Journal of Light & Visual Environment

Papers

Spectral Properties of Medium- or High-Pressure Plasmas Ionized to High Degrees

Tatsumi HIRAMOTO

2006 Volume 30 Issue 1 Pages 3-8
Published: 2006
Released on J-STAGE: June 06, 2006

DOIhttps://doi.org/10.2150/jlve.30.3

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A method for calculating spectral radiances of plasmas produced at high current densities has been proposed. Ionization degrees of the present plasmas at medium or high pressures are so high that LTE states are held. An absorption coefficient of a plasma emitting atomic and ionic lines, and continuum has been expressed with the Gaunt factor being effective from VUV to FIR. The spectral radiance has been calculated with the total absorption coefficient as a function of the temperature, with the use of a filling pressure of an emissive species into lamps as a parameter. Numerical calculation has been done for Xe-filled radiation sources operated at high current densities. Part of the results have been compared with experimental data by other authors. As a result, the proposed method is considered to be available to search for new radiation sources emitting strong atomic and ionic lines as well as intense continua.

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The Effect of Buffer Gas and Excitation Mode in Low Pressure Nitrogen Discharges

Spiros KITSINELIS, Hideki MOTOMURA, Masafumi JINNO

2006 Volume 30 Issue 1 Pages 9-12
Published: 2006
Released on J-STAGE: June 06, 2006

DOIhttps://doi.org/10.2150/jlve.30.9

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In this paper we demonstrate the influence of buffer gas atoms on the emission spectrum of a low-pressure nitrogen discharge. If the conditions of operation of the discharge allow for the population of the energy levels of the buffer gas atoms then energy stored in the metastable states of these atoms can be transferred through collisions to the atoms of the active medium. This results in a higher degree of excitation of the latter with significant effects on the optical output of the source.

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Processes in Low Pressure Mercury-Rare Gas Discharges

Spiros KITSINELIS, Hideki MOTOMURA, Hisayoshi KUROKAWA, Masafumi JINNO

2006 Volume 30 Issue 1 Pages 13-17
Published: 2006
Released on J-STAGE: June 06, 2006

DOIhttps://doi.org/10.2150/jlve.30.13

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The near-UV and visible mercury emissions from low-pressure discharges were studied under a range of rare gas hosts and different modes of operation. The optimization of the emission line intensities is achieved under different buffer gases for different operating modes. It is hypothesized that energy transfer processes occur between the rare gas metastable states and mercury atoms leading to the observed spectra.

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The Influence of Lightness, Chroma and Hue of Chromatic Letters against an Achromatic Background on Readability and Equivalent Luminance Contrast

Naoya HARA, Tarow NOGUCHI

2006 Volume 30 Issue 1 Pages 18-28
Published: 2006
Released on J-STAGE: June 06, 2006

DOIhttps://doi.org/10.2150/jlve.30.18

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The main purpose of coloring an object is to add information and to draw attention to it. However, the visibility of the visual object must not be spoiled by taking these effects too seriously. It is thought that explaining the influence of color on the visibility of an object is useful to show the effect of coloring except for the visibility after securing the visibility of a visual object. The final goal of this research is to show the establishment of visual environment design based on the visibility of chromatic object, and tries to explain the influence on the visibility of the color quantitatively. This paper shows the results of the subjective evaluation experiment. The experiment has various conditions systematized by color difference (lightness, chroma and hue under the CIELAB color system). The readability of chromatic documents was understood by focusing on the color difference as an index that shows the degree of influence of the color on visibility quantitatively. This paper shows the relationship between the color difference and the equivalent luminance contrast that is proposed by the authors to discuss the influence of the color easily.

