TOP / Publications / Abstracts of papers in J. of IEIJ / J. of IEIJ Vol.89, No.5

The Abstracts of the Papers J.Illum. Engng. Inst. Jpn.Vol. 89, 2005

No.5  May

CONTENTS

Papers

Study on Timing of Voice Warning at Crossings

M. AYAMA, T. KATO, N. URUSIBATA, T. YAMAGUCHI and K. OHASHI

225

Prediction of Brightness Using Contrast Profile Method —Brightness Prediction Based on Luminance Contrast, Part2—

Y. NAKAMURA and K. EGAWA

230

Measurement of Work Function of Practical Fluorescent Lamp Electrodes with Emissive Oxides

M. MYOJO and O. FUKUMASA

236

Theory of Illuminance Properties of Multi-point Light Sources with Individual Phosphor-coated White Light-emitting Diodes under Direct Illumination Using Radiation Intensity Distribution Function

Y. UCHIDA and T. TAGUCHI

245

Letter

Effect of the Luminaire's Luminance on Human Brain Waves

K. MATSUSHIMA, S. KATAYAMA, Y. TAKAHASHI, Y. SHIMOMURA, K. IWANAGA and T. KATSUURA

258

 

ABSTRACTS

Study on Timing of Voice Warning at Crossings
Miyoshi AYAMA, Takashi KATO, Naoki URUSHIBATA, Toru YAMAGUCHI and Kunihiro OHASHI

We developed prototype of a new system to warn drivers about unseen pedestrians or bicycles at intersections. We carried out two experiments using a simple simula-tor system and one field experiment. In all the experi-ments, a warning voice was issued to the driver at vari-ous times before making a left or right turn. The drivers were asked to evaluate the timing of the warning subjec-tively. We also monitored accelerator and break pedal activity. The results showed that the best timing is 3 or 4 seconds before entering the intersection. The effects of the warning on the deceleration and breaking showed large individual differences and depended on the ex-perimental conditions.

KEYWORDS : warning system, intersection, proper tim-ing, driverís attention

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Prediction of Brightness Using Contrast Profile Method —Brightness Prediction Based on Luminance Contrast, Part2—
Yoshiki NAKAMURA and Kotoku EGAWA

A formula using the contrast profile method is proposed to predict the brightness of even complicated luminance distribution in the real scene. The appropriateness of using the contrast profile method is first explained based on the multi-channel model of the visual system. Then, the previous formula using target size as a parameter is transformed into a formula using detected spatial wave-length as a parameter. Finally, the formula is checked experimentally using complicated luminance images as stimuli.

KEYWORDS : brightness, apparent brightness, contrast profile, luminance contrast, simultaneous contrast

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Measurement of Work Function of Practical Fluorescent Lamp Electrodes with Emissive Oxides
Minoru MYOJO and Osamu FUKUMASA

In this paper we propose a method for measuring work function of practical fluorescent lamp electrodes with emissive oxides. The work function measurement is based on the matching between the zero-field thermionic emission currents and various dc lamp currents set in a normal glow discharge by means of a lamp voltage moni-toring procedure with an electrode-heating device for thermionic emission measurement. Measuring the work function of practical fluorescent lamp electrodes is a promising approach because changes that occur in the work function of aged-lamp electrodes in some lighting systems will be helpful in evaluating the system.

The paper points out the doubtful approach of taking a rather small value of the Richardson constant. To solve this issue, a temperature-dependent work function is introduced. In the first stage of the paper, the Rich-ardson constant is taken as the theoretical value. As a result, work function φ [eV] of a fluorescent lamp elec-trode halfway through its lamp life was measured and given as:

φ = 0.80+1.36◊10-3 T ( computed from equation with T2)

where T was the electrode temperature [K].

Second, an attempt is made to measure a temperature-dependent work function taking a realistic value of the Richardson constant. The smaller the value of the Rich-ardson constant, the smaller the estimated work func-tion is. Finally, the paper examines how to take a realis-tic value of the Richardson constant.

KEYWORDS : work function, fluorescent lamp, emissive oxide, electron emission, electrode, Richardson constant

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Theory of Illuminance Properties of Multi-point Light Sources with Individual Phosphor-coated White Light-emitting Diodes under Direct Illumination Using Radiation Intensity Distribution Function
Yuji UCHIDA and Tsunemasa TAGUCHI

We described a basic theory of multi-point light sources that comprise white light-emitting diode ( LED ) ar-rays for lighting applications. Evaluating the luminous intensity distribution is very important to understand the illuminance properties in the multi-point LED sources. We thoroughly studied each property of conventional white LEDs using blue LED excitation and a novel type of white LED using near ultraviolet ( UV ) LED excitation, making use of our theory. Individual quaternary multi-point light sources composed of orange, yellow, green and blue ( OYGB ) phosphors, combined with near UV LEDs were fabricated. A theoretical method using the radiation intensity distribution function was carried out to determine chromaticity and luminous properties of the light from these OYGB white LEDs under direct illumination. This shows that OYGB white LEDs have some characteristics that are superior to those of the conventional white LEDs.

KEYWORDS : lighting theory, white LED, phosphor emissions, chromaticity and luminous properties, semi-conductor lighting

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Effect of the Luminaire's Luminance on Human Brain Waves
Koji MATSUSHIMA, Syuji KATAYAMA, Yoshika TAKAHASHI, Yoshihiro SHIMOMURA, Koichi IWANAGA and Tetsuo KATSUURA

KEYWORDS : luminance, luminaire, lighting design, subjective evaluation, physiological estimation

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