Journal of Light
&
Visual Environment

Volume 28 Number 3, December 2004

CONTENTS

Papers

Research Notes

English Abstracts

 The energy loss of an electronic ballast is mainly composed of switch loss and induction loss. The loss decreases when setting the component values so as to reduce the phase angle of the road circuit. However, the lamp current limiting action falls and fails to stably operate the lamp. We have examined the ways to improve the control stability by using the loop transfer function, the bode plot in particular. By designing a control circuit with the experimentally measured loop transfer function and the transfer function of each functional circuit block, the tested lamp was able to operate stably.

KEYWORDS : electronic ballast, load characteristic, frequency response, stability of control, loop transfer function, bode plot

Measurement for the Panum’s Fusional Area in Retinal Fovea Using a Three-Dimention Display Device
D. QIN, M. TAKAMATSU and Y. NAKASHIMA

  The limits of Panum’s fusional area have been studied by many research groups. Those studies, however, focused only on the measuring direction of horizontal and vertical meridian. In this study, a new experimental method was employed by using a three-dimension display device to fully measure the limits of Panum’s fusional area in eight different directions from 0 degree to 360 degrees with a step of 45 degrees in the retinal fovea. The following results were obtained: (1) the horizontal limit of Panum’s fusional area in fovea is larger than the vertical limit; (2) the limits of Panum’s fusional area are almost symmetrical about the horizontal meridian; (3) the limits of Panum’s fusional area are not symmetrical about the vertical meridian; the nasalward limits are obviously larger than the temporalward limits; (4) the form of Panum’s fusional area in retinal fovea is suggested to be an off-centered ellipse instead of a standard ellipse reported in previous works.

KEYWORDS : binocular vision, Panum’s fusional area, disparity, three-dimension display, retinal fovea

 The purpose of this study is to understand what kinds of lighting give us visual harmony in a space where both daylight and artificial lights are used. For this, we examined under what situation the light from windows and the artificial lights could be in harmony. Subjects adjusted artificial lights and evaluated comfortable lighting environment while considering visual harmony of lighting. We made a hypothesis that daylight and the artificial light would be harmonious when the overall lighting in the space was described by a compound of the lights from the window and the whole ceiling. We compared the experimental value of illuminance distribution with supposable value by the hypothesis and analyzed the correlation between the subjective evaluation of the visual harmony and the residual of the above two functions.

KEYWORDS:daylight, artificial light, visual harmony, adjusting light

 The aim of the study was to investigate to what extent variations in natural daylight, as well as in indoor lighting and decoration, would affect the mood of people working indoor. It was assumed that such an impact would be moderated by the personality characteristics of the individuals. The study was carried out in northern Argentina in workplaces consisting mostly of open plan offices, but also some rooms for one or two persons, and a factory plant were included. About 20 per cent completely lacked windows. In spite of the considerable variations in day length, ranging from ten-and-a-half hours in June to fourteen hours in December, no overall seasonal variations in mood could be established. One obvious reason for this may have been the frequent use of shading devices which reduced the impact of the variations in natural daylight between summer and winter. On the other hand, the differences between the interior environments in terms of lighting and decoration did seem to have at least some impact. Both analyses of regression and variance showed interior decoration to be the most important from the emotional point of view. The participants throughout, reported a more positive mood in the colourful environments. The difference was consistent over the year but became significant only during autumn and winter. Individuals of type B (few signs of tension) reported a more positive emotional status throughout the year than those of type A, which is in line with previous results linking type A to anger and hostility.

KEYWORDS : Argentina, daylight, day length, decoration, environment, light, lighting, mood, personality, workers

Definition of a Luminous Stud to Improve the Legibility of Expressway for Drivers
A. BACELAR

 These last years, road marking using luminous studs became current on our roads. It seems to be a good means to guide road users at night or in poor weather conditions when street lighting is missing. Nevertheless really few experiments concern their evaluation in urban expressways. This paper presents an experimentation with road users, who were asked to assess the visibility, legibility, comfort and driving assistance of three luminous studs with questionnaire and to give their preference between different configurations of lighting systems. Following this experimentation and remarks of users, it proposes some physical and environmental characteristics for a typical stud, which will be the best adapted in term of driving assistance and comfort for improving legibility of road.

KEYWORDS:luminous stud, experimentation, legibility, driving assistance

Influence on Depth Perception Caused by Modifying Gradation of Depth Map Images with Gray Level for Computer-Generated Stereogram and Its Subjective Estimation
M. IIZUKA, Y. OOKUMA, Y. NAKASHIMA and M. TAKAMATSU

 There is a lot of information on the internet web site concerning all aspects of sterogram history, science, social organization, and various types of sterograms. A streogram is a two dimensional flat image viewed in such a fashion as to produce a three dimensional effect, i.e., visual depth perception. A variety of software for generating effectively the random dot sterogram (RDS) and single image sterogram (SIS) has been released on the internet web site. On the other hand, various hidden object images often called depth map image (DMI) with gradation in monochrome must be prepared in advance.

 This research note focuses on the influence of the depth perception caused be modifying hidden object images for digital sterogram. The possibility of subjective estimation of the depth is discussed using the simultaneous observation of a few sterogram.

KEYWORDS : computer-generated streogram, depth map image, depth perception, subjective estimation of depth, stereoscopic vison