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Changing Binocular Fusional Area with Retinal Shift in Binocular Vision

Damin QIN, Mamoru TAKAMATSU, Yoshio NAKASHIMA

2006 Volume 30 Issue 1 Pages 29-33
Published: 2006
Released on J-STAGE: June 06, 2006

DOIhttps://doi.org/10.2150/jlve.30.29

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In three-dimensional display systems, binocular disparity must be limited within a certain area, called as “Panum's fusional area”. Otherwise, unsuitable binocular disparity can cause double view or eye fatigue. In this study, we measured the binocular fusional areas in central vision, in the case of peripheral visions of retinal eccentricity of 3 degrees and 6 degrees on horizontal meridian, respectively, using a three-dimensional display. The following results were obtained, (1) in each experiment in central vision, peripheral vision of 3 degrees and 6 degrees, the disparity limit in horizontal meridian is larger than that in vertical meridian; the binocular fusional area is symmetrical about horizontal meridian and is not symmetrical about vertical meridian; the nasalward disparity limits are larger than the temporalward disparity limits; therefore, the form of the binocular fusional area is considered as an ellipse off-centered toward the nasal side on the horizontal meridian. (2) The size of the binocular fusional areas increases with the increase of retinal eccentricity, and the increase of disparity limit on horizontal meridian is faster than that on vertical meridian.

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Research Note

Investigation on the Minimum Maintenance Discharged Power of a Low-Frequency Driven Electrodeless Compact Fluorescent Lamp

-Buffer Gas and Driving Frequency Dependence-

Takeshi ARAKAWA, Katsushi SEKI, Koichi KATASE, Kiyoshi HASHIMOTODANI, ...

2006 Volume 30 Issue 1 Pages 34-38
Published: 2006
Released on J-STAGE: June 06, 2006

DOIhttps://doi.org/10.2150/jlve.30.34

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We have investigated the minimum discharged power to maintain lamp plasma in terms of dependence on buffer gas condition and driving frequency of the electrodeless compact fluorescent lamp (ECFL). It is essential for realization of the low-frequency driven ECFL with inductively coupled plasma technique for household use. Considering the point of cost, the driving frequency of the electrodeless discharge lamp should be lowered because high frequency driving (> 1MHz) requires special components for reduction of EMI noise and circuit power loss with the increase in driving frequency. But it is difficult to maintain plasma at low frequency driving, since induced electric fields, which excited with the induction coil is declined and not receive energy for ionization and discharge sufficiently. Here, we indicated that the condition of minimum power to maintain the H-mode (inductively coupled) discharge described as simple functions of buffer gas pressure and driving frequency for a fixed lamp bulb shape and found that the relation can represent the measured data well. Using that relation, we can easily predict optimum buffer gas pressure from driving frequency and required minimum maintenance power on the commercially available (practical) standpoint.

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Letters

Case Study on Combination of Fluorescent Materials for White LED to Obtain High Color Rendering Indexes

Shunsuke NAYAMA, Kunio ITOH

2006 Volume 30 Issue 1 Pages 39-42
Published: 2006
Released on J-STAGE: June 06, 2006

DOIhttps://doi.org/10.2150/jlve.30.39

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This letter reports on white-LED with high color rendering property. We realized the white-LED whose average Color Rendering Index (CRI) is as high as 94.2 by applying the commercial Red, Yellow, Green and Blue phosphors to near ultraviolet-LED. So far as we know, this value is the highest ever attained in white-LED around the color temperature of 5500[K]. In order to realize the good R_a (average CRI), we made a CRI simulator and simulated the spectrum distribution of white-LED with good R_a. The spectrum distribution obtained by this simulation was proved to be very useful as a landmark for realizing a prototype white-LED with good R_a.

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Change of Wavelength Difference Limit for Binocular Color Fusion with Wavelength and Brightness of Stimuli

Damin QIN, Mamoru TAKAMATSU, Yoshio NAKASHIMA, Xiaolin QIN

2006 Volume 30 Issue 1 Pages 43-45
Published: 2006
Released on J-STAGE: June 06, 2006

DOIhttps://doi.org/10.2150/jlve.30.43

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In this study, we measured the wavelength difference limit for binocular color vision, using a three-dimensional display to present dichoptic stimuli to the left and right eye, respectively. The size of stimulus was 2° arc of visual angle, the wavelength range of the stimuli was selected from 450 nm to 650 nm, and the brightness of the experimental stimuli was set four levels, as 3 cd/m², 7.5 cd/m², 15 cd/m², and 30 cd/m². The following results were obtained: (a) the binocular color fusion ceases when the color difference introduced between the left and right eyes exceeds a certain threshold value. The range of binocular color fusion limit is less than 10∼80 nm. (b) The limit of binocular color fusion becomes smaller with the increase of the brightness of the stimulus.

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