JOURNAL OF THE ILLUMINATING ENGINEERING INSTITUTE OF JAPAN
Online ISSN : 1349-838X
Print ISSN : 0019-2341
ISSN-L : 0019-2341
Volume 86, Issue 5
Displaying 1-7 of 7 articles from this issue
  • Yoshio Watanabe, Ken Ohta
    2002 Volume 86 Issue 5 Pages 279-285
    Published: May 01, 2002
    Released on J-STAGE: July 19, 2011
    JOURNAL FREE ACCESS
    The characteristics of inductively coupled electrodeless discharge lamps using a ferrite core are investigated. The discharge tube has a hollow cylinder shape, and a ferrite core with an excitation coil is inserted into the hollow. A voltage is applied across the coil, and light emission is measured at 100-200kHz. The voltage per turn of the coil is constant at about 7V. The luminous efficacy defined by the input power increases with the number of turns and is independent of operating frequency.
    The characteristics of the inductively coupled electrodeless discharge lamps are analyzed using the equivalent circuit. The luminous efficacy defined by the discharge wattage is independent of the number of turns. The core loss, which is mostly due to eddy current loss, is nearly constant when discharge takes place due to the constant discharge voltage characteristics, whereas the joule loss in the winding coil decreases with an increasing number of turns. Thus, the efficacy defined by the input power increases with the number of turns of the winding coil.
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  • Ichiro Katayama, Kazuyoshi Masumi, Tsutomu Aoki
    2002 Volume 86 Issue 5 Pages 286-291
    Published: May 01, 2002
    Released on J-STAGE: July 19, 2011
    JOURNAL FREE ACCESS
    Using psychological experiments, we investigated the perceived whiteness of a white object under 30 types of illuminants. We used the index we developed in an initial study [J. Illum. Inst. Jpn. Vol.83 No.11 (1999)] and modified in a subsequent study [J. Illum. Inst. Jpn. Vol.85 No.5 (2001)] to evaluate the perceived whiteness. The index is proportional to the total chromatic strength of the spectral stimulus at a constant luminance level; it correlated highly with the experimental results, indicating that it can be used to effectively evaluate the perceived whiteness of a white object under various illuminants.
    Considering the ability of a spectral stimulus to induce brightness and chromatic perception, we investigated the cause of whiteness perception. We found that whiteness perception, the Helmholtz-Kohlrausch effect, the discrimination threshold level of colorimetric purity, and the G0 function studied by Evans are all caused by a basically common color perception mechanism and that they can be explained uniformly by using chromatic strength.
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  • Mitsuyuki Kawakami, Shuichi Matsumoto, Wakako Kaneko
    2002 Volume 86 Issue 5 Pages 292-297
    Published: May 01, 2002
    Released on J-STAGE: July 19, 2011
    JOURNAL FREE ACCESS
    This research examines the ease of reading text on a car navigation screen as a visual display when the luminance of the driver's eye-fixation point differs from that of the screen while driving. To conduct this research, an experiment was performed to determine how such variation in luminance affects the time taken for a driver to read text displayed on a car navigation screen during driving operations. Evaluation indexes in this experiment were locus of eye-fixation point during movement of line of sight, duration of stationary viewpoint, and time taken to read text. Results of this experiment revealed the following.(1) Reading time for a screen luminance of 100cd/m2 was short under nighttime luminance conditions of 2.5cd/m2 exhibiting a difference of about 0.314s compared to 500cd/m2.(2) Reading time for a driving environment of 50Ocd/m2with screen luminance lower at 25cd/ m2 was short exhibiting a difference of about 0.13s.(3) Reading time shortens as the ratio of monitor luminance to luminance while driving increases.
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  • Analysis by the Numerical Experiment
    Naotaka Ikemoto, Minoru Isomura
    2002 Volume 86 Issue 5 Pages 298-307
    Published: May 01, 2002
    Released on J-STAGE: July 19, 2011
    JOURNAL FREE ACCESS
    A method is described for estimating three-dimensional (3-D) shapes from two-dimensional (2-D) shading informationin gray-level images that uses the diffuse reflection components in a luminance distribution with diffuse and specular reflection components. It overcomes the problem of highlights caused by the specular reflection components that occurs when multiple fixed light sources are used, which is a drawback to the “photometric stereo” method proposed by Woodham. First, the bidirectional reflectance distribution function is estimated for the detected area of a gray-level image with highlights. Then, the luminance distribution caused by the diffuse reflection components in the detected area is estimated based on the luminance distribution in a gray-level image without highlights. Numerical shape-measurement experiments using mixed diffuse-specular objects with different characteristic reflectances and shapes showed that the proposed method can accurately measure the 3-D shape of mixed diffuse-specular objects.
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  • Kenichi Yamada, Yasuo Imai, Kenichi Ishii
    2002 Volume 86 Issue 5 Pages 308-312
    Published: May 01, 2002
    Released on J-STAGE: July 19, 2011
    JOURNAL FREE ACCESS
    The optical structures and luminous properties of the light source device composed of blue LEDs and YAG phosphor were examined by using optical simulation. Results showed that the reflection-type light source device had high luminous flux over 1.5 times more than the transmission-type light source device. This suggests that using light reflected from phosphor is an effective way to obtain high output from light sources composed of LEDs and phosphor.
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  • Mitsuyuki Kawakami, Tohru Shibayama
    2002 Volume 86 Issue 5 Pages 313-316
    Published: May 01, 2002
    Released on J-STAGE: July 19, 2011
    JOURNAL FREE ACCESS
    We investigated how color visibility affects work efficiency. In particular, we experimentally invesligated how differ-ences in bue affect the motion of touching a control button. The evaluation indexes were the time it took to respond to astimulus, the time it took to move the hand to the button, and the frequency of motion confusion. We found that different hues affect work efficiency differently. With warm colors, if the background color is achromatic and the brightness is low, yellow is highly visible, resulting in high work efficiency. With cool colors, if the background color is achromatic and the brightness is high, blue or purple results in high work efficiency.
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  • Kazuhiro Sassa, Mamoru Takamatsu, Yoshio Nakashima, Santaro Nakajima
    2002 Volume 86 Issue 5 Pages 318-320
    Published: May 01, 2002
    Released on J-STAGE: July 19, 2011
    JOURNAL FREE ACCESS
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