Volume 20 Number 1, May 1996.

CONTENTS

New Lighting Installations in Japan

Papers

ABSTRACT

Illuminance Distribution Uniformity in a Room : Computer Simulation used Kinoform

Kumiko MITSUBA, Yoshihiko MUTO* and Hiroshi KAYANO
Faculty of Science, Yamaguchi University

The purpose of this paper is to study a uniform illuminance distribution on a floor surface in a room, controlling the daylight incidented from a window with a kinoform. In this paper, the illuminance distribution is computed using finite element procedure. The daylight is irradiated the parallel wall with the window by the kinoform, next, the reflection from the wall surface to the floor surface is computed. The result shows that the illuminance distribution on the floor is improved very much compared with the case that the kinoform is not installed on the window.

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Analysis of Factors on Discernment of Auxiliary Lamps of Motorcycles

Kazumoto MORITA, Jin ichi MASHIKO, Shin'ichiro ITOH, and Takeo OKADA
Traffic Safety and Nuisance Research Institute

Mounting auxiliary lamps similar to the front position lamps is an effective means of improving the visibility of motorcycles. Among possible factors which may influence discernment of the auxiliary lamps, the authors have examined factors such as the surface area, luminous intensity and luminance of the auxiliary lamps conducting outdoor experiments. The auxiliary lamp is made up of amber-colored light emitting diodes (LED) with 32 LEDs in the horizontal direction and 16 LEDs in the vertical direction. The experiments consist of two parts, a static experiment in which the observers observed a stationary motorcycle and a dynamic experiment in which they observed a moving motorcycle. The observers were instructed to evaluate the following three items:
(1) Conspicuousness of the motorcycle
(2) Brightness of the auxiliary lamps
(3) Appropriateness of the auxiliary lamps.
Experimental results and discriminant analysis of the data show that the luminous intensity of the auxiliary lamps strongly influences how the lamps are discerned.

KEYWORDS: motorcycle, auxiliary lamps, conspicuousness, brightness, luminous intensity

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Legibility of Displayed Place Names by In-Vehicle Navigation Devices

Kazumoto MORITA , Jin'ichi MASHIKO, Shin'ichiro ITOH and Takeo OKADA
Traffic Safety and Nuisance Research Institute

The authors have conducted mainly indoor experiments in which they tested the legibility of three place names in Tokyo area displayed by a navigation device by having the observers read the place names as quickly and accurately as possible. The three place names simulate a road sign at an intersection. The reading time and the reading accuracy of the three place names are examined under various experimental conditions, such as the size of the displayed place name, the position of the display device, the observer's age and other factors. For example, to reproduce experimental conditions, three kinds of display devices and display positions are tested; first, head-up display in the central vision, second, head-up display in the peripheral (near central) vision, and third, the conventional LCD display in the peripheral vision. There are thirty observers in three age ranges (in their 20s, 40s, and 60s), with ten in each group. The authors have revealed how the experimental conditions affect the legibility of the three place names displayed by in-vehicle navigation devices.

KEYWORDS: automobile, safety, navigation system, legibility, head-up display

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Categorical Color-Name Regions of A Color Space in Aperture and Surface Color Modes

Keiji UCHIKAWA, Ichiro KURIKI
Imaging Science and Engineering Laboratory Tokyo Institute of Technology

Hiroyuki SHINODA
Department of Electrical and Electronic Engineering Ritsumeikan University

The Paper originally published in Japanese in J.EIJ. Vol77-No6, 1993.

When we indicate or describe an object in everyday lives we often use a color of the object. Although there are a million of colors around us we do not use so many colors, but categorize different colors into several color names. Eleven color names; red, green, yellow, blue, brown, orange, purple, pink, white, black and gray, have been qualified as basic color categories, that are used consistently among observers and occasions. In this study we measured categorical regions in a color space determined with a categorical color naming method using these 11 basic color names. Two color-appearance modes; aperture color mode and surface color mode, were tested. We employed both a color CRT monitor and a OSA uniform color set as test stimuli in the two color-appearance modes. It is shown in our results that both aperture and surface color spaces were consistently divided into the 11 basic color categories, and that positions and borders of color categories depend on luminance (lightness) of test stimuli in the surface color mode, but almost independent of luminance in the aperture color mode. Furthermore, test stimuli made by a color CRT do not appear so different from those by color chips in both color-appearance modes. There are some similarities between our results and the Kelly's chart.

