JOURNAL OF THE ILLUMINATING ENGINEERING INSTITUTE OF JAPAN
Online ISSN : 1349-838X
Print ISSN : 0019-2341
ISSN-L : 0019-2341
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Volume 92, Issue 2
Displaying 1-5 of 5 articles from this issue
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Papers
  • Effect of Spatial-Frequency Distribution in Brightness Perception in Light Environment
    Katsunori Okajima, Shin-nosuke Fujimoto
    2008 Volume 92 Issue 2 Pages 77-82
    Published: February 01, 2008
    Released on J-STAGE: April 11, 2008
    DOIhttps://doi.org/10.2150/jieij.92.77
    JOURNAL FREE ACCESS
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    We conducted a psychophysical experiment using pictures of a light environment as image stimuli. Brightness perception in light environment depends on not only the illumination or mean luminance but also the luminance distribution of the scene. We analyzed the data from the viewpoint of spatial-frequency information processing to estimate the effects of non-uniform luminance distribution on brightness perception. We modified still pictures of scenes of a room (reference images) using two-dimensional frequency analysis. Lowpass-filtering and contrast-gain control operations in the spatial-frequency dimension provided the test images. By adjusting the brightness of the reference images to that of the test images, we derived equi-brightness pairs of the reference and test images. The results showed that even though the mean luminance values of the two images (reference and test stimuli) were equal, the brightness of the lower contrast image was substantially lower and that of the lowpass-filtered image was slightly lower. This suggests that all spatial-frequency channels affect brightness perception and that low spatial-frequency components of non-uniform images are critical factors for increasing brightness.
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  • Brightness Perception Characteristics of Elderly
    —Sitting versus Reclining Posture—
    Sinwon Jeong, Jun Munakata, Kotaroh Hirate
    2008 Volume 92 Issue 2 Pages 83-89
    Published: February 01, 2008
    Released on J-STAGE: April 11, 2008
    DOIhttps://doi.org/10.2150/jieij.92.83
    JOURNAL FREE ACCESS
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    To determine how posture affects the perception of the elderly to judge the brightness of light, an experiment was conducted in which 23 participants older than 65 judged brightness when they were in one of two postures, sitting or reclining. The position and luminance of a light source and the participant’s gaze direction were controlled. The participant was instructed to adjust the brightness of a second light source so that the brightness of both sources was the same. The ratio of the two brightnesses was used as the metric. The accuracy of brightness judgment depended on both the posture (sitting or reclining) and the gaze direction. It also depended on the luminance level regardless of the light source position, gaze direction, and posture. These findings can be used, for example, in the design or elderly-friendly living environments.
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  • Measurement of Spectral Emissivity near Room Temperature with a Vacuum Blackbody Using a Cryogenic Refrigerator
    Hideyuki Minato, Yoshinari Ishido
    2008 Volume 92 Issue 2 Pages 90-98
    Published: February 01, 2008
    Released on J-STAGE: April 11, 2008
    DOIhttps://doi.org/10.2150/jieij.92.90
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    A new type of vacuum blackbody containing both a blackbody cavity and a solid material sample was fabricated using a cryogenic refrigerator. It was to construct a highly sensitive infrared spectral-radiation measurement system using a programmable temperature control device, a Fourier transform infrared spectrophotometer, and two mercury-cadmium-telluride (MCT) detectors. Evaluation showed that the temperature of the blackbody cavity wall was accurately set within ±0.2 K for 173 - 373 K and that the nonlinearity of the system response output at 173 - 373 K was within 0.8% with the proper use of the two MCT detectors. An emissivity comparison experiment using black paint (No. 1) showed that the proposed blackbody cavity method had a coincidence within 0.015 of a diffuse reflectance measuring method at 5 - 11.6 μm. For ceramics, the emissivity temperature dependence for alumina and zirconia at 273 - 373 K was within ±0.06 and ±0.04, respectively.
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  • A Flash Lamp with High Radiant Efficiency in Ultraviolet Ray Region
    Akihiko Tauchi, Chikako Ichimura, Kazuhiko Yoshikawa, Takeki Sakurai
    2008 Volume 92 Issue 2 Pages 99-104
    Published: February 01, 2008
    Released on J-STAGE: April 11, 2008
    DOIhttps://doi.org/10.2150/jieij.92.99
    JOURNAL FREE ACCESS
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    Conventional flash lamps use Xe because its radiation spectra is close to those sunlight. Recently, new applied uses of flash lamps, such as sterilization and surface modification, are attracting attention. We developed a flash lamp effective for these uses, that emits light with higher radiant efficiency in the ultraviolet ray region We optimized the lamp specifications and lighting method, and examind a new gas(Kr) and a mixture of gases(Kr.:Xe=90:10) to be enclosed in the discharge tube.
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