-of-life stops within 6 seconds of starting by using a protection circuit, the breakdown due to ion bombardment will be prevented.
Previous research showed that colored light affects Landolt C test performance, and increasing the relative contribution of short-wavelength (blue) light will reduce pupil size and increase visual acuity. However, whether the evaluation of discomfort glare differs when the color of light differs is unknown. The aim of this research is to investigate the effect of colored lights on the evaluation and range of discomfort glare. Among the nine colored lights we selected, at the same luminance level, blue light causes the most discomfort glare, and green light causes the least discomfort glare. The order of discomfort glare is approximately blue, white, red or yellow, and green. We also found that a subject's evaluation of discomfort glare becomes more intense when color temperature is increased. In addition, after comparing our result with Helmholtz- Kohlrausch phenomenon, we found that people's range of discomfort glare under each colored light were different. Our study shows that the color of light affects the evaluation of discomfort glare. Therefore, using colored lights as a technique to reduce the level of discomfort glare is possible.
A vigilance task like driving a vehicle causes eye fatigue. We previously measured the visual search time for a single flashing light out of 101 stimuli after vigilance tasks of various duration. A CRT display was used to generate the stimuli: containing 1 flashing light and 100 steady lights. We found that the longer the vigilance task, the longer the visual search time. We have now investigated the effect of a vigilance task on the functional visual field. We found that a functional visual field gradually narrows as vigilance task is lengthened. This indicates that narrowing of the functional visual field is a factor contributing to eye fatigue and lengthening of the visual search time.