JOURNAL OF THE ILLUMINATING ENGINEERING INSTITUTE OF JAPAN
Online ISSN : 1349-838X
Print ISSN : 0019-2341
ISSN-L : 0019-2341
Volume 89, Issue 5
Displaying 1-5 of 5 articles from this issue
Papers
  • Miyoshi Ayama, Takashi Kato, Naoki Urushibata, Toru Yamaguchi, Kunihir ...
    2005 Volume 89 Issue 5 Pages 225-229
    Published: 2005
    Released on J-STAGE: August 02, 2005
    JOURNAL FREE ACCESS
    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 simulator system and one field experiment. In all the experiments, a warning voice was issued to the driver at various times before making a left or right turn. The drivers were asked to evaluate the timing of the warning subjectively. 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 experimental conditions.
    Download PDF (676K)
  • —Brightness Prediction Based on Luminance Contrast, Part 2—
    Yoshiki Nakamura, Kotoku Egawa
    2005 Volume 89 Issue 5 Pages 230-235
    Published: 2005
    Released on J-STAGE: August 02, 2005
    JOURNAL FREE ACCESS
    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 wavelength as a parameter. Finally, the formula is checked experimentally using complicated luminance images as stimuli.
    Download PDF (452K)
  • Minoru Myojo, Osamu Fukumasa
    2005 Volume 89 Issue 5 Pages 236-244
    Published: 2005
    Released on J-STAGE: August 02, 2005
    JOURNAL FREE ACCESS
    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 monitoring 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 Richardson constant is taken as the theoretical value. As a result, work function φ[eV] of a fluorescent lamp electrode halfway through its lamp life was measured and given as:
    φ=0.80+1.36×10-3T (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 Richardson constant, the smaller the estimated work function is. Finally, the paper examines how to take a realistic value of the Richardson constant.
    Download PDF (772K)
  • Yuji Uchida, Tsunemasa Taguchi
    2005 Volume 89 Issue 5 Pages 245-257
    Published: 2005
    Released on J-STAGE: August 30, 2005
    JOURNAL FREE ACCESS
    We described a basic theory of multi-point light sources that comprise white light-emitting diode (LED) arrays 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.
    Download PDF (2915K)
Letter
feedback
Top