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Comparison between the Photoluminescence Properties of LaPO ₄:Tb,Ce Phosphor under 254nm Excitation and those under 365nm Excitation

Shigeru FUKUMOTO, Yasufumi HAYASHI
Faculty of Engineering, Setsunan Univercity

Tomoaki HATAYAMA
Graduate School of Engineering, Kyoto Univercity

Tohru NOGUCHI, Sumiaki IBUKI
Faculty of Engineering, Setsunan Univercity

Paper Originally published in Japanese J.EIJ. Vol77-No.10,1993.

LaPO ₄: Tb,Ce phosphors have been used for the green component of three-band emission type fluorescent lamps. We have confirmed that the emission intensity of Tb³⁺ under 254nm excitation is greatly enhanced by the energy transfer from Ce to Tb in the case of Ce co-doping, and the fluorescent intensity-temperature characteristics were also improved by substituting borate for a small part of phosphate, or by additive doping with thorium. In order to apply this phosphors to high pressure mercury lamps which operate at higher wall temperature and loading than low pressure mercury lamps, some characteristics of this phosphors under 365nm excitation were investigated. However, the green emission intensity under 365nm excitation was rather decreased by doping with cerium. The reason for this phenomenon could possibly be caused to energy transfer from Tb³⁺ to Ce³⁺, as excitation spectra of Tb³⁺ and emission spectra of Ce³⁺ overlap each other. Time-resolved spectra have been also observed under 365nm dye laser excitation. The ⁵D₃ --> ⁷F_j emission were found in highly Tb-doped LaPO₄:Tb,Ce phosphors, and new line emissions around 600nm which are considered to be originated by Ce²⁺ were found in (La,Ce,Th)(PO₄,BO₃):Tb phosphors under 365nm pulse excitation.

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EFFECT OF PRINT CONTRAST ON REFLECTED GLARE

Yoshihiko TABUCHI, Hajimu NAKAMURA, Atsushi OSE,
Matsushita Electric Works, Ltd.

Toru NOGUCHI
Faculty of Engineering Setsunan University

Paper originally published in Japanese in J.IEIJ.Vol77 - No.10, 1993

Reducing reflected glare on visual tasks, such as prints in offices, is one of the most important factors in office lighting. Experimental studies the authors are carried out to reduce the reflected glare. The authors studied, through a subjective evaluation, to obtain permissible limit of reflecting source luminance, and found relationships among various lighting factors: permissible limit of light source luminance, illuminance on visual task, luminance contrast between character and background, and print contrast( luminance contrast between character and background without reflected glare ).
(1) Print contrast had considerable effect on the same contrast with reflected glare superposed. The latter required higher luminance contrast without reflected glare with the same background luminance.
(2) Accordingly, with different luminance contrasts without reflected glare, legibilities of character with reflected glare are different, even with the same background luminance and luminance contrast.

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Development and Evaluation of a Solar Ultraviolet-B Radiometer

Shu TAKESHITA , Toshibumi SAKATA and Masako SASAKI
Tokai University

Paper originally published in Japanese in J.IEIJ. vol77-No10, 1993.

A new band-spectral solar ultraviolet-B (UV-B: 290-320 nm) radiometer was developed to achieve a simple and accurate outdoor measurement. The spectral response of the radiometer has a maximum at 305 nm and has a 20-nm bandwidth. In this radiometer, incident solar UV-B irradiance is converted to visible irradiance by a phosphor layer and is detected by a Si-photodiode. The spectral, cosine, azimuth and temperature responses of the radiometer have been evaluated. Contamination by UV-A radiation longer than 320 nm in wavelength is less than 6 % of the measured UV-B radiation. No changes in instrumental sensitivity nor in the spectral response of the radiometer have been found during periodical checks over a two-year span. Results indicate that this radiometer is useful for continuous, high time-resolution measurement of solar UV-B radiation.

KEYWORDS: azimuth response, cosine response, phosphor layer, solar ultraviolet-B irradiance, spectral response, temperature response, UV-B, irradiance, UV-B radiometer

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